Alphabetic List

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1    
Ackerly, D.D., J.S. Coleman, S.R. Morse, and F.A. Bazzaz. 1992. CO2
and Temperature Effects on Leaf Area Production in Two Annual Plant
Species. Ecology 73:1260-1269.

We studied leaf area production in two annual plant species,
Abutilon theophrasti and Amaranthus retroflexus, under three
day/night temperature regimes (18/14C, 28/22C, and 28/31C) and
two concentrations of carbon dioxide (400 and 700 uL/L). The
production of whole-plant leaf area during the first 30 d of growth
was analyzed in terms of the leaf initiation rate, leaf expansion,
individual leaf area, and, in Amaranthus, production of branch
leaves. Temperature and CO2 influenced leaf area production through
stem (the plastochron index), and through shifts in the
relationship between whole-plant leaf area and the number of main
stem nodes. In Abutilon, leaf initiation rate was highest at 38C,
but area of individual leaves was greatest at 28C. Total leaf area
was greatly reduced at 18C due to slow leaf initiation rates.
Elevated CO2 concentration increased leaf initiation rate at 28C,
resulting in an increase in whole-plant leaf area. In Amaranthus,
leaf initiation rate increased with temperature, and was increased
by elevated CO2 at 28C. Individual leaf area was greatest at 28C,
and was increased by elevated CO2 at 28C but decreased at 38C.
Branch leaf area displayed a similar response to CO2, but was
greater at 38C. Overall, whole-plant leaf area was slightly
increased at 38C relative to 28C, and elevated CO2 levels
resulted in increased leaf area at 28C but decreased leaf area at
38C. The effects on leaf area closely parallel rates of biomass
accumulation in the same experiment, suggesting that responses of
developmental processes to elevated CO2 and interacting factors may
play an important role in mediating effects on plant growth.

Abutilon theophrasti/Amaranthus retroflexus

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF AREA DEVELOPMENT,
OLD FIELD COMMUNITIES, PLASTOCHRON INDEX, TEMPERATURE

2    
Acock, B. 1990. Effects of CO2 on Photosynthesis, Plant Growth and
Other Processes. IN: Impact of CO2, Trace Gases, and Climate Change
on Global Agriculture, ASA Special Publication No. 53 (B.A.
Kimball, N.J. Rosenberg, and L.H. Allen Jr., eds.), American
Society of Agronomy, Madison, Wisconsin, pp. 45-60.

KEYWORDS: AGRICULTURE, ALLOCATION, CROPS, GROWTH, PHOTOSYNTHESIS,
PHYSIOLOGICAL CO2 RESPONSES, REVIEW

3    
Acock, B., M.C. Acock, and D. Pasternak. 1990. Interactions of CO2
Enrichment and Temperature on Carbohydrate Production and
Accumulation in Muskmelon Leaves. Journal of the American Society
of Horticultural Science 115:525-529.

We examined how temperature and stage of vegetative growth affect
carbohydrate production and accumulation in Cucumis melo L.
'Haogen' grown at various CO2 concentrations ([CO2]). Carbohydrate
production was measured by net assimilation rate either on a leaf-area basis (NARa) or a leaf dry-weight basis (NARw); carbohydrate
accumulation was measured by leaf starch plus sugar content.
Twenty-four- and 35-day-old muskmelon plants were grown for 11 days
in artificially lighted cabinets at day/night temperatures of 20/20
or 40/20C and at [CO2] of 300 or 1500 uL/L. NARa and NARw both
increased with increasing [CO2], but the CO2 effect was smaller at
low temperature, especially for plants at the later stage of
vegetative growth. NARw was a better indicator of total dry-weight
gain than was NARa. Both suboptimal temperatures and CO2 enrichment
caused carbohydrates to accumulate in the leaves at both stages of
vegetative growth. NARw was correlated negatively with leaf starch
plus sugar content. The rate of decrease in NARw with increasing
leaf starch plus sugar content was significantly greater for CO2-enriched plants. Leaf starch plus sugar content >0.03 to 0.04 kg/kg
of leaf residual dry weight at the end of a dark period may
indicate that temperature is suboptimal for growth. Plants grown at
the same temperature had higher leaf starch plus sugar content if
they were CO2-enriched than if grown in ambient [CO2], suggesting
that an optimal temperature for growth in ambient [CO2] may be
suboptimal in elevated [CO2].

muskmelon/Cucumis melo

KEYWORDS: CARBOHYDRATES, GROWTH ANALYSIS, GROWTH STAGES, NAR, SPAR
UNITS, TEMPERATURE

4    
Acock, B., M.C. Acock, V.R. Reddy, and D.N. Baker. 1985. The
Simulation, with GLYCIM, of Soybean Crops Grown in the Field and at
Various CO2 Concentrations in Open-top Chambers during 1982, 011 in
Green Report Series, Response of Vegetation to Carbon Dioxide. U.S.
Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept.
of Agriculture, Agric. Res. Serv., Washington, D.C.

soybean

KEYWORDS: CROP MODEL, MODELING, OPEN-TOP CHAMBERS, SIMULATION

5    
Acock, B., and L.H. Allen Jr. 1985. Crop Responses to Elevated
Carbon Dioxide Concentrations. IN: Direct Effects of Increasing
Carbon Dioxide on Vegetation, DOE/ER-0238 (B.R. Strain and J.D.
Cure, eds.), Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C., pp. 53-97.

KEYWORDS: CROP MODEL, ENVIRONMENTAL INTERACTIONS, PHOTOSYNTHESIS,
REVIEW, TRANSPIRATION, WUE

6    
Acock, B., D.N. Baker, V.R. Reddy, J.M. McKinion, F.D. Whisler, D.
Del Castillo, and H.F. Hodges. 1982. Soybean Responses to Carbon
Dioxide: Measurement and Simulation 1981, 004 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, and U.S. Dept. of
Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: ALLOCATION, CANOPY PHOTOSYNTHESIS, MODELING, RESPIRATION,
ROOTS, SPAR UNITS

7    
Acock, B., and D. Pasternak. 1986. Effects of CO2 Concentration on
Composition, Anatomy, and Morphology of Plants. IN: Physiology,
Yield and Economics, Vol. II (H.Z. Enoch and B.A. Kimball, eds.),
Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc.,
Boca Raton, Florida, pp. 41-52.

In summary, we can say that species differ in their response to
high CO2. Plants which are using CAM are relatively unresponsive.
Other plants with the C4 pathway show modest dry weight gains but
large reductions in transpiration rate. Plants which only have the
C3 pathway, or well-watered CAM plants which are behaving like C3
plants, exhibit modest reductions in transpiration rate and large
gains in dry weight, resulting in a variety of changes in plant
composition, anatomy, and morphology. We know too little to even
begin dividing C3 species into response groups. However, we can
describe a typical or average response as follows. All organs on
the plants become heavier with roots gaining proportionally more
dry weight than stems, and stems more than leaves. The additional
dry matter in the root is mainly used to increase root length with
very little going to increase the density of the root tissue.
Additional dry matter going to the stem causes increases in its
height and diameter and little increase in the density of the
tissue. Additional dry matter going to the leaves causes both a
small increase in leaf area and a small increase in leaf thickness.
There is an increase in structural dry matter which is probably
greater than can be explained by the increase in number of
mesophyll cell layers, although no one has even done a definitive
experiment on this. Finally, there is an increase in starch
accumulating in the leaves which, depending on the circumstances,
can be very large. Branch and tiller numbers are frequently
increased, as are the number of flowers. Either the weight or
number of individual fruits is increased.

KEYWORDS: ALLOCATION, C3, C4, REVIEW

8    
Acock, B., V.R. Reddy, D. Del Castillo, H.F. Hodges, D.N. Baker,
J.M. McKinion, and F.D. Whisler. 1983. Soybean Responses to Carbon
Dioxide: Measurement and Simulation 1982, 008 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, and U.S. Dept. of
Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, MODELING, PHOTOSYNTHESIS MODEL,
RESPIRATION, SIMULATION, SPAR UNITS, WATER STRESS, YIELD

9    
Acock, B., V.R. Reddy, H.F. Hodges, D.N. Baker, and J.M. McKinion.
1985. Photosynthetic Response of Soybean Canopies to Full-Season
Carbon Dioxide Enrichment. Agronomy Journal 77:942-947.

Global atmospheric CO2 concentration ([CO2]) is increasing as a
result of the burning of fossil fuels. At present there is little
information about how agronomic crops will respond to future high
[CO2]. To investigate the basic process that will be most affected,
soybean canopies were continuously exposed to various [CO2] and
photosynthetic rates were measured throughout the growing season.
Soybean was grown to physiological maturity in sunlit controlled-environment chambers in CO2 concentrations of 330, 450, 600 and 800
uL/L. Carbon dioxide fluxes were measured on the canopies at 15-min
intervals every day and used to calculate photosynthetic and
respiration rates. Gross photosynthetic rate increased with each
increment in [CO2] regardless of stage of development, but there
was considerable day-to-day and seasonal variation. Seasonal
changes in photosynthetic rate were associated with developmental
changes in the crop. Photosynthetic rates were low during early
vegetative development, even after the canopy had closed, but
increased threefold just before flowering to reach a peak during
flowering at stage R2. They then decreased by 30% or more until
just before the start of pod expansion (R3) when a 45% increase
occurred. Thereafter, photosynthetic rates decreased slowly and
continuously to final harvest. The daily curves of photosynthetic
rate vs. photosynthetic photon flux density were further analyzed
to determine canopy light utilization efficiency () and canopy
conductance to CO2 transfer (). Plants grown in 800 uL/L [CO2] had
a value of  that averaged about 40% higher than that for plants
grown in 330 uL/L and a value of  that averaged about 24% lower
for the season. Differences in  between these treatments were
significant throughout the season, while initial differences in 
between treatments became less obvious after late vegetative growth
stage VII.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, LIGHT UTILIZATION
EFFICIENCY, PHOTOSYNTHESIS MODEL, SPAR UNITS

10   
Acock, B., V.R. Reddy, F.D. Whisler, D.N. Baker, J.M. McKinion,
H.F. Hodges, and K.J. Boote. 1983. The Soybean Crop Simulator
GLYCIM: Model Documentation, 002 in Green Report Series, Response
of Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon
Dioxide Research Division, and U.S. Dept. of Agriculture, Agric.
Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CROP MODEL, MODELING

11   
Acock, B., and A. Trent. 1991. The Soybean Crop Simulator GLYCIM:
Documentation for the Modular Version 91, 017 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, and U.S. Dept. of
Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CROP MODEL, GENERIC MODEL, SIMULATION

12   
Aizawa, K., Y. Nakamura, and S. Miyachi. 1985. Variation of
Phosphoenolpyruvate Carboxylase Activity in Dunaliella Associated
with Changes in Atmospheric CO2 Concentration. Plant Cell
Physiology 26:1199-1203.

In Dunaliella tertiolecta, D. bioculata and D. viridis the
activities of phosphoenolpyruvate carboxylase and carbonic
anhydrase were higher in the cells grown in ordinary air (low-CO2
cells) than in those grown in air enriched with 1-5% CO2 (high-CO2
cells), whereas in Porphyridium cruentum R-1 there was no
difference in phosphoenolpyruvate carboxylase activity between
these two types of cells. Apparent Km (NaHCO3) values for
photosynthesis in low-CO2 cells of all species tested were smaller
than those in high-CO2 cells. Most of the 14C was incorporated into
3-phosphoglycerate, sugar mono- and di-phosphates during the
initial periods of photosynthetic NaH14CO3-fixation, indicating
that both types of cells in D. tertiolecta are C3 plants.

Dunaliella tertiolecta/Dunaliella bioculata/Dunaliella
viridis/Porphyridium cruentum

KEYWORDS: ALGAE, AQUATIC PLANTS, CARBONIC ANHYDRASE, CELL CULTURE,
ENZYMES, PHOSPHOENOLPYRUVATE CARBOXYLASE

13   
Akey, D.H., and B.A. Kimball. 1989. Growth and Development of the
Beet Armyworm on Cotton Grown in an Enriched Carbon Dioxide
Atmosphere. Southwestern Entomologist 14:255-260.

Growth and development were studied in the beet armyworm (BAW),
Spodoptera exigua (Hbner), reared on cotton seedlings at high (640
uL/L) or ambient (320 uL/L) carbon dioxide (CO2) levels and at two
fertilizer levels. Under high fertilization, female BAW reared on
CO2 enriched seedlings weighed significantly less (87.3 mg) than
controls (101.0 mg) and had a significantly longer developmental
time (14.2 versus 12.4 days for controls). Male BAW followed the
same pattern, but the differences were not statistically
significant. Combined (male and female) survival rates for BAW
reared on CO2-enriched cotton seedlings on a high fertilizer level
were 19.1 compared to 41.6% for controls; more females survived
than males by a significant ratio of 2:1.

cotton/Gossypium hirsutum

KEYWORDS: BEET ARMYWORM, INSECTS, OPEN-TOP CHAMBERS, SPODOPTERA
EXIGUA

14   
Akey, D.H., B.A. Kimball, and J.R. Mauney. 1988. Growth and
Development of the Pink Bollworm, Pectinophora gossypiella
(Lepidoptera: Gelechiidae), on Bolls of Cotton Grown in Enriched
Carbon Dioxide Atmospheres. Environmental Entomology 17:452-455.

The pink bollworm, Pectinophora gossypiella (Saunders), was reared
on the bolls of cotton plants grown in CO2-enriched (649 uL/L) and
ambient (371 uL/L) chambers and in two open field plots, one with
free-air CO2 enrichment (522 uL/L) and one without enrichment
(ambient CO2, 360 uL/L). The effects of increased CO2 levels on
growth and development were examined. There was no difference in
pupal weights of pink bollworm raised on CO2-enriched cotton
compared with those raised on ambient CO2 cotton (26.80 versus
26.64 mg, respectively). Also, there was no difference in
developmental time (21-27 d). Analysis of percent seed damage by
larvae showed no differences between CO2-enriched and ambient CO2
cotton. These results were attributed to the nutritional qualities
of the seed remaining the same (specifically the carbon:nitrogen
ratio) despite CO2 and photosynthetic changes in the plant.

cotton/Gossypium hirsutum

KEYWORDS: CARBON:NITROGEN RATIO, INSECTS, OPEN-TOP CHAMBERS,
PECTINOPHORA GOSSYPIELLA, PINK BOLLWORM, SEED DAMAGE, SEEDS

15   
Allen, L.H., Jr. 1990. Plant Responses to Rising Carbon Dioxide and
Potential Interactions with Air Pollutants. Journal of
Environmental Quality 19:15-34.

As global population increases and industrialization expands,
carbon dioxide (CO2) and toxic air pollutants can be expected to be
injected into the atmosphere at increasing rates. This analysis
reviews a wide range of direct plant responses to rising CO2,
increasing levels of gaseous pollutants, and climate change, and
potential interactions among the factors. Although several
environmental interactions on stomata and foliage temperatures are
reviewed briefly, a comprehensive review of effects of potential
climatic change on plants is not a major objective of this
analysis. Research shows that elevated CO2 increases photosynthetic
rates, leaf area, biomass, and yield. Elevated CO2 also reduces
transpiration rate per unit leaf area, but not in proportion to
reduction of stomatal conductance, because foliage temperature
tends to rise. With increasing leaf area and foliage temperature,
water use per unit land area is scarcely reduced by elevated CO2.
Increases in photosynthetic water-use efficiency are caused
primarily by increased photosynthesis rather than reduced
transpiration. Gaseous pollutants (O3, SO2, NOx, H2S) affect plants
adversely primarily by entry through the stomata. An example
calculation showed that reduction in stomatal conductance by
doubled CO2 could potentially reduce the effects of ambient O3 and
SO2 by 15%. However, information on the interaction of CO2 and air
pollutants is scanty. More research is needed on these
interactions, because regional changes in air pollutants are
occurring concurrently with global changes in CO2.

KEYWORDS: AIR POLLUTION, CLIMATE CHANGE, CONDUCTANCE, REVIEW,
TRANSPIRATION, WUE

16   
Allen, L.H., Jr. 1991. Effects of Increasing Carbon Dioxide Levels
and Climate Change on Plant Growth, Evapotranspiration, and Water
Resources. IN: Managing Water Resources in the West under
Conditions of Climate Uncertainty; 1990 Nov. 14-16; Scottsdale,
Arizona (Committee on Climate Uncertainty and Water Resources
Management, ed.), National Academy Press, Washington, D.C., pp.
101-147.

soybean/Glycine max

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, CLIMATE MODEL,
EVAPOTRANSPIRATION, GCM'S, MODELING, REVIEW, STREAMFLOW, WUE

17   
Allen, L.H., Jr. 1992. Free-Air CO2 Enrichment Field Experiments:
An Historical Overview. Critical Reviews in Plant Sciences 11:121-134.

KEYWORDS: EXPOSURE METHODS, FACE

18   
Allen, L.H., Jr., and S.E. Beladi. 1990. Free-Air CO2 Enrichment
(FACE): Analysis of Gaseous Dispersion Arrays for the Study of
Rising Atmospheric CO2 Effects on Vegetation. 1983-1989 Progress
Report, 057 in Green Report Series, Response of Vegetation to
Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.,
Washington, D.C.

KEYWORDS: EXPOSURE METHODS, FACE

19   
Allen, L.H., Jr., E.C. Bisbal, K.J. Boote, and P.H. Jones. 1991.
Soybean Dry Matter Allocation under Subambient and Superambient
Levels of Carbon Dioxide. Agronomy Journal 83:875-883.

Rising atmospheric carbon dioxide concentration [CO2] is expected
to cause increases in crop growth and yield. The objective of this
study was to investigate effects of subambient, as well as
superambient, [CO2] on soybean [Glycine max (L.) Merr.] dry matter
production and allocation for two reasons: to assess response of
plants to prehistoric as well as future expected CO2 levels and to
increase confidence in [CO2] response curves by imposing a wide
range of [CO2] treatments. Soybean was grown in outdoor, sunlit,
controlled-environment chambers at CO2 levels of 160, 220, 280,
330, 660, and 990 umol (CO2)/mol (air). Total dry matter growth
rates during the linear phase of vegetative growth were 5.0, 8.4,
10.9, 12.5, 18.2, and 20.7 g/m2/d for the above respective [CO2].
Samples taken from 24 to 94 d after planting showed that the
percentage of total plant mass in leaf trifoliates decreased with
increasing [CO2] whereas the percentage in structural components
(petioles and stems) increased. At final harvest the respective
[CO2] treatments resulted in 38, 53, 62, 100, 120 and 92% seed
yield with respect to the 330 umol/mol treatment. Total dry weight
responses were similar. Late season spider mite damage of the 990
and 280 umol/mol treatments reduced yields. These data confirm not
only that rising CO2 should increase plant growth, but also that
plant growth was probably seriously limited by atmospheric [CO2] in
preindustrial revolution times back to the previous global
glaciation.

soybean/Glycine max

KEYWORDS: ALLOCATION, GROWTH, PRE-INDUSTRIAL CO2 CONCENTRATION,
SPAR UNITS, YIELD

20   
Allen, L.H., Jr., E.C. Bisbal, W.J. Campbell, and K.J. Boote. 1990.
Carbon Dioxide Effects on Soybean Developmental Stages and
Expansive Growth. Soil and Crop Science Society of Florida,
Proceedings 49:124-131.

Crop productivity is expected to increase as atmospheric carbon
dioxide (CO2) continues to rise. The purpose of this paper is to
examine the response of soybean [Glycine max (L.) Merr., cv. Bragg]
stages of development and plant size to CO2 concentration during
four experiments (1981-1984) in outdoor controlled-environment
chambers. Attached lysimeters contained Arredondo fine sand (loamy,
siliceous, hyperthermic Grossarenic Paleudult). Air temperature and
dewpoint temperature were controlled to common set-points within
each year with CO2 concentration being the treatment variable among
chambers. Vegetative and reproductive developmental stages were
determined at frequent intervals during each experiment. Growth
parameters of mainstem height, total mainstem plus branch stem
length, number of mainstem nodes with branches, mainstem diameter,
and leaf areas were measured during at least one experiment.
Vegetative stages progressed slightly faster and the final number
of nodes was slightly greater with increased CO2 concentration. All
size parameters clearly increased with increasing CO2
concentration. Growth responses per unit CO2 concentration change
were greater over the subambient range (160 to 330 umol/mol) than
over the superambient range (330 to 990 umol/mol). For soybean,
plant expansive growth will increase as atmospheric CO2 continues
to rise, whereas direct effects of CO2 (without interaction of
potential climatic changes) will have little effect on phenology.

soybean/Glycine max

KEYWORDS: GROWTH, PHENOLOGY, PRE-INDUSTRIAL CO2 CONCENTRATION, SPAR
UNITS

21   
Allen, L.H., Jr., and K.J. Boote. 1992. Vegetation, Effect of
Rising CO2. IN: Encyclopedia of Earth System Science, Vol. 4,
Academic Press, Inc., New York, pp. 409-416.

KEYWORDS: AIR POLLUTION, CLIMATE, NUTRITION, REVIEW, TEMPERATURE,
TRANSPIRATION

22   
Allen, L.H., Jr., K.J. Boote, J.W. Jones, P.H. Jones, R.R. Valle,
B. Acock, H.H. Rogers, and R.C. Dahlman. 1987. Response of
Vegetation to Rising Carbon Dioxide: Photosynthesis, Biomass, and
Seed Yield of Soybean. Global Biogeochemical Cycles I:1-14.

Elevated carbon dioxide throughout the lifespan of soybean causes
an increase in photosynthesis, biomass, and seed yield. A
rectangular hyperbola model predicts a 32% increase in soybean seed
yield with a doubling of carbon dioxide from 315 to 630 ppm and
shows that yields may have increased by 13% from about 1800 A.D. to
the present due to global carbon dioxide increases. Several other
sets of data indicate that photosynthetic and growth response to
rising carbon dioxide of many species, including woody plants, is
similar to that of soybean. Calculations suggest that enough carbon
could be sequestered annually from increased photosynthesis and
biomass production due to the rise in atmospheric carbon dioxide
from 315 ppm in 1958 to about 345 ppm in 1986 to reduce the impact
of deforestation in the tropics on the putative current flux of
carbon from the biosphere to the atmosphere.

soybean/Glycine max

KEYWORDS: CARBON CYCLE, CARBON SEQUESTERING, DEFORESTATION, GROWTH
MODEL, PRE-INDUSTRIAL CO2 CONCENTRATION, REVIEW

23   
Allen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones,
R.R. Valle, and E.C. Bisbal. 1985. Subambient and Superambient
Carbon Dioxide Effects on Growth, Nonstructural Carbohydrates,
Biochemistry of Photosynthesis and Transpiration of Soybeans. 1984
Progress Report, 031 in Green Report Series, Response of Vegetation
to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.,
Washington, D.C.

soybean/Glycine max

KEYWORDS: CARBOHYDRATES, GROWTH, PHOTOSYNTHESIS, PRE-INDUSTRIAL CO2
CONCENTRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS,
TRANSPIRATION

24   
Allen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones,
C.V. Vu, R. Valle, and W.J. Campbell. 1982. Effects of Increased
Carbon Dioxide on Photosynthesis and Agricultural Productivity of
Soybeans. 1981 Progress Report, 003 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, and U.S. Dept. of Agriculture,
Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, CONDUCTANCE,
GROWTH, GROWTH STAGES, NITROGEN, RIBULOSE BISPHOSPHATE CARBOXYLASE,
SPAR UNITS, YIELD

25   
Allen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones,
C.V. Vu, R.R. Valle, W.J. Campbell, P.R. Harris, and K.F. Heimburg.
1984. Effects of Increased Carbon Dioxide and Water Stress
Interactions on Photosynthesis, Transpiration, and Productivity of
Soybeans. 1983 Progress Report, 014 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, and U.S. Dept. of Agriculture,
Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CI:CA, GROWTH, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, SPAR UNITS, TRANSPIRATION, WATER STRESS, WUE, YIELD

26   
Allen, L.H., Jr., B.G. Drake, H.H. Rogers, and J.H. Shinn. 1992.
Field Techniques for Exposure of Plants and Ecosystems to Elevated
CO2 and Other Trace Gases. Critical Reviews in Plant Sciences
11:85-119.

KEYWORDS: EXPOSURE METHODS, REVIEW, SCALING

27   
Allen, L.H., Jr., R.R. Valle, J.W. Mishoe, J.W. Jones, and P.H.
Jones. 1990. Soybean Leaf Gas Exchange Responses to CO2 Enrichment.
Soil and Crop Science Society of Florida, Proceedings 49:192-198.

Carbon dioxide concentration of the atmosphere is expected to
double within the next century. This study was undertaken to
determine the leaf gas exchange responses of soybean (Glycine Max
(L.) Merr. cv. Bragg) grown continuously at 330, 450, 600, and 800
L (CO2)/million L (air), or volume parts per million volumes (vpm),
in sunlit, controlled-environment chambers. The chambers were
secured to soil bins filled with a reconstructed profile of
Arredondo fine sand (a loamy siliceous hyperthermic Grossarenic
Paleudult). A gas exchange system was used to measure leaf and air
temperatures, flow rates, cuvette input and exit CO2 concentrations
and vapor pressures, and incident solar photosynthetically active
radiation (PAR). These measurements were used to calculate the
carbon dioxide exchange rate (CER), transpiration rate (TRATE),
stomatal resistance (rs), and leaf internal airspace
(intercellular) CO2 concentration (Ci) of fully expanded, sunlit
leaves held in a flat, horizontal position. Results indicated that
leaf CER increased linearly over the CO2 concentration range of 330
to 800 vpm. Differences in leaf transpiration rates between the 800
and 330 vpm CO2 treatment were small. Water-use efficiency,
CER/TRATE, increased as CO2 level increased, mainly due to an
increase in CER. Both leaf stomatal resistance and leaf temperature
increased with increasing CO2 concentrations at fixed PAR. The
ratio of Ci to external CO2 concentration (Ce) was approximately
constant across the range of [CO2] treatments. These findings
showed no tendency for CO2-saturation of soybean leaf CER (and
hence no evidence of CO2-induced feedback inhibition of
photosynthetic rate) over the CO2 concentration range of 330 to 800
vpm.

soybean/Glycine max

KEYWORDS: CI:CA, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC FEEDBACK
INHIBITION, SPAR UNITS, TRANSPIRATION, WUE

28   
Allen, L.H., Jr., J.C.V. Vu, R.R. Valle, K.J. Boote, and P.H.
Jones. 1988. Nonstructural Carbohydrates and Nitrogen of Soybean
Grown under Carbon Dioxide Enrichment. Crop Science 28:84-94.

Carbon dioxide (CO2) concentration has been rising in the
atmosphere for over a century. This study was conducted to
determine the effects of anticipated future levels of CO2 on
nonstructural carbohydrates and N of soybean [Glycine max (L.)
Merr. cv. Bragg]. Plants were grown at Gainesville, FL from seed to
maturity in six sunlit, controlled-environment chambers that
maintained CO2 at 330, 330, 450, 600, 800, and 800 umol (CO2)/mol
(air). Attached lysimeters contained Arredondo fine sand (loamy,
siliceous, hyperthermic Grossarenic Paleudult). Leaflet blades were
sampled five times per day at 48 and 69 d after planting (DAP). At
48 DAP, average daytime starch conc. of leaflets increased with
increasing CO2 from 85 g/kg of dry wt at 330 umol/mol to 205 g/kg
at 800 umol/mol. On each date, the daytime rate of starch
accumulation combined over all CO2 treatments was 6 g/kg. Specific
leaf weight increased significantly throughout the day both at 48
(0.64 g/m2/h) and 69 DAP (0.29 g/m2/h). Total Kjeldahl N (TKN)
conc., expressed on a g/m2 basis, showed no change over the day.
Total final dry wt increased 18, 34, and 54% at 450, 600 and 800
umol/mol, respectively. The TKN harvested per plant increased 25,
26 and 45% in the 450, 600 and 800 umol/mol CO2 treatments,
respectively. Plants in the 450 umol/mol CO2 treatment partitioned
more biomass to seed than the other CO2 treatments. With that
exception, we saw no great differences among treatment partitioning
at final harvest, and thus interpret the main effect of CO2
enrichment to be enhanced photoassimilation by soybean canopies
while maintaining consistent allometric relationships of the
plants.

soybean/Glycine max

KEYWORDS: ALLOCATION, CARBOHYDRATES, NITROGEN, SPAR UNITS, SPECIFIC
LEAF WEIGHT

29   
Allen, S.G., S.B. Idso, and B.A. Kimball. 1990. Interactive Effects
of CO2 and Environment on Net Photosynthesis of Water-Lily.
Agriculture, Ecosystems and Environment 30:81-88.

Water-lily (Nymphaea marliac) plants were grown out of doors in
570-L stock tanks contained in plastic-walled, open-topped CO2-enrichment chambers continuously supplied with either 640 or 340
(ambient) uL CO2/L air. Net photosynthesis (Pn) of water-lily
leaves in each CO2 treatment was measured hourly between 0800 and
1600 h MST on 26 October and 10 and 24 November 1987. Air
temperature and net solar radiation were measured at the same time.
The 3 days on which Pn was measured provided an air temperature
range of 10.3-33.2C and a net solar radiation range of 30-659
W/m2. Significant linear relationships were established between Pn
and air temperature and Pn and net solar radiation for both CO2
treatments. Significant interactive effects of CO2 and air
temperature and CO2 and net solar radiation were also found to
affect Pn. In conditions generally unfavorable for Pn (low light
and low temperature), there was no difference in Pn rate between
the two CO2 treatments. In conditions that were favorable for Pn
(high light and high temperature), however, Pn in the 640 uL CO2/L
air treatment was as much as 60% greater than in the ambient CO2
treatment.

Nymphaea marliac/water lily

KEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, LIGHT, OPEN-TOP
CHAMBERS, TEMPERATURE

30   
Allen, S.G., S.B. Idso, B.A. Kimball, and M.G. Anderson. 1988.
Relationship between Growth Rate and Net Photosynthesis of Azolla
in Ambient and Elevated CO2 Concentrations. Agriculture, Ecosystems
and Environment 20:137-141.

Azolla pinnata was grown out-of-doors at Phoenix, AZ, U.S.A. in
open-topped plastic-walled chambers supplied with either 340 or 640
uL CO2/L air. Net photosynthesis and growth rate were measured
weekly between September 1985 and May 1986 and a significant
(P<0.01) positive correlation was established between these two
parameters in both CO2 environments. Regression coefficients for
the linear regression of growth rate onto net photosynthesis were
not significantly different in the two CO2 environments, indicating
that the rate of growth per unit of CO2 uptake is not influenced by
an atmospheric CO2 concentration-environment interaction.

Azolla pinnata

KEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, GROWTH RATE, OPEN-TOP CHAMBERS

31   
Allen, S.G., S.B. Idso, B.A. Kimball, J.T. Baker, L.H. Allen Jr.,
J.R. Mauney, J.W. Radin, and M.G. Anderson. 1990. Effects of Air
Temperature on Atmospheric CO2-Plant Growth Relationships, TR048 in
Yellow Report Series, DOE/ER-0450T, Dept. of Energy, Carbon Dioxide
Research Program. NTIS, U.S. Dept. of Commerce, Springfield,
Virginia.

KEYWORDS: CARBOHYDRATES, CONDUCTANCE, PHENOLOGY, PHOTOSYNTHESIS,
REVIEW, TEMPERATURE, YIELD

32   
Alpert, P., F.R. Warembourg, and J. Roy. 1992. Transport of Carbon
among Connected Ramets of Eichhornia crassipes (Pontederiaceae) at
Normal and High Levels of CO2. American Journal of Botany 78:1459-1466.

The floating stoloniferous plant, Eichhornia crassipes, has high
rates of productivity and rapidly invades new sites. Because the
transport of carbon among connected ramets in known to increase the
growth of clonal plants, we asked whether there is intraclonal
carbon transport in E. Crassipes. Because net photosynthesis of E.
Crassipes is significantly higher at high levels of atmospheric
CO2, we also asked if high CO2 can change patterns of carbon
transport in ways that might modify clonal growth. We exposed
individual ramets within groups of connected ramets to 14-CO2 for
15-45 min and measured the distribution of 14-C in the group after
4 days of growth at 350, 700, 1,400, or 2,800 uL/L CO2. At 350 uL/L
CO2, a parent ramet exported approximately 10% of the 14-C that it
assimilated to its first rooted offspring ramet. The offspring
exported a similar percentage of the 14-C it assimilated toward the
parent; two-thirds of this 14-C was retained by the parent, and
one-third moved into new offspring of the parent. In all ramets,
imported carbon moved into leaves as well as roots. At the higher
levels of CO2, the percentage of assimilated carbon exported from
a parent ramet to the leaf blades of its first offspring was lower
by half. High CO2 had little other effect on carbon transport. E.
crassipes maintains bidirectional transport of carbon between
ramets even under uniform and favorable environmental conditions
and when external CO2 levels are very high.

Eichhornia crassipes/water hyacinth

KEYWORDS: 14C, AQUATIC PLANTS, ASSIMILATE EXPORT, CARBON BUDGET,
GREENHOUSE, HYDROPONIC CULTURE, VEGETATIVE REPRODUCTION

33   
Alscher, G., and H. Krug. 1989. On-line Control of CO2 Enrichment
in Protected Cultivation. Acta Horticulturae 248:321-327.

As a base for experiments on CO2 on-line control the CO2 fluxes in
greenhouses are simulated and potential control strategies
presented. Some approaches are tested, others outlined for
discussion. Preliminary experiments with lettuce were performed
with CO2 supply depending on wind velocity and irradiance.
Additionally, intermittent CO2 application was tested. Results
indicate that the efficiency of CO2 enrichment varies relying on
season and year. If planted in October cutting off CO2 supply led
to extended growth periods with increased energy demands. If
planted in January no significant differences in growing periods
occurred between constant CO2 treatments, intermittent CO2 supply
and cutting off due to wind velocity and irradiance, except
differences to the control. Simulations for optimizing CO2 on-line
control are in progress.

lettuce/Lactuca sativa

KEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2,
GREENHOUSE, INTERMITTENT ENRICHMENT, SIMULATION

34   
Amthor, J.S. 1991. Respiration in a Future, Higher-CO2 World.
Plant, Cell and Environment 14:13-20.

Apart from its impact on global warming, the annually increasing
atmospheric [CO2] is of interest to plant scientists primarily
because of its direct influence on photosynthesis and
photorespiration in C3 species. But in addition, 'dark'
respiration, another major component of the carbon budget of higher
plants, may be affected by a change in [CO2] independent of an
increase in temperature. Literature pertaining to an impact of
[CO2] on respiration rate is reviewed. With an increase in [CO2],
respiration rate is increased in some cases, but decreased in
others. The effects of [CO2] on respiration rate may be direct or
indirect. Mechanisms responsible for various observations are
proposed. These proposed mechanisms relate to changes in: (1)
levels of nonstructural carbohydrates, (2) growth rate and
structural phytomass accumulation, (3) composition of phytomass,
(4) direct chemical interactions between CO2 and respiratory
enzymes, (5) direct chemical interactions between CO2 and other
cellular components, (6) dark CO2 fixation rate, and (7) ethylene
biosynthesis rate. Because a range of (possibly interactive)
effects exists, and present knowledge is limited, the impact of
future [CO2] on respiration rate cannot be predicted. Theoretical
considerations and types of experiments that can lead to an
increase in the understanding of this issue are outlined.

KEYWORDS: CARBON BUDGET, RESPIRATION, REVIEW

35   
Amthor, J.S., G.W. Koch, and A.J. Bloom. 1992. CO2 Inhibits
Respiration in Leaves of Rumex crispus L. Plant Physiology 98:757-760.

Curly dock (Rumex crispus L.) was grown from seed in a glasshouse
at an ambient CO2 partial pressure of about 35 pascals. Apparent
respiration rate (CO2 efflux in the dark) of expanded leaves was
then measured at ambient CO2 partial pressure of 5 to 95 pascals.
Calculated intercellular CO2 partial pressure was proportional to
ambient CO2 partial pressure in these short term experiments. The
CO2 level strongly affected apparent respiration rate: a doubling
of the partial pressure of CO2 typically inhibited respiration by
25 to 30%, whereas a decrease in CO2 elicited a corresponding
increase in respiration. These responses were readily reversible.
A flexible, sensitive regulatory interaction between CO2 (a
byproduct of respiration) and some component(s) of heterotrophic
metabolism is indicated.

Rumex crispus/curly dock

KEYWORDS: CI:CA, GREENHOUSE, RESPIRATION

36   
Anderson, I.H., C. Dons, S. Nilsen, and M.K. Haugstad. 1985.
Growth, Photosynthesis and Photorespiration of Lemna gibba:
Response to Variations in CO2 and O2 Concentrations and Photon Flux
Density. Photosynthesis Research 6:87-96.

Dry weight and Relative Growth Rate of Lemna gibba were
significantly increased by CO2 enrichment up to 6000 uL CO2/L. This
high CO2 optimum for growth is probably due to the presence of
nonfunctional stomata. The response to high CO2 was less or absent
following four days growth in 2% O2. The Leaf Area Ratio decreased
in response to CO2 enrichment as a result of an increase in dry
weight per frond. Photosynthetic rate was increased by CO2
enrichment up to 1500 uL CO2/L during measurement, showing only
small increases with further CO2 enrichment up to 5000 uL CO2/L at
a photon flux density of 210 umol/m2/s and small decreases at 2000
umol/m/s. The actual rate of photosynthesis of those plants
cultivated at high CO2 levels, however, was less than the air grown
plants. The response of photosynthesis to O2 indicated that the
enhancement of growth and photosynthesis by CO2 enrichment was a
result of decreased photorespiration. Plants cultivated in low O2
produced abnormal morphological features and after a short time
showed a reduction in growth.

Lemna gibba/duckweed

KEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH, LIGHT, OXYGEN, RESPIRATION

37   
Andersson, N.E. 1991. The Influence of Constant and Diurnally
Changing CO2 Concentrations on Plant Growth and Development.
Journal of Horticultural Science 66:569-574.

Plants of Ficus benjamina and miniature rose (Rosa hybrida cv. Red
Minimo) were grown under four CO2 treatments. Two had constant CO2
levels (600 and 900 ppm) and the other two had diurnal changes in
CO2 levels, one increasing from 600 to 1500 ppm and one decreasing
from 1500 to 600 ppm, each in four steps of 300 ppm during the day-time. In all treatments 900 ppm CO2 was maintained during the night
when supplementary light was used, except in the treatment with
constant 600 ppm where 600 ppm was also continued throughout the
night. Plant growth was monitored under both decreasing and
increasing natural daylength and irradiance. The tallest plants and
greatest increment in height for Ficus occurred with plants grown
under constant CO2 concentration at 900 ppm. In both experiments
with miniature roses the number of flower buds was significantly
increased under diurnally changing CO2 concentration or when the
CO2 level was constant at 600 ppm compared with a constant 900 ppm.
Time to flowering was decreased by constant CO2 at 900 as compared
with the other treatments.

Ficus benjamina/Rosa hybrida

KEYWORDS: COMMERCIAL USE OF CO2, DIURNAL CYCLE, FLOWER PRODUCTION,
FLOWERING, GREENHOUSE, HORTICULTURAL CROPS

38   
Andre, M., F. Cotte, A. Gerbaud, D. Massimino, J. Massimino, and C.
Richaud. 1989. Effect of CO2 and O2 on Development and
Fructification of Wheat in Closed Systems. Advances in Space
Research 9:(8)17-(8)28.

The cultivation of wheat (Triticum aestivum L.) was performed in
controlled environment chambers with the continuous monitoring of
photosynthesis, dark respiration, transpiration and main nutrient
uptakes. A protocol in twin chambers was developed to compare the
specific effects of low O2 and high CO2. Each parameter is able to
influence photosynthesis but different effects are obtained in the
development, fructification and seed production, because of the
different effects of each parameter on the ratio of reductive to
oxidative cycle of carbon. The first main conclusion is that low
level of O2, at the same rate of biomass production, strongly acts
on the rate of ear appearance and on seed production. Ear
appearance was delayed and seed production reduced with a low O2
treatment (about 4%). The O2 effect was not mainly due to the
repression of the oxidative cycle. The high CO2 treatment (700 to
900 uL/L) delayed ear appearance by 4 days, but did not reduce seed
production. High CO2 treatment also reduced transpiration by 20%.
Two hypotheses were proposed to explain the similarities and the
difference in the O2 and CO2 effects on the growth of wheat.

Triticum aestivum/wheat

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
OXYGEN, RESPIRATION, SEED PRODUCTION

39   
Andre, M., and H. Du Cloux. 1993. Interaction of CO2 Enrichment and
Water Limitations on Photosynthesis and Water-Use Efficiency in
Wheat. Plant Physiology and Biochemistry 31:103-112.

Wheat plants (Triticum aestivum L. cv. Capitole) were grown in twin
closed growth chambers with continuous monitoring of CO2 and water
exchanges. During the vegetative stage the effect of CO2
enrichment, from 330 to 660 uL/L, was studied under an irradiance
of 660 uE/m2/s with an optimum watering. Comparisons were made with
successive experiments in which daily water supply was fixed to a
fraction (0.62-0.5-0.25) of the maximal transpiration of previous
experiments. In a well watered canopy, the doubling of CO2
decreased transpiration by only 8%. Water use efficiency was
increased (factor 1.45) mainly by the stimulation of
photosynthesis. Under restricted water supply, photosynthesis of
plants was more limited than transpiration. The inhibition of
photosynthesis and the increase of water use efficiency can be
predicted by a simple diffusion model applied to the response curve
of photosynthesis to CO2, measured on canopy in standard conditions
of watering. The main hypothesis is that the equivalent stomatal
conductance is reduced proportionally to the water availability,
without closure by patching. Under enriched CO2, the same reduction
of leaf surface by water limitation was observed. Photosynthesis
was less affected. Therefore, water use efficiency was again
increased. Doubling CO2 concentration can compensate for water
stress inhibition on CO2 assimilation. That model also predicts
interactions of CO2 and water stress observed on water-use-efficiency which was increased by a factor up to 5 in comparison
with well-watered plants in standard atmosphere. The implications
of this study on global change models are discussed.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, CONTROLLED
ENVIRONMENT CHAMBERS, GRASSES, PHOTOSYNTHESIS MODEL, TRANSPIRATION,
WATER STRESS, WUE

40   
Andre, M., H. Du Cloux, and C. Richaud. 1986. Wheat Response to CO2
Enrichment: CO2 Exchanges, Transpiration and Mineral Uptakes. IN:
Controlled Ecological Life Support System: CELLS '85 Workshop, 1985
July 16-19, NASA Report TM88215 (R. MacElroy, N.V. Martello, and D.
Smernoff, eds.), AMES Research Center, Moffett Field, California,
pp. 405-428.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH ANALYSIS, NITROGEN, NUTRITION, PHOSPHORUS, PLANT DENSITY,
POTASSIUM, TRANSPIRATION, WATER STRESS, WUE

41   
Andre, M., H. Ducloux, C. Richaud, D. Massimino, A. Daguenet, J.
Massimino, and A. Gerbaud. 1987. Etude des Relations entre
Photosynthese Respiration, Transpiration et Nutrition Minerale chez
le Ble. Advances in Space Research 7:(4)105-(4)114.

La croissance du Ble Triticum aestivum a ete etudiee en
environnement controle et ferme pendant une periode de 70 jours.
Les echanges gazeux (Photosynthese, Respiration) hydriques
(Transpiration) et al consommation en elements mineraux (Azote,
Phosphore, Potassium) ont ete mesures en continu. On prsentera les
relations dynamiques observees entre les differentes fonctions
physiologiques, d'une part sous l'influence de la croissance et
d'autre part en reponse a des modifications de l'environnement.
L'influence de la teneur en CO2 pendant la croissance (teneur
normale ou doublee) sera mise en evidence. In French.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM, RESPIRATION,
TRANSPIRATION

42   
Andreeva, T.F., L.E. Strogonova, S.Y. Voevudskaya, S.N. Maevskaya,
and N.N. Cherkanova. 1989. Effect of Enhanced CO2 Concentration on
Photosynthesis, Carbohydrate and Nitrogen Metabolism, and Growth
Processes in Mustard Plants. Fiziologiya Rastenii 36:40-48.

We investigated prolonged (8- to 10-day) influence of enhanced
carbon dioxide content (0.03-0.05%) in the air on photosynthesis of
mustard plants (Brassica juncea L.), on their carbohydrate and
nitrogen metabolism, and on the course of growth processes.
Considerable attention is devoted to the question of the effect of
leaf starch excess on the rate of photosynthesis. It is
demonstrated that mustard plants in the vegetative phase of growth
under conditions of enhanced CO2 concentration in the air exhibit
higher pure productivity of photosynthesis and a higher rate of
photosynthesis than in plants growing at normal CO2 content in the
atmosphere. Increase of apparent photosynthesis is realized without
supplementary synthesis of fraction I protein. Increase in the rate
of photosynthesis is accompanied by intensification of nitrogen
metabolism, increase of growth, and accumulation of biomass. An
excess of assimilates in the form of starch accumulates in the
chloroplasts (25% of leaf dry mass at 27/24). Starch content
increases significantly in plants grown under conditions of reduced
temperature compared with ones grown at a higher temperature (34.4%
of leaf dry mass at 20/17 as compared with 20.1% at 32/27). It
is concluded that high starch content in the leaves is not a cause
of photosynthesis suppression. Decline of photosynthesis is
observed only when the starch excess disturbs structure of the
chloroplasts.

mustard/Brassica juncea

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, FRACTION
1 PROTEIN, NITROGEN, PHOTOSYNTHESIS, TEMPERATURE

43   
Apel, P. 1989. Influence of CO2 on Stomatal Numbers. Biologia
Plantarum (Praha) 3:72-74.

From nine different plant species grown at 1500 cm3/m3 CO2 five
responded with a significant increase in stomatal numbers per mm2
as compared with plants grown under normal air conditions. Within
a collection of twelve french bean cultivars remarkable cultivar
differences with regard to the CO2 enhancement effect on stomatal
numbers was found.

Phaseolus vulgaris/Vicia faba/Lycopersicon esculentum/Acer
pseudoplatanus/Triticum aestivum/Hordeum vulgare/Secale
cereale/Avena sativa/Zea mays/bean/broad bean/tomato/sycamore
maple/wheat/barley/rye/oat/corn

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES,
STOMATAL DENSITY

44   
Arnone, J.A., III. 1988. Photosynthesis, Carbon Allocation, and
Nitrogen Fixation in Red Alder. Doctoral Dissertation, Yale
University, Dissertation Abstracts Vol.50:08-B, p.3244 (96 pp.).

Research reported in the three sections of this dissertation
addresses the problem of the effect of potentially high carbon
costs of nitrogen fixation by alder-Frankia symbioses on host plant
biomass productivity. Effects of root nodulation and nitrogen
fixation on plant biomass productivity and allocation patterns were
evaluated by growing inoculated and uninoculated red alder
seedlings in atmospheres containing ambient (350 uL/L) and elevated
(650 uL/L) levels of CO2, with and without combined nitrogen (20
mg/L NH4NO3) supplied in modified N-free Hoagland's nutrient
solution. Effect of nodulation, CO2 enrichment, substrate nitrogen,
and the feedback interaction on early seedling development and
aboveground and belowground growth were also tested using the same
plant material. Root:shoot ratios for plants in all treatments
decreased over the course of the experiment. This occurred more
rapidly in nodulated plants and was attributed to more rapid
attainment of balanced root:shoot growth. This and evidence
supporting the hypothesis that whole plant internal carbon/nitrogen
balance regulated aboveground and belowground growth is presented
and discussed.

Alnus rubra/red alder

KEYWORDS: ALLOCATION, CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT
CHAMBERS, NITROGEN, NITROGEN FIXATION, TREES

45   
Arnone, J.A., III, and J.C. Gordon. 1990. Effect of Nodulation,
Nitrogen Fixation and CO2 Enrichment on the Physiology, Growth and
Dry Mass Allocation of Seedlings of Alnus rubra Bong. New
Phytologist 116:55-66.

Inoculated and uninoculated Alnus rubra Bong. seedlings were grown
for 47 days in atmospheres containing ambient (350 uL CO2/L) and
elevated (650 uL CO2/L) levels of CO2, with and without combined
nitrogen (20 mg/L) supplied as ammonium nitrate. Five plants from
each treatment were harvested 15, 30, and 47 days after exposure to
CO2 treatments began. Evidence for the presence of a positive
feedback loop between nitrogen fixation and photosynthesis was
observed in nodulated plants growing at elevated CO2. These plants
had greater whole-plant photosynthesis and nitrogenase activity,
leaf area and nitrogen content, as well as nodule and plant dry
mass, relative to nodulated plants grown at ambient CO2 and non-nodulated plants grown at both CO2 levels. This feedback may be an
important way in which the potential carbon drain of nitrogen
fixation on the host plant could be compensated; increased nitrogen
availability resulting in stimulated leaf area growth and whole-plant photosynthesis. The relative amount of dry mass allocated to
below ground decreased for all seedlings over time, and the amount
allocated above ground increased. This shift in allocation occurred
slowly and at a constant rate in non-nodulated plants and more
rapidly and abruptly when plants were nodulated. The proportion of
dry mass allocated below ground was consistently greater in non-nodulated plants grown at high CO2. Dry mass partitioning among
other organs was not directly affected by nodulation, CO2
enrichment, or other treatment interactions.

Alnus rubra

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN
FIXATION, NODULATION, TREES

46   
Arp, W.J. 1991. Effects of Source-Sink Relations on Photosynthetic
Acclimation to Elevated CO2. Plant, Cell and Environment 14:869-875.

While photosynthesis of C3 plants is stimulated by an increase in
the atmospheric CO2 concentration, photosynthetic capacity is often
reduced after long-term exposure to elevated CO2. This reduction
appears to be brought about by end product inhibition, resulting
from an imbalance in the supply and demand of carbohydrates. A
review of the literature revealed that the reduction of
photosynthetic capacity in elevated CO2 was most pronounced when
the increased supply of carbohydrates was combined with small sink
size. The volume of pots in which plants were grown affected the
sink size by restricting root growth. While plants grown in small
pots had a reduced photosynthetic capacity, plants grown in the
field showed no reduction or an increase in this capacity. Pot
volume also determined the effect of elevated CO2 on the root:shoot
ratio--the root:shoot ratio increased when root growth was not
restricted and decreased in plants grown in small pots. The data
presented in this paper suggest that plants growing in the field
will maintain a high photosynthetic capacity as the atmospheric CO2
level continues to rise.

KEYWORDS: PHOTOSYNTHETIC ACCLIMATION, POT VOLUME, REVIEW,
ROOT:SHOOT RATIO, SOURCE-SINK BALANCE

47   
Arp, W.J. 1991. Vegetation of a North American Salt Marsh and
Elevated Atmospheric Carbon Dioxide. Doctoral Dissertation,
Centrale Huisdrukkerij Vrije Universiteit, Amsterdam.

Distichlis spicata/Spartina patens/Scirpus olneyi

KEYWORDS: C3, C4, EVAPOTRANSPIRATION, GROWTH, HALOPHYTES, LEAF
PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, SALT
MARSH, SOURCE-SINK BALANCE, SPECIES COMPETITION, WATER STATUS

48   
Arp, W.J., and B.G. Drake. 1991. Increased Photosynthetic Capacity
of Scirpus olneyi after 4 Years of Exposure to Elevated CO2. Plant,
Cell and Environment 14:1003-1006.

While a short-term exposure to elevated atmospheric CO2 induces a
large increase in photosynthesis in many plants, long-term growth
in elevated CO2 often results in a smaller increase due to reduced
photosynthetic capacity. In this study, it was shown that, for a
wild C3 species growing in its natural environment and exposed to
elevated CO2 for four growing seasons, the photosynthetic capacity
has actually increased by 31%. An increase in photosynthetic
capacity has been observed in other species growing in the field,
which suggests that photosynthesis of certain field grown plants
will continue to respond to elevated levels of atmospheric CO2.

sedge/Scirpus olneyi

KEYWORDS: LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC
ACCLIMATION

49   
Arp, W.J., B.G. Drake, W.T. Pockman, P.S. Curtis, and D.F. Whigham.
1993. Interactions between C3 and C4 Salt Marsh Plant Species
during Four Years of Exposure to Elevated Atmospheric CO2.
Vegetatio 104/105:133-143.

Elevated atmospheric CO2 is known to stimulate photosynthesis and
growth of plants with the C3 pathway but less of plants with the C4
pathway. An increase in the CO2 concentration can therefore be
expected to change the competitive interactions between C3 and C4
species. The effect of long term exposure to elevated CO2 (ambient
CO2 concentration + 340 umol CO2/mol) on a salt marsh vegetation
with both C3 and C4 species was investigated. Elevated CO2
increased the biomass of the C3 sedge Scirpus olneyi growing in a
pure stand, while the biomass of the C4 grass Spartina patens in a
monospecific community was not affected. In the mixed C3/C4
community the C3 sedge showed a very large relative increase in
biomass in elevated CO2 while the biomass of the C4 species
declined. The C4 grass Spartina patens dominated the higher areas
of the salt marsh, while the C3 sedge Scirpus olneyi was most
abundant at the lower elevations, and the mixed community occupied
intermediate elevations. Scirpus growth may have been restricted by
drought and salt stress at the higher elevations, while Spartina
growth at the lower elevations may be affected by the higher
frequency of flooding. Elevated CO2 may affect the species
distribution in the salt marsh if it allows Scirpus to grow at
higher elevations where it in turn may affect the growth of
Spartina.

Spartina patens/Scirpus olneyi/Distichlis spicata

KEYWORDS: AQUATIC PLANTS, C3, C4, COMMUNITY LEVEL CO2 RESPONSES,
GROWTH, HALOPHYTES, OPEN-TOP CHAMBERS, SALT MARSH, SALT STRESS,
SPECIES COMPETITION, WATER STRESS

50   
Artus, N.N. 1990. Two Mutants of Arabidopsis thaliana That Become
Chlorotic in Atmospheres Enriched with CO2. Plant, Cell and
Environment 13:575-580.

Two nonallelic, nuclear recessive mutants of Arabidopsis thaliana
(L.) Heynh. which become chlorotic when grown in an atmosphere
enriched to 20,000 cm3 CO2/m3 have been isolated. For one of the
mutants, chlorosis begins at the veins and gradually spreads to the
interveinal regions. A minimum photon flux density of ca 50
umol/m2/s is required for this response. For the other mutant, the
yellowing is independent of the light intensity and begins at the
basal regions of the leaves and spreads to the tips. The injurious
effects of CO2 seem to be restricted to photosynthetic tissues,
since root elongation and callus growth were not inhibited by a
high atmospheric CO2 concentration for either mutant. Neither
mutant became chlorotic in a low O2 atmosphere that suppressed
photorespiration as effectively as the elevated CO2 does. Thus, the
mutations do not impose a requirement for photorespiration. The
possibilities that the high CO2-sensitive phenotypes are caused by
an effect of CO2 in stomata, on ethylene synthesis, or on mineral
uptake are discussed but are considered unlikely.

Arabidopsis thaliana

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, MUTANT

51   
Ashenden, T.W., R. Baxter, and C.R. Rafarel. 1992. An Inexpensive
System for Exposing Plants in the Field to Elevated Concentrations
of CO2. Plant, Cell and Environment 15:365-372.

An inexpensive, potentially mobile field exposure system is
described which may be easily constructed by a small workshop. It
may be operated as an open-top with a frustum or covered with a
polycarbonate 'lid'. The system is cost-effective for CO2 exposure
work because the small size allows provision of CO2-enriched
atmospheres over prolonged periods at relatively low cost. A
preliminary assessment of the chambers has been made and
concentrations can be maintained at +/- 6% for a target atmosphere
of 680 cm3/m3 CO2 under normal operating conditions. Other chamber
environmental conditions are reported.

KEYWORDS: EXPOSURE METHODS, OUTDOOR GROWTH CHAMBERS

52   
Aston, A.R. 1984. The Effect of Doubling Atmospheric CO2 on
Streamflow: a Simulation. Journal of Hydrology 67:273-280.

There is a potential for atmospheric CO2 to rise four- or six-fold,
and at some time in the foreseeable future a doubling of stomatal
resistance seems, on present evidence, to be inevitable. A
distributed deterministic process model was used to simulate the
effects of changed stomatal resistance on streamflow of a 5-ha
experimental catchment and a large (417 km2) water-supply area. The
results indicated that we can expect streamflow to increase from 40
to 90% as a consequence of doubling of atmospheric CO2
concentration.

KEYWORDS: HYDROLOGIC MODEL, STREAMFLOW

53   
Austin, M.P. 1992. Modelling the Environmental Niche of Plants:
Implications for Plant Community Response to Elevated CO2 Levels.
Australian Journal of Botany 40:615-630.

No simple natural gradients in CO2 concentration exist for testing
predictions about changes in plant communities in response to
elevated CO2. However indirect effects of CO2 via temperature
increases can be tested by reference to natural analogues.
Physiologists, vegetation modellers of climate change and community
ecologists assume very different temperature responses for plants.
Physiologists often assume a skewed non-monotonic curve with a tail
towards low temperatures, forest modellers using FORET type models,
a symmetric curve, and community ecologists a skewed response with
a tail towards high temperatures. These assumptions are reviewed in
relation to niche theory, and recent propositions concerning the
continuum concept. Confusion exists between the different
approaches over the shape of response curves to temperature.
Distinctions need to be made between responses due to growth
(physiological response), potential fitness (fundamental niche) and
observed performance (realised niche). These types of response
should be quantified and related to each other if process-models
are to be tested for predictive success by reference to naturally
occurring communities and temperature gradients. An example of a
statistical method for quantifying the realised environmental niche
response of a species to temperature is provided. It is based on
generalised linear modelling (GLM) of presence/absence data on
Eucalyptus fastigata for 8377 sites in southern New South Wales,
Australia. Seven environmental variables or factors are considered:
mean annual temperature, mean annual rainfall, mean monthly solar
radiation, topographic position, rainfall seasonality, lithology,
and soil; nutrient status. The temperature response is modelled by
a Beta-function, log y + a + alpha log (t - a) + sigma log (b - t),
where t is temperature and letters are parameters. The probability
of occurrence is shown to be a skewed function of mean annual
temperature. Any process-models of climate change for vegetation
incorporating temperature changes due to elevated CO2 must be
capable of generating such realised environmental niche responses
for species.

Eucalyptus fastigata

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL
INTERACTIONS, FOREST, MODELING, NICHE THEORY, SPECIES RANGE

54   
Badger, M. 1992. Manipulating Agricultural Plants for a Future High
CO2 Environment. Australian Journal of Botany 40:421-429.

This paper discusses the potential ways in which C3 plant
performance may benefit from a future high-CO2 environment. These
include increases in the efficiencies for light, nitrogen and water
utilisation, particularly at elevated temperatures, resulting from
the improvement which will occur in the performance of the primary
carboxylating enzyme, Rubisco. However, while growth experiments at
elevated CO2 indicate that C3 plants show stimulation of dry matter
accumulation, the potential gains are greatly ameliorated by a
redistribution of plant resources. This primarily occurs via a
reduction in the leaf area ratio which offsets increases in the net
assimilation rate. In addition, there may be an overcommitment of
nitrogen in key photosynthetic components such as Rubisco and the
thylakoid electron transport system. It is concluded that plants
may not be genetically adapted to optimise their growth and
performance at elevated CO2 and that consideration should be given
to exploring avenues for manipulating plants for more optimal
responses. Targets for improvement of growth at elevated CO2
include (1) altering source-sink relations; (2) improving the
redistribution of nitrogen between the photosynthetic machinery and
the rest of the plant; and (3) changing the response of stomata to
CO2 and humidity to increase water-use efficiency even further than
is currently predicted.

KEYWORDS: AGRICULTURE, C3, C4, ENVIRONMENTAL INTERACTIONS, GROWTH
ANALYSIS, LIGHT, NITROGEN, PHENOLOGY, REVIEW, RIBULOSE BISPHOSPHATE
CARBOXYLASE, SOURCE-SINK BALANCE, TEMPERATURE, WUE

55   
Baille, A. 1989. Greenhouse Microclimate and Its Management in Mild
Winter Climates. Acta Horticulturae 246:23-36.

KEYWORDS: GREENHOUSE

56   
Bailly, J., and J.R. Coleman. 1988. Effect of CO2 Concentration on
Protein Biosynthesis and Carbonic Anhydrase Expression in
Chlamydomonas reinhardtii. Plant Physiology 87:833-840.

The effect of external inorganic carbon (Ci) concentrations on
protein biosynthesis and carbonic anhydrase (CA) mRNA abundance
were examined in the eukaryotic alga Chlamydomonas reinhardtii.
Transfer of high CO2 (5%) grown algae to air levels of CO2 resulted
in the transitory synthesis of two polypeptides of approximately
49,000 and 52,000 daltons as well as prolonged synthesis and
accumulation of the 37,000 dalton CA monomer and an unidentified
20,000 dalton polypeptide. The gene coding for carbonic anhydrase
was isolated from a genomic expression library and subjected to
restriction endonuclease analysis. Southern blot analysis of
chromosomal DNA indicates that only a single copy of the gene is
present. The 2.5 kilobase DNA fragment hybridizes specifically to
a 1.4 kilobase transcript in RNA isolated from air-grown cells and
from cells grown on 5% CO2 that have been exposed to air levels of
CO2. Maximum mRNA abundance was observed after 1 to 3 hours of
exposure to air. Transfer of air-grown cells to a high CO2
environment resulted in the elimination of the CA transcript after
60 minutes of exposure. Changes in CA transcript abundance in
response to external Ci concentrations occurred in the presence or
absence of light.

Chlamydomonas reinhardtii

KEYWORDS: ALGAE, AQUATIC PLANTS, CARBONIC ANHYDRASE, CELL CULTURE,
ENZYMES, GENE EXPRESSION

57   
Baker, J.T., and L.H. Allen Jr. 1993. Contrasting Crop Species
Responses to CO2 and Temperature: Rice, Soybean and Citrus.
Vegetatio 104/105:239-260.

The continuing increase in atmospheric carbon dioxide concentration
([CO2]) and projections of possible future increases in global air
temperatures have stimulated interest in the effects of these
climate variables on plants and, in particular, on agriculturally
important food crops. Mounting evidence from many different
experiments suggests that the magnitude and even direction of crop
responses to [CO2] and temperature is almost certain to be species
dependent and very likely, within a species, to be cultivar
dependent. Over the last decade, [CO2] and temperature experiments
have been conducted on several crop species in the outdoor,
naturally-sunlit, environmentally controlled, plant growth chambers
by USDA-ARS and the University of Florida, at Gainesville, Florida,
USA. The objectives for this paper are to summarize some of the
major findings of these experiments and further to compare and
contrast species responses to [CO2] and temperature for three
diverse crop species: rice (Oryza sativa, L.), soybean (Glycine
max, L.) and citrus (various species). Citrus had the lowest growth
and photosynthetic rates but under [CO2] enrichment displayed the
greatest percentage increases over ambient [CO2] control
treatments. In all three species the direct effect of [CO2]
enrichment was always an increase in photosynthetic rate. In
soybean, photosynthetic rate depended on current [CO2] regardless
of the long-term [CO2] history of the crop. In rice, photosynthetic
rate measured at a common [CO2], decreased with increasing long-term [CO2] growth treatment due to a corresponding decline in RuBP
carboxylase content and activity. Rice specific respiration
decrease from subambient to ambient and superambient [CO2] due to
a decrease in plant tissue nitrogen content and a decline in
specific maintenance respiration rate. In all three species, crop
water use decreased with [CO2] enrichment but increased with
increases in temperature. For both rice and soybean, [CO2]
enrichment increased growth and grain yield. Rice grain yields
declined by roughly 10% per each 1C rise in day/night temperature
above 28/21C.

rice/Oryza sativa/soybean/Glycine max/citrus/Citrus
sinensis/Poncirus trifoliata

KEYWORDS: ENVIRONMENTAL INTERACTIONS, EVAPOTRANSPIRATION, NITROGEN,
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, PRE-INDUSTRIAL CO2
CONCENTRATION, RESPIRATION, REVIEW, RIBULOSE BISPHOSPHATE
CARBOXYLASE, TEMPERATURE, WUE, YIELD

58   
Baker, J.T., L.H. Allen Jr., and K.J. Boote. 1990. Growth and Yield
Responses of Rice to Carbon Dioxide Concentration. Journal of
Agricultural Science, Cambridge 115:313-320.

Rice plants (Oryza sativa L., cv. IR30) were grown in paddy culture
in outdoor, naturally sunlit, controlled-environment, plant growth
chambers at Gainesville, Florida, USA, in 1987. The rice plants
were exposed throughout the season to subambient (160 and 250),
ambient (330) or superambient (500, 660, 900 umol CO2/mol air) CO2
concentrations. Total shoot biomass, root biomass, tillering, and
final grain yield increased with increasing CO2 concentration, the
greatest increase occurring between the 160 and 500 umol CO2/mol
air treatments. Early in the growing season, root:shoot biomass
ratio increased with increasing CO2 concentration; although the
ratio decreased during the growing season, net assimilation rate
increased with increasing CO2 concentration and decreased during
the growing season. Differences in biomass and lamina area among
CO2 treatments were largely due to corresponding differences in
tillering response. The number of panicles/plant was almost
entirely responsible for differences in final grain yield among CO2
treatments. Doubling the CO2 concentration from 330 to 660 umol
CO2/mol air resulted in a 32% increase in grain yield. These
results suggest that important changes in the growth and yield of
rice may be expected in the future as the CO2 concentration of the
earth's atmosphere continues to rise.

rice/Oryza sativa

KEYWORDS: ALLOCATION, GROWTH ANALYSIS, PRE-INDUSTRIAL CO2
CONCENTRATION, SPAR UNITS

59   
Baker, J.T., L.H. Allen Jr., and K.J. Boote. 1992. Response of Rice
to Carbon Dioxide and Temperature. Agricultural and Forest
Meteorology 60:153-166.

The current increase in atmospheric carbon dioxide concentration
([CO2]) along with predictions of possible future increases in
global air temperatures have stimulated interest in the effects of
[CO2] and temperature on the growth and yield of food crops. This
study was conducted to determine the effects and possible
interactions of [CO2] and temperature on the growth and yield of
rice (Oryza sativa L., cultivar IR-30). Rice plants were grown for
a season in outdoor, naturally sunlit, controlled-environment, and
plant growth chambers. Temperature treatments of 28/21/25,
34/27/31, and 40/33/37C (daytime dry bulb air temperature/night-time dry bulb air temperature/paddy water temperature) were
maintained in [CO2] treatments of 330 and 660 umol CO2/mol air. In
the 40/33/37C temperature treatment, plants in the 330 umol/mol
[CO2] treatment died during stem extension while the [CO2] enriched
plants survived but produced sterile panicles. Plants in the
34/27/31C temperature treatments accumulated biomass and leaf area
at a faster rate early in the growing season than plants in the
28/21/25C temperature treatments. Tillering increased with
increasing temperature treatment. Grain yield increases owing to
[CO2] enrichment were small and non-significant. This lack of [CO2]
response on grain yield was attributed to the generally lower
levels of solar irradiance encountered during the late fall and
winter when this experiment was conducted. Grain yields were
affected much more strongly by temperature than [CO2] treatment.
Grain yields declined by an average of approximately 7-8% per 1C
rise in temperature from the 28/21/25 to 34/27/31C temperature
treatment. The reduced grain yields with increasing temperature
treatment suggests potential detrimental effects on rice production
in some areas if air temperatures increase, especially under
conditions of low solar irradiance.

rice/Oryza sativa

KEYWORDS: GROWTH, SPAR UNITS, TEMPERATURE, YIELD

60   
Baker, J.T., L.H. Allen Jr., and K.J. Boote. 1992. Temperature
Effects on Rice at Elevated CO2 Concentration. Journal of
Experimental Botany 43:959-964.

The continuing increase in atmospheric carbon dioxide concentration
([CO2]) and projections of possible future increases in global air
temperatures have stimulated interest in the effects of these
climate variables on agriculturally important food crops. This
study was conducted to determine the effects of [CO2] and
temperature on rice (Oryza sativa L., cv. IR-30). Rice plants were
grown season-long in outdoor, naturally sunlit, controlled-environment, plant growth chambers in temperature regimes ranging
from 25/18/21C to 37/30/34C (daytime dry bulb air
temperature/night-time dry bulb air temperature/paddy water
temperature) and [CO2] of 660 umol CO2/mol air. An ambient chamber
was maintained at a [CO2] of 330 umol/mol and temperature regime of
28/21/25C. Carbon dioxide enrichment at 28/21/25C increased both
biomass accumulation and tillering and increased grain yield by
60%. In the 660 umol/mol [CO2] treatment, grain yield decreased
from 10.4 to 1.0 Mg/ha with increasing temperature from 28/21/25C
to the 37/30/34C temperature treatment. Across this temperature
range, the number of panicles/plant nearly doubled while the number
of seeds/panicle declined sharply. These results indicate that
while future increase in atmospheric [CO2] are likely to be
beneficial to rice growth and yield, potentially large negative
effects on rice yield are possible if air temperatures also rise.

rice/Oryza sativa

KEYWORDS: GROWTH, SEED PRODUCTION, SPAR UNITS, TEMPERATURE, YIELD

61   
Baker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.
1989. Response of Soybean to Air Temperature and Carbon Dioxide
Concentration. Crop Science 29:98-105.

Documented increases in global atmospheric CO2 concentration have
stimulated interest in the direct effects of CO2 on plant growth
and yield as well as the interactive effects of CO2 with other
major climatic variables. This study was conducted to determine the
effects and interactions of CO2 concentration and air temperature
on the development, growth, total nonstructural carbohydrate (TNC),
and final seed yield of soybean [Glycine max (L.) Merr., cv. Bragg]
grown season-long in naturally lit, controlled-environment
chambers. Day/night air temperatures of 26/19, 31/24 and 36/29C
were maintained in CO2 treatments of 330 and 660 umol CO2/mol air.
Both CO2 enrichment and increasing air temperature decreased main
stem plastochron interval, while increasing air temperature
increased final mainstem node number. Leaf area and above-ground
biomass increased with CO2 enrichment and with temperature from
26/19C to 31/24C. The nonlinear increase with temperature in leaf
area, aboveground biomass, and plastochron interval was attributed
to the highest temperature treatment being near or above the
optimum for soybean growth and development. Seed yield increased
with CO2 enrichment due mainly to an increase in seed number rather
than weight per seed. Individual seed weight decreased, while seed
number increased with increasing temperature. Leaflet TNC was
relatively stable throughout the day. Stem TNC was less affected by
CO2 than by temperature treatment and decreased with increasing
temperature. These results indicate that the response of soybean to
elevated CO2 concentration is highly temperature dependent.

soybean/Glycine max

KEYWORDS: CARBOHYDRATES, REPRODUCTION, SEEDS, SPAR UNITS,
TEMPERATURE, YIELD

62   
Baker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.
1990. Developmental Responses of Rice to Photoperiod and Carbon
Dioxide Concentration. Agricultural and Forest Meteorology 50:201-210.

The documented increase in the carbon dioxide concentration of the
Earth's atmosphere has stimulated interest in the effects of CO2 on
plants and in particular the future prospects for the world's food
supplies. While rice is a major food crop, relatively little is
known about the effects of CO2 concentration on the timing of
physiological growth stages and total growth duration, which are
important aspects of a rice cultivar's adaptability to the
environment of a particular geographic region. The objective of
this study was to determine the developmental responses of a
modern, improved rice cultivar (Oryza sativa, cultivar 'IR-30') to
a range of CO2 concentrations under two contrasting photoperiods.
Rice plants were grown season-long in an outdoor, naturally lit,
computer-controlled environment, plant growth chambers in CO2
concentrations of 160, 250 (subambient), 330 (ambient), 500, 660
and 900 (superambient) umol CO2/mol air. The entire experiment was
conducted twice during 1987. The first or early planted rice (EPR)
experiment was conducted with photoperiod extension lights during
the vegetative phase of development, while the second or late-planted rice (LPR) experiment was conducted using only naturally
occurring photoperiod. In both experiments, mainstem leaf
developmental rates were greater during vegetative rather than
reproductive growth stages and leaf appearance rates increased with
CO2 treatment during vegetative development. In the LPR experiment,
panicle initiation and boot stage occurred earlier and total growth
duration was shortened for rice plants in the superambient compared
with ambient and subambient CO2 treatments. This acceleration of
plant development with increasing CO2 treatment was associated with
a CO2-induced decrease in the number of mainstem leaves formed
during the vegetative phase of growth. The reduced developmental
response of rice plants to CO2 in the EPR compared with the LPR
experiment was attributed to the artificially extended photoperiod
during the EPR experiment forcing a delay in the onset of
reproductive development particularly in the superambient
treatments. The CO2-induced acceleration of development and
shortening of total growth duration should become a topic of
interest for rice agronomists and breeders involved with selecting
rice cultivars and agronomic practices for a particular geographic
region in view of the continued increases in global atmospheric CO2
concentration.

rice/Oryza sativa

KEYWORDS: GROWTH STAGES, PHOTOPERIOD, PRE-INDUSTRIAL CO2
CONCENTRATION, SPAR UNITS

63   
Baker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.
1990. Rice Photosynthesis and Evapotranspiration in Subambient,
Ambient, and Superambient Carbon Dioxide Concentrations. Agronomy
Journal 82:834-840.

The current global rise in atmospheric carbon dioxide concentration
[CO2], has stimulated interest in the response of agricultural
crops to [CO2]. The objectives were to determine the effects of
[CO2] on photosynthesis, evapotranspiration, and water use
efficiency of rice (Oryza sativa L., cv. IR-30). Rice plants were
grown in naturally sunlit, plant growth chambers in subambient (160
and 250), ambient (330), or superambient (500, 660, and 900 umol
CO2/mol air) [CO2] treatments. Photosynthetic light response curves
were analyzed to obtain estimates of canopy light utilization
efficiency () and canopy conductance to CO2 transfer ().
Estimates of  increased with increasing [CO2] treatment with the
greatest increase in the 160 to 500 umol/mol treatments. Estimates
of  were more variable than those of  and were not different
among [CO2] treatments. Photosynthetic rates increased with
increasing [CO2] treatment from 160 to 500 umol/mol followed by a
leveling off of the response among the superambient [CO2]
treatments. Evapotranspiration decreased while water-use efficiency
increased with increasing [CO2]. Short-term cross-switching of
[CO2] among the chambers revealed a profound adaptive response to
long-term [CO2] growth treatment. The lack of further
photosynthetic response above the 500 umol/mol [CO2] treatment
appears to indicate a need to select or screen rice cultivars for
increased response to superambient [CO2] in order to more fully
take advantage of future increases in global atmospheric [CO2].

rice/Oryza sativa

KEYWORDS: CANOPY PHOTOSYNTHESIS, LIGHT, PRE-INDUSTRIAL CO2
CONCENTRATION, SPAR UNITS, TRANSPIRATION, WUE

64   
Baker, J.T., L.H. Allen Jr., K.J. Boote, A.J. Rowland-Bamford, J.W.
Jones, P.H. Jones, G. Bowes, and S.L. Albrecht. 1988. Response of
Rice to Subambient and Superambient Carbon Dioxide Concentrations
1986-1987 Progress Report, 043 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, and U.S. Dept. of Agriculture, Agric. Res.
Serv., Washington, D.C.

rice/Oryza sativa

KEYWORDS: ALLOCATION, ANABAENA VARIABILIS, CANOPY PHOTOSYNTHESIS,
CARBOHYDRATES, CYANOBACTERIA, GROWTH STAGES, PRE-INDUSTRIAL CO2
CONCENTRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS,
STOMATAL DENSITY, TRANSPIRATION, YIELD

65   
Baker, J.T., L.H. Allen Jr., K.J. Boote, A.J. Rowland-Bamford, J.W.
Jones, P.H. Jones, G. Bowes, and F. Laugel. 1989. Temperature and
CO2 Effects on Rice. 1988 Progress Report, 053 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, and U.S. Dept. of
Agriculture, Agric. Res. Serv., Washington, D.C.

Oryza sativa/rice

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, EVAPOTRANSPIRATION,
GROWTH STAGES, RESPIRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR
UNITS, SUCROSEPHOSPHATE SYNTHASE, TEMPERATURE, YIELD

66   
Baker, J.T., F. Laugel, K.J. Boote, and L.H. Allen Jr. 1992.
Effects of Daytime Carbon Dioxide Concentration on Dark Respiration
in Rice. Plant, Cell and Environment 15:231-239.

Rising atmospheric carbon dioxide concentration ([CO2]) has
generated considerable interest in the response of agricultural
crops to [CO2]. The objectives of this study were to determine the
effects of a wide range of daytime [CO2] on dark respiration of
rice (Oryza sativa L. cv. IR-30). Rice plants were grown season-long in naturally sunlit plant growth chambers in subambient (160
and 250), ambient (330), or superambient (500, 660 and 900 umol
CO2/mol air) [CO2] treatments. Canopy dark respiration, expressed
on a ground area basis (Rd) increased with increasing [CO2]
treatments and was very similar among the superambient treatments.
The trends in Rd over time and in response to increasing daytime
[CO2] treatment were associated with and similar to trends
previously described for photosynthesis. Specific respiration rate
(Rdw) decreased with time during the growing season and was higher
in the subambient than the ambient and superambient [CO2]
treatments. This greater Rdw in the subambient [CO2] treatments was
attributed to a higher specific maintenance respiration rate and
was associated with higher plant tissue nitrogen concentration.

rice/Oryza sativa

KEYWORDS: NITROGEN, PRE-INDUSTRIAL CO2 CONCENTRATION, RESPIRATION,
SPAR UNITS

67   
Baker, R.G.E., and D.J. Boatman. 1990. Some Effects of Nitrogen,
Phosphorus, Potassium and Carbon Dioxide Concentration on the
Morphology and Vegetative Reproduction of Sphagnum cuspidatum Ehrh.
New Phytologist 116:604-611.

Five experiments are described which were designed to investigate
the effects of varying the concentrations of nitrate, phosphate,
potassium and carbon dioxide in the culture solution on the
morphology and vegetative reproduction of Sphagnum cuspidatum Ehrh.
The plants were grown axenically from spores sown on agar
containing inorganic salts and then transferred to aqueous culture
solutions through which air containing enhanced concentrations of
carbon dioxide was passed. In three of the experiments the plants
were grown in a balanced inorganic salt solution at various
dilutions and in two of these the concentration of carbon dioxide
in the gas bubbled through the solution was varied. The
concentrations of nitrogen, phosphorus and potassium were varied
independently and in combination in the remaining experiments while
the concentration of carbon dioxide was kept constant. In some of
the experiments the minimum concentrations of nitrogen and
potassium supplied were considerably below the minimum average
concentrations recorded in rain but the minimum concentration of
phosphorus supplied was within the upper part of the range recorded
in rain. Within the ranges supplied the concentrations of all three
elements and of carbon dioxide affected interfascicle length and
vegetative reproduction (innovation formation) but it was concluded
that the element limiting innovation formation in natural
conditions is phosphorus.

Sphagnum cuspidatum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN, NUTRITION,
PHOSPHORUS, POTASSIUM, VEGETATIVE REPRODUCTION

68   
Baldocchi, D.D., R. White, and J.W. Johnston. 1989. A Wind Tunnel
Study to Design Large, Open-top Chambers for Whole-tree Pollutant
Exposure Experiments. Journal of the Air Pollution Control
Association 39:549-1556.

A wind tunnel study was conducted to determine the optimal design
features of a large, open-top chamber, as needed for pollution
exposure studies on mature trees. An optimally-designed, open-top
chamber must minimize the incursion of ambient air through its
opening and maintain a uniform treatment concentration throughout
the chamber. The design features of interest are the diameter and
height of the chamber and the deflection angle and opening size of
any frustum that may be mounted on top of a model chamber. Design
specifications depend on the turbulence regime about the chamber,
which is influenced by the nature of the surrounding vegetation.
Consequently, our investigation was performed on scale-model, open-top chambers in a wind tunnel populated with a model coniferous
forest. Turbulence measurements demonstrated the similarity between
the turbulence regime of the model and a natural forest. A
hydrocarbon tracer was injected into the wind tunnel flow to
characterize chamber performance. The main design features of open-top chambers are the velocity of air exiting through the top and
the relationship between the length scale of the turbulence and the
diameter of the chamber opening. As exit velocities increase, the
proportion of eddies with sufficient force to penetrate into the
chamber decrease. Therefore, for equal volumetric air flows,
smaller opening sizes increase the exit velocities and reduce the
number and extent of ambient air incursions. Almost total exclusion
of ambient air is achieved as the exit velocity of the air exceeds
the magnitude of one standard deviation of the vertical wind
velocity measured at the chamber top. The incursion of ambient air
is also reduced when the diameter of the chamber opening is smaller
than the characteristic length scale of the turbulence, a measure
of mean eddy size. Frusta deflect air flow over the chamber. Three
prototypes, with 30-, 45- and 60-degree angles were tested. A 30-degree frustum slightly improves the performance of the chamber and
is more effective in preventing ambient air from entraining into
the chamber opening than frusta with either a 45- or 60-degree
angle. A flatter frustum allows for a smoother transition in the
wind velocity streamline and is less apt to cause wake turbulence,
as is the case with steeper frusta. Knowledge of the turbulence
characteristics of plant canopies are readily available in the
literature and can aid scientists and engineers in designing the
optimal chamber and frusta dimensions for their particular
application. Therefore, the empirical approach to chamber design
can be avoided, and substantial savings can be realized.

KEYWORDS: AIR POLLUTION, EXPOSURE METHODS, OPEN-TOP CHAMBERS

69   
Ball, M.C., and R. Munns. 1992. Plant Responses to Salinity under
Elevated Atmospheric Concentrations of CO2. Australian Journal of
Botany 40:515-525.

This review explores effects of elevated CO2 concentrations on
growth in relation to water use and salt balance of halophytic and
non-halophytic species. Under saline conditions, the uptake and
distribution of sodium and chloride must be regulated to protect
sensitive metabolic sites from salt toxicity. Salt-tolerant species
exclude most of the salt from the transpiration stream, but the
salt flux from a highly saline soil is still considerable. To
maintain internal ion concentrations within physiologically
acceptable levels, the salt influx to leaves must match the
capacities of leaves for salt storage and/or salt export by either
retranslocation or secretion from glands. Hence the balance between
carbon gain and the expenditure of water in association with salt
uptake is critical to leaf longevity under saline conditions.
Indeed, one of the striking features of halophytic vegetation, such
as mangroves, is the maintenance of high water use efficiencies
coupled with relatively low rates of water loss and growth. These
low evaporation rates are further reduced under elevated CO2
conditions. This, with increased growth, leads to even higher water
use efficiency. Leaves of plants grown under elevated CO2
conditions might be expected to contain lower salt concentrations
than those grown under ambient CO2 if salt uptake is coupled with
water uptake. However, salt concentrations in shoot tissues are
similar in plants grown under ambient and elevated CO2 conditions
despite major differences in water use efficiency. This phenomenon
occurs in C3 halophytes and in both C3 and C4 non-halophytes. These
results imply shoot/root communication in regulation of the salt
balance to adjust to environmental factors affecting the
availability of water and ions at the roots (salinity) and those
affecting carbon gain in relation to water loss at the leaves
(atmospheric concentrations of water vapour and carbon dioxide).

KEYWORDS: C3, C4, HALOPHYTES, REVIEW, SALT STRESS

70   
Barlow, E.W.R., and J. Conroy. 1988. Influence of Elevated
Atmospheric Carbon Dioxide on the Productivity of Australian
Forestry Plantations. IN: Greenhouse: Planning for Climate Change
(G.I. Pearman, ed.), E.J. Brill, New York, pp. 520-533.

Australia produced $2.7 billion worth of forest products in 1983-84
but a further $1.3 billion worth, principally softwood, were
imported. Because of this ever increasing demand for softwood,
there is a move away from utilization of native hardwoods and by
2020 AD, when the atmospheric CO2 concentration is likely to be
greater than 450 ppmv, 75% of forest products are projected to come
from coniferous plantations. This move towards Pinus radiata is a
result of both demand for softwood and lack of indepth
investigations of the potential of Australian native species,
particularly eucalypts, for plantation forestry. Pinus radiata is
the major plantation softwood in southern Australia and is
presently grown at sites where phosphorus deficiency and repeated
episodes of drought are common. Consequently, we are investigating
the growth response of pines to elevated CO2 at a range of
phosphorus and water levels. When phosphorus was adequate, doubling
CO2 concentration more than doubled the rate of photosynthesis and
increased the total plant dry weight by about 40%. However, there
was no response when phosphorus was deficient. In contrast, there
was a slightly higher response under simulated drought conditions.
A further possible effect of rising CO2 levels is that the climatic
range of P. radiata may be altered due to a reduction in water use
or an increase in the drought tolerance of the trees. We found that
CO2 enrichment did not affect either of these factors but the
water-use efficiency was increased when phosphorus was adequate.
All families of P. radiata do not respond to CO2 enrichment in the
same manner. In a study investigating the response of four families
to elevated CO2 at two phosphorus levels, we have identified a
considerable variation between the families in their response to
CO2 and phosphorus. To date our studies have indicated that the
projected increase in atmospheric CO2 levels is likely to have a
significant influence on the productivity of Australia's P. radiata
plantations. But this will only occur if phosphorus fertilization
is adequate. If the rise in CO2 results in climatic change the
range of P. radiata may be even further restricted because there
will be no concomitant decrease in water use or increase in drought
tolerance. There is an urgent need for complementary studies of the
response of Australian native species to elevated CO2 at realistic
levels of phosphorus and water to enable more accurate prediction
of the productivity and water use of Australian native forests and
eucalyptus plantations.

Pinus radiata

KEYWORDS: ALLOCATION, CONDUCTANCE, FAMILY RESPONSES, FOREST,
GROWTH, LEAF PHOTOSYNTHESIS, NUTRITION, PHOSPHORUS, POT VOLUME,
REVIEW, TREES, WATER STRESS, WUE

71   
Baron, J.J., and S.F. Gorski. 1986. Response of Eggplant to a Root
Environment Enriched with CO2. HortScience 21:495-498.

Several elevated concentrations of CO2 were injected into the root
atmosphere to determine the influence of CO2 concentration in the
soil on the growth of eggplant (Solanum melongena L.). Elevated CO2
levels in the root atmosphere consistently increased stem diameter
while a significant increase in plant total dry weight and leaf
area only occurred during long day/warm temperature conditions.
Under periods of short days and low light levels, 15% CO2 reduced
total dry weight and leaf area. Applications of 14-CO2 to the root
zone demonstrated that 14C eggplant roots absorb CO2 from the soil
environment and translocate labeled compounds into the shoot.

Solanum melongena/eggplant

KEYWORDS: 14C, FIZZ IRRIGATION, HORTICULTURAL CROPS, SOIL CO2
CONCENTRATION

72   
Barr, A.G., K.M. King, G.W. Thurtell, and M.E.D. Graham. 1990.
Humidity and Soil Water Influence the Transpiration Response of
Maize to CO2 Enrichment. Canadian Journal of Plant Science 70:941-948.

The impact of increasing atmospheric CO2 on the productivity of C4
crops may vary with soil water availability. This study
investigates the hypothesis that elevating CO2 in Zea mays L.
reduces the degree to which transpiration is limited by soil water
at high vapor pressure deficits or low soil water contents. Plants
growing in controlled environments at 300 and 600 umol/mol CO2 were
exposed daily to five levels of vapor pressure deficit as water was
withheld and the soil dried over an 8-d period. Doubling CO2 caused
an overall reduction of 23% in the transpiration rate and 34% in
the leaf conductance, but the effect of CO2 on transpiration and
leaf conductance was greatest at high soil water content and low
vapor pressure deficit, when soil water least limited
transpiration. Implications for the productivity of C4 crops in the
field are discussed.

corn/Zea mays

KEYWORDS: C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
HUMIDITY, TRANSPIRATION, VPD, WATER STRESS

73   
Barson, M.M., and R.M. Gifford. 1990. Carbon Dioxide Sinks: The
Potential Role of Tree Planting in Australia. IN: Greenhouse and
Energy (D.J. Swain, ed.), CSIRO, Australia, pp. 433-443.

Reforestation has been suggested as a possible policy option at
several recent international 'greenhouse effect' forums. The issue
of deforestation/reforestation may be the subject of a protocol for
which detailed arrangements will be developed following the
establishment of a non-obligatory Framework Convention on Climate
Change in the early 1990's. Although forestry cannot in principle
offer a permanent solution to continuous emission of CO2 from
fossil fuel burning, its expansion could assist in slowing down net
emissions. This would 'buy time' to reduce rates of CO2 emission
and to develop strategies to adapt to global atmospheric and
climate change. A simple model is developed to explore the dynamics
of carbon sequestration by new forest plantations. The areal extent
of land suitable for reforestation is also examined. It is
concluded from one optimistic scenario that a program of planting
40,000 ha/y of new forest onto non-forested land could, after 20 y
absorb about 5-12 Mt (C) p.a. (7-17 per cent 1987-88 total
Australian emissions) as long as planting at that rate continued.

KEYWORDS: MODELING, REFORESTATION, TREES

74   
Bauerle, W.L., D. Kretchman, and L. Tucker-Kelly. 1986. CO2
Enrichment in the U.S. IN: Status and CO2 Sources, Vol. I (H.Z.
Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of
Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 49-57.

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE

75   
Bazzaz, F.A. 1990. The Response of Natural Ecosystems to the Rising
Global CO2 Levels. Annual Review of Ecology and Systematics 21:167-196.

KEYWORDS: CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2 RESPONSES,
ECOSYSTEM LEVEL CO2 RESPONSES, ENVIRONMENTAL INTERACTIONS, FAMILY
RESPONSES, HERBIVORY, PHYSIOLOGICAL CO2 RESPONSES, POPULATION LEVEL
CO2 RESPONSES, REVIEW, SOIL MICROORGANISMS, SPECIES COMPETITION,
SPECIES RANGE

76   
Bazzaz, F.A., D.D. Ackerly, F.I. Woodward, and L. Rochefort. 1992.
CO2 Enrichment and Dependence of Reproduction on Density in an
Annual Plant and a Simulation of Its Population Dynamics. Journal
of Ecology 80:643-651.

1. Populations of an annual plant, Abutilon theophrasti, were grown
at four densities (100, 500, 1500 and 4000/m2) and two CO2
concentrations (350 and 700 uL/L) to examine the influence of CO2
environment on density-dependent patterns of demography and
reproduction. Variables measured included survivorship, proportion
of plants flowering and fruiting, number of fruiting individuals,
number of seeds per individual, total seed production per
population, mean seed mass, and germination of seeds produced in
each environment. 2. All variables, except the number of fruiting
individuals, declined with increasing density, and at the highest
density no individuals set seed. The number of fruiting individuals
was highest at a density of 500/m2. In the elevated CO2
environment, survivorship was significantly reduced but the
proportion of plants flowering and fruiting and the number of
fruiting individuals in each population all increased. Total
population seed production was higher in the elevated CO2
environment at all densities, although the differences were not
significant. Significant effects of CO2 concentration were observed
only for population-level variables, but not for mean individual
fecundity or seed size. Seed germination declined with increasing
maternal density, and no germination was recorded for seeds
produced at 1500 /m2. 3. Simple models of population dynamics,
utilizing difference equations, were constructed to examine
potential population-level consequences of these density and CO2
effects. In the absence of a persistent seed pool, the simulated
populations exhibited damped or stable oscillations under low
germination values, but displayed non-cyclic ('chaotic')
oscillations or went extinct for higher germination due to the
complete failure of seed-set at high density. Because of its higher
fecundity, the elevated-CO2 population generally exhibited greater
oscillations, and the critical germination value at which the
simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2 population.

Abutilon theophrasti

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, MODELING, OLD FIELD
COMMUNITIES, PLANT DENSITY, POPULATION MODEL, REPRODUCTION,
SIMULATION, SURVIVORSHIP

77   
Bazzaz, F.A., J.S. Coleman, and S.R. Morse. 1990. Growth Responses
of Seven Major Co-occurring Tree Species of the Northeastern United
States to Elevated CO2. Canadian Journal of Forest Research
20:1479-1484.

We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (Fagus grandifolia Ehrh.),
paper birch (Betula papyrifera Marsh.), black cherry (Prunus
serotina Ehrh.), white pine (Pinus strobus L.), red maple (Acer
rubrum L.), sugar maple (Acer saccharum Marsh.), and eastern
hemlock (Tsuga canadensis (L.) Carr.). We also tested whether the
degree of shade tolerance of species and the age of seedlings
affected plant responses to enhanced CO2 levels. Seedlings that
were at least 1 year old, for all species except beech, were
removed while dormant from Harvard Forest, Petersham,
Massachusetts. Seeds of red maple and paper birch were obtained
from parent trees at Harvard Forest, and seeds of American beech
were obtained from a population of beeches in Nova Scotia.
Seedlings and transplants were grown in one of four plant growth
chambers for 60 d (beech, paper birch, red maple, black cherry) or
100 d (white pine, hemlock, sugar maple) under CO2 levels of 400 or
700 uL/L. Plants were then harvested for biomass and growth
determinations. The results showed that the biomass of beech, paper
birch, black cherry, sugar maple, and hemlock significantly
increased in elevated CO2, but the biomass of red maple and white
pine only marginally increased in these conditions. Furthermore,
there were large differences in the magnitude of growth enhancement
by increased levels of CO2 between species, so it seems reasonable
to predict that one consequence of rising levels of CO2 may be to
increase the competitive ability of some species relative to
others. Additionally, the three species exhibiting the largest
increase in growth with increased CO2 concentrations were the
shade-tolerant species (i.e., beech, sugar maple, and hemlock).
Thus, elevated CO2 levels may enhance the growth of relatively
shade-tolerant forest trees to a greater extent than growth of
shade-intolerant trees, at least under the light and nutrient
conditions of this experiment. We found no evidence to suggest that
the age of tree seedlings greatly affected their response to
elevated CO2 concentration.

American beech/Fagus grandifolia/paper birch/Betula
papyrifera/black cherry/Prunus serotina/white pine/Pinus
strobus/red maple/Acer rubrum/sugar maple/Acer saccharum/eastern
hemlock/Tsuga canadensis

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, SHADE TOLERANCE,
SPECIES COMPETITION, TREES

78   
Bazzaz, F.A., and E.D. Fajer. 1992. Plant Life in CO2-Rich World.
Scientific American 266:68-74.

KEYWORDS: C3, C4, CO2 ENRICHMENT STUDIES, ECOSYSTEM LEVEL CO2
RESPONSES, INSECTS, PHOTOSYNTHESIS, REVIEW

79   
Bazzaz, F.A., and K. Garbutt. 1988. The Response of Annuals in
Competitive Neighborhoods: Effects of Elevated CO2. Ecology 69:937-946.

Four members of an annual community were used to investigate the
effects of changing neighborhood complexity and increased CO2
concentration on competitive outcome. Plants were grown in
monoculture and in all possible combinations of two, three, and
four species in CO2-controlled growth chambers at CO2
concentrations of 350, 500, and 700 uL/L with ample moisture and
high light. Species responded differently to enhanced CO2 level.
Some species (e.g., Abutilon theophrasti) had increased biomass
with increasing CO2, while others (e.g., Amaranthus retroflexus)
had decreased biomass with increasing CO2 concentration. In
mixtures, species tended to interact strongly, and, in some cases,
the interaction canceled out the effects of CO2. Furthermore, there
were clear differences in species behavior in different competitive
neighbors. In general, competitive arrays that had C3 species
depressed the response of C4 species, especially Amaranthus.
Ambrosia artemisiifolia was the strongest competitor in the
assemblage. Strong statistical interactions between CO2 and the
identity of the competing species in mixtures were found to be
primarily due to the as yet unexplained response of plants with CO2
at 500 uL/L. The potential effects of CO2 on community structure
could be profound, particularly at the intermediate levels of CO2
that are predicted to be reached during the first half of the next
century.

Ambrosia artemisiifolia/Abutilon theophrasti/Amaranthus
retroflexus/Setaria faberii

KEYWORDS: C3, C4, OLD FIELD COMMUNITIES, SPECIES COMPETITION,
SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

80   
Bazzaz, F.A., K. Garbutt, E.G. Reekie, and W.E. Williams. 1989.
Using Growth Analysis to Interpret Competition between a C3 and a
C4 Annual under Ambient and Elevated CO2. Oecologia 79:223-235.

Detailed growth analysis in conjunction with information on leaf
display and nitrogen uptake was used to interpret competition
between Abutilon theophrasti, a C3 annual, and Amaranthus
retroflexus, a C4 annual, under ambient (350 uL/L) and two levels
of elevated (500 and 700 uL/L) CO2. Plants were grown both
individually and in competition with each other. Competition caused
a reduction in growth in both species, but for different reasons.
In Abutilon, decreases in leaf area ratio (LAR) were responsible,
whereas decreased unit leaf rate (ULR) was involved in the case of
Amaranthus. Mean canopy height was lower in Amaranthus than
Abutilon which may explain the low ULR of Amaranthus in
competition. The decrease in LAR of Abutilon was associated with an
increase in root:shoot ratio implying that Abutilon was limited by
competition for below ground resources. The root:shoot ratio of
Amaranthus actually decreased with competition, and Amaranthus had
a much higher rate of nitrogen uptake per unit of root than did
Abutilon. These latter results suggest that Amaranthus was better
able to compete for below ground resources than Abutilon. Although
the growth of both species was reduced by competition, generally
speaking, the growth of Amaranthus was reduced to a greater extent
than that of Abutilon. Regression analysis suggests that the
success of Abutilon in competition was due to its larger starting
capital (seed size) which gave it an early advantage over
Amaranthus. Elevated CO2 had a positive effect upon biomass in
Amaranthus, and to a lesser extent, Abutilon. These effects were
limited to the early part of the experiment in the case of the
individually grown plants, however. Only Amaranthus exhibited a
significant increase in relative growth rate (RGR). In spite of the
transitory effect of CO2 upon size in individually grown plants,
level of CO2 did effect final biomass of competitively grown
plants. Abutilon grown in competition with Amaranthus had a greater
final biomass than Amaranthus at ambient CO2 levels, but this
difference disappeared to a large extent at elevated CO2. The high
RGR of Amaranthus at elevated CO2 levels allowed it to overcome the
difference in initial size between the two species.

Abutilon theophrasti/Amaranthus retroflexus

KEYWORDS: C3, C4, GROWTH ANALYSIS, NITROGEN, OLD FIELD COMMUNITIES,
ROOT:SHOOT RATIO, SPECIES COMPETITION, SUNLIT CONTROLLED
ENVIRONMENT CHAMBERS

81   
Bazzaz, F.A., K. Garbutt, and W.E. Williams. 1985. Effect of
Increased Atmospheric Carbon Dioxide Concentration on Plant
Communities. IN: Direct Effects of Increasing Carbon Dioxide on
Vegetation, DOE/ER-0238 (B.R. Strain and J.D. Cure, eds.), U.S.
Dept. of Energy, Carbon Dioxide Research Division, Washington,
D.C., pp. 155-204.

KEYWORDS: C3, C4, CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2
RESPONSES, FLOWERING, REVIEW, SPECIES COMPETITION

82   
Bazzaz, F.A., K. Garbutt, and W.E. Williams. 1985. The Effect of
Elevated Atmospheric CO2 on Plant Communities, TR023 in Yellow
Report Series, DOE/EV/04329-5, Dept. of Energy, Carbon Dioxide
Research Division. NTIS, U.S. Dept. of Commerce, Springfield,
Virginia.

KEYWORDS: AIR POLLUTION, C3, C4, CONDUCTANCE, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH, GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS,
LIGHT, NUTRITION, PHENOLOGY, REPRODUCTION, REVIEW, SPECIES
COMPETITION, SULFUR DIOXIDE, WATER STRESS, WUE

83   
Bazzaz, F.A., and K.D.M. McConnaughay. 1992. Plant-plant
Interactions in Elevated CO2 Environments. Australian Journal of
Botany 40:547-563.

Increasing atmospheric carbon dioxide concentrations present a
novel resource condition for plant communities. In order to
understand and predict how plant community structure and function
may be altered in a high CO2 world, we need to understand how
interactions among neighboring plants within a community will alter
the growth and reproduction of component species. Because CO2 is
readily diffusible, plants have little influence on the CO2
acquisition of their neighbors, except within particularly dense
canopies. Thus, plants seldom compete directly for CO2. Rather, CO2
availability is likely to alter plant-plant interactions indirectly
through its effects on plant growth and competition for other
resources. As a consequence, competitive outcome under elevated CO2
atmospheres within even simple systems is not easy to predict. For
example, under some conditions, C4 species in competitive
assemblages have improved competitive ability relative to C3
competitors as a result of CO2 enrichment, contrary to expectations
based on their photosynthetic pathways. It is now clear that
individually grown plants can differ substantially from those
within mono- or multispecific stands in response to CO2 enrichment.
At present, our understanding of how stands of interacting plants
modify the availability of CO2 and other resources is incomplete.
We urgently need information about how elevated CO2 atmospheres
influence stand formation and population dynamics, specifically
with regard to the identities, numbers, sizes and reproductive
fitnesses of individuals within single and multiple species stands,
if we are to make multi-generational predictions concerning the
fate of populations and communities in an elevated CO2 world.

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL
INTERACTIONS, PLANT-PLANT INTERACTIONS, REVIEW, TEMPERATURE

84   
Beer, S. 1986. The Fixation of Inorganic Carbon in Plant Cells. IN:
Physiology, Yield, and Economics, Vol. II (H. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 3-11.

The initial fixation of atmospheric inorganic carbon (CO2) in plant
cells is carried out via either the C3 or C4 pathway. The first
step of the C3 pathway is the fixation of CO2 by a five-carbon
compound to yield two molecules of PGA (a three-carbon compound).
PGA is subsequently reduced to form sugars. In the so-called C3
plants, this is the only pathway for incorporation of CO2. The
enzyme (RuBPcase) catalyzing CO2 fixation in the C3 pathway may
also act as an oxygenase. When doing so, glycolate (a two-carbon
compound) is formed together with PGA, and there is no net carbon
gain of the process. In the further metabolism of glycolate, CO2 is
released. This is called photorespiration and its rate is, in
contrast to mitochondrial or dark respiration, strongly enhanced by
O2 and light. In the C4 pathway, atmospheric CO2 is fixed, via the
enzyme PEPcase, by a three-carbon compound to yield one molecule of
malate or aspartate (four-carbon compounds). In C4 plants, this
occurs in mesophyll cells. Malate or aspartate is then transported
to bundle sheath cells where it is decarboxylated, and the released
CO2 is refixed via the C3 pathway. There is no apparent
photorespiration in C4 plants, because CO2 levels in the vicinity
of RuBPcase are probably elevated and any CO2 released from the
bundle sheath cells is efficiently refixed via PEPcase in the
mesophyll cells. In CAM plants, atmospheric CO2 is fixed into
malate during the night while the decarboxylation and refixation of
CO2 occurs in the daytime. The C4 pathway provides C4 and CAM
plants with an efficient carbon-capturing system complementing the
basic C3 pathway. In C4 plants this leads to a higher net CO2
incorporation rate than in C3 plants under high light and
temperature regimes such as are found in the tropics. In CAM plants
it allows for nightly CO2 fixation in arid climates where opening
of stomates during the day would cause excessive water loss.

KEYWORDS: C3, C4, CAM, ENZYMES, METABOLITES, PHOTOSYNTHESIS, REVIEW

85   
Beerling, D.J., and W.G. Chaloner. 1993. The Impact of Atmospheric
CO2 and Temperature Change on Stomatal Density: Observations from
Quercus robur Lammas Leaves. Annals of Botany 71:231-235.

A comparative study of leaves formed on shoots during the spring
and summer (lammas) of Quercus robur from three contrasting
geographical locations (Cardiff, Durham and London) gives a measure
of the effect of temperature on stomatal density. This is of value
in attempting to distinguish the effects of CO2 and temperature on
observed stomatal density changes under different CO2 and
temperature conditions through the Quaternary. These leaves of
normal and lammas shoots will have developed under similar CO2
levels but different environmental temperatures. Our results
demonstrate that leaves formed under the warmer summer temperatures
had reduced stomatal densities and indices from all sites, compared
with their spring counterparts. This trend was also detected from
measurements of spring and summer leaves made upon herbarium
material collected from the same tree in 1840. The results suggest
that for Q. robur temperature overrides the influence of irradiance
intensity and small seasonal (</= 10 ppmv) variations of CO2
concentration in determining stomatal density. In accordance with
previous work we have also documented a decline in stomatal density
since 1840 by examining herbarium leaf material in response to the
rising atmospheric CO2 concentration determined from ice core
studies. In conclusion, if we are to understand changes in stomatal
density as a response to CO2 linked temperature changes (the
'greenhouse effect') it is important to distinguish the effects of
these two environmental parameters on plants.

Quercus robur

KEYWORDS: STOMATAL DENSITY, STOMATAL INDEX, TEMPERATURE

86   
Beerling, D.J., and W.G. Chaloner. 1993. Stomatal Density Responses
of Egyptian Olea europaea L. Leaves to CO2 Change Since 1327 BC.
Annals of Botany 71:431-435.

We have attempted to separate the effects of CO2 and temperature
change on stomatal density by examining ancient leaf material of
Olea europaea L. The distribution of this species is confined to a
Mediterranean type climate, so that O. europaea leaves of different
ages will have formed under similar temperatures but different CO2
levels over the last 3000 years. Stomatal density measurements have
been made upon leaves of O. europaea originating from King
Tutankhamun's tomb dating from 1327 BC, and have been compared with
values obtained from Egyptian O. europaea material dating from pre-332 BC, 1818 and 1978 AD. Together, the four dates provide a record
of how the plant has responded to increases in atmospheric CO2
concentration during that time. The results demonstrate that in
accordance with similar studies examining the stomatal density
response of plants over three time scales (hundreds, thousands and
tens of thousands of years) stomatal density falls as CO2 levels
increase. Since we have examined a natural system with leaves
developing under similar environmental temperatures the results
confirm observations from experimental studies in which plants were
grown under the same temperature but different CO2 regimes.

Olea europaea/olive

KEYWORDS: STOMATAL DENSITY, STOMATAL INDEX

87   
Beerling, D.J., W.G. Chaloner, B. Huntley, J.A. Pearson, M.J.
Tooley, and F.I. Woodward. 1992. Variations in the Stomatal Density
of Salix herbacea L. under the Changing Atmospheric CO2
Concentrations of Late- and Post-glacial Time. Philosophical
Transactions of the Royal Society, London (Series B) 336:215-224.

The rapidly rising CO2 concentration of the past 200 years has been
shown to be accompanied by a fall in stomatal density in the leaves
of temperate trees. The present study attempts to investigate the
relationship of atmospheric CO2 change and stomatal density in the
arctic-alpine shrub, Salix herbacea, over the longer time span of
11,500 years offered by fossil leaves from post-glacial deposits.
Comparisons of fossil material from Scotland and Norway are made
with leaves from living populations growing in Austria, Greenland
and Scotland. The Austrian material, from an altitudinal gradient
between 2000 and 2670 m above sea level, gives added comparisons of
contemporary differences of CO2 partial pressure with altitude. The
results of our investigation indicate, rather surprisingly, that
the rising CO2 concentration of the past 11,500 years has been
accompanied by an increase in the stomatal density of S. herbacea
in contrast to the shorter-term observations on the herbarium
material of temperate trees. The most likely explanation appears to
centre on the temperature and water availability of the early post-glacial environment overriding the effect of the lower CO2 regime.
However, the scale of the time interval involved may also be
significant. Natural selection over the 11,500 year period
concerned may have favoured a different response to what is, in
effect, an acclimatory response observed in trees within the period
of rapid CO2 rise of the past 200 years.

Salix herbacea

KEYWORDS: PRE-INDUSTRIAL CO2 CONCENTRATION, STOMATAL DENSITY

88   
Beeson, R.C., Jr., and M.E.D. Graham. 1991. CO2 Enrichment of
Greenhouse Roses Affects Neither Rubisco nor Carbonic Anhydrase
Activities. Journal of the American Society of Horticultural
Science 116:1040-1045.

The effect of prolonged CO2 enrichment on the activities of
ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and
carbonic anhydrase (CA) of greenhouse roses were studied. Plants of
Rosa x hybrida 'Red Success' were grown for 2 years at ambient and
900 uL CO2/L during winter and spring with 75 umol/m2/s
photosynthetically active radiation supplemental lighting for 2
years. Measurements of initial and Mg++-CO2-activated activities of
Rubisco and CA were made during shoot development and at different
positions within the plant canopy. Generally, there were no
significant differences measured in the enzyme activites between
the two CO2 concentrations. The results suggest that the
photosynthetic capacity did not change and that there were no
characteristic adaptations to long-term growth (up to 20 weeks) at
elevated CO2 concentrations. The maintenance of Rubisco and CA
activities with prolonged exposure to CO2-enriched atmospheres is
proposed as the reason for long-term yield increases in roses when
grown in enriched environments.

Rosa hybrida/rose

KEYWORDS: CARBONIC ANHYDRASE, ENZYMES, FLOWER PRODUCTION,
HORTICULTURAL CROPS, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE
BISPHOSPHATE CARBOXYLASE

89   
Bellamy, L.A., and B.A. Kimball. 1986. CO2 Enrichment Duration and
Heating Credit as Determined by Climate. IN: Physiology, Yield, and
Economics, Vol. II (H.Z. Enoch and B.A. Kimball, eds.), Carbon
Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca
Raton, Florida, pp. 168-197.

To determine if it is economical to invest in CO2 enrichment
equipment, a detailed economic analysis considering the increases
in income and operating expenses should be performed. The procedure
for such an analysis is straightforward (e.g., Chapter 13) but it
is necessary to make estimates of the percent increase in yield,
the amount of CO2 used, and of any reduction in heating energy
requirements resulting from a combustion-type CO2 generator. For
any given greenhouse and crop, these three factors will vary with
the local climate and in particular, with the outside air
temperature, and global solar radiation. It is practical to enrich
with CO2 only while a greenhouse is closed and not ventilated.
Therefore, CO2 enrichment duration equals day length minus
ventilation time. Using Kimball's MEB program curves were generated
which show the ventilation time fraction a 0.05 m3/m2/s capacity
(47 greenhouse volume changes per hour) fan would need to operate
to maintain a given set point temperature as a function of
transmitted solar radiation for various ambient air temperatures.
Similar curves were generated showing the heating credit from a CO2
generator rated at 42.5 W/m2 (CO2 output 9.5 g/m2/h). Hourly solar
radiation and temperature data for days typical of each month of
the year for six climate regions were generated using simple models
from values of monthly mean minimum and maximum temperatures and
mean total daily global radiation. Such data should be available
nearby to most greenhouse locations. The hourly climate data for
each of the typical monthly days were used in conjunction with the
ventilation time fraction curves to compute the ventilation
requirement throughout the year for six locations--Oslo, Norway; De
Bilt, Netherlands; Milan, Italy; Columbus, Ohio, U.S.; Tokyo,
Japan; Tel Aviv, Israel. The number of hours at which the
greenhouse operated in five ventilation classes (0%, 0 to 20%, 20
to 50%, 50 to 100%, 100%) for a 30C ventilation temperature
setpoint were plotted. For all sites except Tel Aviv, enrichment is
possible throughout the whole day during winter. At Oslo, a
greenhouse can remain unventilated and enriched for up to 7 months
of the year. The areas in each ventilation class were measured to
estimate the corresponding annual number of hours of possible CO2
enrichment. From these CO2 enrichment duration values, the required
amounts of CO2 can be estimated. The amount of solar radiation
received by the crop during each of the ventilation classes was
also determined, so that the percent increase in yield due to CO2
enrichment could be calculated. A greenhouse in Oslo can remain
closed and CO2 enriched for 79% of the total annual daylight hours,
yet only 51% of the total radiation is received by the crop during
this time. Using the assumption that yield is directly proportional
to transmitted solar radiation, yields with and without CO2
enrichment were compared for the six locations to assess the effect
of climate on percent yield increase. Annual yields could be
increased 2% at Tel Aviv and 26% at Oslo if enrichment is limited
to when the greenhouse remains completely closed. If CO2 is pulsed
into the greenhouse between intervals of fan operation, these CO2
response values can increase to 22 and 48%, respectively. The
effects on CO2 enrichment duration of using 'hot' CO2 from a
combustion-type generator rather than 'cold' CO2 from other sources
were computed for the Tel Aviv location. Using a 27C greenhouse
air temperature for the ventilation setpoint, average daily CO2
enrichment duration (0% ventilation) was 4.0 hr during the winter
using cold CO2, but decreased to 2.6 hr with hot CO2. Finally, the
annual heating credit was determined for each of the six locations
for 15C day heating setpoint, and the annual and winter savings in
heating energy requirements were tabulated. The proportion of
annual CO2 enrichment duration (0% ventilation) that was heating
credit time ranged from 49% for Oslo to 8% for Tel Aviv.

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE

90   
Bentley, B.L., and N.D. Johnson. 1990. Plants as Food for
Herbivores: The Roles of Nitrogen Fixation and Carbon Dioxide
Enrichment. IN: Plant-Animal Interactions: Evolutionary Ecology in
Tropical and Temperate Regions (P.W. Price, T.M. Lewinsotin, G.W.
Fernandes, and W.W. Benson, eds.), John Wiley & Sons, Inc., pp.
257-272.

KEYWORDS: CARBON:NITROGEN RATIO, HERBIVORY, INSECTS, NITROGEN
FIXATION, REVIEW

91   
Berntson, G.M., and F.I. Woodward. 1992. The Root System
Architecture and Development of Senecio vulgaris in Elevated CO2
and Drought. Functional Ecology 6:324-333.

1. The impact of elevated CO2 and drought on the architecture and
development of root systems of Senecio vulgaris was examined and
implications for water and nutrient uptake discussed. Plants were
grown in miniature rhizotrons to non-destructively monitor the
development of roots in situ at both an elevated (700 umol/mol) and
ambient (350 umol/mol) atmospheric CO2 concentration and high or
low supply of water. 2. CO2 and water had a significant impact on
the way that S. vulgaris root systems filled the soil matrix.
Elevated CO2 resulted in more branched, longer root systems that
foraged through larger volumes of soil. Under elevated CO2 and a
low water supply, root systems had branching and foraging patterns
and root length similar to those grown under ambient CO2 with a
high water supply. 3. Overall, water had a more pronounced impact
on the growth rate of S. vulgaris roots than did CO2. The density
of rooting remained unchanged across all treatments. Thus, under
elevated CO2 the intensity of foraging S. vulgaris root systems
might be unchanged while the extent of foraging by these root
systems, as indicted by the horizontal spread of roots, may be
increased.

Senecio vulgaris

KEYWORDS: GREENHOUSE, GROWTH ANALYSIS, RHIZOTRON, ROOT:SHOOT RATIO,
ROOTS, WATER STRESS

92   
Besford, R.T. 1990. The Greenhouse Effect: Acclimation of Tomato
Plants Growing in High CO2, Relative Changes in Calvin Cycle
Enzymes. Journal of Plant Physiology 136:458-463.

Tomato plants (cv. Findon Cross) were grown in a normal
concentration of CO2 (approximately 340 vpm) or in elevated CO2
(1000 vpm) with a 12 h photoperiod of 400 umol quanta/m2/s, PAR.
The activities of three Calvin cycle enzymes, RuBPco (E.C.
4.1.1.39), 3 phosphoglyceric acid phosphokinase (E.C. 2.7.2.3) and
NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (E.C.
1.2.1.13) were determined in extracts from the unshaded 5th leaf
during leaf development. RuBPco activity was reduced in the high-CO2 grown leaves at 60% expansion compared with leaves grown in 340
vpm CO2, but there were no apparent differences in the other two
Calvin cycle enzymes at this stage of expansion. With subsequent
leaf development in high CO2 there was an accelerated decline in
all three enzyme activities. The loss of RuBPco activity was
studied further by raising antibodies to RuBPco and the large
subunit of RuBPco (LSU) was detected in electroblotted crude
extracts from normal and high-CO2 grown plants. This specific
immunoassay estimated a 75% reduction of LSU in the high-CO2 grown
leaf at full expansion.

Lycopersicon esculentum

KEYWORDS: CALVIN CYCLE ENZYMES, CONTROLLED ENVIRONMENT CHAMBERS,
ENZYMES, PHOTOSYNTHETIC ACCLIMATION

93   
Besford, R.T. 1993. Photosynthetic Acclimation in Tomato Plants
Grown in High CO2. Vegetatio 104/105:441-448.

The effects of prolonged CO2 enrichment of tomato plants on
photosynthetic performance and Calvin cycle enzymes, including the
amount and activity of ribulose-1,5-bisphosphate carboxylase
(RuBPco), were determined. Also the light-saturated rate of
photosynthesis (Pmax) of the 5th leaf throughout leaf development
was predicted based on the amount and kinetics of RuBPco. With
short-term CO2 enrichment, i.e. only during the photosynthesis
measurements, Pmax of the young leaves did not increase while the
leaves reaching full expansion more than doubled their net rate of
CO2 fixation. However, with longer-term CO2 enrichment, i.e.
growing the crop in high CO2, the plants did not maintain this
photosynthetic gain. Compared with leaves of plants grown in normal
ambient CO2 the high CO2-grown leaves, when almost fully expanded,
contained only about half as much RuBPco protein and Pmax in 300
and 1000 vpm CO2 was similarly reduced. The loss of RuBPco protein
may be a factor associated with the accelerated fall in Pmax since
Pmax was close to that predicted from the amount and kinetics of
RuBPco assuming RuBP saturation. Acclimation to high CO2 is
fundamentally different from acclimation to high light. In contrast
to acclimation to high light, acclimation to high CO2 does not
usually involve an increase in photosynthetic machinery so the
synthesis and maintenance costs (as indicate by the dark
respiration rate) are generally lower.

Lycopersicon esculentum/tomato

KEYWORDS: CALVIN CYCLE ENZYMES, CONTROLLED ENVIRONMENT CHAMBERS,
HYDROPONIC CULTURE, LEAF AREA DEVELOPMENT, LEAF PHOTOSYNTHESIS,
LIGHT, PHOTOSYNTHETIC ACCLIMATION, PROTEINS, RIBULOSE BISPHOSPHATE
CARBOXYLASE

94   
Besford, R.T., and D.W. Hand. 1989. The Effects of CO2 Enrichment
and Nitrogen Oxides on some Calvin Cycle Enzymes and Nitrite
Reductase in Glasshouse Lettuce. Journal of Experimental Botany
40:329-336.

Glasshouse lettuce (cvs Pascal and Talent) was grown during late
autumn and early winter in an atmosphere polluted with nitrogen
oxides (NOx) generated from direct-fired natural gas burners used
for CO2 enrichment and warm air heating (high CO2 + NOx treatment).
Concentrations of 0.3-0.4 vpm NOx were detected during the daytime
when near 3-fold CO2 enrichment (1000 vpm) was practised without
heating. In cold weather, the CO2 and NOx levels were dependent on
the amount of heating required to maintain minimum temperatures of
5C (night) and 7C (day). Concentrations of between 2000-5000 vpm
CO2 and 1-2.5 vpm NOx were recorded at night during an intensely
cold period in early January just prior to sampling for leaf
enzymes. The plants were compared with those grown in unpolluted
atmospheres with either a natural (340 vpm) or an enriched level
(1000 vpm) of CO2. Pascal grown in elevated CO2 had less activity
per g fresh weight of RuBPc (E.C. 4.1.1.39), 3PGA phosphokinase
(E.C. 2.7.2.3) and NADP-G3P dehydrogenase (E.C 12.1.13) than plants
grown in a normal ambient CO2 atmosphere. The cytoplasmic enzyme
PEPc (E.C. 4.1.1.31) was not significantly affected by the pure CO2
enrichment. With high CO2 + NOx the activities of the Calvin cycle
enzymes were restored to values close to those present in non-enriched plants, while the activity of PEPc was increased. The
activity of nitrite reductase (NiR) (E.C. 1.7.7.1) was increased in
Pascal and Talent by high CO2 + NOx. Immunoblotting techniques were
used to show that the increase in activity of this enzyme was
accompanied by an increase in the steady state concentration of the
protein. Only one molecular form of NiR was detected by
immunoblotting, and it would appear that the 'induction' of NiR
activity resulted from increased net enzyme synthesis rather than
activation of pre-existing enzyme. At the time of sampling no
visible damage by high CO2 and NOx was evident and the lack of
symptoms may have been associated with the enhanced levels of
nitrite reductase in these cultivars.

Lactuca sativa

KEYWORDS: AIR POLLUTION, CALVIN CYCLE ENZYMES, ENZYMES, GREENHOUSE,
METABOLITES, NITROGEN OXIDES, PHOSPHOENOLPYRUVATE CARBOXYLASE

95   
Besford, R.T., L.J. Ludwig, and A.C. Withers. 1990. The Greenhouse
Effect: Acclimation of Tomato Plants Growing in High CO2,
Photosynthesis and Ribulose-1, 5-Bisphosphate Carboxylase Protein.
Journal of Experimental Botany 41:925-931.

Tomato plants were grown in solution culture in a controlled
environment at 20C with a 12 h photoperiod of 400 umol quanta/m2/s
PAR with either normal ambient CO2, approximately 340 vpm, or with
1000 vpm CO2. The short- and long-term effects of CO2 enrichment on
photosynthesis were determined together with the levels of
ribulose-1,5-bisphosphate carboxylase (RuBPco) EC. 4.1.1.39 protein
and activity throughout leaf development of the unshaded 5th leaf
above the cotyledons. The high CO2 concentration during growth did
not appreciably affect the rate of leaf expansion or final leaf
area but did increase the fresh weight per unit area of leaf. With
short-term CO2 enrichment, i.e. only during the photosynthesis
measurements, the light-saturated photosynthetic rate (Pmax) of
young leaves did not increase while those reaching full expansion
more than doubled their net rate of CO2 fixation. However, with
longer term CO2 enrichment, i.e. growing the crop in high CO2, the
plants did not maintain this photosynthetic gain. While the CO2
concentration during growth did not affect the peak in Pmax
measured in 300 vpm CO2 or Pmax measured in 1000 vpm CO2, RuBPco
protein or its activity, the subsequent ontogenetic decline in
these parameters was greatly accelerated by the high CO2 treatment.
Compared with plants grown in normal ambient CO2 the high CO2 grown
leaves, when almost fully expanded, contained only approximately
half as much RuBPco protein and Pmax in 300 vpm CO2 and Pmax in
1000 vpm CO2 were similarly reduced. The loss of RuBPco protein may
be a major factor associated with the accelerated fall in Pmax
since it was close to that predicted from the amount and kinetics
of RubBPco assuming RuBP saturation. In the oldest leaves examined
grown in high CO2 additional factors may be limiting photosynthesis
since RuBPco kinetics marginally overestimated Pmax in 300 vpm CO2
and the initial slope of photosynthesis in response to
intercellular CO2 was also less than expected from the extractable
RuBPco.

Lycopersicon esculentum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES, LEAF
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE BISPHOSPHATE
CARBOXYLASE

96   
Betsche, T., F. Morin, F. Cotte, F. Gaugain, and M. Andr. 1989.
Gas Exchanges, Chlorophyll a Fluorescence, and Metabolite Levels in
Leaves of Trifolium subterraneum during Long-term Exposure to
Elevated CO2. IN: Progress in Photosynthesis Research, Proc. VIIIth
International Congress on Photosynthesis, Stockholm, Sweden, 1989.

High CO2 stimulates photosynthesis of C3-plants initially, but then
photosynthesis often declines and undesirable effects such as
excessive starch accumulation and yellowing of leaves can occur.
Results from chlorophyll a fluorescence measurements and metabolite
determinations indicate that high CO2 can perturb photosynthesis
probably on the level of phosphate recycling. We propose that the
absence of photorespiration in high CO2 causes phosphate deficiency
in the chloroplast stroma and a low phosphorylation potential in
the cytosol. Both conditions favour the synthesis of starch.

Trifolium subterraneum

KEYWORDS: CARBOHYDRATES, FLUORESCENCE, GREENHOUSE, METABOLITES,
PHOSPHORUS, PHOTOSYNTHETIC FEEDBACK INHIBITION

97   
Bhattacharya, N.C. 1992. Prospects of Agriculture in a Carbon
Dioxide-enriched Environment. IN: A Global Warming Forum:
Scientific, Economic and Legal Overview (R.A. Geyer, ed.), CRC
Press, Inc., Boca Raton, Florida.

The CO2 concentration in the atmosphere is steadily increasing. It
has been predicted that it will double the preindustrial level (270
umol/mol) by the year 2080. Investigations conducted on different
food and fiber crops in response to elevated CO2 in phytotrons,
glasshouses, open-top chambers, SPAR units, and Face environments
have generally showed increases in growth and yields of most of the
crops, although some plants responded negatively to increased
concentrations of CO2. The increased growth of plants in a CO2-enriched environment may rapidly deplete nutrients from the soil
and consequently, positive effects of CO2 may not persist under low
fertility levels. Similarly, interactive effects of high CO2 with
high temperature may not be good for all plant species because of
specific temperature requirements for each plant. In certain cases,
plants may remain vegetative at high temperatures throughout the
growth cycle. Therefore, cropping patterns may have to be modified
with the increase in atmospheric temperature in the future world of
high CO2. Interestingly, water use efficiency of plants in a CO2-enriched environment may have beneficial effects in tropical and
subtropical regions of the world where water is limited for crop
production. Elevated CO2 in the atmosphere results in increased
concentrations of carbohydrates and 'dilution' of other metabolites
such as chlorophyll, proteins, amino acids, carotene and reduced
nutrients in plant tissues. Increasing atmospheric CO2 may alter
plant/herbivore interactions. The impact of leaf-eating herbivores
may increase as the level of atmospheric CO2 rises. Furthermore, C3
weeds may grow faster than C4 crops of agricultural importance in
a CO2-enriched environment, and vice versa. In unmanaged
ecosystems, these effects of elevated CO2 may cause marked changes.

KEYWORDS: AGRICULTURE, CARBOHYDRATES, HERBIVORY, NUTRITION,
PHOTOSYNTHESIS, REVIEW, TEMPERATURE, WATER STRESS, WEEDS

98   
Bhattacharya, N.C., S. Bhattacharya, and B.R. Strain. 1989. Isozyme
Polymorphism during Rooting at Elevated CO2. HortScience 24:302-305.

The effects of CO2 enrichment and IAA on adventitious root
formation of hypocotyl cuttings of Impatiens balsamina L.
'Camellia' were examined. Root numbers increased significantly at
675 and 1000 uL CO2/L compared to 350 uL/L. In the presence of IAA,
the number of roots increased at 675 and 1000 uL CO2/L and the
effect was most pronounced with 5 ug IAA/ml at 675 uL CO2/L. IAA-treated cuttings, compared to those in deionized water, exhibited
slightly increased intensities of some of the isoperoxidases
coinciding with root initiation and development in a CO2-enriched
atmosphere. The data also indicate that at least two isozymes of
peroxidase are associated with root development.

Impatiens balsamina

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES, GROWTH
REGULATORS, IAA, PEROXIDASE, ROOTING

99   
Bhattacharya, N.C., S. Bhattacharya, B.R. Strain, and P.K. Biswas.
1989. Biochemical Changes in Carbohydrates and Proteins of Sweet
Potato Plants (Ipomoea batatas [L.] Lam.) in Response to Enriched
CO2 Environment at Different Stages of Growth and Development.
Journal of Plant Physiology 135:261-266.

Sweet potato (Ipomoea batatas [L.] Lam., cv. Georgia Jet) plants
were grown at different CO2 concentrations (350, 675 and 1000
umol/mol) in controlled environment conditions. The effect of CO2
enrichment on carbohydrate concentrations in leaves, stems, roots
and tubers at different stages of growth and development were
investigated. The glucose, sucrose and starch concentrations in
leaves increased during 0-35 days after planting as compared to
stems and roots receiving increased CO2 concentrations. However,
starch and glucose concentrations increased significantly in tubers
during the 50-65 day interval which corresponded with rapid growth
of tubers at high CO2 concentrations. Increasing CO2 concentrations
did not raise the protein content of leaves, roots or tubers at any
stages of growth and development. CO2 enrichment increased the
soluble protein concentration in stems during the 20-50 day growth
interval which subsequently decreased at maturity.

Ipomoea batatas/sweet potato

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
STAGES, PROTEINS

100  
Bhattacharya, N.C., S. Bhattacharya, B.R. Strain, P.K. Biswas, and
M.E.M. Tolbert. 1986. An Insight into the Mechanism of Auxin Action
in Rooting Hypocotyl Cuttings of Impatiens balsamina Grown in
Phytotron under Enriched CO2 Environment. IN: Proc., Thirteenth
Annual Meeting; 3-7 Aug. 1986; St. Petersburg Beach, Florida (W.C.
Wilson, ed.), Plant Growth Regulator Society of America, Department
of Citrus, Lake Alfred, Florida, p. 92.

Impatiens balsamina

KEYWORDS: AUXIN, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
REGULATORS, ROOTING

101  
Bhattacharya, N.C., P.K. Biswas, S. Bhattacharya, N. Sionit, and
B.R. Strain. 1985. Growth and Yield Response of Sweet Potato to
Atmospheric CO2 Enrichment. Crop Science 25:975-981.

Tuber growth of sweet potato (Ipomoea batatas) is a sink that may
be limited by source capacity under present ambient CO2 levels.
Hence, sweet potato may demonstrate more response to predicted
increases in atmospheric CO2 than many other annual plants. The
present investigation was undertaken to determine the long-term
effects of CO2 enrichment on some physiological parameters, growth,
and yield, as well as on the source-sink relationship in sweet
potato at different stages of growth. Plants of the cultivar
Georgia Jet were grown from stem cuttings in a mixture of gravel
and vermiculite in controlled environment chambers at 350, 675, and
1000 uL/L CO2 and were irrigated with one-half strength Hoagland's
solution. The temperature was 28C during 14-h days and 20C during
10-h nights. The length of main stem, total branch length, number
of branches, and leaf area were increased for plants grown at 675
or 1000 uL/L CO2. The production of total dry matter of plants
increased at each harvest interval in response to CO2 enrichment
but it was greatest in 1000 uL/L CO2. Specific leaf weight also
increased with increased CO2 concentration. The number and diameter
of tubers increased at high CO2 concentration. At the final
harvest, the dry weight of roots and tubers increased 1.8 and 2.6
times in plants grown at 675 and 1000 uL/L CO2, respectively,
compared to those grown at 350 uL/L CO2. Carbon dioxide enrichment
resulted in the modulation of sink capacity to enhance the
production of tubers in sweet potato.

sweet potato/Ipomoea batatas

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, SOURCE-SINK BALANCE, TUBERS, YIELD

102  
Bhattacharya, N.C., P.P. Ghosh, S. Bhattacharya, D.R. Hileman, and
P.K. Biswas. 1988. Effects of Abscisic Acid on Rooting Stem
Cuttings of Sweet Potato in Open Top Chambers under Enriched CO2
Environment. Biologia Plantarum (Praha) 30:204-209.

Ten centimeter long stem cuttings of sweet potato (Ipomoea batatas
L. cv. Georgia Jet) with intact apex and leaves were cultured in
distilled water as well as in varying concentrations of abscisic
acid (ABA) in open top chambers at 364, 438 and 666 cm3/m3 CO2. Low
concentration of ABA promoted rooting and elongation of roots at
364 cm3/m3 CO2 while rooting was suppressed at enriched levels of
CO2. However, biomass production in shoots and roots was higher in
666 than in 364 cm3/m3 CO2.

sweet potato/Ipomoea batatas

KEYWORDS: ABA, GROWTH REGULATORS, OPEN-TOP CHAMBERS, ROOTING

103  
Bhattacharya, N.C., D.R. Hileman, P.P. Ghosh, R.L. Musser, S.
Bhattacharya, and P.K. Biswas. 1990. Interaction of Enriched CO2
and Water Stress on the Physiology of and Biomass Production in
Sweet Potato Grown in Open-top Chambers. Plant, Cell and
Environment 13:933-940.

The objective of this study was to investigate the effects of water
stress in sweet potato (Ipomoea batatas L. [Lam.] 'Georgia Jet') on
biomass production and plant-water relationships in an enriched CO2
atmosphere. Plants were grown in pots containing sandy loam soil
(Typic Paleudult) at two concentrations of elevated CO2 and two
water regimes in open-top field chambers. During the first 12 d of
water stress, leaf xylem potentials were higher in plants grown in
a CO2 concentration of 438 and 666 umol/mol than in plants grown at
364 umol/mol. The 364 umol/mol CO2 grown plants had to be rewatered
2 d earlier than the high CO2-grown plants in response to water
stress. For plants grown under water stress, the yield of storage
roots and root:shoot ratio were greater at high CO2 than at 364
umol/mol; the increase, however, was not linear with increasing CO2
concentrations. In well-watered plants, biomass production and
storage root yield increased at elevated CO2, and these were
greater as compared to water-stressed plants grown at the same CO2
concentration.

sweet potato/Ipomoea batatas

KEYWORDS: GROWTH, OPEN-TOP CHAMBERS, TUBERS, WATER STRESS

104  
Bhattacharya, S., N.C. Bhattacharya, P.K. Biswas, and B.R. Strain.
1985. Response of Cow Pea (Vigna unguiculata L.) to CO2 Enrichment
Environment on Growth, Dry-matter Production and Yield Components
at Different Stages of Vegetative and Reproductive Growth. Journal
of Agricultural Science, Cambridge 105:527-534.

This study examines the effects of increased atmospheric carbon
dioxide concentrations on vegetative and reproductive growth and
partitioning of biomass during pod and seed development of cow pea
in controlled environment chambers at 350, 675, and 1000 uL CO2/L.
The length of main stem and branches, the number of leaves and
branches, and leaf area were all greater at high CO2 than at low
CO2 concentration. The appearance of flowers was 10-12 days earlier
in high CO2 than in ambient CO2 atmosphere. The senescence of
leaves started about 7 days earlier in plants grown at 675 and 1000
uL CO2/L than in those grown at 350 uL CO2/L. The rate of leaf
senescence was more rapid in 1000 uL/L than in 675 uL CO2/L. The
dry weight of roots, stems and leaves increased with CO2
enrichment, being greater in 675 uL/L than in 1000 uL CO2/L. Plants
grown in 675 and 1000 uL/L produced more pods and seeds than in 350
uL CO2/L. Total seed weight and number of pods, as well as number
of seeds per pod, were significantly greater in CO2 enriched
atmosphere than ambient CO2 level. Although CO2 enrichment caused
a significant increase in the total number and weight of seeds as
well as pods, it did not affect the ratio of seed dry weight to the
total dry weight of above-ground plant parts (harvest index). It is
concluded from the present investigation that CO2 enrichment
significantly enhanced vegetative as well as reproductive growth
resulting in the increase in yield and early plant maturation in
this leguminous crop.

cowpea/Vigna unguiculata

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, GROWTH STAGES, REPRODUCTION, SEED PRODUCTION, YIELD

105  
Bhattacharya, S., N.C. Bhattacharya, and B.R. Strain. 1985. Rooting
of Sweet Potato Stem Cuttings under CO2-enriched Environment and
with IAA Treatment. HortScience 20:1109-1110.

Stem cuttings of sweet potato (Ipomoea batatas L. 'Georgia Jet')
with intact apex and leaves were cultured in water or in different
concentrations of IAA and were maintained in controlled environment
chambers at 350, 675, or 1000 ppm CO2. The temperature was 20C
during a 14-hr day and 14 during a 10-hr dark period. The
photosynthetic photon flux density was 550 umol/s/m2 (27.7
mol/m2/day). Elevated CO2 concentrations stimulated the production
of roots in the presence of IAA, and this effect was more
pronounced at 675 ppm than at 1000 ppm CO2 atmosphere.

sweet potato/Ipomoea batatas

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH REGULATORS, IAA,
ROOTING

106  
Bhattacharya, S., J.F. Eatman, P.K. Biswas, and M.E.M. Tolbert.
1988. CO2 Enrichment and its Relationship to Bioconversion of
Cellulosic Biomass of Sweet Potato (Ipomoea batatas L.) into
Fermentable Sugars. Biomass 15:259-268.

Sweet potatoes (Ipomoea batatas L. (Lam.) 'Georgia-Jet') were grown
in open field plots and open top chambers at CO2 concentrations of
354, 531, 506 and 659 uL/L for 90 days. The leaves and stems after
the harvest were used as substrates for the production of
fermentable sugars. Elevated CO2 concentrations increased the
cellulose content of stems, being most pronounced at 506 uL/L.
Hemicellulose content of leaves and stems as well as lignin content
of stems decreased as a result of CO2 enrichment. The increase in
cellulosic biomass in plants grown in CO2 enriched environment
resulted in increased conversion of cellulose into fermentable
sugars. The saccharification was greater in stems than in leaves.
It was also found that chemical pretreatment of stems and leaves
enhanced the enzymatic hydrolysis and the yields of glucose were
higher than those from untreated stems and leaves.

sweet potato/Ipomoea batatas

KEYWORDS: BIOMASS CONVERSION, OPEN-TOP CHAMBERS

107  
Biswas, P.K., D.R. Hileman, J.R. Allen, N.C. Bhattacharya, J.Y. Lu,
R.D. Pace, and H.H. Rogers. 1985. Field Studies of Sweet Potatoes
and Cowpeas in Response to Elevated Carbon Dioxide, 022 in Green
Report Series, Response of Vegetation to Carbon Dioxide. U.S. Dept.
of Energy, Carbon Dioxide Research Division, Washington, D.C., and
Tuskegee University, Tuskegee, Alabama.

sweet potato/cowpea/Ipomoea batatas/Vigna unguiculata

KEYWORDS: CONDUCTANCE, CROPS, GROWTH, NITROGEN, NITROGEN FIXATION,
OPEN-TOP CHAMBERS, YIELD

108  
Biswas, P.K., D.R. Hileman, N.C. Bhattacharya, P.P. Ghosh, S.
Bhattacharya, J.H. Johnson, and N.T. Mbikayi. 1986. Growth, Yield
and Plant Water Relationships in Sweet Potatoes in Response to
Carbon Dioxide Enrichment, 030 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, Washington, D.C., and Tuskegee University,
Tuskegee, Alabama.

sweet potato/Ipomoea batatas

KEYWORDS: GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
WATER STATUS, WATER STRESS, YIELD

109  
Black, C.C., Jr. 1986. Effects of CO2 Concentration on
Photosynthesis and Respiration of C4 and CAM Plants. IN:
Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 29-40.

With C4 plants, CO2 enrichment will have a small, probably less
than 25%, enhancement of plant growth or biomass production.
However, water use efficiency will increase severalfold with a
doubling or tripling of air CO2 levels. With CAM plants, CO2
enrichment should be done at night. Little daytime CO2 uptake
occurs in most CAM plants, but enrichment late in the day and at
night likely will be beneficial to growth. No long-term growth work
has been done with CO2 enrichment and the production of CAM plants,
but the available research indicates night enrichment should be
beneficial.

KEYWORDS: C4, CAM, ENZYMES, METABOLITES, PHOTOSYNTHESIS,
RESPIRATION, REVIEW

110  
Bolin, B., B.R. Doos, J. Jager, and R.A. Warrick (eds.). 1986. The
Greenhouse Effect, Climatic Change, and Ecosystems. John Wiley &
Sons, New York.

KEYWORDS: CLIMATE, CO2 ENRICHMENT STUDIES, REVIEW

111  
Boone, M.Y.L., R.W. Rickman, and F.D. Whisler. 1990. Leaf
Appearance Rates of Two Winter Wheat Cultivars under High Carbon
Dioxide Conditions. Agronomy Journal 82:718-724.

The mechanisms describing leaf appearance and tillering are vital
to the modeling of wheat canopy development. How these two factors
will be affected by increasing global atmospheric [CO2] in cool or
warm climates is not fully understood. Two southeastern USA adapted
wheat (Triticum aestivum L.) cultivars, Coker 762 and Stacy, were
grown under nearly nonlimiting conditions including elevated [CO2]
(600 uL/L) and under six air temperature regimes (ranging from 4/-1
to 18/7C d/night and progressively increasing to 16/4 to 29/18C
d/night during the season) to observe leaf and tiller appearance
rates and to compare tillering rates to those predicted by the
Fibonacci series as approximated by Binet's equation. Both
cultivars exhibited an abrupt one-time change in their phyllochron
interval for all six temperatures. This change occurred just prior
to double ridge formation. The vegetative growth phase phyllochron
interval of the two cultivars was significantly different only in
the 21/10C temperature treatment. In the two lowest temperature
treatments (16/4 and 18/7C), the cultivars differed in phyllochron
interval during the reproductive growth phase. The tillering rate
of wheat followed closely the theoretical development predicted by
Binet's equation during the vegetative phase of development.

wheat/Triticum aestivum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH MODEL, GROWTH
STAGES, TEMPERATURE

112  
Bottner, P., and M.M. Couteaux. 1991. Effect of Plant Activity on
Decomposition: Soil-plant Interactions in Response to Increasing
Atmospheric CO2 Concentration. IN: Ecosystem Research Report No.1,
Decomposition and Accumulation of Organic Matter in Terrestrial
Ecosystems: Research Priorities and Approaches; 1991 Sept. 2-4;
Doorwerth, The Netherlands (N. van Breemen, ed.).

KEYWORDS: LITTER DECOMPOSITION, LITTER QUALITY, MODELING,
RHIZOSPHERE

113  
Bottner, P., and M.M. Couteaux. 1992. Reponse de la Matiere
Organique des Sols. IN: Les Recherches en France sur les
Ecosystemes Forestiers (G. Landmann, ed.), Ministere de
l'Agriculture et de la Foret, Paris, pp. 25-26.

In French.

KEYWORDS: SOIL MICROORGANISMS

114  
Bottomley, P.A., H.H. Rogers, and S.A. Prior. 1993. NMR Imaging of
Root Water Distribution in Intact Vicia faba L. Plants in Elevated
Atmospheric CO2. Plant, Cell and Environment 16:335-338.

The effect of elevated atmospheric CO2 on water distribution in the
intact roots of Vicia faba L. bean seedlings grown in natural soil
was studied noninvasively with proton (1-H) nuclear magnetic
resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric
CO2 enriched air at 675 cm3/m3 produced significant increase in
water imaged in upper roots, hypogeal cotyledons and lower stems in
response to a short-term drying-stress cycle. Above ground, drying
produced negligible stem shrinkage and stomatal resistance was
unchanged. In contrast, the same drying cycle caused significant
depletion of water imaged in the same upper root structures in
control plants subject to ambient CO2 (350 m3/m3), and stem
shrinkage and increased stomatal resistance. The results suggest
that inhibition of transpiration caused by elevated CO2 does not
necessarily result in attenuation of water transport from lower
root structures. Inhibition of water loss from upper roots and
lower stem in elevated CO2 environments may be a mitigating factor
in assessing deleterious effects of greenhouse changes on crops
during periods of dry climate.

Vicia faba/broad bean

KEYWORDS: NMR IMAGING, WATER STATUS

115  
Bouwman, A.F. . 1990. Soils and the Greenhouse Effect. John Wiley
& Sons, Ltd., New York.

KEYWORDS: SOIL MICROORGANISMS, SOIL RESPIRATION

116  
Bowes, G. 1991. Growth at Elevated CO2: Photosynthetic Responses
Mediated through Rubisco. Plant, Cell and Environment 14:795-806.

The global uptake of CO2 in photosynthesis is about 120 gigatons
(GT) of carbon per year. Virtually all passes through one enzyme,
ribulose bisphosphate carboxylase/oxygenase (rubisco), which
initiates both the photosynthetic carbon reduction, and
photorespiratory carbon oxidation, cycles. Both CO2 and O2 are
substrates; CO2 also activates the enzyme. In C3 plants, rubisco
has a low catalytic activity, operates below its Km(CO2), and is
inhibited by O2. Consequently, increases in the CO2/O2 ratio
stimulate C3 photosynthesis and inhibit photorespiration. CO2
enrichment usually enhances the productivity of C3 plants, but the
effect is marginal in C4 species. It also causes acclimation in
various ways: anatomically, morphologically, physiologically or
biochemically. So, CO2 exerts secondary effects in growth
regulation, probably at the molecular level, that are not
predictable from its primary biochemical role in carboxylation.
After an initial increase with CO2 enrichment, net photosynthesis
often declines. This is a common acclimation phenomenon, less so in
field studies, that is ultimately mediated by decline in rubisco
activity, though the RuBP/Pi-regeneration capacities of the plant
may play a role. The decline is due to decreased rubisco protein,
activation state, and/or specific activity, and it maintains the
rubisco fixation and RuBP/Pi-regeneration capacities in balance.
Carbohydrate accumulation is sometimes associated with reduced net
photosynthesis, possibly causing feedback inhibition of the
RuBP/Pi-regeneration capacities, or chloroplast disruption. As
exemplified by field-grown soybeans and salt marsh species, a
reduction in net photosynthesis and rubisco activity is not
inevitable under CO2 enrichment. Strong sinks or rapid
translocation may avoid such acclimation responses. Over geological
time, aquatic autotrophs and terrestrial C4 and CAM plants have
genetically adapted to a decline in the external CO2/O2 ratio, by
the development of mechanisms to concentrate CO2 internally; thus
circumventing O2 inhibition of rubisco. Here rubisco affinity for
CO2 is less, but its catalytic activity is greater, a situation
compatible with a high-CO2 internal environment. In aquatic
autotrophs, the CO2 concentrating mechanisms acclimate to the
external CO2, being suppressed at high CO2. It is unclear, whether
a doubling in atmospheric CO2 will be sufficient to cause a de-adaptive trend in the rubisco kinetics of future C3 plants,
producing higher catalytic activities.

KEYWORDS: ENZYMES, PHOTORESPIRATION, PHOTOSYNTHESIS, PHOTOSYNTHETIC
FEEDBACK INHIBITION, REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASE

117  
Bowes, G., A.J. Rowland-Bamford, and L.H. Allen Jr. 1990.
Regulation of Rubisco Activity of Carboxyarabinitol-1-Phosphate and
Elevated Atmospheric CO2 in Rice and Soybean Cultivars. IN:, Vol.
III (M. Baltscheffsky, ed.), Current Research in Photosynthesis,
Kluwer Academic Publishers, The Netherlands, pp. 399-402.

The degree of rubisco dark inhibition not only shows species, but
also intercultivar, and development differences. As with total
activity, rubisco activation is developmentally influenced; so for
rice, assays of whole leaf extracts integrate various rubisco
states. The growth CO2 and temperature have interactive effects on
the activity, activation, and dark inhibition of rice rubisco.
Detrimental temperature effects on total rubisco activity may be
compounded by elevated atmospheric CO2.

rice/Oryza sativa/soybean/Glycine max

KEYWORDS: CALVIN CYCLE ENZYMES, CONTROLLED ENVIRONMENT CHAMBERS,
CULTIVAR RESPONSES, ENZYMES, GROWTH STAGES, LIGHT, PHOTOSYNTHETIC
FEEDBACK INHIBITION, RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE
BISPHOSPHATE CARBOXYLASE, SPAR UNITS, TEMPERATURE

118  
Bowman, W.D., and B.R. Strain. 1987. Interaction between CO2
Enrichment and Salinity Stress in the C4 Non-halophyte Andropogon
glomeratus (Walter) BSP. Plant, Cell and Environment 10:267-270.

Increasing atmospheric CO2 may result in alleviation of salinity
stress in salt-sensitive plants. In order to assess the effect of
enriched CO2 on salinity stress in Andropogon glomeratus, a C4 non-halophyte found in the higher regions of salt marshes, plants were
grown at 350, 500 and 650 cm3/m3 CO2 with 0 or 100 mol/m3 NaCl
watering treatments. Increases in leaf area and biomass with
increasing CO2 were measured in salt-stressed plants, while
decreases in these same parameters were measured in non-salt-stressed plants. Tillering increases substantially with increasing
CO2 in salt-stressed plants, resulting in the increased biomass.
Six weeks following initiation of treatments, there was no
difference in photosynthesis on a leaf area basis with increasing
CO2 in salt-stressed plants, although short-term increases probably
occurred. Stomatal conductance decreased with increasing CO2 in
salt-stressed plants, resulting in higher water-use efficiency, and
may have improved the diurnal water status of the plants.
Concentrations of Na+ and Cl- were higher in salt- stressed plants,
while the converse was found for K+. There were no differences in
leaf ion content between CO2 treatments in the salt-stressed
plants. Decreases in photosynthesis in salt-stressed plants
occurred primarily as a result of decreased internal (non-stomatal)
conductance.

Andropogon glomeratus

KEYWORDS: C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, SALT STRESS

119  
Bown, A.W. 1985. CO2 and Intracellular pH. Plant, Cell and
Environment 8:459-465.

The experimental determination of cytoplasmic and vacuolar pH
values is discussed. Despite variation in these values evidence
indicates that intracellular pH values are normally regulated
within narrow limits. The regulatory mechanisms proposed involve
the metabolic consumption of OH- and the active efflux of H+. The
evidence for intracellular pH modification in response to CO2
hydration and the production of HCO3- and H+ is examined.
Theoretical calculations and experimental data indicate that CO2
concentrations as high as 5% will lower intracellular pH.
Conversely, variation in CO2 levels around atmospheric
concentrations is unlikely to perturb intracellular pH. High CO2
levels are found in bulky tissues, and flooded root systems.
Evidence is presented that the slow diffusion of dissolved CO2
compared to gaseous CO2 results in its accumulation. It is proposed
that the accumulation of respiratory CO2 may reduce intracellular
pH values when plant tissues, cells or protoplasts are maintained
in a liquid culture medium. Finally, the possible role of dark CO2
fixation and organic acid synthesis in the regulation of
intracellular pH is examined.

KEYWORDS: INTRACELLULAR PH, PHOSPHOENOLPYRUVATE CARBOXYLASE, REVIEW

120  
Bravdo, B. 1986. Effect of CO2 Enrichment on Photosynthesis of C3
Plants. IN: Physiology, Yield, and Economics, Vol. II (H.Z. Enoch
and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse
Crops, CRC Press, Inc., Boca Raton, Florida, pp. 13-27.

KEYWORDS: C3, CONDUCTANCE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHESIS
MODEL, REVIEW

121  
Breen, P.J., J.D. Hesketh, and D.B. Peters. 1986. Field
Measurements of Leaf Photosynthesis of C3 and C4 Species under High
Irradiance and Enriched CO2. Photosynthetica 20:281-285.

Leaf net photosynthetic CO2 exchange rates (Pn) were measured on
field-grown C3 (Glycine max L. Merr., Gossypium hirsutum L.,
Phaseolus vulgaris L., and Vigna unguiculata L. and C4 (Amaranthus
hybridus L.) dicotyledonous species at available sunlight,
available sunlight plus an additional 1000 umol (photon)/m2/s at
the bottom surface of the leaf, and in CO2 air mixtures of 370,
780, 1500 and 3000 cm3/m3. Three kinds of Pn:CO2 responses were
encountered: (1) hyperbolic up to 3000 cm3/m3, (2) hyperbolic up to
1500 cm3/m3, with less than predicted Pn at 300 cm3/m3, and (3)
almost no response between 370 and 3000 cm3/m3 CO2 in air. The
shapes of these response curves varied with growth stage. In
general, leaves of all C3 species approached the same CO2 and
radiant energy saturation Pn value of 70-75 umol CO2/m2/s, but some
required higher CO2 concentrations than others before such rates
were attained.

Glycine max/soybean/Gossypium hirsutum/cotton/Phaseolus
vulgaris/bean/Vigna unguiculata/cowpea/Amaranthus hybridus/pigweed

KEYWORDS: C3, C4, GROWTH STAGES, LEAF PHOTOSYNTHESIS, LIGHT

122  
Brooks, A., K.C. Woo, and S.C. Wong. 1988. Effects of Phosphorus
Nutrition on the Response of Photosynthesis to CO2 and O2,
Activation of Ribulose Bisphosphate Carboxylase and Amounts of
Ribulose Bisphosphate and 3-Phosphoglycerate in Spinach Leaves.
Photosynthesis Research 15:133-141.

Phosphorus-deficient spinach plants were grown by transferring them
to nutrient solutions without PO4. Photosynthetic rates were
measured at a range of intercellular CO2 partial pressures from 50-500 ubar and then the leaves were freeze-clamped in situ to measure
ribulose bisphosphate carboxylase (Rubisco) activity and metabolite
concentrations. Compared with control leaves, deficient leaves had
significantly lower photosynthetic rates, percentage activation of
Rubisco, and amounts of ribulose bisphosphate and 3-phosphoglycerate at all CO2 partial pressures. After feeding 10 mM
PO4 to the petioles of detached deficient leaves, all these
measurements increased within 2 hours. At atmospheric CO2 partial
pressure the photosynthetic rate was stimulated in 19 mbar O2
compared with 200 mbar. At higher CO2 partial pressures this
stimulation was less but the percentage stimulation in deficient
leaves was no different from controls in either CO2 partial
pressure. It was concluded that phosphorus deficiency affects both
Rubisco activity and the capacity for ribulose bisphosphate
regeneration, and possible causes are discussed.

spinach/Spinacia oleracea

KEYWORDS: LEAF PHOTOSYNTHESIS, METABOLITES, NUTRITION, OXYGEN,
PHOSPHORUS, RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE BISPHOSPHATE
CARBOXYLASE

123  
Brown, K., and K.O. Higginbotham. 1986. Effects of Carbon Dioxide
Enrichment and Nitrogen Supply on Growth of Boreal Tree Seedlings.
Tree Physiology 2:223-232.

The effects of two levels of atmospheric carbon dioxide (350 uL/L,
750 uL/L) and three levels of nitrogen (15.5 mM, 1.55 mM, 0.155 mM
N) on biomass accumulation and partitioning were examined in aspen
(Populus tremuloides Michx.) and white spruce (Picea glauca
(Moench) Voss) seedlings grown in controlled environment rooms for
100 days after germination. Nitrogen supply had pronounced effects
on biomass accumulation, height, and leaf area of both species.
Root weight ratio of white spruce was significantly increased at
the lowest level of nitrogen, whereas RWR of aspen did not change
much with increasing levels of nitrogen. Carbon dioxide enrichment
significantly increased (1) the leaf and total biomass of spruce
seedlings grown in the high-N regime, (2) the RWR of seedlings in
the medium-N regime, and (3) the root biomass of seedlings in the
low-N regime after 100 days. Carbon dioxide enrichment of aspen
temporarily increased biomass and height in all three nitrogen
regimes. Root, stem, and leaf mass, height, and leaf area of aspen
were increased only at the 30-day harvest in the high-N treatment
and at 50 and 60 days in the low-N treatment. Height, stem biomass,
and leaf biomass of aspen seedlings were significantly increased by
CO2 enrichment after 40 days in the medium-N treatment. These
effects did not persist, possibly because of the onset of mineral
nutrient supply limitations with increasing plant size.

Picea glauca/white spruce/Populus tremuloides/aspen

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
GROWTH ANALYSIS, NITROGEN, NUTRITION, TREES

124  
Brown, K.R. 1989. Effects of Nitrogen Availability and Atmospheric
Carbon Dioxide Enrichment on Growth, Water Use, and Nutrition of
Seedlings of Boreal Trees. Doctoral Dissertation, University of
Alberta, Dissertation Abstracts Vol. 50:07-B, p.2703.

Seedlings of two boreal tree species were studied. Populus
tremuloides dominates early successional, relatively fertile sites;
Picea glauca dominates later successional sites with slower rates
of nutrient turnover. Seedlings were grown for 100 days at ambient
(350 uL/L) or high (750 uL/L) levels of atmospheric CO2 and
fertilized with high-N (15.5 mM-N, medium-N (1.55 mM-N), or low-N
(0.155 mM-N) solutions. High CO2 increased leaf and total mass of
high-N Picea, and root mass of low-N Picea after 100 days. High CO2
increased mass, height, and leaf area of Populus at 30 days in the
high-N regime, at 40 days in the medium-N regime, and at 60 days in
the low-N regime; in each treatment, effects did not persist to the
following harvest. High CO2 accelerated the time-dependent
decreases in concentrations of N and P (all N treatments) and Ca
and Mg (high-N and medium-N treatments) to deficient levels,
preventing the continuation of growth enhancement. In a second
experiment, the effects of CO2 enrichment to 650 uL/L were examined
with plant N concentrations held constant at high or low levels
using the relative addition technique of nutrient supply. In the
high-N regime, elemental concentrations were higher in P.
tremuloides than in P. glauca and were unaffected by CO2
enrichment. Relative growth rates (RGR) and net assimilation rates
(NAR) of Picea (high-N regime) and of Populus (high-N, low-N)
increased with CO2 enrichment. The absolute effect of CO2
enrichment on NAR increased with foliar N content and was greater
in Populus at a given foliar concentration of N. Nitrogen status
had greater effects on root:shoot ratios of Picea than of Populus;
CO2 enrichment did not affect root:shoot ratios in either species.
High CO2 reduced transpiration by 60% in Populus under both N
regimes, but did not affect transpiration by Picea. Nitrogen
productivity of Populus may have increased with CO2 enrichment.
Thus, methods of nutrient supply may affect plant nutrient status
over time and therefore affect plant response to CO2 enrichment.
The effect of CO2 enrichment increases with nutrient status and is
potentially greater in early successional boreal trees, given
adequate nutrient supplies.

Populus tremuloides/Picea glauca

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, GROWTH ANALYSIS,
NITROGEN, NUTRITION, SUCCESSIONAL COMMUNITIES, TREES

125  
Brown, K.R. 1991. Carbon Dioxide Enrichment Accelerates the Decline
in Nutrient Status and Relative Growth Rate of Populus tremuloides
Michx. Seedlings. Tree Physiology 8:161-173.

Populus tremuloides

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS,
NUTRITION, TREES

126  
Brugink, G.T., H.G. Wolting, J.H.A. Dassen, and V.G.M. Bus. 1988.
The Effect of Nitric Oxide Fumigation at Two CO2 Concentrations on
Net Photosynthesis and Stomatal Resistance of Tomato (Lycopersicon
lycopersicum L. cv. Abunda). New Phytologist 110:185-191.

Net photosynthesis of 5-week-old tomato plants (Lycopersicon
lycopersicum L. cv. Abunda was measured in clean air or with NO
fumigation, for five consecutive days under simulated winter
glasshouse conditions: temperature 22C, VPD 0.4 kPa, irradiance 30
W/m2 and daylength 8-9 h. NO concentrations applied were 0 or 1
uL/L in combination with CO2 concentrations of 350 or 1000 uL/L. A
reduction in net photosynthesis due to NO became apparent in the
third day of measurement. On the fifth day this reduction was 38%
of the control at 350 uL/L CO2 and 24% at 1000 uL/L CO2. The
increase in photosynthesis due to CO2 enrichment was initially 50%;
this effect was strongly reduced after 5 d in the presence of NO.
Plants did not recover in the dark after the daily fumigation
treatment, the level to which photosynthesis was reduced at the end
of the day being the level at which it started the next day. The
decrease in photosynthesis could not be explained by an increased
stomatal resistance, and the plants did not show visible symptoms
of injury. Practical implications of the results are discussed.

Lycopersicon lycopersicum

KEYWORDS: AIR POLLUTION, CANOPY PHOTOSYNTHESIS, CONDUCTANCE,
GREENHOUSE, NITROGEN OXIDES, PHOTOSYNTHESIS

127  
Brugnoli, E., K.T. Hubick, S. von Caemmerer, S.C. Wong, and G.D.
Farquhar. 1988. Correlation between the Carbon Isotope
Discrimination in Leaf Starch and Sugars of C3 Plants and the Ratio
of Intercellular and Atmospheric Partial Pressures of Carbon
Dioxide. Plant Physiology 88:1418-1424.

Carbon isotope discrimination ([delta]) was analyzed in leaf starch
and soluble sugars, which represent most of the recently fixed
carbon. Plants of three C3 species (Populus nigra L. x P. deltoides
Marsh., Gossypium hirsutum L. and Phaseolus vulgaris L.) were kept
in the dark for 24 hours to decrease contents of starch and sugar
in leaves. Then gas exchange measurements were made with constant
conditions for 8 hours, and subsequently starch and soluble sugars
were extracted for analysis of carbon isotope composition. The
ratio of intercellular, Pi, and atmospheric, Pa, partial pressures
of CO2 was calculated from gas exchange measurements, integrated
over time and weighted by assimilation rate, for comparison with
the carbon isotope ratios in soluble sugars and starch. Carbon
isotope discrimination in soluble sugars correlated strongly
(r=0.93) with Pi/Pa in all species, as did delta in leaf starch
(r=0.84). Starch was found to contain significantly more 13C than
soluble sugar, and possible explanations are discussed. The strong
correlation found between [delta] and Pi/Pa suggests that carbon
isotope analysis in leaf starch and soluble sugars may be used for
monitoring, indirectly, the average of Pi/Pa weighted by CO2
assimilation rate, over a day. Because Pi/Pa has a negative
correlation with transpiration efficiency (mol CO2/mol H20) of
isolated plants, delta in starch and sugars may be used to predict
differences in this efficiency. This new method may be useful in
ecophysiological studies and in selection for improved
transpiration efficiency in breeding programs for C3 species.

Populus nigra/Populus deltoides/Gossypium hirsutum/Phaseolus
vulgaris

KEYWORDS: CARBOHYDRATES, CI:CA, GREENHOUSE, ISOTOPE DISCRIMINATION,
LEAF PHOTOSYNTHESIS

128  
Bugbee, B.G., and F.B. Salisbury. 1988. Exploring the Limits of
Crop Productivity. I. Photosynthetic Efficiency of Wheat in High
Irradiance Environments. Plant Physiology 88:869-878.

The long-term vegetative and reproductive growth rates of a wheat
crop (Triticum aestivum L.) were determined in three separate
studies (24, 45, and 79 days) in response to a wide range of
photosynthetic photon fluxes (PPF, 400-2080 micromoles per square
meter per second; 22-150 moles per square meter per day; 16-20-hour
photoperiod) in a near-optimum, controlled-environment. The CO2
concentration was elevated to 1200 micromoles per mole, and water
and nutrients were supplied by liquid hydroponic culture. An
unusually high plant density (2000 plants per square meter) was
used to obtain high yields. Crop growth rate and grain yield
reached 138 and 60 grams per square meter per day, respectively;
both continued to increase up to the highest integrated daily PPF
level, which was three times greater than a typical daily flux in
the field. The conversion efficiency of photosynthesis (energy in
biomass/energy in photosynthetic photons) was over 10% at low PPF
but decreased to 7% as PPF increased. Harvest index increased from
41 to 44% as PPF increased. Yield components for primary,
secondary, and tertiary culms were analyzed separately. Tillering
produced up to 7000 heads per square meter at the highest PPF
level. Primary and secondary culms were 10% more efficient (higher
harvest index) than tertiary culms; hence cultural, environmental,
or genetic changes that increase the percentage of primary and
secondary culms might increase harvest index and thus grain yield.
Wheat is physiologically and genetically capable of much higher
productivity and photosynthetic efficiency than has been recorded
in a field environment.

wheat/Triticum aestivum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH RATE, HARVEST
INDEX, LIGHT, YIELD

129  
Bultot, F., G.L. Dupriez, and D. Gellens. 1988. Estimated Annual
Regime of Energy-Balance Components, Evapotranspiration and Soil
Moisture for a Drainage Basin in the Case of a CO2 Doubling.
Climatic Change 12:39-56.

Assuming a doubling of the atmospheric CO2 concentration,
parameters of an empirical formula for calculating the daily net
terrestrial radiation under the climatic conditions of Belgium are
determined. The developed method takes into account information
yielded by climate models about the CO2 impact. Annual regimes of
the energy balance components are calculated for a drainage basin
in Belgium. A daily step conceptual hydrological model (developed
at the Royal Meteorological Institute of Belgium) was run to
estimate the effective evapotranspiration and the soil moisture in
the 2xCO2 case; results of this simulation are compared with the
present day condition.

KEYWORDS: CLIMATE MODEL, HYDROLOGIC MODEL, RADIATION, SIMULATION

130  
Bunce, J.A. 1990. Short- and Long-Term Inhibition of Respiratory
Carbon Dioxide Efflux by Elevated Carbon Dioxide. Annals of Botany
65:637-642.

Dark carbon dioxide efflux rates of recently fully expanded leaves
and whole plants of Amaranthus hypochondriacus L., Glycine max (L.)
Merr., and Lycopersicon esculentum Mill. grown in controlled
environments at 35 and 70 Pa carbon dioxide pressure were measured
at 35 and 70 Pa carbon dioxide pressure. Harvest data and whole-plant 24-h carbon dioxide exchange were used to determine relative
growth rates, net assimilation rates, leaf area ratios, and the
ratio of respiration to photosynthesis under the growth conditions.
Biomass at a given time after planting was greater at the higher
carbon dioxide pressure in G. max and L. esculentum, but not the C4
species, A. hypochondriacus. Relative growth rates for the same
range of masses were not different between carbon dioxide
treatments in the two C3 species, because higher net assimilation
rates at the higher carbon dioxide pressure were offset by lower
leaf area ratios. Whole plant carbon dioxide efflux rates per unit
of mass were lower in plants grown and measured at the higher
carbon dioxide pressure in both G. max and L. esculentum, and were
also smaller in relation to daytime net carbon dioxide influx.
Short-term responses of respiration rate to carbon dioxide pressure
were found in all species, with carbon dioxide efflux rates of
leaves and whole plants lower when measured at higher carbon
dioxide pressure in almost all cases.

tomato/soybean/Lycopersicon esculentum/Glycine max/Amaranthus
hypochondriacus/amaranth

KEYWORDS: C3, C4, CANOPY PHOTOSYNTHESIS, GROWTH ANALYSIS,
RESPIRATION

131  
Bunce, J.A. 1992. Light, Temperature and Nutrients as Factors in
Photosynthetic Adjustment to an Elevated Concentration of Carbon
Dioxide. Physiologia Plantarum 86:173-179.

The short-term stimulation of the net rate of carbon dioxide
exchange of leaves by elevated concentrations of CO2 usually
observed in C3 plants sometimes does not persist. Experiments were
conducted to test whether the patterns of response to the
environment during growth were consistent with the hypothesis that
photosynthetic adjustment to elevated CO2 concentration is due to
(1) feedback inhibition or (2) nutrient stress. Soybean [Glycine
max (L.) Merr. cv. Williams] and sugar beet (Beta vulgaris L. cv.
Mono Hye-4) were grown from seed at 350 and 700 uL/L CO2 at 20 and
25C, at a photon flux density of 0.5 and 1.0 mmol/m2/s and with
three nutrient regimes until the third trifoliate leaf of soybean
or the sixth leaf of sugar beet had finished expanding. Net rates
of CO2 exchange of the most recently expanded leaves were then
measured at both 350 and 700 uL/L CO2. Plants grown at the elevated
CO2 concentration had net rates of leaf CO2 exchange which were
reduced by 33% in sugar beet and 23% in soybean when measured at
350 uL/L CO2 and when averaged over all treatments. Negative
photosynthetic adjustment to elevated CO2 concentration was not
greater at 20 than at 25C, was not greater with limiting
nutrients. Furthermore, in soybean, negative photosynthetic
adjustment could be induced by a single night at elevated CO2
concentration, with net rates of CO2 exchange the next day equal to
those of leaves of plants grown from seed at the elevated
concentration of CO2. These patterns do not support either the
feedback-inhibition or the nutrient-stress hypothesis of
photosynthetic adjustment to elevated concentrations of CO2.

soybean/Glycine max/sugar beet/Beta vulgaris

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, PHOTOSYNTHETIC FEEDBACK
INHIBITION, TEMPERATURE

132  
Bunce, J.A. 1992. Stomatal Conductance, Photosynthesis and
Respiration of Temperate Deciduous Tree Seedlings Grown Outdoors at
an Elevated Concentration of Carbon Dioxide. Plant, Cell and
Environment 15:514-549.

Seedlings of temperate deciduous tree species were grown outdoors
at ambient and at an elevated concentration of carbon dioxide to
examine how aspects of their gas exchange would be altered by
growth at elevated carbon dioxide concentration. Leaf conductances
to water vapour and net carbon dioxide exchange rates were
determined periodically near midday. Whole-plant carbon dioxide
efflux rates in darkness were also determined. The stomatal
conductance of leaves of plants grown and measured at 700 cm3/m3
carbon dioxide did not differ from that of plants grown and
measured at 350 cm3/m3 in Malus domestica, Quercus prinus and
Quercus robur at any measurement time. In Acer saccharinum, lower
conductances occurred for plants grown and measured at elevated
carbon dioxide concentration only at measurement temperature above
33C. Photosynthetic adjustment to elevated carbon dioxide
concentration was evident only in Q. robur. All species examined
had lower rates of dark respiration per unit of mass when grown and
measured at elevated carbon dioxide concentration.

Acer rubrum/Acer saccharinum/Quercus prinus/Quercus robur/Malus
domestica

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, RESPIRATION, TREES

133  
Bunce, J.A. 1993. Effects of Doubled Atmospheric Carbon Dioxide
Concentration on the Responses of Assimilation and Conductance to
Humidity. Plant, Cell and Environment 16:189-197.

Experiments were performed to determine if growth at elevated
partial pressure of CO2 altered the sensitivity of leaf water
vapour conductance and rate of CO2 assimilation to the leaf-to-air
difference in the partial pressure of water vapour (delta w).
Comparisons were made between plants grown and measured at 350 and
700 uPa/Pa partial pressure of CO2 for amaranth, soybean and
sunflower grown in controlled environment chambers, soybean grown
outdoors in pots, and orchard grass grown in field plots. In
amaranth, soybean and orchard grass, both the absolute and the
relative sensitivity of conductance to delta w at the leaf surface
were less in plants grown and measured at elevated CO2. In
sunflower, there was no change in the sensitivity of conductance to
delta w for the two CO2 partial pressures. Tests in soybeans and
amaranth showed that the change in sensitivity resulted from
elevated CO2 during the measurement of the delta w response.
Assimilation rate of CO2 was not altered by delta w in amaranth,
which has C4 metabolism. In sunflower, the assimilation rate of
plants grown and measured at elevated CO2 was insensitive to delta
w, consistent with the response of assimilation rate to
intercellular CO2 partial pressure in the prevailing range. In
soybean, the sensitivity of assimilation rate to delta w was not
different between CO2 treatments, in contrast to what would be
expected from the response of assimilation rate to intercellular
CO2 partial pressure.

Amaranthus hypochondriacus/amaranth/Dactylis
glomerata/orchardgrass/Glycine max/soybean/Helianthus
annuus/sunflower

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, OUTDOOR GROWTH CHAMBERS, TRANSPIRATION, VPD

134  
Bunce, J.A., and F. Caulfield. 1991. Reduced Respiratory Carbon
Dioxide Efflux During Growth at Elevated Carbon Dioxide in Three
Herbaceous Perennial Species. Annals of Botany 67:325-330.

Long-term effects of elevated carbon dioxide on respiration were
investigated in Dactylis glomerata, Lolium perenne and Medicago
sativa in controlled environment chambers, and in D. glomerata and
M. sativa in field plots. Plants were grown at 35 and 70 Pa carbon
dioxide pressure. Dark carbon dioxide efflux rates were determined
for whole plants during the first 40 d of growth in the controlled
environment chambers, and for the ecosystems during the first year
of growth in the field. Elevated carbon dioxide increased the rate
of biomass accumulation in all species. In controlled environments,
efflux rates per unit of biomass were 30-40% lower in the elevated
carbon dioxide treatment in L. perenne and  M. sativa at similar
relative growth rates. In D. glomerata, efflux rates did not differ
between treatments, but relative growth rate was 50% higher at the
elevated carbon dioxide. In the field, M. sativa plots at elevated
carbon dioxide had 15% less carbon dioxide efflux per unit of
ground area, in spite of greater biomass production. Plots with D.
glomerata had equal rates of carbon dioxide efflux, but the plot
with elevated carbon dioxide had higher biomass production. Thus,
in all cases respiratory carbon dioxide efflux was reduced at
elevated carbon dioxide, at least relative to the biomass
accumulated.

Dactylis glomerata/Lolium perenne/Medicago sativa

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, GROWTH ANALYSIS,
OPEN-TOP CHAMBERS, RESPIRATION

135  
Burch, D.W. 1986. Economics of CO2 Enrichment in Greenhouses. IN:
Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 199-209.

The economic feasibility of any long-term commitment of capital is
dependent on initial capital cost and further input/output
relationships and prices which normally cannot be known in advance,
but about which in many instances, it may seem reasonable to
surmise. In the case of CO2 enrichment of the greenhouse
atmosphere, the factors of primary importance are (1) the added
market value of the crop due to CO2 enrichment, (2) the cost of CO2
and other expenses, (3) any heating or tax credits, and (4) the
cost of equipment and terms of financing. A comprehensive equation
was presented for projecting cash flow for several years, and a
criteria equation was presented to determine the internal rate of
return. A numerical example illustrated use of the equation.
Prospects appear to be favorable for profitability of CO2
enrichment in cold climates, where it is a recommended practice.
However, costs and incremental value of production may vary widely,
particularly as ventilation requirements increase in warmer
climates, so each case should be examined on an individual basis.
The economic analysis equations presented here offer a satisfactory
framework for case-by-case evaluations of the profitability of CO2
enrichment. Moreover, they can be used to compare alternative
methods of financing and even to compare the attractiveness of an
investment in CO2 enrichment relative to investments in other
greenhouse equipment or to investments in financial instruments.

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, REVIEW

136  
Burger, J., S. Miyachi, P. Galland, and H. Senger. 1988. Quantum
Requirements of Photosynthetic Oxygen Evolution and 77K
Fluorescence Emission Spectra in Unicellular Green Algae Grown
under Low-and High-CO2-Conditions. Botanica Acta 101:229-232.

Quantum requirements of photosynthetic oxygen evolution at 682 nm
and fluorescence spectra at liquid nitrogen temperature (77K), were
investigated in Dunaliella tertiolecta, Chlamydomonas reinhardtii
C-9, Chlorella vulgaris 11 g, Chlorella vulgaris C3, and Chlorella
pyrenoidosa 8b grown under low- and high-CO2 conditions.
Dunaliella, Chlamydomonas and C. vulgaris 11 g show higher quantum
requirements and a higher ratio of F710-740/F680-695 fluorescence
when grown under low-CO2 conditions, indicating a change in
excitation energy distribution towards PS-I. In C. pyrenoidosa the
quantum requirement for low-CO2 grown cells is higher than in high-CO2 grown cells, but there was practically no change in the
fluorescence ratio. In C. vulgaris C3, the quantum requirements of
low- and high-CO2 grown cells are the same, but the fluorescence
ratio is higher in high-CO2 grown cells than in low-CO2 grown
cells. These results indicate that most of the low-CO2 grown cells
require more PS-I light than high-CO2 grown cells. It is possible
that this energy is used for cyclic electron flow. In C. vulgaris
C3, a mechanism may exist for excitation energy distribution which
leads to the same quantum requirements under low- and high-CO2
conditions.

Dunaliella tertiolecta/Chlamydomonas reinhardtii/Chlorella
vulgaris/Chlorella pyrenoidosa

KEYWORDS: ALGAE, AQUATIC PLANTS, CELL CULTURE, FLUORESCENCE, OXYGEN
EVOLUTION, QUANTUM REQUIREMENT

137  
Burnett, R.B., U.N. Chaudhuri, E.T. Kanemasu, and M.B. Kirkham.
1985. Sorghum at Elevated Levels of CO2, 024 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, Washington, D.C.

sorghum/Sorghum bicolor

KEYWORDS: ALLOCATION, C4, EVAPOTRANSPIRATION, GROWTH STAGES,
OUTDOOR GROWTH CHAMBERS, RHIZOTRON, ROOT:SHOOT RATIO, ROOTS, WUE,
YIELD

138  
Butler, G.D., B.A. Kimball, and J.R. Mauney. 1986. Populations of
Bemisia tabaci (Homoptera: Aleyrodidae) on Cotton Grown in Open-top
Field Chambers Enriched with CO2. Environmental Entomology 15:61-63.

Atmospheric CO2 levels are anticipated to rise from the current
ambient level of ca. 350 uL/L to 500-600 uL/L in the next 50 to 75
years. Plant scientists are artificially enhancing the CO2
environment of crop plants to increase photosynthesis, which is
currently limited by inadequate levels of CO2. It is not known how
increases of CO2 might affect consumers in the food chain.
Population levels of sweetpotato whitefly (SPWF), Bemisia tabaci
(Gennadius), were assessed with sticky traps placed in a field
experiment wherein cotton was grown in open-top field chambers that
were enriched with CO2 at levels approaching 200% ambient
concentration levels. Although trapping started at the first of
June, only an occasional SPWF was caught until early August. At
that time populations began to increase at an exponential rate
similar to that observed in commercial cotton fields in Arizona and
California in previous years. There was no difference in rate of
buildup of SPWF in ambient and CO2-enriched chambers in either wet
or dry irrigation treatment. Thus, it seems that raised CO2 levels,
either natural or artificial, do not affect SPWF populations.

Gossypium hirsutum/cotton

KEYWORDS: BEMISIA TABACI, HERBIVORY, INSECTS, OPEN-TOP CHAMBERS,
SWEET POTATO WHITE FLY

139  
Byrd, G.T., and R.H. Brown. 1989. Environmental Effects on
Photorespiration of C3-C4 Species. I. Influence of CO2 and O2
during Growth on Photorespiratory Characteristics and Leaf Anatomy.
Plant Physiology 90:1022-1028.

The possibility of altering CO2 exchange of C3-C4 species by
growing them under various CO2 and O2 concentrations was examined.
Growth under CO2 concentrations of 100, 350 and 750 micromoles per
mole had no significant effect on CO2 exchange characteristics or
leaf anatomy of Flaveria pringlei (C3), Flaveria floridana (C3-C4),
or Flaveria trinervia (C4). Carboxylation efficiency and CO2
compensation concentrations in leaves of F. floridana developed
under the different CO2 concentrations were intermediate to F.
pringlei and F. trinervia. When grown for 12 days at an O2
concentration of 20 millimoles per mole, apparent photosynthesis
was strongly inhibited in Panicum milloides (C3-C4) and to a lesser
degree in Panicum laxum (C3). In P. milloides, acute starch buildup
was observed microscopically in both mesophyll and bundle sheath
cells. Even after only 4 days exposure to 20 millimoles per mole
O2, the presence of starch was more pronounced in leaf cross-sections of P. milloides compared to those at 100 and 210
millimoles per mole. Even though this observation suggests that P.
milloides has a different response to low O2 with respect to
translocation of photosynthate or sink activity than C3 species,
the concentration of total available carbohydrates increased in
shoots of all species by 33% or more when grown at low O2. This
accumulation occurred even though relative growth rates of Festuca
arundinacea (C3) and P. milloides grown for 4 days at 210
millimoles per mole O2, were inhibited 83 and 37%, respectively,
when compared to plants grown at 20 millimoles per mole O2.

Flaveria trinervia/Flaveria floridana/Flaveria pringlei/Festuca
arundinacea/Panicum milloides/Panicum laxum

KEYWORDS: ANATOMY, C3, C4, CARBOHYDRATES, CARBOXYLATION EFFICIENCY,
CO2 COMPENSATION POINT, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, OXYGEN, RESPIRATION

140  
Campagna, M.A., and H.A. Margolis. 1989. Influence of Short-term
Atmospheric CO2 Enrichment on Growth, Allocation Patterns, and
Biochemistry of Black Spruce Seedlings at Different Stages of
Development. Canadian Journal of Forest Research 19:773-782.

Black spruce seedlings (Picea mariana Mill.) were exposed to either
elevated (1000 ppm) or ambient (340 ppm) atmospheric CO2 levels at
different stages of seedling development over a winter greenhouse
production cycle. Seedlings germinated in early February and were
placed in CO2 chambers for either 3 or 6 weeks during March, April,
May, or August. Total seedling biomass increased under high CO2
conditions for the March, April, and May stages of development, but
showed no significant response in August. The greater part of the
CO2 response occurred during the second 3 weeks of exposure in
March and April but during the first 3 weeks of exposure in May. In
September, those seedlings exposed to CO2 in April and May had 30
and 14%, respectively, greater biomass than control seedlings, but
seedlings from the other stages of development no longer had
significant differences remaining from the CO2 treatment. This
suggests that it could be very efficient to give a short well-timed
CO2 pulse at the beginning of the production cycle in hopes of
producing a size difference that is maintained throughout the
remainder of the greenhouse production cycle under ambient levels
of CO2. Short-term exposure to elevated CO2 also increased the
ratio of shoot dry weight to total height for the March, April, and
May stages of development. The ratio of total nonstructural
carbohydrates to free amino acids was negatively correlated
(r2=0.98) with the allocation of new growth between shoots and
roots as measured by the allocation coefficient, k (milligrams
shoot growth per milligram root growth). As seedlings developed
along their seasonal growth cycle, ratios of total nonstructural
carbohydrates to free amino acids increased and the values for k
decreased. The effect of CO2 enrichment on these two factors is
discussed. Monitoring total nonstructural carbohydrate and free
amino acid concentrations in foliage could have potential as a
method to predict the percentage of carbon allocation to root
systems of entire forest stands as well as of individual tree
seedlings.

Picea mariana/black spruce

KEYWORDS: ALLOCATION, AMINO ACIDS, CARBOHYDRATES, COMMERCIAL USE OF
CO2, GREENHOUSE, GROWTH STAGES, ROOT:SHOOT RATIO, TREES

141  
Campbell, D.E., and R. Young. 1986. Short-term CO2 Exchange
Response to Temperature, Irradiance, and CO2 Concentration in
Strawberry. Photosynthesis Research 8:31-40.

Relative importance of short-term environmental interaction and
preconditioning to CO2 exchange response was examined in Fragaria
ananassa (strawberry, cv. Quinault). Tests included an orthogonal
comparison of 15 to 60-min and 6 to 7-h exposures to different
levels of temperature (16 to 32C), photosynthetically active
radiation (PAR, 200 to 800 uE/m2/s), and CO2 (300 to 600 uL/L) on
successive days of study. Plants were otherwise maintained at 21C,
300 uE/m2/s PAR and 300-360 uL/L CO2 as standard conditions.
Treatment was restricted to the mean interval of 14 h daily
illumination and the first 3-4 days of each test week over a 12-week cultivation period. CO2 exchange rates were followed with each
step-change in environmental level including ascending/descending
temperature/PAR within a test period, initial response at standard
conditions on successive days of testing, and measurement at
reduced O2. Response generally supported prior concepts of leaf
biochemical modeling in identifying CO2 fixation as the major site
of environmental influence, while overall patterns of whole plant
CO2 exchange suggested additional effects for combined
environmental factors and preconditioning. These included a
positive interaction between temperature and CO2 concentration on
photosynthesis at high irradiance and a greater contribution by
'dark' respiration at lower PAR than previously indicated. The
further importance of estimating whole plant CO2 exchange from
repetitive tests and measurements was evidenced by a high
correlation of response to prior treatment both during the daily
test period and on consecutive days of testing.

strawberry/Fragaria ananassa

KEYWORDS: CANOPY PHOTOSYNTHESIS, ENVIRONMENTAL INTERACTIONS, LIGHT,
OXYGEN, PHOTOSYNTHESIS MODEL, RESPIRATION, TEMPERATURE

142  
Campbell, W.J., L.H. Allen Jr., and G. Bowes. 1987. Effects of
Short-term and Long-term Exposures to Varying CO2 Concentrations on
Soybean Photosynthesis. IN: Progress in Photosynthesis Research,
Vol. IV (J. Biggens, ed.), Martinus Nijhoff Publishers, Dordrecht,
The Netherlands, pp. IV.5.253-IV.5.256.

Soybean plants grown at twice atmospheric concentrations of CO2 had
greater leaf photosynthesis rates than plants grown at atmospheric
concentrations of CO2, across a range of measurement CO2 levels.
Several explanations for this were explored.

soybean/Glycine max

KEYWORDS: ENZYMES, LEAF PHOTOSYNTHESIS, RIBULOSE BISPHOSPHATE
CARBOXYLASE, SPAR UNITS

143  
Campbell, W.J., L.H. Allen Jr., and G. Bowes. 1988. Effects of CO2
Concentration on Rubisco Activity, Amount, and Photosynthesis in
Soybean Leaves. Plant Physiology 88:1310-1316.

Growth at an elevated CO2 concentration resulted in an enhanced
capacity for soybean (Glycine max L. Merr. cv Bragg) leaflet
photosynthesis. Plants were grown from seed in outdoor controlled-environment chambers under natural solar irradiance. Photosynthetic
rates, measured during the seed filling stage, were up to 150%
greater with leaflets grown at 660 compared to 330 microliters of
CO2 per liter when measured across a range of intercellular CO2
concentrations and irradiance. Soybean plants grown at elevated CO2
concentrations had heavier pod weights per plant, 44% heavier with
660 compared to 330 microliters of CO2 per liter grown plants, and
also greater specific leaf weights. Ribulose 1,5-bisphosphate
carboxylase/oxygenase (rubisco) activity showed no response (mean
activity of 96 micromoles of CO2 per square meter per second
expressed on a leaflet area basis) to short-term (about 1 hour)
exposures to a range of CO2 concentrations (110-880 microliters per
liter), nor was a response of activity (mean activity of 1.01
micromoles of CO2 per minute per milligram of protein) to growth
CO2 concentration (160-990 microliters per liter) observed. The
amount of rubisco protein was constant, as growth CO2 concentration
was varied, and averaged 55% of the total leaflet soluble protein.
Although CO2 is required for activation of rubisco, results
indicated that within the range of CO2 concentrations used (110-990
microliters per liter), rubisco activity in soybean leaflets, in
the light, was not regulated by CO2.

soybean/Glycine max

KEYWORDS: ENZYMES, LEAF PHOTOSYNTHESIS, METABOLITES, PHOTOSYNTHETIC
ACCLIMATION, PROTEINS, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR
UNITS

144  
Campbell, W.J., L.H. Allen Jr., and G. Bowes. 1990. Response of
Soybean Canopy Photosynthesis to CO2 Concentration, Light and
Temperature. Journal of Experimental Botany 41:427-433.

Photosynthetic rates of outdoor-grown soybean (Glycine max L. Merr.
cv. Bragg) canopies increased with increasing CO2 concentration
during growth, before and after canopy closure (complete light
interception), when measured over a wide range of solar irradiance
values. Total canopy leaf area was greater as the CO2 concentration
during growth was increased from 160 to 990 mm3/dm3. Photosynthetic
rates of canopies grown at 330 and 660 mm3 CO2/dm3 were similar
when measured at the same CO2 concentrations and high irradiance.
There was no difference in ribulose bisphosphate
carboxylase/oxygenase (rubisco) activity or ribulose 1,5-bisphosphate (RuBP) concentration between plants grown at the two
CO2 concentrations. However, photosynthetic rates averaged 87%
greater for the canopies grown and measured at 660 mm3 CO2/dm3. A
10C difference in air temperature during growth resulted in only
a 4C leaf temperature difference, which was insufficient to change
the photosynthetic rate or rubisco activity in canopies grown and
measured at either 330 or 660 mm3 CO2/dm3. RuBP concentrations
decreased as air temperature during growth was increased at both
CO2 concentrations. These data indicate that the increased
photosynthetic rates of soybean canopies at elevated CO2 are due to
several factors, including: more rapid development of the leaf area
index; a reduction in substrate CO2 limitation; and no downward
acclimation in photosynthetic capacity, as occur in some other
species.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, LIGHT, PHOTOSYNTHETIC ACCLIMATION,
RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR
UNITS, TEMPERATURE

145  
Caporn, S.J.M. 1989. The Effects of Oxides of Nitrogen and Carbon
Dioxide Enrichment on Photosynthesis and Growth of Lettuce (Lactuca
sativa L.). New Phytologist 111:473-481.

The response of glasshouse crops to the nitrogen oxide pollutants
which may be generated during enrichment with CO2 has been studied
in controlled environments. Lettuce (Lactuca sativa L. cv.
Ambassador) was grown in air containing either low CO2 (380
umol/mol), high CO2 (1200 umol/mol), or high CO2 plus oxides of
nitrogen (NOx). Carbon dioxide enrichment increased the rate of
emergence and expansion of leaves and the growth of young plants.
Addition of NOx (2 umol/mol NO and c. 0.5 umol/mol NO2) to CO2-enriched air significantly reduced the yield, compared with the
'clean', high CO2 treatment, without producing visible symptoms of
toxicity. Fumigation of single plants in high CO2 with NOx rapidly
inhibited photosynthesis per unit leaf area. This did not appear to
be due to a reduction in stomatal conductance. Removal of NOx from
the atmosphere caused a rapid and complete recovery in the rate of
photosynthesis. Studies were made of the effects of growing plants
for long periods in atmospheres containing high CO2 and NOx on the
photosynthetic capacity of single leaves when measured in NOx-free
air. The decrease in photosynthetic rate as the fourth leaf aged
occurred earlier in plants grown in CO2-enriched air than in those
from the low CO2 treatment. Leaves which developed in the CO2-enriched air containing NOx did not suffer any long-term damage to
photosynthetic activity in comparison with those of the 'clean'
high CO2. In mature leaves the principal long-term effect of
enrichment (with or without NOx) was to reduce the rate of
photosynthesis in saturating CO2. In contrast, there was less
effect on the rate of photosynthesis in low CO2. The absence of a
long-term effect of NOx on the photosynthetic capacity suggested
that photosynthesis by the lettuce crop will be inhibited only
during the transient periods of NOx accumulation in the glasshouse.

lettuce/Lactuca sativa

KEYWORDS: AIR POLLUTION, CANOPY PHOTOSYNTHESIS, CONDUCTANCE,
GREENHOUSE, GROWTH, LEAF PHOTOSYNTHESIS, NITROGEN OXIDES

146  
Caporn, S.J.M., T.A. Mansfield, and D.W. Hand. 1990. The Critical
Influence of Temperature on the Inhibition of Photosynthesis by
Oxides of Nitrogen in Lettuce. Acta Horticulturae 268:103-110.

The photosynthetic response of lettuce to the oxides of nitrogen
(NOx) generated during enrichment with CO2 has been studied at
different temperatures. The steady rates of net photosynthesis of
lettuce fell within several minutes following the addition of
nitric oxide to the cuvette. This did not appear to have been
caused by a reduction in the stomatal conductance. Removal of the
pollutant gas resulted in a rapid and complete recovery in the rate
of photosynthesis. Gas exchange by a small stand of lettuce was
measured in a novel growth chamber with fine thermal control. In
high CO2 (1000 vpm) and at 16, 10 and 6C a transient fumigation
with 2.0 vpm NO reduced CO2 uptake by 7, 11 and 29% respectively.
Deposition of NO into the canopy was 46% less at 6 than at 16C.
Uptake of the pollutant, therefore, did not explain the increased
inhibition of photosynthesis. The greater damage at low temperature
may be due to a reduced capacity to metabolize some toxic products
of NOx assimilation. Methods of CO2 enrichment which vent the flue
gases from the burners directly into the glasshouse air may not be
entirely suitable for winter crops grown at low temperatures.

lettuce/Lactuca sativa

KEYWORDS: AIR POLLUTION, COMMERCIAL USE OF CO2, CONDUCTANCE, LEAF
PHOTOSYNTHESIS, NITROGEN OXIDES, TEMPERATURE

147  
Caporn, S.J.M., T.A. Mansfield, and D.W. Hand. 1991. Low
Temperature-enhanced Inhibition of Photosynthesis by Oxides of
Nitrogen in Lettuce (Lactuca sativa L.). New Phytologist 118:309-313.

The response of photosynthetic gas exchange to oxides of nitrogen
(NOx) was studied in leaves of lettuce (Lactuca sativa L.) at
different temperatures. Exposure to high concentrations (e.g. 1.3
umol NOx/mol), similar to those often found in commercial
glasshouses, caused a rapid inhibition of the net assimilation of
CO2. This appeared to be by a direct effect on photosynthesis
rather than by a change in the stomatal conductance. In ambient CO2
(345 umol/mol), the percentage inhibition at 10 and 5C was
approximately 3x and 5x, respectively, that measured at 20C. This
effect of temperature also occurred when measured in CO2 enriched
air (1050 umol/mol), which would normally accompany NOx in a
glasshouse. The extent of photosynthetic inhibition caused by NOx
was, however, always less in high than in low CO2. The results
suggest that when burning fuel to raise the CO2 concentration and
heat the glasshouse air, growers should avoid generating high
concentrations of NOx in conditions of low temperature.

lettuce/Lactuca sativa

KEYWORDS: AIR POLLUTION, COMMERCIAL USE OF CO2, CONDUCTANCE,
CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS, NITROGEN
OXIDES, TEMPERATURE

148  
Carlson, T.N., and J.A. Bunce. 1991. The Effect of Atmospheric
Carbon Dioxide Doubling on Transpiration. IN: Tenth Conference on
Biometeorology and Aerobiology and the Special Session on
Hydrometeorology; 1991 Sept. 10-13; Salt Lake City, Utah (Preprint
Volume, ed.), American Meteorological Society, Boston,
Massachusetts, pp. 196-199.

KEYWORDS: CONDUCTANCE, CROPS, PHOTOSYNTHESIS, TRANSPIRATION,
TRANSPIRATION MODEL

149  
Challa, H., and A.H.C.M. Schapendonk. 1986. Dynamic Optimization of
CO2 Concentration in Relation to Climate Control in Greenhouses.
IN: Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 147-160.

KEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2,
GREENHOUSE, MODELING

150  
Chaudhuri, U.N., R.B. Burnett, E.T. Kanemasu, and M.B. Kirkham.
1986. Effect of Elevated Levels of CO2 on Winter Wheat under Two
Moisture Regimes, 029 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, Washington, D.C.

wheat/Triticum aestivum

KEYWORDS: CONDUCTANCE, EVAPOTRANSPIRATION, OUTDOOR GROWTH CHAMBERS,
RHIZOTRON, ROOTS, WATER STATUS, WATER STRESS, WUE, YIELD

151  
Chaudhuri, U.N., R.B. Burnett, E.T. Kanemasu, and M.B. Kirkham.
1987. Effect of Elevated Levels of CO2 on Winter Wheat under Two
Moisture Regimes, 040 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, Washington, D.C.

wheat/Triticum aestivum

KEYWORDS: ALLOCATION, CARBOHYDRATES, CONDUCTANCE, FLUORESCENCE,
OUTDOOR GROWTH CHAMBERS, RHIZOTRON, ROOTS, TRANSPIRATION, WATER
STRESS, YIELD

152  
Chaudhuri, U.N., R.B. Burnett, M.B. Kirkham, and E.T. Kanemasu.
1986. Effect of Carbon Dioxide on Sorghum Yield, Root Growth, and
Water Use. Agricultural and Forest Meteorology 37:109-122.

The concentration of atmospheric carbon dioxide (CO2) is rising.
The effect of higher than ambient levels of CO2 on plants grown in
the sub-humid central Great Plains of the U.S.A. has not been
investigated. Therefore, an experiment was conducted at Manhattan,
Kansas, to study the effect of elevated levels of CO2 on grain
sorghum [Sorghum bicolor (L.) Moench]. During the summer of 1984,
the sorghum was grown in rhizotrons in which root and shoot growth
could be monitored throughout the growth cycle. The tops of the
plants were enclosed in plastic chambers, which contained one of
four concentrations of CO2: 330 (ambient), 485, 660, and 795 uL/L.
Enriched CO2 delayed the boot, half bloom, and soft dough stages.
Sorghum grown at elevated concentrations of CO2 yielded more roots
and shoots than plants grown with 330 uL/L. At all soil-profile
depths, root numbers and weights were higher at elevated CO2 than
at ambient CO2. However, water use per unit dry matter of leaf,
stem, root, and grain was decreased 13, 30, 31 and 29%,
respectively, in plants grown at 795 uL/L CO2 compared to plants at
330 uL/L CO2. Although elevated CO2 levels increased the stomatal
resistance and leaf temperature, an increase in leaf area indices
resulted in a lower canopy resistance.

sorghum/Sorghum bicolor

KEYWORDS: CONDUCTANCE, GROWTH, GROWTH STAGES, OUTDOOR GROWTH
CHAMBERS, RHIZOTRON, ROOTS, TRANSPIRATION, WUE, YIELD

153  
Chaudhuri, U.N., E.T. Kanemasu, and M.B. Kirkham. 1989. Effect of
Elevated Levels of CO2 on Winter Wheat under Two Moisture Regimes,
050 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C.

wheat/Triticum aestivum

KEYWORDS: GROWTH STAGES, OUTDOOR GROWTH CHAMBERS, RHIZOTRON,
TRANSPIRATION, WATER STRESS, WUE, YIELD

154  
Chaudhuri, U.N., M.B. Kirkham, and E.T. Kanemasu. 1990. Carbon
Dioxide and Water Level Effects on Yield and Water Use of Winter
Wheat. Agronomy Journal 82:637-641.

Increasing levels of atmospheric CO2 may have major effects on
yield and water use of winter wheat (Triticum aestivum L.). The
objective was to determine the effect of elevated levels of CO2 on
grain yield and water use from planting to harvest under two water
levels. 'Newton' winter wheat was grown in the field under ambient
(340 uL/L) and elevated levels (485, 660, and 825 uL/L) of CO2,
during three growing seasons, in 16 underground boxes (77 cm long,
37 cm wide, and 180 cm deep) containing a Muir silt loam (fine-silty, mixed, mesic Cumulic Haplustoll). Water in half of the boxes
was maintained at 0.38 m3/m3 (high water level) and in the other
half between 0.14 to 0.25 m3/m3 (low water level). Boxes were
weighed in the fall and spring to determine the amount of water use
by transpiration. Plastic chambers (121 by 92 by 168 cm) covered
the boxes to maintain different CO2 levels. Grain yield of the
high-water-level wheat grown under ambient CO2 was about the same
as the grain yield of low-water-level wheat grown at the highest
level of CO2 (825 uL/L) (3-yr means: 725 and 707 g/m2,
respectively). Similar results were obtained for yield components
(spike number, spike weight, kernels/spike, and kernel weight).
High-water-level wheat grown with 825 uL/L CO2 transpired more
water than low-water-level wheat grown under ambient levels of CO2
(3-yr means: 453 and 370 L/m2, respectively). Under high and low
water levels, 29 and 31% less water was required, respectively, to
produce a gram of grain when the CO2 concentration was raised from
ambient to 825 uL/L. Results show that the water requirement of
wheat is reduced by about 30% by elevated (1.4 times present
ambient) CO2.

wheat/Triticum aestivum

KEYWORDS: OUTDOOR GROWTH CHAMBERS, REPRODUCTION, RHIZOTRON,
TRANSPIRATION, WATER STRESS, YIELD

155  
Chaudhuri, U.N., M.B. Kirkham, and E.T. Kanemasu. 1990. Root Growth
of Winter Wheat under Elevated Carbon Dioxide and Drought. Crop
Science 30:853-857.

With the atmospheric concentration of CO2 increasing, it is
important to know how this will affect crop growth. The objective
of this study was to determine the effect of enriched CO2 on root
growth of winter wheat (Triticum aestivum L. 'Newton') under both
well-watered and dry conditions. The wheat was grown for 3 yr in 16
plastic chambers (121 by 92 by 168 cm) in the field under ambient
CO2 (340 uL/L) and elevated levels of CO2 (485, 660, and 825 uL/L).
Each chamber was placed over an underground box (77 by 37 cm at the
top; 180 cm deep) containing a Muir silt loam (fine-silty, mixed,
mesic Cumulic Haplustoll). The boxes could be pulled out of the
ground for observation of the roots. Half of the boxes were
maintained at field capacity (0.38 m3/m3) (well-watered or not
stressed plants) and half between 0.14 to 0.25 m3/m3 (drought-stressed plants). At harvest, root dry weights at different depths
and stem dry weight were determined. Roots of plants grown under
the three elevated levels of CO2 penetrated to the maximum depth of
observation (176 cm) before roots of plants grown under the ambient
level. At harvest, the difference in root growth between elevated
and ambient levels of CO2 was most pronounced at the top level (0-
to 10-cm depth). Roots of drought-stressed plants grown with 825
uL/L CO2 had a greater dry weight than roots of well-watered plants
grown with ambient CO2. The ratio of root to stem weight usually
showed no trend (neither increase or decrease) with increasing CO2
concentration. Total dry weight at harvest of well-watered roots
grown at ambient CO2 (3-yr mean: 118 g/m2) was similar to that of
drought-stressed roots grown at the highest level of CO2 (3-yr
mean: 123 g/m2). The results indicated that high CO2 (825 uL/L) can
compensate for restrictions in root growth by drought.

wheat/Triticum aestivum

KEYWORDS: GROWTH, OUTDOOR GROWTH CHAMBERS, RHIZOTRON, ROOT:SHOOT
RATIO, ROOTS, WATER STRESS

156  
Chaves, M.M., and J.S. Pereira. 1992. Water Stress, CO2 and Climate
Change. Journal of Experimental Botany 43:1131-1139.

Climate change may bring about increased aridity of large areas of
Europe. Higher temperatures, larger water deficits and high light
stress are likely to occur in conjunction with elevated atmospheric
CO2. This raises the question whether a high CO2 concentration in
the atmosphere can compensate for the decrease in carbon gain in
water-stressed plants. The processes which determine dry matter
production and the ways they are affected by soil water deficits
are discussed. It is now well established that in most species and
under most circumstances stomata are the main limiting factor to
carbon uptake under water deficit, the photosynthetic machinery
being highly resistant to dehydration. However, when other stresses
are superimposed, a decline in photosynthetic capacity may be
observed. In the short term, under drought conditions, the increase
in CO2 in the atmosphere may diminish the importance of stomatal
limitation for carbon assimilation, inhibit photorespiration,
stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent evidence seems to indicate that under
conditions of high irradiance, plants growing at elevated CO2 may
develop protection towards photoinhibition, which might otherwise
result in significant losses in plant production under stress
conditions. In the longer term though, a negative acclimation of
photosynthesis appears to occur in many species, an explanation for
which still needs to be clearly identified. Similarly, the effects
of extended exposure to elevated CO2 under arid conditions are not
known. Plant production is more closely related to the integral of
photosynthesis over time and total foliage area than to the
instantaneous rates of the photosynthetic process. Water deficits
result in more respiratory losses. However, experimental as well as
simulatory evidence suggests that doubling CO2 concentration in the
air may improve carbon assimilation and compensate partially for
the negative effects of water stress even if we assume a down-regulation of the photosynthetic process as a result of acclimation
to elevated CO2.

KEYWORDS: CLIMATE CHANGE, CONDUCTANCE, FLUORESCENCE, LIGHT,
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, REVIEW, SIMULATION,
WATER STRESS

157  
Chen, J.J., and J.M. Sung. 1990. Gas Exchange Rate and Yield
Responses of Virginia-type Peanut to Carbon Dioxide Enrichment.
Crop Science 30:1085-1089.

Poor seed fill and resultant seed-coat shriveling occur commonly on
Virginia-type peanut (Arachis hypogaea L.) grown in Taiwan. The
phenomenon may be linked to the limitation in photosynthate supply
at seed filling. The objective of this study was to evaluate the
effect of CO2 enrichment (1000 uL CO2/L) and depegging on CO2
exchange rate (CER) and yield responses of pot-grown Virginia-type
peanut. Carbon dioxide enrichments were applied to the plants at
pod filling. Depegging effect was examined contrasting the controls
and the plants maintaining 38 to 40 pegs throughout the growing
period. The results indicated that short-term CO2 enrichment (CO2
treatment for 10 d) improved leaf and canopy CER. Long-term CO2
enrichment (CO2 treatments throughout pod filling) tended to ease
leaf ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) and
chlorophyll (chl) deteriorations. Electrophoresis patterns of leaf
soluble protein extracts confirmed this finding. Seed yield per
plant was increased with high CO2 treatment applied at seed-filling
period, but the production of marketable seeds was improved only in
the plants receiving CO2 and depegging treatments. The poor seed-fill characteristic observed in Virginia-type peanut is attributed
to excessive sink load and low canopy CER.

peanut/Arachis hypogaea

KEYWORDS: LEAF PHOTOSYNTHESIS, OUTDOOR GROWTH CHAMBERS, PROTEINS,
RIBULOSE BISPHOSPHATE CARBOXYLASE, SEED PRODUCTION, SOURCE-SINK
BALANCE, YIELD

158  
Chu, C.C., J.S. Coleman, and H.A. Mooney. 1992. Controls of Biomass
Partitioning between Roots and Shoots: Atmospheric CO2 Enrichment
and the Acquisition and Allocation of Carbon and Nitrogen in Wild
Radish. Oecologia 89:580-587.

The effects of CO2 enrichment on plant growth, carbon and nitrogen
acquisition and resource allocation were investigated in order to
examine several hypotheses about the mechanisms that govern dry
matter partitioning between shoots and roots. Wild radish plants
(Raphanus sativus x raphanistrum) were grown for 25 d under three
different atmospheric CO2 concentrations (200 ppm, 330 ppm and 600
ppm) with stable hydroponic 150 umol/L nitrate supply. Radish
biomass accumulation, photosynthetic rate, water use efficiency,
nitrogen per unit leaf area, and starch and soluble sugar levels in
leaves increased with increasing atmospheric CO2 concentration,
whereas specific leaf area and nitrogen concentration of leaves
significantly decreased. Despite substantial changes in radish
growth, resource acquisition and resource partitioning, the rate at
which leaves accumulated starch over the course of the light period
and the partitioning of biomass between roots and shoots were not
affected by CO2 treatment. This phenomenon was consistent with the
hypothesis that root/shoot partitioning is related to the daily
rate of starch accumulation by leaves during the photoperiod, but
is inconsistent with hypotheses suggesting that root/shoot
partitioning is controlled by some aspect of plant C/N balance.

radish/Raphanus sativus/Raphanus raphanistrum

KEYWORDS: ALLOCATION, CARBOHYDRATES, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH ANALYSIS, NITROGEN, ROOT:SHOOT RATIO

159  
Coleman, J.S., and F.A. Bazzaz. 1992. Effects of CO2 and
Temperature on Growth and Resource Use of Co-occurring C3 and C4
Annuals. Ecology 73:1244-1259.

We examined how CO2 concentrations and temperature interacted to
affect growth, resource acquisition, and resource allocation of two
annual plants that were supplied with a single pulse of nutrients.
Physiological and growth measurements were made on individuals of
Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) grown in
environments with atmospheric CO2 levels of 400 or 700 uL/L and
with light/dark temperatures of 28/22 or 38/31C. Elevated CO2
and temperature treatments had significant independent and
interactive effects on plant growth, resource allocation, and
resource acquisition (i.e., photosynthesis and nitrogen uptake),
and the strength and direction of these effects were often
dependent on plant species. For example, final biomass of
Amaranthus was enhanced by elevated CO2 at 28 but was depressed at
38. For Abutilon, elevated CO2 increased initial plant relative
growth rates at 28 but not at 38, and had no significant effects
on final biomass at either temperature. These results are
interpreted in light of the interactive effects of CO2 and
temperature on the rates of net leaf area production and loss, and
on net whole-plant nitrogen retention. At 28C, elevated CO2
stimulated the initial production of leaf area in both species,
which led to an initial stimulation of biomass accumulation at the
higher CO2 level. However, in elevated CO2 at 28, the rate of net
leaf area loss for Abutilon increased while that of Amaranthus
decreased. Furthermore, high CO2 apparently enhanced the ability of
Amaranthus to retain nitrogen at this temperature, which may have
helped to enhance photosynthesis, whereas nitrogen retention was
unaffected in Abutilon. Thus, at 28, final biomass of Abutilon was
not stimulated in a high CO2 environment whereas the final biomass
of Amaranthus was. At 38, Abutilon had slightly reduced peak leaf
areas under elevated CO2 in comparison to ambient CO2 grown plants,
but increased rates of photosynthesis per unit leaf area early in
the experiment apparently compensated for reduced leaf area. For
Amaranthus at 38, peak leaf area production was not affected by
CO2 treatment, but the rate of net leaf area loss hastened under
elevated CO2 conditions and was accompanied by substantial
reductions of whole-plant nitrogen content and leaf photosynthesis
This may have led to the reduced biomass accumulation of high CO2
grown plants that we observed during the last 30 d of growth.
Plants of both species grown in elevated CO2 exhibited reduced
tissue-specific rates of nitrogen absorption, increased plant
photosynthetic rate per unit of conductance, and increased initial
allocation of biomass to roots, irrespective of temperature. Plants
of both species grown under an elevated temperature regime had
substantially decreased reproductive allocation, increased
allocation to stem biomass, and increased plant water flux at both
CO2 treatments. The age of plants also affected our interpretations
of plant responses to CO2 and temperature treatments. For example,
significant effects of CO2 treatment on the growth of Abutilon were
evident early, prior to the initiation of flowering, when nitrogen
availability would have been highest and pot space would not have
been limited. Nevertheless, the opposite was true for Amaranthus,
in which significant effects of CO2 treatment on plant growth were
not detectable until the final 30 d of the experiment. Elevated CO2
interacted with temperature to affect plant productivity in
different ways than would have been predicted from plant responses
to elevated CO2 alone. Furthermore, a majority of the interactive
effects of CO2 concentration and temperature on plant growth could
be interpreted in light of their effects on the rates of net leaf
area production and loss, nitrogen retention, and, to a lesser
degree, photosynthesis and resource partitioning.

Amaranthus retroflexus/Abutilon theophrasti

KEYWORDS: ALLOCATION, C3, C4, CONDUCTANCE, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, NITROGEN, OLD
FIELD COMMUNITIES, PHOTOSYNTHESIS, ROOT:SHOOT RATIO, SENESCENCE,
TEMPERATURE

160  
Coleman, J.S., L. Rochefort, F.A. Bazzaz, and F.I. Woodward. 1991.
Atmospheric CO2, Plant Nitrogen Status and the Susceptibility of
Plants to an Acute Increase in Temperature. Plant, Cell and
Environment 14:667-674.

Elevated levels of CO2 in the atmosphere are expected to affect
plant performance and may alter global temperature patterns.
Changes in mean air temperatures that might be induced by rising
levels of CO2 and other greenhouse gases could also be accompanied
by increased variability in daily temperatures such that acute
increases in air temperature may be more likely than at present.
Consequently, we investigated whether plants grown in a CO2
enriched atmosphere would be differently affected by a heat shock
than plants grown at ambient CO2 levels. Plants of a C3 annual
(Abutilon theophrasti), a C3 annual crop (Sinapis alba) and a C4
annual (Amaranthus retroflexus) were grown from seed in growth
chambers under either 400 or 700 cm3/m3 CO2, and were fertilized
with either a high or low nutrient regime. Young seedlings of S.
alba, as well as plants of all species in either the vegetative or
reproductive phase of growth were exposed to a 4-h heat shock in
which the temperature was raised an additional 14-23C (depending
on plant age). Total biomass and reproductive biomass were examined
to determine the effect of CO2, nutrient and heat shock treatments
on plant performance. Heat shock, CO2, and nutrient treatments, all
had some significant effects on plant performance, but plants from
both CO2 treatments responded similarly to heat shocks. We also
found, as expected, that plants grown under high CO2 had
dramatically decreased tissue N concentrations relative to plants
grown under ambient conditions. We predicted that high-CO2-grown
plants would be more susceptible to a heat shock than ambient-CO2-grown plants, because the reduced N concentration of high-CO2-grown
plants could result in the reduced synthesis of heat shock proteins
and reduced thermotolerance. Although we did not examine heat shock
proteins, our results showed little relationship between plant
nitrogen status and the ability of a plant to tolerate an acute
increase in temperature.

Abutilon theophrasti/Amaranthus retroflexus/Sinapis alba/white
mustard

KEYWORDS: GROWTH, GROWTH STAGES, HEAT SHOCK, NITROGEN,
REPRODUCTION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, TEMPERATURE

161  
Combe, L., J.M. Bertolini, and P. Quetin. 1990. Growth and
Photosynthesis of CO2-enriched Primrose. Acta Horticulturae 268:55-62.

Primula obconica potted plants were cultivated in a glasshouse at
normal (350 +/- 50 uL/L) or enriched (800 +/- 100 uL/L) CO2
concentration in the air. Final growth and yield were measured:
fresh and dry matter were significantly increased by CO2-enrichment
(+94% and +77% respectively). Similarly leaf number increased but
flower number did not. Plant quality was better. Net CO2-gas
exchange rates were measured on a small population (10 pots =30
plants =1 m2) in a growth chamber where irradiance and CO2 could be
controlled. Net photosynthesis curves were the same for both
control and enriched plants: there was no CO2 adaptive effect. The
effect of temperature (14C and 18C) on photosynthesis was not
significant. At high irradiance (450 uE PAR/m2/s) and low CO2
concentration (<350 uL/L) some plants sets displayed lowered
photosynthesis rate, probably due to photoinhibition. Ageing (5 to
13 weeks after transplantation) caused a reduction of
photosynthesis rate except at 350 uL/L. Hence CO2-enrichment should
be applied preferably at the beginning of cultivation.

Primula obconica

KEYWORDS: FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL CROPS,
LIGHT, SENESCENCE, TEMPERATURE

162  
Combe, L., and A. Kobilinsky. 1985. Effet de la Fumure Carbonee sur
la Photosynthese de Radis (Raphanus sativus) en Serre en Hiver.
Photosynthetica 19:550-560.

Carbon dioxide dependence of net photosynthetic rate [Pn(C) curves]
was studied in Raphanus sativus L. plants grown in a greenhouse
with and without CO2 enrichment [ca. 1000 and 350 cm3 (CO2)/m3] for
a week. Pn decreased with increasing plant age (6 to 23 d); the
decrease was higher under lower irradiance (I). CO2 concentration
did not modify the age effect on Pn. When I (400-700 nm) increased
from 200 to 270 umol/m2/s (average of three days before the Pn
measurement), Pn increased unless the plants were very young (6d).
The effect of I was higher in old plants and under CO2 enrichment.
CO2 enrichment induced a higher decrease in Pn under low I and in
older plants. The CO2 enrichment effect appeared only after more
than one day of treatment. After the enrichment had been stopped,
the effect persisted for at least one day and disappeared 3 d after
the treatment had been stopped. In French.

radish/Raphanus sativus

KEYWORDS: GREENHOUSE, LEAF PHOTOSYNTHESIS, LIGHT, SENESCENCE

163  
Condon, M.A., T.W. Sasek, and B.R. Strain. 1992. Allocation
Patterns in Two Tropical Vines in Response to Increased Atmospheric
CO2. Functional Ecology 6:680-685.

1.  Our study addresses two questions.  (a) When net primary
productivity increases in tropical vines, is there an increasing
allocation of the gains to growth in height?  (b) Are allocation
patterns of vines from different types of tropical forests similar
or different?
2.  We chose congeneric tuberous vines from two types of tropical
forest (Psiguria  racemosa) from tropical premontane moist forest
and Psiguria umbrosa from tropical dry forest) and grew seedlings
at three concentrations of ambient CO2 in controlled environment
chambers.
3.  Both species increased markedly in height: average height of
Psiguria racemosa increased 5.5 times at 1000 umol/mol CO2, and
average height of Psiguria umbrosa increased 7.1 times, compared to
plants at 350 umol/mol CO2. In Psiguria racemosa, biomass
allocation to shoot growth relative to root growth increased from
55% at 350 umol/mol CO2 to 78% at 1000 umol/mol CO2, whereas
allocation ratios remained constant in Psiguria umbrosa.
4.  Differences in allocation patterns may reflect adaptive
responses to environmental constraints imposed by different
habitats.  For Psiguria umbrosa, which is deciduous and often dies
back during the dry season, allocation to root biomass may be
important for the development of storage root tissue that may
affect future growth and height.

Psiguria racemosa/Psiguria umbrosa

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, TROPICAL
FOREST, TUBERS, VINES

164  
Conroy, J., E.W. Barlow, and D.I. Bevege. 1986. Response of Pinus
radiata Seedlings to Carbon Dioxide Enrichment at Different Levels
of Water and Phosphorus: Growth, Morphology and Anatomy. Annals of
Botany 57:165-177.

Eight week old seedlings of Pinus radiata D. Don, grown at three
levels of phosphorus, were subjected to three watering regimes and
to CO2 concentrations of either 330 or 660 uL/L for 22 weeks.
Carbon dioxide enrichment increased total dry weight by an average
of 30 per cent. In phosphorus deficient seedlings the increase was
only 13 per cent, whereas under water stress it was 38 per cent.
The NAR responded similarly to CO2. The number, length, diameter
and specific weight of the needles was also increased by CO2
enrichment, the effect being reduced by phosphorus deficiency but
not by water stress. The increase in needle diameter was due to an
increase in cell size rather than cell number. It may be inferred
that increases in the yield of field grown P. radiata will occur
even at sites where water limits growth. However, there is little
possibility of improving growth where phosphorus deficiency is
chronic.

Pinus radiata

KEYWORDS: ANATOMY, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
MORPHOLOGY, PHOSPHORUS, TREES, WATER STRESS

165  
Conroy, J.P. 1992. Influence of Elevated Atmospheric CO2
Concentrations on Plant Nutrition. Australian Journal of Botany
40:445-456.

The rising levels of atmospheric CO2 are likely to increase biomass
production of C3 species in both natural and managed ecosystems
because photosynthetic rates will be higher. The greatest absolute
increase in productivity will occur when nitrogen and phosphorus
availability in the soil is high. Low nitrogen does not preclude a
growth response to high CO2, whereas some C3 species fail to
respond to high CO2 when phosphorus is low, possibly because
insufficient phosphorus is available to maintain maximum
photosynthetic activity at high CO2. C3 plants response to high CO2
because the flux of carbon through the photoreductive cycle is
increased and photorespiration is suppressed. This change in
metabolism appears to alter the foliar nutrient concentration
required to promote maximum productivity (critical concentration).
Higher phosphorus concentrations are needed at elevated CO2,
whereas the nitrogen requirement is reduced by CO2 enrichment.
Since critical concentrations are used to evaluate nutrient status
of crop and forest species and to manage fertiliser programs, they
will need reassessing as the atmospheric CO2 concentration rises.
Another consequence of the altered nutrient requirement at high CO2
is that the nitrogen concentrations of foliage, roots and grain are
consistently lower in plants grown at elevated CO2, irrespective of
availability of nitrogen in the soil. In natural ecosystems,the
lower nitrogen to carbon ratio of the litter may alter rates of
nutrient cycling. For farmers, the rising CO2 concentrations could
cause the reductions in grain nitrogen, and therefore protein
content. This could have important implications for baking quality
of hard wheats as well as affecting the nutrient value of grain
such as rice.

KEYWORDS: LITTER QUALITY, NITROGEN, NUTRITION, PHOSPHORUS, REVIEW

166  
Conroy, J.P., M. Kuppers, B. Kuppers, J. Virgona, and E.W.R.
Barlow. 1988. The Influence of CO2 Enrichment, Phosphorus
Deficiency and Water Stress on the Growth, Conductance and Water
Use of Pinus radiata D. Don. Plant, Cell and Environment 11:91-98.

Seedlings of Pinus radiata D. Don were grown in growth chambers for
22 weeks with two levels of phosphorus, under either well-watered
or water-stressed conditions at CO2 concentrations of either 330 or
660 mm3/dm3. Plant growth, water use efficiency and conductance
were measured and the relationship between these and needle
photosynthetic capacity, water use efficiency and conductance was
determined by gas exchange at week 22. Phosphorus deficiency
decreased growth and foliar surface area at both CO2
concentrations; however, it only reduced the maximum photosynthetic
rates of the needles at 660 mm3 CO2/dm3 (plants grown and measured
at the same CO2 concentration). Water stress reduced growth and
foliar surface area at both CO2 concentrations. Increases in needle
photosynthetic rates appeared to be partly responsible for the
increased growth at high CO2 where phosphorus was adequate. This
effect was amplified by accompanying increases in needle
production. Phosphorus deficiency inhibited these responses because
it severely impaired needle photosynthetic function. The relative
increase in growth in response to high CO2 was higher in the
periodically water-stressed plants. This was not due to the
maintenance of cell volume during drought. Plant water use
efficiency was increased by CO2 enrichment due to an increase in
dry weight rather than a decrease in shoot conductance and,
therefore, transpirational water loss. Changes in needle
conductance and water use efficiency in response to high CO2 were
generally in the same direction as those at the whole plant level.
If the atmospheric CO2 level reaches the predicted concentration of
660 mm3/dm3 by the end of the next Century, then the growth of P.
radiata will only be increased in areas where phosphorus nutrition
is adequate. Growth will be increased in drought-affected regions
but total water use is unlikely to be reduced.

Pinus radiata/Monterey pine

KEYWORDS: CONDUCTANCE, LEAF PHOTOSYNTHESIS, NUTRITION, PHOSPHORUS,
WATER STRESS, WUE

167  
Conroy, J.P., P.J. Milham, and E.W.R. Barlow. 1992. Effect of
Nitrogen and Phosphorus Availability on the Growth Response of
Eucalyptus grandis to High CO2. Plant, Cell and Environment 15:843-847.

The response of Eucalyptus grandis seedlings to elevated
atmospheric CO2 concentrations was examined by growing seedlings at
either 340 or 660 umol CO2/mol for 6 weeks. Graded increments of
phosphorus and nitrogen fertilizers were added to a soil deficient
in these nutrients to establish if the growth response to
increasing nutrient availability was affected by CO2 concentration.
At 660 umol CO2/mol, seedling dry weight was up to five times
greater than at 340 umol CO2/mol. The absolute response was largest
when both nitrogen and phosphorus availability was high but the
relative increase in dry weight was greatest at low phosphorus
availability. At 340 umol CO2/mol and high nitrogen availability,
growth was stimulated by addition of phosphorus up to 76 mg/kg
soil. Further additions of phosphorus had little effect. However,
at 660 umol CO2/mol, growth only began to plateau at a phosphorus
addition rate of 920 mg/kg soil. At 340 umol CO2/mol and high
phosphorus availability, increasing nitrogen from 40 to 160 mg/kg
soil had little effect on plant growth. At high CO2, growth reached
a maximum at between 80 and 160 mg nitrogen/kg soil. Total uptake
of phosphorus was greater at high CO2 concentration at all
fertilizer addition rates, but nitrogen uptake was either lower or
unchanged at high CO2 concentration except at the highest nitrogen
fertilizer rate. The shoot to root ratio was increased by CO2
enrichment, primarily because the specific leaf weight was greater.
The nitrogen and phosphorus concentration in the foliage was lower
at elevated CO2 concentration partly because of the higher specific
leaf weight. These results indicate that critical foliar
concentrations currently used to define nutritional status and
fertilizer management may need to be reassessed as the atmospheric
CO2 concentration rises.

Eucalyptus grandis

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, NITROGEN,
NUTRITION, PHOSPHORUS, TREES

168  
Conroy, J.P., P.J. Milham, D.I. Bevege, and E.W.R. Barlow. 1990.
Influence of Phosphorus Deficiency on the Growth Response of Four
Families of Pinus radiata Seedlings to CO2-Enriched Atmospheres.
Forest Ecology and Management 30:175-188.

Four half-sib families of Pinus radiata (D. Don) (20080, 20010,
20022 and 20062) were grown in pots under conditions where P was
either deficient or adequate and water was supplied daily.
Seedlings of all four families were exposed to 340 (ambient levels)
or 660 uL CO2/L in controlled environment chambers for 16 weeks.
Families 20010 and 20062 were grown at the same CO2 concentrations
for 22 weeks. A subset of plants grown in the chambers were subject
to drought and their water potentials and relative water contents
measured. In the glasshouse experiment, photosynthesis, conductance
and elongation of needles were measured. The fresh and dry-weights
of the tops of the plants were measured in both experiments.
Elevated CO2 concentrations increased shoot growth in all families,
apparently through increases in photosynthesis. At 340 uL CO2/L,
family 20062 accumulated the most dry-weight and 20010 the least.
However, family 20010 responded so strongly to 660 uL CO2/L that it
produced as much dry-matter as 20062. Phosphorus deficiency
generally diminished the response to high CO2. Again, 20010 was
outstanding in that its CO2 response was least reduced by P
deficiency. Carbon dioxide enrichment did not increase the drought-tolerance of any of the four families, either by reducing
conductance or by facilitating osmotic adjustment. These results
provide strong indications that the higher levels of atmospheric
CO2 expected in the next century will increase the growth of P.
radiata where P availability is adequate, but may reduce growth in
areas where rainfall is low. Finally, the capacity to respond to
CO2 enrichment appears to be widely distributed among superior P.
radiata genotypes selected by the Forestry Commission of New South
Wales. However the magnitude of response varies considerably,
particularly where P is deficient.

Pinus radiata

KEYWORDS: CARBOHYDRATES, CONDUCTANCE, CONTROLLED ENVIRONMENT
CHAMBERS, FAMILY RESPONSES, GROWTH, NUTRITION, PHOSPHORUS,
PHOTOSYNTHESIS, TREES, WATER STRESS

169  
Conroy, J.P., P.J. Milham, M. Mazur, and E.W.R. Barlow. 1990.
Growth, Dry Weight Partitioning and Wood Properties of Pinus
radiata D. Don after 2 Years of CO2 Enrichment. Plant, Cell and
Environment 13:329-337.

Advanced selections (families 20010 and 20062) of P. radiata D. Don
were exposed to either 340 or 660 umol CO2/mol for 2 years to
establish if growth responses to high CO2 would persist during the
development of woody tissues. The experiment was carried out in
glasshouses and some of the trees at each CO2 concentration were
subjected to phosphorus deficiency and to periodic drought. CO2
enrichment increased whole-plant dry matter production irrespective
of water availability, but only when phosphorus supply was
adequate. The greatest increase occurred during the exponential
period of growth and appeared to be tied to increased rates of
photosynthesis, which caused accelerated production of leaf area.
The increase in whole-plant dry matter production was similar for
both families; however, family 20010 partitioned larger amounts of
dry weight to the trunks than family 20062, which favoured the
roots and branches. Wood density was generally increased by
elevated CO2 and for family 20010 this increase was due to
thickening of the tracheid walls. Tracheid length was similar at
both CO2 levels but differed between families. These results
suggest that, as the atmospheric CO2 concentration rises, field-grown P. radiata should produce more dry weight at sites where
phosphorus is not acutely deficient, even where drought limits
growth; however, increases in wood production are likely only for
genotypes which continue to partition at least the same proportion
of dry weight to wood in the trunk.

Pinus radiata

KEYWORDS: ALLOCATION, ANATOMY, FAMILY RESPONSES, GREENHOUSE,
NUTRITION, PHOSPHORUS, TREES, WATER STRESS, WOOD PROPERTIES

170  
Conroy, J.P., P.J. Milham, M.L. Reed, and E.W. Barlow. 1990.
Increases in Phosphorus Requirements for CO2-Enriched Pine Species.
Plant Physiology 92:977-982.

Pinus radiata D. Don (half-sib families 20010 and 20062) and Pinus
caribaea var hondurensis (an open-pollinated family) were grown for
49 weeks at seven levels of phosphorus and at CO2 concentrations of
either 340 or 660 microliters per liter, to establish if the
phosphorus requirements differed between the CO2 concentrations and
if mycorrhizal associations were affected. When soil phosphorus
availability was low, phosphorus uptake was increased by elevated
CO2. This may have been related to changes in mycorrhizal
competition. When the phosphorus concentration in the youngest
fully expanded needles was above 600 milligrams per kilogram the
shoot weight of all pine families was greater at high CO2 due to
increases in rates of photosynthesis. More dry weight was
partitioned to the stems of P. radiata family 20010 and P.
caribaea. At foliar phosphorus concentrations above 1000 milligrams
per kilogram (P. radiata) and 700 milligrams per kilogram (P.
caribaea), growth did not increase at 340 microliters of CO2 per
liter. Soluble sugar levels in the same needles mirrored the growth
response, but the starch concentration declined with increasing
phosphorus. At 660 microliters of CO2 per liter, shoot weight and
soluble sugar concentrations were still increasing up to a foliar
P concentration of 1800 milligrams per kilogram for P. radiata and
1600 milligrams per kilogram for P. caribaea. The starch
concentration did not decline. These results indicate that higher
foliar phosphorus concentrations are required to realize the
maximum growth potential of pines at elevated CO2.

Pinus radiata/Pinus caribaea

KEYWORDS: ALLOCATION, CARBOHYDRATES, CONTROLLED ENVIRONMENT
CHAMBERS, FLUORESCENCE, GROWTH, LEAF PHOTOSYNTHESIS, MYCORRHIZAE,
NUTRITION, PHOSPHORUS, TREES

171  
Conroy, J.P., R.M. Smillie, M. Kuppers, D.I. Bevege, and E.W.
Barlow. 1986. Chlorophyll a Fluorescence and Photosynthetic and
Growth Responses of Pinus radiata to Phosphorus Deficiency, Drought
Stress, and High CO2. Plant Physiology 81:423-429.

Needles from phosphorus deficient seedlings of Pinus radiata D. Don
grown for 8 weeks at either 330 or 660 uL CO2/L displayed
chlorophyll a fluorescence induction kinetics characteristic of
structural changes within the thylakoid chloroplast membrane, i.e.,
constant yield fluorescence (Fo) was increased and induced
fluorescence ([Fp-Fi]/Fo) was reduced. The effect was greatest in
the undroughted plants grown at 660 uL CO2/L. By week 22 at 330 uL
CO2/L acclimation to P deficiency had occurred as shown by the
similarity in the fluorescence characteristics and maximum rates of
photosynthesis of the needles from the two P treatments. However,
acclimation did not occur in the plants grown at 660 uL CO2/L. The
light saturated rate of photosynthesis of needles with adequate P
was higher at 660 uL CO2/L than at 330 uL CO2/L, whereas
photosynthesis of P deficient plants showed no increase when grown
at the higher CO2 concentration. The average growth increase due to
CO2 enrichment was 14% in P deficient plants and 32% when P was
adequate. In drought stressed plants grown at 330 uL CO2/L, there
was a reduction in the maximal rate of quenching of fluorescence
(Rq) after the major peak. Constant yield fluorescence was
unaffected but induced fluorescence was lower. These results
indicate that electron flow subsequent to photosystem II was
affected by drought stress. At 660 uL CO2/L this response was
eliminated showing that CO2 enrichment improved the ability of the
seedlings to acclimate to drought stress. The average growth
increase with CO2 enrichment was 37% in drought stressed plants and
19% in unstressed plants.

Pinus radiata

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, FLUORESCENCE, GROWTH,
LEAF PHOTOSYNTHESIS, NUTRITION, TREES, WATER STRESS

172  
Conroy, J.P., J.M. Virgona, R.M. Smillie, and E.W. Barlow. 1988.
Influence of Drought Acclimation and CO2 Enrichment on Osmotic
Adjustment and Chlorophyll a Fluorescence of Sunflower during
Drought. Plant Physiology 86:1108-1115.

Osmotic adjustment occurred during drought in expanded leaves of
sunflowers (Helianthus annuus var Hysun 30) which had been
continuously exposed to 660 microliters CO2 per liter or had been
previously acclimated to drought. The effect was greatest when the
treatments were combined and was negligible in nonacclimated plants
grown at 340 microliters CO2 per liter. The concentrations of
ethanol soluble sugars and potassium increased during the drought
but they did not account for the osmotic adjustment. The delay in
the decline in conductance and relative water content and in the
loss of structural integrity with increasing drought was dependent
on the degree of osmotic adjustment. Where it was greatest,
conductance fell from 5.8 millimeters per second on the first day
of drought to 1.3 millimeters per second on the fourth day and was
approximately the same level on the eighth day. The relative water
content remained constant at 85% for three days and fell to 36% on
the sixth day. There was no evidence of leaf desiccation even on
the eighth day. In contrast, the conductance of leaves showing
minimal adjustment fell rapidly after the first day of drought and
was negligible after the fourth, at which time the relative water
content was 36%. By the sixth day of drought, areas near the
margins of the leaves were desiccating and the plants did not
recover upon rewatering. Despite the differences in the rate of
change of conductance and relative water content during drought,
photosynthetic electron transport activity, inferred from
measurements of chlorophyll a fluorescence in vivo and PSII
activity of isolated thylakoids, remained functional until
desiccation occurred.

sunflower/Helianthus annuus

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
FLUORESCENCE, OSMOTIC ADJUSTMENT, WATER STATUS, WATER STRESS

173  
Cooper, C.F. 1986. Carbon Dioxide Enhancement of Tree Growth at
High Elevations. Science 231:859.

Technical comment.

bristlecone pine/limber pine

KEYWORDS: ALTITUDE, PHOTOSYNTHESIS, TREE-RING ANALYSIS, TREES

174  
Cornic, G., and J.-M. Briantais. 1991. Partitioning of
Photosynthetic Electron Flow between CO2 and O2 Reduction in a C3
Leaf (Phaseolus vulgaris L.) at Different CO2 Concentrations and
during Drought Stress. Planta 183:178-184.

Photosystem II chlorophyll fluorescence and leaf net gas exchanges
(CO2 and H2O) were measured simultaneously on bean leaves
(Phaseolus vulgaris L.) submitted either to different ambient CO2
concentrations or to a drought stress. When leaves are under
photorespiratory conditions, a simple fluorescence parameter delta
F/Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990: 87-92;
delta F = difference between maximum, Fmv and steady-state
fluorescence emissions) allows the calculation of the total rate of
photosynthetic electron-transport and the rate of electron
transport to O2. These rates are in agreement with the measurements
of leaf O2 absorption using 18-O2 and the kinetic properties of
ribulose-1,5-bisphosphate carboxylase/oxygenase. The fluorescence
parameter, delta F/Fm, showed that the allocation of photosynthetic
electrons to O2 was increased during the desiccation of a leaf.
Decreasing leaf net CO2 uptake, either by decreasing the ambient
CO2 concentration or by dehydrating a leaf, had the same effect on
the partitioning of photosynthetic electrons between CO2 and O2
reduction. It is concluded that the decline of net CO2 uptake of a
leaf under drought stress is only due, at least for a mild
reversible stress (causing at most a leaf water deficit of 35%), to
stomatal closure which leads to a decrease in leaf internal CO2
concentration. Since, during the dehydration of a leaf, the
calculated internal CO2 concentration remained constant or even
increased we conclude that this calculation is misleading under
such conditions.

Phaseolus vulgaris/bean

KEYWORDS: 18-O2, C3, CI:CA, FLUORESCENCE, LEAF PHOTOSYNTHESIS,
OXYGEN, RESPIRATION, WATER STRESS

175  
Coudret, A., F. Ferron, and D. Laffray. 1985. High CO2 Partial
Pressure Effects on Dark and Light CO2 Fixation and Metabolism is
Vicia faba Leaves. Photosynthesis Research 7:115-126.

Stomatal opening on Vicia faba can be induced by high CO2 partial
pressures (10.2%) in dark as well as in light. Stomatal aperture
was measured in both cases with a hydrogen porometer. The
distribution of 14C among early products of photosynthesis was
studied. Comparisons are made with carboxylations occurring when
stomata were open in the dark with CO2-free air and in light with
0.034% CO2. Results showed that in high CO2 partial pressures in
light, less radioactivity was incorporated in Calvin cycle
intermediates and more in sucrose.   carboxylations and
photorespiration seemed to be inhibited. In the dark in both CO2
conditions, 14C incorporation was found in malate and aspartate but
also in serine and glycerate in high CO2 conditions. In light these
changes in metabolic pathways may be related with the deleterious
effects recorded on leaves after long-term expositions to high
partial pressure of CO2.

Vicia faba

KEYWORDS: 14C, CONTROLLED ENVIRONMENT CHAMBERS, METABOLITES,
PHOTORESPIRATION, STOMATA

176  
Couteaux, M.M., P. Bottner, H. Rouhier, and G. Billes. 1992.
Atmospheric CO2 Increase and Plant Material Quality: Production,
Nitrogen Allocation and Litter Decomposition of Sweet Chestnut. IN:
Responses of Forest Ecosystems to Environmental Changes (A. Teller,
P. Mathy, and J.N.R. Jeffers, eds.), Elsevier Applied Science,
London, pp. 429-436.

Two-year-old sweet chestnut trees were grown for two other years in
a doubled CO2 atmosphere. The result was an increase by 20% of the
net production and, as an effect of dilution, a decrease of the
nitrogen concentration in the storage organs and in the leaf litter
compared to a control grown in ambient air in the same conditions.
The produced litter - with a C:N twice higher than the control -
was used for a decomposition experiment conducted over 10 months in
experimental units that can be leached. After sterilization, the
litter was inoculated with a mixed microflora and animal groups in
order to induce a food web of increasing complexity (microflora +
Protozoa; + nematodes; + Collembola; + Isopoda). In the units
inoculated with the most diversified fauna, the respiration
increased as the trophic complexity increased to a maximum of 30%
higher than in the control units while in the units inoculated only
with microflora and protozoa, the decomposition was reduced by 60%.
This stimulating effect in the complex units was due to a change in
the composition (white-rot fungi invasion) and activity of the
microflora induced by the presence of the fauna.

sweet chestnut/Castanea sativa

KEYWORDS: ALLOCATION, CARBON:NITROGEN RATIO, COLLEMBOLA, FUNGI,
ISOPODA, LITTER DECOMPOSITION, MICROFLORA, NEMATODES, NITROGEN,
OUTDOOR GROWTH CHAMBERS, PROTOZOA, RESPIRATION, ROOTS, TREES

177  
Couteaux, M.M., M. Mousseau, M.L. Celerier, and P. Bottner. 1991.
Increased Atmospheric CO2 and Litter Quality: Decomposition of
Sweet Chestnut Leaf Litter with Animal Food Webs of Different
Complexities. Oikos 61:54-64.

Two-year-old chestnut trees were grown for two yr under ambient
(350 ppm) and enriched (700 ppm) CO2 concentrations, in two
naturally lit growth chambers. The doubling of CO2 resulted in a
dilution of the nitrogen concentration in the leaf litter, with C:N
ratios of 40 and 75 for the ambient and enriched CO2
concentrations, respectively. The litter was sterilized and
inoculated with microflora and animal groups of increasing
complexity (microflora + Protozoa + nematodes + Collembola +
Isopoda) and incubated over 24 wk. Every two wk, the CO2 release
was measured and the litter was leached with demineralized H2O. The
following analyses were performed on the leachates: pH, total
nitrogen, dissolved and particulate (Protozoa, nematodes and
Rotifera). The initial decomposition stages (the first 12 wk) were
dominated by the litter quality factor: CO2 release and nitrogen
losses in leachates were higher and carbon losses lower in water
leaching from the litter with low C:N ratio. Towards the late
stages, when carbon mineralization decreased in the control litter,
the animal effect emerged in litter with a high C:N ratio. Two
groups appeared: (1) In the microflora + Protozoa units, carbon
mineralization was reduced by 60% compared with the control litter.
(2) In the diversified food web combinations, it became
progressively higher with increasing complexity of the animal
community and was enhanced by 30% compared with the control litter.
This unexpected fundamental difference was explained by a change in
the composition and activity of the microflora. Litter bleaching,
respiration, C and N leaching and acidification rose with
increasing animal complexity of the systems. Biological and
chemical reasons explaining the invasion by white-rot fungi and its
activity only in the material with a high C:N ratio are discussed.
During the 24 wk, nitrogen and phosphorus mineralization was very
low, indicating a high incorporation of the nutrient in the soil
biomass.

sweet chestnut/Castanea sativa

KEYWORDS: CARBON:NITROGEN RATIO, COLLEMBOLA, FUNGI, ISOPODA, LITTER
DECOMPOSITION, MICROFLORA, NEMATODES, OUTDOOR GROWTH CHAMBERS,
PROTOZOA, ROTIFERA

178  
Critten, D.L. 1991. Optimization of CO2 Concentration in
Greenhouses: A Modelling Analysis for the Lettuce Crop. Journal of
Agricultural Engineering Research 48:261-271.

The dependence of photosynthesis of crops on light irradiance and
CO2 concentration are reviewed. A two-dimensional representation of
a lettuce crop is developed into a form suitable for maximizing
grower income by enhancing CO2 concentration. Analytical
relationships for the optimal CO2 concentration are set up for a
commercial lettuce crop and solved. Optimal concentrations are
shown to depend linearly on irradiance levels, and on the square
root of the inverse of the ventilation rate and on the ratio of
lettuce price to CO2 cost/kg. Using hourly values of incident
radiation measured at Cardington, Bedfordshire, ventilation rates
are predicted and optimal CO2 concentrations obtained. Optimal
incomes so produced are compared with those for fixed CO2
enhancement levels under the same ambient conditions. Results
indicate that a corresponding improvement of 10% in income is
possible, though verification using measured greenhouse parameters
is required.

lettuce/Lactuca sativa

KEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2,
HORTICULTURAL CROPS, MODELING, PHOTOSYNTHESIS, SIMULATION

179  
Cure, J.D. 1985. Carbon Dioxide Doubling Responses: A Crop Survey.
IN: Direct Effects of Increasing Carbon Dioxide on Vegetation,
DOE/ER-0238 (B.R. Strain and J.D. Cure, eds.), Dept. of Energy,
Carbon Dioxide Research Division, Washington, D.C., pp. 99-116.

KEYWORDS: AGRICULTURE, ALLOCATION, C3, C4, CONDUCTANCE,
ENVIRONMENTAL INTERACTIONS, HARVEST INDEX, LIGHT, NAR, NUTRITION,
PHOTOSYNTHETIC ACCLIMATION, REVIEW, ROOT:SHOOT RATIO, TEMPERATURE,
TRANSPIRATION, WATER STRESS, YIELD

180  
Cure, J.D., and B. Acock. 1986. Crop Responses to Carbon Dioxide
Doubling: A Literature Survey. Agricultural and Forest Meteorology
38:127-145.

Atmospheric carbon dioxide (CO2) concentration will probably double
by the middle of the next century. Since this is widely expected to
increase crop yields, the Department of Energy has established a
research program to gather data on the effects of CO2 on plants and
to develop models that can be used to predict how plants will
behave in a future high-CO2 world. This paper identifies strengths
and weaknesses in the knowledge base for modelling plant responses
to CO2. It is based on an extensive tabulation of published
information on responses of ten leading crop species to elevated
CO2. The response variables selected for examination were: (a) net
carbon exchange rate, (b) net assimilation rate, (c) biomass
accumulation, (d) root:shoot ratio, (e) harvest index, (f)
conductance, (g) transpiration rate and (h) yield. The results were
expressed as a predicted percentage change of the variable in
response to a doubled CO2 concentration. In most instances, a
linear model was used to fit the response data. Overall, the net
CO2 exchange rate of crops increased 52% on first exposure to a
doubled CO2 concentration. For net assimilation rate, the increases
were smaller, but fell with time in a similar way. The C4 crops
responded very much less than C3 crops. The responses of biomass
accumulation and yield were similar to that for carbon fixation
rate. Yield increased on average 41% for a doubling of CO2
concentration. The variation in harvest index was small and erratic
except for soybeans, where it decreased with a doubling of CO2
concentration. Conductance and transpiration were both inversely
related to CO2 concentration. Transpiration decreased 23% on
average for a doubling of CO2. Crop responses to CO2 during water
stress were variable probably because high CO2 both increased leaf
area (which increases water use) and reduced stomatal conductance
(which decreases water use). However, low nutrient concentrations
limited the responses of most crops to CO2. The absolute increase
in photosynthetic rate in response to high CO2 concentration was
always greater in high light than in low light, but this was not
necessarily true of the relative increase. In all except one study,
responses to CO2 were larger at high temperature than at low. Most
of these studies were done in high light intensity. In low light
intensity, the effect of temperature on the CO2 response was
smalle.

KEYWORDS: AGRICULTURE, ALLOCATION, C3, C4, CONDUCTANCE,
ENVIRONMENTAL INTERACTIONS, GROWTH, HARVEST INDEX, LIGHT, NAR,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, REVIEW, ROOT:SHOOT RATIO,
TRANSPIRATION, WATER STRESS, YIELD

181  
Cure, J.D., L.F. Galloway, M. El Dodo, D.W. Israel, and T.W. Rufty
Jr. 1989. Growth and Carbon Budgets of Soybean Leaves Exposed to
Elevated Carbon Dioxide, 048 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, Washington, D.C.

soybean/Glycine max

KEYWORDS: ASSIMILATE PARTITIONING, CARBON BUDGET, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH, LEAF AREA DEVELOPMENT, LEAF
PHOTOSYNTHESIS, REMOBILIZATION, SOURCE-SINK BALANCE

182  
Cure, J.D., L.F. Galloway, D.W. Israel, and T.W. Rufty Jr. 1986.
Influence of Nutrition on Vegetation Response to Carbon Dioxide. I.
Interactions of Nitrogen and Phosphorus Supply on Soybean Growth
and Nutritional Parameters, 033 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division; Washington, D.C.

soybean/Glycine max

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, NITROGEN,
NUTRITION, PHOSPHORUS, YIELD

183  
Cure, J.D., D.W. Israel, and T.W. Rufty Jr. 1988. Nitrogen Stress
Effects on Growth and Seed Yield of Nonnodulated Soybean Exposed to
Elevated Carbon Dioxide. Crop Science 28:671-677.

Limitations in nutrient availability apparently can restrict plant
response to CO2 enrichment; however, the alterations in
physiological processes associated with such restrictions have not
been defined. This experiment was conducted to investigate certain
physiological responses of N-limited soybean [Glycine max (L.)
Merr. cv. Lee] plants growing in a CO2 enriched environment and to
examine their role in determining growth and yield. The
nonnodulating soybean plants were grown to maturity in controlled
environment chambers at 350 or 700 uL/L CO2 and at 0.05, 1.0, 2.5,
5.0 or 10.0 mM KNO3 supplied in nutrient solution. Substantial
increases in whole-plant growth and seed yield occurred in both CO2
treatments with increasing nitrate levels; the increases were
greater, however, at high CO2. At all NO3 levels except the lowest,
exposure to high CO2 resulted in increased total leaf area, mean
net assimilation rate, NO3 uptake, and N utilization efficiency.
Increased NO3 uptake was associated with larger root systems, as
uptake per unit of root mass was lower than controls. Carbon
dioxide enrichment had little effect on dry matter partitioning
among plant parts or harvest index. Alterations in partitioning
were related to differences in NO3 supply. The results suggest that
atmospheric CO2 enrichment can stimulate seed yield of soybean even
when the availability of N in the rhizosphere is limited.

Glycine max/soybean

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
NITROGEN, NUTRITION, SEED PRODUCTION, YIELD

184  
Cure, J.D., T.W. Rufty Jr., and D.W. Israel. 1987. Assimilate
Utilization in the Leaf Canopy and Whole-Plant Growth of Soybean
during Acclimation to Elevated CO2. Botanical Gazette 148:67-72.

Young vegetative soybeans (Glycine max 'Ransom') were exposed to
control (350 uL/L CO2) or CO2 enriched (700 uL/L CO2) environments
continuously for 22 days. Alterations in carbon acquisition,
assimilate utilization by the leaf canopy and whole-plant growth
were followed to characterize plant acclimation at high CO2. Whole-plant dry weight (DW) progressively increased at high CO2 relative
to the control throughout the experiment. The initial DW increases
were associated with the accumulation of nonstructural assimilates
in leaves and increased specific leaf weight (SLW). After 3 days,
however, DW began to accumulate rapidly in stems and roots under
high CO2, and SLW no longer increased relative to controls. Total
leaf area did not increase significantly at high CO2 until 13 days
after the start of treatments. Net assimilation rates declined
under both CO2 conditions but remained higher at 700 uL/L CO2
throughout the experiment. The increases in stem and root DW during
week 1 at high CO2 were accompanied by (1) an early increase in the
estimated rate of assimilate utilization in the canopy during the
dark phase of the diurnal cycle and (2) a later increase in the
estimated rate of assimilate utilization during the light phase.
The results indicate that dark mobilization of assimilates from
source leaves responded to variations in assimilate accumulation
but that export of assimilates from source leaves in the light
adjusted more slowly and appeared to be coordinated with large
changes in sink activity in the whole plant.

soybean/Glycine max

KEYWORDS: ACCLIMATION, ASSIMILATE PARTITIONING, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH, REMOBILIZATION, SOURCE-SINK BALANCE

185  
Cure, J.D., T.W. Rufty Jr., and D.W. Israel. 1988. Phosphorus
Stress Effects on Growth and Seed Yield Responses of Nonnodulated
Soybean to Elevated Carbon Dioxide. Agronomy Journal 80:897-902.

The influence of P availability on plant responses to elevated
atmospheric CO2 concentrations has received limited research
attention. Therefore, an experiment was conducted to examine the
effect of a wide range of P availabilities on plant response to
enriched atmospheric CO2. Nonnodulating soybean [Glycine max (L.)
Merr., 'Lee'] plants were grown from germination to maturity in
controlled environment chambers at 350 or 700 uL/L CO2 and supplied
with a complete nutrient solution containing either 0.005, 0.10,
0.25, 0.50, or 1.00 mM P. Growth and seed yield were maximized at
the 0.25 and 0.50 mM P concentrations at 350 and 700 uL/L CO2,
respectively. Growth and yield were significantly increased by CO2
enrichment at all except the lowest P concentration. The
stimulation of growth at high CO2 was consistently associated with
increased leaf area, net assimilation rate, P uptake, and P
utilization efficiency in the production of dry matter. When
averaged over the four highest P levels, total root mass was
increased 63% by CO2 enrichment, but P uptake efficiency per unit
root mass was decreased 22%. The yield enhancement of 23 to 57% at
high CO2 was associated with increases in the number and size of
seed. Carbon dioxide enrichment had no significant effect on
harvest index. The results indicate that CO2 enrichment can result
in stimulation of growth and yield of nonnodulated, NO3-fed soybean
plants, even at concentrations of P that limit plant growth at
ambient CO2 concentration.

soybean/Glycine max

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
NUTRITION, PHOSPHORUS, SEED PRODUCTION, YIELD

186  
Cure, J.D., T.W. Rufty Jr., and D.W. Israel. 1989. Alterations of
Soybean Leaf Development and Photosynthesis in a CO2-Enriched
Atmosphere. Botanical Gazette 150:337-345.

This study was conducted to characterize changes in the canopy
photosynthetic leaf area of developing soybean (Glycine max [L.]
Merr. cv. Lee) exposed to a CO2-enriched atmosphere. Young,
vegetative plants were exposed to 350 or 700 uL/L CO2 for 15 d.
Plant dry mass and total leaf area were greater in the CO2-enriched
environment. Emergence and expansion rates of main stem leaves
increased at high CO2, but the areas of individual leaves at full
expansion were affected very little (5-10% greater than controls).
More rapid leaf expansion rates occurred in the light and dark.
Under CO2-enriched conditions, the net CO2 exchange rates of all
leaves on the main stem were higher before and after full
expansion. Stomatal conductance was lower in high CO2 only after
leaves approached full expansion. Leaf development on the lateral
branches also was increased at high CO2, accounting for 40% of the
total increase in leaf area by the end of the experiment. We
conclude that more rapid rates of leaf development under CO2
enrichment likely resulted from increased photosynthesis rates and
that both direct and indirect effects were involved.

soybean/Glycine max

KEYWORDS: ACCLIMATION, CONDUCTANCE, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, LEAF
PHOTOSYNTHESIS

187  
Cure, J.D., T.W. Rufty Jr., and D.W. Israel. 1991. Assimilate
Relations in Source and Sink Leaves during Acclimation to a CO2-Enriched Atmosphere. Physiologia Plantarum 83:687-695.

Evidence from previous studies suggested that adjustments in
assimilate formation and partitioning in leaves might occur over
time when plants are exposed to enriched atmospheric CO2. We
examined assimilate relations of source (primary unifoliate) and
developing sink (second mainstem trifoliate) leaves of soybean
[Glycine max (L.) Merr. cv. Lee] plants for 12 days after transfer
from a control (350 uL/L) to a high (700 uL/L) CO2 environment.
Similar responses were evident in the two leaf types. Net CO2
exchange rate (CER) immediately increased and remained elevated in
high CO2. Initially, the additional assimilate at high CO2 levels
in the light was utilized in the subsequent dark period. After
approximately 7 days, assimilate export in the light began to
increase and by 12 days reached rates 3 to 5 times that of the
control. In the developing sink leaf, high rates of export in the
light occurred as the leaf approached full expansion. The results
indicate that a specific acclimation process occurs in source
leaves which increases the capacity for assimilate export in the
light phase of the diurnal cycle as plants adjust to enriched CO2
and a more rapid growth rate.

soybean/Glycine max

KEYWORDS: ACCLIMATION, ASSIMILATE PARTITIONING, CONTROLLED
ENVIRONMENT CHAMBERS, PHOTOSYNTHESIS, REMOBILIZATION, SOURCE-SINK
BALANCE

188  
Curry, R.B., R.M. Peart, J.W. Jones, K.J. Boote, and L.H. Allen Jr.
1990. Response of Crop Yield to Predicted Changes in Climate and
Atmospheric CO2 Using Simulation. Transactions of the ASAE 33:1383-1390.

Soybean growth and yield for 19 locations in southeastern U.S.A.
were simulated for 30 years (1951-80) of climate data. Three
different climate change scenarios, with and without supplemental
irrigation, were used with the SOYGRO crop model. The three climate
scenarios were standard historic data and two scenarios based on
changes predicted by two general circulation models (GCM) for a
doubling of atmospheric carbon dioxide. Results were analyzed for
four different conditions: normal weather, doubled CO2 alone,
climate change alone, and the combined effect of climate change and
doubled CO2. Results indicate 1) yields vary widely with climate
scenario; 2) increased water use and irrigation need for the
combined case of doubled CO2 and climate change; and 3) simulation
is a useful tool for this type of study.

soybean/Glycine max

KEYWORDS: AGRICULTURE, CLIMATE, CROP MODEL, SIMULATION, YIELD

189  
Curtis, P.S., L.M. Balduman, B.G. Drake, and D.F. Whigham. 1990.
Elevated Atmospheric CO2 Effects on Belowground Processes in C3 and
C4 Estuarine Marsh Communities. Ecology 71:2001-2006.

Belowground carbon allocation is a major component of a plant's
carbon budget, yet relatively little is known about the response of
roots to elevated atmospheric CO2. We have exposed three brackish
marsh communities dominated by perennial macrophytes to twice
ambient CO2 concentrations for two full growing seasons using open
top chambers. One community was dominated by the C3 sedge Scirpus
olneyi, one was dominated by the C4 grass Spartina patens, and one
was a mixture of S. olneyi, S. patens, and Distichlis spicata, a C4
grass. Root and rhizome growth were studied in the 2nd yr of
exposure by measuring growth into peat cores previously excavated
and refilled with sphagnum peat devoid of roots. Growth under
elevated CO2 resulted in an 83% increase in root dry mass per core
in the Scirpus community. Those roots were also significantly lower
in percentage of nitrogen than roots from ambient-grown plants.
There was no effect of elevated CO2 on root growth or nitrogen
content in the Spartina community or in the C4 component of the
mixed community.

Scirpus olneyi/Spartina patens/Distichlis spicata

KEYWORDS: ALLOCATION, AQUATIC PLANTS, C3, C4, GROWTH, HALOPHYTES,
NITROGEN, OPEN-TOP CHAMBERS, ROOTS, SALT MARSH

190  
Curtis, P.S., B.G. Drake, P.W. Leadley, W.J. Arp, and D.F. Whigham.
1989. Growth and Senescence in Plant Communities Exposed to
Elevated CO2 Concentrations on an Estuarine Marsh. Oecologia 78:20-26.

Three high marsh communities on the Chesapeake Bay were exposed to
a doubling in ambient CO2 concentration for one growing season.
Open-top chambers were used to raise CO2 concentrations ca. 340 ppm
above ambient over monospecific communities of Scirpus olneyi (C3)
and Spartina patens (C4), and a mixed community of S. olneyi, S.
patens, and Distichlis spicata (C4). Plant growth and senescence
were monitored by serial, nondestructive censuses. Elevated CO2
resulted in increased shoot densities and delayed senescence in the
C3 species. This resulted in an increase in primary productivity in
S. olneyi growing in both the pure and mixed communities. There was
no effect of CO2 on growth in the C4 species. These results
demonstrate that elevated atmospheric CO2 can cause increased
aboveground production in a mature, unmanaged ecosystem.

Scirpus olneyi/Spartina patens/Distichlis spicata

KEYWORDS: C3, C4, COMMUNITY LEVEL CO2 RESPONSES, GROWTH, GROWTH
ANALYSIS, HALOPHYTES, NET PRIMARY PRODUCTIVITY, OPEN-TOP CHAMBERS,
SALT MARSH, SENESCENCE

191  
Curtis, P.S., B.G. Drake, and D.F. Whigham. 1989. Nitrogen and
Carbon Dynamics in C3 and C4 Estuarine Marsh Plants Grown under
Elevated CO2 in situ. Oecologia 78:297-301.

Carbon dioxide concentrations were elevated in three estuarine
communities for an entire growing season. Open top chambers were
used to raise CO2 concentrations ca. 336 ppm above ambient in
monospecific communities of Scirpus olneyi (C3) and Spartina patens
(C4), and a mixed community of S. olneyi, S. patens and Distichlis
spicata (C4). Nitrogen and carbon concentration (% wt) of
aboveground tissue was followed throughout growth and senescence.
Green shoot %N was reduced and %C was unchanged under elevated CO2
in S. olneyi. This resulted in a 20%-40% increase in tissue C/N
ratio. There was no effect of CO2 on either C4 species. Maximum
aboveground N (g/m2) was unchanged in S. olneyi, indicating that
increased productivity under elevated CO2 was dependent on
reallocation of stored N. There was no change in the N recovery
efficiency of S. olneyi in pure stand and a decrease in the mixed
community. Litter C/N ratio was not affected by elevated CO2
suggesting that decomposition and N mineralization rates will also
remain unchanged. Continued growth responses to elevated CO2 could,
however, be limited by the ability of S. olneyi to increase the
total aboveground N pool.

Scirpus olneyi/Spartina patens/Distichlis spicata

KEYWORDS: ALLOCATION, AQUATIC PLANTS, C3, C4, CARBON:NITROGEN
RATIO, HALOPHYTES, LITTER DECOMPOSITION, LITTER QUALITY,
MINERALIZATION, NITROGEN, NUTRITION, OPEN-TOP CHAMBERS, SALT MARSH

192  
Curtis, P.S., and J.A. Teeri. 1992. Seasonal Responses of Leaf Gas
Exchange to Elevated Carbon Dioxide in Populus grandidentata.
Canadian Journal of Forest Research 22:1320-1325.

Rising atmospheric carbon dioxide concentrations may have important
consequences for forest ecosystems. We studied above- and below-ground growth and leaf gas exchange responses of Populus
grandidentata Michx. to elevated CO2 under natural forest
conditions over the course of a growing season. Recently emerged P.
grandidentata seedlings were grown in native, nutrient-poor soils
at ambient and twice ambient (707 ubar (1 bar=100 kPa)) CO2 partial
pressure for 70 days in open-top chambers in northern lower
Michigan. Total leaf area and shoot and root dry weight all
increased in high CO2 grown plants. Photosynthetic light and CO2
response characteristics were measured 28, 45, and 68 days after
exposure to elevated CO2. In ambient grown plants, light saturated
assimilation rates increased from day 28 to day 45 and then
declined at day 68 (15 September). This late-season decline,
typical of senescing Populus leaves, was due both to a decrease in
the initial slope of the net CO2 assimilation versus intercellular
CO2 partial pressure relationship and to decreased CO2 saturated
assimilation rates. Specific leaf nitrogen (mg N/cm2 leaf area) did
not change during this period, although leaf carbon content and
leaf weight (mg/cm2) both increased. In ambient grown plants
stomatal conductance also declined at day 68. In contrast, plants
grown at elevated CO2 showed no late-season decline in
photosynthetic capacity or changes in leaf weight, suggesting a
delay in senescence with long-term exposure to high CO2. High CO2
grown plants also maintained photosynthetic sensitivity to
increasing Ci throughout the exposure period, while ambient CO2
grown plants were insensitive to Ci above 400 ubar on day 68. These
results indicate the potential for direct CO2 fertilization of P.
grandidentata in the field and provide evidence for a new mechanism
by which elevated atmospheric CO2 could influence seasonal carbon
gain.

Populus grandidentata

KEYWORDS: ACCLIMATION, LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
SENESCENCE, TREES

193  
Dahlman, R.C. 1993. CO2 and Plants: Revisited. Vegetatio
104/105:339-355.

The decade-long USA research program on the direct effects of CO2
enrichment on vegetation has achieved important milestones and has
produced a number of interesting and exciting findings. Research
beginning in 1980 focused on field experiments to determine whether
phenomena observed in the laboratory indeed occurred in natural
environments. The answer is yes. Data obtained from numerous field
studies show mixed response of crop and native species to CO2
enrichment however. Nearly all experiments demonstrate that plants
exhibit positive gain when grown at elevated CO2; although the
magnitude varies greatly. Most crop responses range from 30 to 50%
increase in yield. Results from long-term experiments with woody
species and ecosystems are even more variable. Huge growth
responses (100 to nearly 300% increase relative to controls) are
reported from several tree experiments and the salt-marsh ecosystem
experiment. Other results from experiments with woody species and
the tundra ecosystem suggest little or no effect of CO2 on
physiology, growth or productivity. Numerous studies of the
physiology of the CO2 effect are continuing in attempts to
understand controlling mechanisms and to explain the variable
growth responses. Particular emphasis needs to be given to
physiological measures of interactions involving the CO2 effect and
other environmental influences, and to the wide-ranging
observations of photosynthesis acclimation to CO2. Prospects for
future research are identified.

KEYWORDS: CO2 ENRICHMENT STUDIES, CROPS, ECOSYSTEM LEVEL CO2
RESPONSES, ENVIRONMENTAL INTERACTIONS, GROWTH, PHOTOSYNTHETIC
ACCLIMATION, REVIEW, TREES

194  
Dahlman, R.C., B.R. Strain, and H.H. Rogers. 1985. Research on the
Response of Vegetation to Elevated Atmospheric Carbon Dioxide.
Journal of Environmental Quality 14:1-8.

The global rise in atmospheric CO2 is an established phenomenon.
Irrespective of whether a CO2-induced climate change occurs, it is
abundantly clear that the earth's mantle of vegetation will be
directly affected by increased CO2 levels. Carbon dioxide is
essential for plant growth (plants obtain C from CO2 in the
atmosphere); a higher level of CO2 will increase the rate of
photosynthesis. Quantitative information on the CO2-induced growth
response for field situations is needed for assessments of (i)
possible benefits to agriculture, (ii) the amount of fossil C that
can be sequestered by CO2-accelerated growth of the biosphere, and
(iii) unknown or unidentified effects of CO2 on the physiology,
structure, and function of plants and ecosystems. Along with
knowledge of CO2 effects on climate and other factors, information
on direct plant effects will be used in comprehensive evaluations
of policy options related to increasing atmospheric CO2. Herein, a
discussion of the plan by the U.S. Department of Energy (DOE) to
address the CO2 problem is presented along with research results
from two programs, one agricultural and the other ecological.

KEYWORDS: AGRICULTURE, ECOSYSTEM LEVEL CO2 RESPONSES, REVIEW

195  
Davis, T.D., and J.R. Potter. 1989. Relations between Carbohydrate,
Water Status and Adventitious Root Formation in Leafy Pea Cuttings
Rooted under Various Levels of Atmospheric CO2 and Relative
Humidity. Physiologia Plantarum 77:185-190.

Three levels of atmospheric CO2 and 2 levels of relative humidity
(RH) during the rooting period were tested for their effect on
several factors presumed to influence adventitious root formation
in leafy pea (Pisum sativum L. cv. Alaska) cuttings. Compared to
normal CO2 levels (350 uL/L), neither 1800 nor 675 uL/L CO2
affected the rooting percentage or the number of roots per cutting.
However, 1800 uL/L CO2 increased root and shoot dry weight, root
length, carbohydrate levels in the base of the cuttings and water
potential ( w) of cuttings compared to normal levels of CO2.
Compared to 87% RH, 55% RH decreased all of the above parameters,
including the number of roots per cutting. A polyvinyl chloride
antitranspirant (which partially blocks stomata and slows
photosynthesis) applied simultaneously with 87% RH increased  w and
root length but lowered all of the other above parameters, compared
to 87% RH without antitranspirant. Increasing current photosynthate
(products of photosynthetic activity after excision), carbohydrate,
or  w either alone or together was associated with increased root
system size but not necessarily with increased rooting percentage
or root number. The data are consistent with a hypothesis that the
number of roots per cutting increased with increasing current
photosynthate and carbohydrate until some other factor became
limiting. Also, the effect of  w on rooting percentage and root
number was mediated through its effect on current photosynthate and
carbohydrate.

Pisum sativum

KEYWORDS: ANTITRANSPIRANT, CARBOHYDRATES, CONTROLLED ENVIRONMENT
CHAMBERS, RELATIVE HUMIDITY, ROOTING, VPD, WATER STATUS

196  
de Bruin, H.A.R., and C.M. Jacobs. 1993. Impact of CO2 Enrichment
on the Regional Evapotranspiration of Agro-ecosystems, a
Theoretical and Numerical Modelling Study. Vegetatio 104/105:307-318.

This paper gives a brief overview of factors determining
evapotranspiration of vegetated surfaces. It indicates which of
these factors are sensitive to CO2 enrichment. A qualitative
analysis is presented of the impact of large scale climate changes.
Data in literature indicate that the surface resistance of
vegetated areas may change within the range -25% and +50% if the
atmospheric CO2-concentration doubles. The impact of such changes
on regional scale transpiration is evaluated using a numerical
model in which the interaction between the evapotranspiration and
the Planetary Boundary Layer is accounted for. It is concluded that
the impact of CO2 enrichment on the transpiration at the regional
scale is relatively small for aerodynamically smooth surfaces
(between +7% and -11%). For aerodynamically rough surfaces the
effects are somewhat larger (between +15% and -21%).

KEYWORDS: CLIMATE CHANGE, CONDUCTANCE, EVAPOTRANSPIRATION,
MODELING, REVIEW

197  
de Cortzar, V.G., and P.S. Nobel. 1990. Worldwide Environmental
Productivity Indices and Yield Predictions for a CAM Plant, Opuntia
ficus-indica, Including Effects of Doubled CO2 Levels. Agricultural
and Forest Meteorology 49:261-279.

The productivity of Opuntia ficus-indica was predicted for 253
regions on a worldwide basis using data from 1464 weather stations
within 60 of the equator. First, the climatic data were used to
calculate daily values of a PAR index, a temperature index and a
water index. These indices, each of which has a maximum value of
unity when that environmental factor is not limiting net CO2 uptake
by O. ficus-indica over a 24-h period, were multiplied together to
give an environmental productivity index, which indicates how the
three environmental factors limit net CO2 uptake and hence
productivity. The photosynthetically active radiation (PAR) index
for a canopy of closely spaced plants that have a high productivity
per unit ground area was >/= 0.20 for 25% of the earth's land
surface. The temperature index annually was >/= 0.50 for 81% of the
earth's land surface, indicating that local temperatures do not
greatly limit net CO2 uptake by this species. The water index was
>/= 0.50 for 79% of the earth's surfaces for O. ficus-indica which
exhibits Crassulacean acid metabolism with its accompanying high
water-use efficiency. Predicted productivities for O. ficus-indica
without irrigation were at least 10 metric tons/ha/y, the value for
many important annual agronomic crops, for 41% of the earth's land
area. Irrigation increased such high productivity regions to 77% of
the earth's land surface area within 60 of the equator. For
simulations that included the worldwide changes in PAR, temperature
and rainfall patterns that will most likely accompany a doubling in
the ambient CO2 level, the high productivity of 10 tons/ha/y was
predicted to occur for 54% of the earth's land surface area. Under
elevated CO2, the predicted productivity of O. ficus-indica
increased for most of the U.S.A. and a productivity of 32 tons/ha/y
was predicted for western South America.

Opuntia ficus-indica

KEYWORDS: CAM, CLIMATE, ENVIRONMENTAL INTERACTIONS, LIGHT, NET
PRIMARY PRODUCTIVITY, SIMULATION, TEMPERATURE, WATER STRESS

198  
Del Castillo, D., B. Acock, V.R. Reddy, and M.C. Acock. 1989.
Elongation and Branching of Roots on Soybean Plants in a Carbon
Dioxide-Enriched Aerial Environment. Agronomy Journal 81:692-695.

Plants grown in high CO2 concentrations ([CO2]) often have a higher
root weight than those grown in low [CO2]. It is usually assumed
that the plants with this extra root weight can explore a greater
volume of soil and will, therefore, have more water available to
them. To test this assumption, soybean [Glycine max (L.) Merr. cv.
Forrest] plants were grown in outdoor, sunlit plant-growth chambers
in [CO2] of 330, 450, 600, and 800 uL/L throughout the growing
season. The soil containers in the growth chambers had a glass side
and new root growth appearing at the glass was measured and marked
two or three times each week. Root weight at the end of the season
(93 d after emergence) was 26 to 31% higher in [CO2]-enriched
chambers compared with the 330 uL/L treatment, and cumulative root
length was approximately proportional to [CO2]. However, CO2
treatment did not affect the rate of elongation of individual root
axes. Instead, there was a significant linear increase in the
number of actively growing roots with increased [CO2]. Plants grown
in 800 uL/L had 65% more actively growing roots than plants grown
in 330 uL/L. Thus, growing a plant in high [CO2] enabled it to
explore a given volume of soil more thoroughly, but did not
increase the volume of soil explored.

soybean/Glycine max

KEYWORDS: GROWTH, ROOTS, SPAR UNITS

199  
Delgado, E., J. Azcon-Bieto, X. Aranda, J. Palazon, and H. Medrano.
1992. Leaf Photosynthesis and Respiration of High CO2-grown Tobacco
Plants Selected for Survival under CO2 Compensation Conditions.
Plant Physiology 98:949-954.

Four self-pollinated, doubled-haploid tobacco, (Nicotiana tabacum
L.) lines (SP422, SP432, SP435, and SP451), selected as haploids by
survival in a low CO2 atmosphere, and the parental cv Wisconsin-38
were grown from seed in a growth room kept at high CO2 levels (600-700 parts per million). The selected plants were much larger
(especially SP422, SP432, and SP451) than Wisconsin-38 nine weeks
after planting. The specific leaf dry weight and the carbon (but
not nitrogen and sulfur) content per unit area were also higher in
the selected plants. However, the chlorophyll, carotenoid, and
alkaloid contents and the chlorophyll a/b ratio varied little. The
net CO2 assimilation rate per unit area measured in the growth room
at high CO2 was not higher in the selected plants. The CO2
assimilation rate versus intercellular CO2 curve and the CO2
compensation point showed no substantial differences among the
different lines, even though these plants were selected for
survival under CO2 compensation point conditions. Adult leaf
respiration rates were similar when expressed per unit area but
were lower in the selected lines when expressed per unit dry
weight. Leaf respiration rates were negatively correlated with
specific leaf dry weight and with the carbon content per unit area
and were positively correlated with nitrogen and sulfur content of
the dry matter. The alternative pathway was not involved in
respiration in the dark in these leaves. The better carbon economy
of tobacco lines selected for low CO2 survival was not apparently
related to an improvement of photosynthesis rate but could be
related, at least partially, to a significantly reduced respiration
(mainly cytochrome pathway) rate per carbon.

tobacco/Nicotiana tabacum

KEYWORDS: ALKALOIDS, COMPENSATION POINT, LEAF PHOTOSYNTHESIS,
NITROGEN, PIGMENTS, RESPIRATION, SULFUR

200  
Delgado, E., M.A.J. Parry, D.W. Lawlor, A.J. Keys, and H. Medrano.
1993. Photosynthesis, Ribulose-1,5-bisphosphate Carboxylase and
Leaf Characteristics of Nicotiana tabacum L. Genotypes Selected by
Survival at Low CO2 Concentrations. Journal of Experimental Botany
44:1-7.

The photosynthetic characteristics (responses to CO2 and light),
ribulose-1,5-bisphosphate carboxylase (Rubisco) properties, and the
size and number of cells of the mesophyll of Nicotiana tabacum L.
leaves of genotypes selected for survival at low atmospheric CO2
concentrations are described. When grown in the greenhouse with
nutrient solution, the total dry matter production of the selected
genotypes was 23% greater than that of the parent genotype; this
increase was related to a greater number of mesophyll cells of
smaller size in the selected plants compared to the parent.
However, it was not related to changes in the photosynthetic
characteristics nor to Rubisco properties. These results suggest
that the increased dry matter accumulation of the selected
genotypes is not due to a reduction in photorespiration nor an
increase in the CO2 assimilation rates. Rather, the selection of
haploid tobacco plantlets in low CO2 has resulted in plants with
greater leaf areas (shown in previous work), due to the produciton
of more cells of smaller size and to lower respiration rates per
unit of leaf dry mass (previous work), thus increasing light
capture, reducing the loss of assimilates and increasing total
plant dry matter production.

tobacco/Nicotiana tabacum

KEYWORDS: ANATOMY, GREENHOUSE, LEAF PHOTOSYNTHESIS, RIBULOSE
BISPHOSPHATE CARBOXYLASE

201  
den Hertog, J., and I. Stulen. 1990. The Effects of an Elevated
Atmospheric CO2-concentration on Dry Matter and Nitrogen
Allocation. IN: The Greenhouse Effect and Primary Productivity in
European Agro-ecosystems; 5-10 April 1990; Wageningen, The
Netherlands (J. Goudriaan, H. van Keulen, and H.H. van Laar, eds.),
Pudoc, Wageningen, pp. 27-30.

Plantago major/broadleaf plantain/Urtica dioica/stinging nettle

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, NITROGEN, ROOT:SHOOT RATIO, ROOTS

202  
den Hertog, J., I. Stulen, and H. Lambers. 1993. Assimilation,
Respiration and Allocation of Carbon in Plantago major as Affected
by Atmospheric CO2 Levels: A Case Study. Vegetatio 104/105:369-378.

The response of Plantago major ssp. pleiosperma plants, grown on
nutrient solution in a climate chamber, to a doubling of the
atmospheric CO2 concentration was investigated. Total dry matter
production was increased by 30% after 3 weeks fo exposure, due to
a transition stimulation of the relative growth rate (RGR) during
the first 10 days. Thereafter RGR returned to the level of control
plants. Photosynthesis, expressed per unit leaf area, was
stimulated during the first two weeks of the experiment, thereafter
it dropped and nearly reached the level of the control plants. Root
respiration was not affected by increased atmospheric CO2 levels,
whereas shoot, dark respiration was stimulated throughout the
experimental period. Dry matter allocation over leaves stems and
roots was not affected by the CO2 level. SLA was reduced by 10%,
which can partly be explained by an increased dry matter content of
the leaves. Both in the early and later stages of the experiment,
shoot respiration accounted for a larger part of the carbon budget
in plants grown at elevated atmospheric CO2. Shifts in the total
carbon budget were mainly due to the effects on shoot respiration.
Leaf growth accounted for nearly 50% of the C budget at all stages
of the experiment and in both treatments.

Plantago major/broadleaf plantain

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, HYDROPONIC CULTURE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, RESPIRATION

203  
DeWitt, C.A., R.E. Waldron, and J.R. Lambert. 1983. Effects of
Carbon Dioxide Enrichment on Nitrogen Fixation in Soybeans 1982,
010 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, GROWTH, NITROGEN FIXATION, SPAR
UNITS, WUE

204  
Dietz, K.-J., U. Schreiber, and U. Heber. 1985. The Relationship
between the Redox State of Q(A) and Photosynthesis in Leaves at
Various Carbon-dioxide, Oxygen and Light Regimes. Planta 166:219-226.

The response of chlorophyll fluorescence elicited by a low-fluence-rate modulated measuring beam to actinic light and to superimposed
1-s pulses from a high-fluence-rate light source was used to
measure the redox state of the primary acceptor, Q(A) of
photosystem II in leaves which were photosynthesizing under steady-state conditions. The leaves were exposed to various O2 and CO2
concentrations and to different energy fluence rates of actinic
light to assess the relationship between rates of photosynthesis
and the redox state of Q(A). Both at low and high fluence rates,
the redox state of Q(A) was little altered when the CO2
concentration was reduced from saturation to about 600 uL/L
although photosynthesis was decreased particularly at high fluence
rates. Upon further reduction in CO2 content the amount of reduced
Q(A) increased appreciably even at low fluence rates where light
limited CO2 reduction. Both in the presence and in the absence of
CO2, a more reduced Q(A) was observed when the O2 concentration was
below 2%. Q(A) was almost fully reduced when leaves were exposed to
high fluence rates under nitrogen. Even at low fluence rates, Q(A)
was more reduced in shade leaves of Asarum europaeum and Fagus
sylvatica than in leaves of Helianthus annuus and Fagus sylvatica
grown under high light. Also, in shade leaves the redox state of
Q(A) changed more during a transition from air containing 350 uL/L
CO2 to CO2-free air than in sun leaves. The results are discussed
with respect to the energy status and the CO2-fixation rate of
leaves.

Helianthus annuus/Fagus sylvatica/Asarum europaeum

KEYWORDS: FLUORESCENCE, LEAF PHOTOSYNTHESIS, OXYGEN

205  
Dons, C. 1988. Effects of Long-Term CO2 Enrichment under Different
Irradiance Regimes on Growth and Photosynthesis in Lemna gibba.
Photosynthetica 22:328-334.

Cultivation in CO2-enriched air increased the growth rate of Lemna
gibba only when day/night light cycling was used. Starch content
increased with CO2 enrichment and irradiance (I). Reduced CO2
assimilation and growth in plants grown under high continuous I and
CO2-enriched air may be due to high starch levels. Changes in leaf
area ratio and dry mass content were associated with increased
starch content. Also morphological changes occurred in high-CO2-grown plants.

Lemna gibba/duckweed

KEYWORDS: AQUATIC PLANTS, CARBOHYDRATES, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH, LIGHT, MORPHOLOGY, PHOTOSYNTHESIS, PHOTOSYNTHETIC
FEEDBACK INHIBITION

206  
Doorduin, J.C. 1990. Effects of CO2 and Plant Density on Growth and
Yield of Glasshouse Grown Freesias. Acta Horticulturae 268:171-177.

It has been demonstrated for many glasshouse crops that increasing
the CO2 concentration leads to improved quality and yield, while
concentrations below the ambient level lead to loss of quality and
yield. Relatively few experimental data are known for freesia in
this area and on freesia holdings CO2 enrichment is applied only to
a limited extent. For this reason in an experiment 4 CO2
concentrations were combined with 4 plant densities to investigate
the effect of CO2 on quality and yield of the cultivar 'Blue
Heaven'. The CO2 concentrations realised were 265, 360, 560 and 860
ppm. Plant densities were 57, 78, 100 and 121 corms per net square
metre. The concentration of 265 ppm resulted in a 20% lower yield
of stems, corms and cormlets and a reduction of stem quality as
compared to 360 ppm. Increasing the concentration to 560 ppm
resulted in a 20% higher yield and an improved quality as compared
to 360 ppm. Levels exceeding 560 ppm did not improve yield or
quality. Higher plant densities did not give higher yields but
evidently reduced quality. Vase life was not affected by
differences in CO2 concentrations or plant densities.

freesia

KEYWORDS: FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL CROPS

207  
Downton, W.J.S., W.J.R. Grant, and E.K. Chacko. 1990. Effect of
Elevated Carbon Dioxide on the Photosynthesis and Early growth of
Mangosteen (Garcinia mangostana L.). Scientia Horticulturae 44:215-225.

The Mangosteen is a potentially important new crop for tropical
northern Australia if its long establishment time can be
substantially reduced. The effect of enriching the atmosphere with
up to 1000 ubar CO2 on the growth and photosynthesis of mangosteen
seedlings was examined over the course of a year in an attempt to
accelerate early plant development. It was initially found to be
necessary to reduce photon irradiance from 450 to 200 umol
photons/m2/s (400-700 nm) to overcome photoinhibition of
photosynthesis, and to reduce CO2 from 1000 to 800 ubar to
encourage greening of newly formed leaves. A major effect of CO2
enrichment was to stimulate earlier lateral branching which
accelerated the development of leaf area and plant carbon gain.
Photosynthetic rates of mangosteen leaves were found to be very low
and the 800-ubar CO2 atmosphere increased CO2 fixation by 40-60%
compared to control leaves measured at 400 ubar CO2. As a result,
total plant dry weight increased by 77%. The stimulatory effect of
CO2 was greatest on root and stem dry weight, which doubled.
Although a smaller proportion of dry weight was partitioned into
leaves compared with control plants, CO2 enrichment increased
average leaf size by about 10%, specific leaf dry weight by 17% and
total leaf area by 28%. By comparison, plants from the same
apomictic seedling population grown under shadehouse conditions in
Darwin, Australia, developed more slowly, consistent with
descriptions in the literature, and were substantially smaller and
lower in dry weight compared to the plants grown under controlled
conditions, even in the absence of CO2 enrichment, and had not
developed lateral branches by harvest time. Reasons for this
difference are suggested which may enable improvement of the early
growth of mangosteen plants under field nursery conditions.

mangosteen/Garcinia mangostana

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LEAF
PHOTOSYNTHESIS, LIGHT, TREES

208  
Downton, W.J.S., W.J.R. Grant, and B.R. Loveys. 1987. Carbon
Dioxide Enrichment Increases Yield of Valencia Orange. Australian
Journal of Plant Physiology 14:493-501.

The response to elevated CO2 of 3-year-old fruiting Valencia orange
scions (Citrus sinensis (L.) Osbeck) on citrange rootstock (C.
sinensis x Poncirus trifoliata (L.) Raf.) was studied over a 12-month period under controlled environmental conditions. CO2
enrichment to approx. 800 ubar CO2 which commenced just prior to
anthesis shortened the period of fruitlet abscission. Trees
enriched to 800 ubar CO2 retained 70% more fruit, which at harvest
were not significantly smaller in diameter or lower in fresh weight
than fruit from control trees grown at approx. 400 ubar CO2. Fruit
from the CO2 enriched trees also did not differ from the controls
in soluble solids content, dry weight, seed number or rind
thickness. The progression of fruit coloration was more rapid for
the CO2-enriched trees. Dry weight of leaves and branches from the
scion portion of the trees and the roots and stem of the rootstock
portion did not differ between treatments at time of harvest. Leaf
areas were also similar. However, specific leaf dry weight was 25%
greater for the CO2 enriched treatment. Changes in dry matter
partitioning resulted from the greater fruit yield (58% increase in
dry weight) with CO2 enrichment. Photosynthetic rates observed at
intervals over the experimental period were always lower in the CO2
enriched treatment compared to controls when measured at the same
partial pressure of CO2. However photosynthetic rates in the CO2
enriched cabinet were always higher because of the increased level
of CO2. The extent of this difference between the treatments varied
with fruit development and increased from 23% higher photosynthetic
rates in the CO2 enriched chamber at the end of flowering to 77%
higher rates when fruits were 5 cm in diameter and decreased to 18%
higher rates when fruit coloration was well advanced. Flushes of
leaves that developed during the experiment also showed similar
photosynthetic responses to CO2 enrichment and their photosynthetic
rates declined as fruit matured. These results indicate that crop
yield by fruit trees will increase as global levels of CO2 continue
to rise, at least in those species that experience source
limitation during fruit development.

Valencia orange/Citrus sinensis

KEYWORDS: CROPS, GREENHOUSE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, REPRODUCTION, SOURCE-SINK BALANCE, TREES, YIELD

209  
Doyle, T.W. 1987. Seedling Response to CO2 Enrichment under
Stressed and Non-stressed Conditions. IN: Proceedings of the
International Symposium on Ecological Aspects of Tree Ring Analysis
(G.C. Jacoby and J.W. Hornbeck, eds.), NTIS, Springfield, Virginia,
pp. 494-500.

Loblolly pine and sweetgum seedlings were obtained from a Duke
University phytotron study, where three groups were grown in
different atmospheres of CO2 (i.e., 350, 500, 650 ppmv). Seedlings
were grown over three growing seasons, and included a set of water-stressed and non-stressed individuals. X-ray densitometry was used
to evaluate growth and density characteristics of the wood samples.
Cross-sectional discs of these samples were radiographed and
scanned with a microdensitometer to determine ring width, area,
density and mass for each growth year. Results indicated
significant differences in wood production (ring width, area and
mass) between the lowest treatment of CO2 (350 ppmv) and the higher
concentration (500 and 650 ppmv) treatments. While only a few
density parameters demonstrated significant changes with increasing
CO2, almost all showed a systematic increase in density with
increasing CO2 concentration. Ring area and mass displayed the
greatest degree of change between treatments. Induced drought
effects appeared only to strengthen the CO2-growth association.
These findings suggest that naturally stressed trees are also
likely to exhibit some growth effect with increasing atmospheric
CO2. And because the greatest margin of response existed between
350 and 500 ppmv, this study emphasizes the importance and need to
determine growth responses at preindustrial era CO2 concentrations
in order to more accurately identify the postulated 'fertilizer'
effect on modern forests.

loblolly pine/sweetgum/Liquidambar styraciflua/Pinus taeda

KEYWORDS: GREENHOUSE, GROWTH, TREE-RING ANALYSIS, TREES, WATER
STRESS, WOOD PROPERTIES

210  
Doyle, T.W., F.G. Taylor, M.L. Parker, C.F. Cooper, and D.C. West.
1985. Preliminary Ring-Width and Ring-Density Data for Deriving
Wood Mass Chronologies of Coniferous Species from the Northwest
U.S. and Canada, 025 in Green Report Series, Response of Vegetation
to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, Washington, D.C., and Environmental Sciences Division,
Oak Ridge National Laboratory, Oak Ridge, Tennessee.

white spruce/red pine/Douglas-fir/Western hemlock/Western red
cedar/Engelmann spruce/lodgepole pine/yellow cedar/black spruce

KEYWORDS: TREE-RING ANALYSIS, TREES

211  
Drake, B., W. Arp, P.S. Curtis, P.W. Leadley, J. Sager, and D.
Whigham. 1986. Effects of Elevated CO2 on Chesapeake Bay Wetlands.
I. Description of the Study Site, 034 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, Washington, D.C.

Spartina patens/Distichlis spicata/Scirpus olneyi

KEYWORDS: AQUATIC PLANTS, EXPOSURE METHODS, HALOPHYTES, LITTER
QUALITY, OPEN-TOP CHAMBERS, SALT MARSH, WATER STATUS

212  
Drake, B.G. 1992. A Field Study of the Effects of Elevated CO2 on
Ecosystem Processes in a Chesapeake Bay Wetland. Australian Journal
of Botany 40:579-595.

Open top chambers are being used in a long-term project to
determine the effects of elevated CO2 on ecosystem processes on a
Chesapeake Bay wetland. Three communities are studied: mono-specific stands of the C3 sedge, Scirpus olneyi, and the C4 grass,
Spartina patens, and a mixed community of these two species and the
C4 grass, Distichlis spicata. Treatment began in the spring of 1987
and will continue through the 1994 growing season. During the first
4 years of exposure, elevated CO2 had the following effects on
mono-specific stands of the C3 sedge, Scirpus olneyi: increased
quantum yield and photosynthetic capacity, reduced dark
respiration, increased numbers of shoots, roots and rhizomes,
reduced nitrogen concentration of all tissues, increased nitrogen
fixation and increased ecosystem carbon accumulation. In a mixed
community of the sedge and C4 grass species, Spartina patens and
Distichlis spicata, biomass of the C3 component increased over 100%
and this was accompanied by decreased biomass in the C4 component
of the community. Elevated CO2 reduced water loss, increased water
potential and delayed senescence in all three species. Many factors
contributed to CO2 stimulated carbon accumulation in the plant
community dominated by the C3 sedge, Scirpus olneyi, including:
sustained high photosynthetic capacity, decreased respiration,
delayed senescence, and allocation of the additional carbon to
roots and rhizomes. The complex interaction of these diverse
responses suggests that the rising atmospheric CO2 may have a
significant impact on ecosystem processes.

Spartina patens/Scirpus olneyi/Distichlis spicata

KEYWORDS: ANATOMY, AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS,
CO2 COMPENSATION POINT, ECOSYSTEM LEVEL CO2 RESPONSES,
EVAPOTRANSPIRATION, GRASSES, HALOPHYTES, INSECTS, LEAF AREA
DEVELOPMENT, LIGHT, NITROGEN, OPEN-TOP CHAMBERS, PIGMENTS, PLANT-FUNGUS INTERACTIONS, RESPIRATION, SALT MARSH, SPECIES COMPETITION,
STOMATAL DENSITY, WUE

213  
Drake, B.G., W. Arp, J. Craig, P.S. Curtis, P.W. Leadley, and D.
Whigham. 1987. Effects of Elevated CO2 on Chesapeake Bay Wetlands.
II. Gas Exchange and Microenvironment in Open Top Chambers, 038 in
Green Report Series, Response of Vegetation to Carbon Dioxide. U.S.
Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C.

Scirpus olneyi/Spartina patens/Distichlis spicata

KEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, CONDUCTANCE,
EXPOSURE METHODS, HALOPHYTES, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC
ACCLIMATION, SALT MARSH

214  
Drake, B.G., W.J. Arp, L. Balduman, R. Cousimano, J. Dacey, D.
D'Abundo, K. Hogan, S. Long, W.T. Pockman, P. Utley, A.C. Villegas,
and D. Whigham. 1990. Effects of Elevated Co2 on Chesapeake Bay
Wetlands. V. Ecosystem and Whole Plant Responses. April-November
1989, 055 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C.

Scirpus olneyi/Spartina patens

KEYWORDS: CANOPY PHOTOSYNTHESIS, ECOSYSTEM LEVEL CO2 RESPONSES,
EVAPOTRANSPIRATION, HALOPHYTES, LEAF PHOTOSYNTHESIS, METHANE,
NITROGEN, OPEN-TOP CHAMBERS, QUANTUM REQUIREMENT, RESPIRATION,
ROOTS, SALT MARSH, WATER STATUS, WUE

215  
Drake, B.G., W.J. Arp, L. Balduman, P.S. Curtis, J. Johnson, D.
Kabara, P.W. Leadley, W.T. Pockman, D. Seliskar, M.L. Sutton, D.
Whigham, and L. Ziska. 1989. Effects of Elevated CO2 on Chesapeake
Bay Wetlands. IV. Ecosystem and Whole Plant Responses. April-November 1988, 051 in Green Report Series, Response of Vegetation
to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, Washington, D.C.

Scirpus olneyi/Spartina patens/Distichlis spicata/Glycine
max/soybean/Lycopersicon esculentum/tomato/Manihot
esculentum/Amaranthus hypochondriacus/amaranth/Acacia mangium/Ficus
obtusifolia/Paspallum conjugatum/Pharus latifolia/Psychotria
limonensis/Tabebuia rosea

KEYWORDS: AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS, CARBON
BUDGET, COMMUNITY LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION, GROWTH,
HALOPHYTES, LEAF PHOTOSYNTHESIS, LITTER DECOMPOSITION, LITTER
QUALITY, NITROGEN, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION,
RESPIRATION, ROOTS, SALT MARSH, SPECIES COMPETITION

216  
Drake, B.G., P.S. Curtis, W.J. Arp, P.W. Leadley, J. Johnson, and
D. Whigham. 1988. Effects of Elevated CO2 on Chesapeake Bay
Wetlands. III. Ecosystem and Whole Plant Responses in the First
Year of Exposure, April-November 1987, 044 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, Washington, D.C.

Spartina patens/Distichlis spicata/Scirpus olneyi

KEYWORDS: CANOPY PHOTOSYNTHESIS, EXPOSURE METHODS, HALOPHYTES, LEAF
PHOTOSYNTHESIS, NET PRIMARY PRODUCTIVITY, NITROGEN, OPEN-TOP
CHAMBERS, PHOTOSYNTHESIS MODEL, SENESCENCE, WATER STATUS

217  
Drake, B.G., and P.W. Leadley. 1991. Canopy Photosynthesis of Crops
and Native Plant Communities Exposed to Long-term Elevated CO2.
Plant, Cell and Environment 14:853-860.

There have been seven studies of canopy photosynthesis of plants
grown in elevated atmospheric CO2: three of seed crops, two of
forage crops and two of native plant ecosystems. Growth in elevated
CO2 increased canopy photosynthesis in all cases. The relative
effect of CO2 was correlated with increasing temperature: the least
stimulation occurred in tundra vegetation grown at an average
temperature near 10C and the greatest in rice grown at 43C. In
soybean, effects of CO2 were greater during leaf expansion and pod
fill than at other stages of crop maturation. In the longest
running experiment with elevated CO2 treatment to date,
monospecific stands of a C3 sedge, Scirpus olneyi (Grey), and a C4
grass, Spartina patens (Ait.) Muhl., have been exposed to twice
normal ambient CO2 concentrations for four growing seasons, in open
top chambers on a Chesapeake Bay salt marsh. Net ecosystem CO2
exchange per unit green biomass (NCEb) increased by an average of
48% throughout the growing season of 1988, the second year of
treatment. Elevated CO2 increased net ecosystem carbon assimilation
by 88% in the Scirpus olneyi community and 40% in the Spartina
patens community.

Scirpus olneyi/Spartina patens

KEYWORDS: AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS, COMMUNITY
LEVEL CO2 RESPONSES, HALOPHYTES, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC
ACCLIMATION, REVIEW, TEMPERATURE

218  
Drake, B.G., P.W. Leadley, W.J. Arp, D. Nassiry, and P.S. Curtis.
1989. An Open Top Chamber for Field Studies of Elevated Atmospheric
CO2 Concentration on Saltmarsh Vegetation. Functional Ecology
3:363-371.

Small open top chamber (0.8 m x 1.0 m) were developed to maintain
elevated CO2 concentrations in three plant communities in a
brackish marsh ecosystem. Mean annual CO2 concentrations were 340
+/- 22 uL/L in chambers which received no added CO2 and 686 +/- 30
uL/L in chambers with elevated CO2 concentrations. Light quality
was not effected in the photosynthetically active wavelengths but
the chamber reduced light quantity by 10%. Night-time air
temperatures inside the chamber (Ti) averaged 2C above air
temperature outside the chamber (To) due to heating from the air
blowers. Air temperature profiles through the plant canopy and
boundary layer showed that daytime temperature differences (Ti -To)
were greater than night-time differences and this day/night
difference also depended on the plant community. Effects of the
chamber on the micro-environment of the plant communities resulted
in a significant growth enhancement in the plant community
dominated by the C3 sedge Scirpus olneyi Grey but not in the other
two communities.

Scirpus olneyi/Spartina patens/Distichlis spicata

KEYWORDS: AQUATIC PLANTS, C3, C4, COMMUNITY LEVEL CO2 RESPONSES,
EXPOSURE METHODS, HALOPHYTES, OPEN-TOP CHAMBERS, SALT MARSH

219  
Drake, B.G., H.H. Rogers, and L.H. Allen Jr. 1985. Methods of
Exposing Plants to Elevated Carbon Dioxide. IN: Direct Effects of
Increasing Carbon Dioxide on Vegetation, DOE/ER-0238 (B.R. Strain
and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research
Division, Washington, D.C., pp. 11-51.

KEYWORDS: EXPOSURE METHODS, REVIEW

220  
Dubois, D., M. Winzeler, and J. Nosberger. 1990. Fructan
Accumulation and Sucrose:sucrose fructosyltransferase Activity in
Stems of Spring Wheat Genotypes. Crop Science 30:315-319.

Stems of wheat (Triticum aestivum L.) accumulate water-soluble
carbohydrates (WSC) during the first 3 wk after anthesis. These
reserves can later contribute to grain filling. Two spring wheat
genotypes ('Kolibri' and breeding line D) were tested in growth
chambers to determine if they differ in the accumulation of WSC
components and in the activation of sucrose:sucrose
fructosyltransferase (SST) in stem tissue. Concentration of CO2 was
supplied at 1000 or 300 uL CO2/L after anthesis to alter
photosynthate production. The WSC accumulation in the penultimate
internode during the first 18 d post anthesis (DPA) was
substantially higher in Genotype D than in Kolibri. The WSC
accumulation up to 7 DPA was due to increases in hexoses and
sucrose. Sucrose concentration was initially lower in Kolibri than
in Genotype D, but increased to a comparable level for both
genotypes and both CO2 treatments. Fructan synthesis was initiated
at 7 DPA. At 18 DPA, fructan was the dominant component of WSC.
Under both CO2 treatments Genotype D accumulated substantially
higher fructan concentrations than Kolibri. In a second experiment,
induction of SST activity was observed during the first 9 DPA in
the penultimate internode of plants grown at 1000 and 200 uL CO2/L.
There was a positive relationship between sucrose concentration and
in vivo SST activity, suggesting that sucrose induced SST activity;
however, Kolibri exhibited a much lower SST activity at given
sucrose concentration. Thus, the low fructan synthesis of Kolibri
is associated with an initial lower sucrose concentration and with
a less effective activation of SST by sucrose.

Triticum aestivum/wheat

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR
RESPONSES, ENZYMES

221  
Duchein, M.-C., A. Bonicel, and T. Betsche. 1993. Photosynthetic
Net CO2 Uptake and Leaf Phosphate Concentrations in CO2 Enriched
Clover (Trifolium subterraneum L.) at Three Levels of Phosphate
Nutrition. Journal of Experimental Botany 44:17-22.

Net CO2-uptake of sets of clover plants (Trifolium subterraneum L.)
was measured over 3 weeks in ambient air and in a highly CO2-enriched atmosphere (400 Pa CO2). Phosphate (P) in the nutrient
solution was varied between 0.05 mol/m3 P (reduced P) and 2.0
mol/m3 P (high P). In ambient air, the daily increments of the
daily rate of net CO2-uptake (DICU; a parameter related to relative
growth) were higher at reduced P than at high P. Stimulation by
high CO2 of net CO2-uptake in the first day was less at reduced P
than at high P. In the following days, high CO2 markedly inhibited
DICU at reduced P, and thus growth stimulation by high CO2 ceased
after between 4 and 12 d. By contrast, at high P, DICU increased
more than 2-fold upon CO2-enrichment, and thus growth stimulation
by high CO2 was maintained. Intermediate results were obtained with
half-strength Hoagland's solution (0.5 mol/m3 P). Leaf pools of
inorganic ortho P, soluble esterified P, and total P declined
markedly in high CO2 when P-nutrition had been reduced.
Considerable decline also occurred in high CO2 when P-nutrition had
been increased suggesting that P-uptake was not well tuned with net
CO2-uptake (growth). It is proposed that high CO2 can perturb the
P-metabolism of clover, the impairment being less at high levels of
P-nutrition. With regard to high CO2 as a growth stimulus, these
results demonstrate that increasing P-nutrition to a level
supraoptimal in ambient air can considerably improve the growth of
a C3-plant in high CO2.

Trifolium subterraneum/clover

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NUTRITION, PHOSPHORUS

222  
du Cloux, H., M. Andre, A. Gerbaud, and A. Daguenet. 1989. Wheat
Response to CO2 Enrichment: Effect on Photosynthetic and
Photorespiratory Characteristics. Photosynthetica 23:145-153.

The effects of doubling atmospheric CO2 concentration on
photosynthesis and photorespiration were studied on wheat
cultivated for 37 or 72 d in growth chambers at a density of
planting of 200 and 40 plants per m2. Net photosynthetic rate (Pn)
was measured continuously during the experiments and response
curves to CO2 were made at intervals. Differences observed between
the CO2 curves of the plants grown in normal and CO2 enriched
atmosphere could be explained by the greater leaf area of the
second group of plants. Photorespiration was tested by the Warburg
effect or measured directly on isolated plants by the uptake of 18-O2. Oxygen uptake was reduced by 40% by the high CO2 treatment, but
high CO2 plants were identical to the control group when returned
to the same conditions. The enhancement of dry matter production
was due to the kinetic response of Pn to CO2, as there was no
appreciable long-term adaptation of the kinetic characteristics of
photosynthesis.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
OXYGEN, PHOTORESPIRATION, PHOTOSYNTHETIC ACCLIMATION, PLANT DENSITY

223  
du Cloux, H.C., M. Andre, A. Daguenet, and J. Massimino. 1987.
Wheat Response to CO2 Enrichment: Growth and CO2 Exchanges at Two
Plant Densities. Journal of Experimental Botany 38:1421-1431.

The vegetative growth of wheat (Triticum aestivum L., var.
Capitole) was followed for almost 40 d after germination in
controlled conditions. Four different treatments were carried out
by combining two air concentrations of CO2, either normal (330
mm3/dm3) or doubled (660 mm3/dm3) with two plant densities, either
200 plants/m2 or 40 plants/m2. Throughout the experiment the CO2
gas exchanges of each canopy were measured 24 h/d. These provided
a continuous growth curve for each treatment, which were compared
with dry weights. After a small stimulation at the start (first 13
d), no further effect of CO2 enrichment was observed on relative
growth rate (RGR). However, RGR was stimulated throughout the
experiment when plotted as a function of biomass. The final
stimulation of dry weight at 660 mm3/dm3 CO2 was a factor of 1.45
at high density and 1.50 at low density; contrary to other studies,
no diminution of this CO2 effect on dry weight was observed over
time. Nevertheless, at low density, a transient additional
enhancement of biomass (up to 1.70) was obtained at a leaf area
index (LAI) below 1. This effect was attributed to a different
build up of the gain of carbon in the case of an isolated plant or
a closed canopy. In the former, the stimulation of leaf area and
the net assimilation rate are both involved; in the latter the
enhancement becomes independent of the effect on leaf area because
the canopy photosynthesis per unit ground area as a function of LAI
reaches a plateau.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, PLANT DENSITY

224  
Dugal, A., S. Yelle, and A. Gosselin. 1990. Influence of CO2
Enrichment and its Method of Distribution on the Evolution of Gas
Exchanges in Greenhouse Tomatoes. Canadian Journal of Plant Science
70:345-356.

Net photosynthesis, stomatal conductance, internal CO2
concentration and transpiration were measured on the fifth well-developed and excised leaf of tomato seedlings (Lycopersicon
esculentum Mill. 'Vedettos') 48-83 d old. These measurements were
taken in order to monitor the evolution of the gas exchanges of
seedlings exposed to concentrations of 330 or 1000 ppm,
continuously, to 1000 ppm from 06:00 h to 10:00 h or to 1000 and
330 ppm alternately every 2 h. CO2 enrichment substantially
increased the net photosynthesis rate of the seedlings,
particularly at the beginning of the experiment. The long-term
effects of CO2 enrichment subsided after a few weeks of treatment.
Intermittent CO2 enrichment was partially helpful in remedying the
loss of effectiveness of the CO2 after a long period of enrichment.
High CO2 concentrations reduced the opening of the stomata. Our
work shows that maintaining a high internal CO2 content in the
leaves would indirectly reduce the stomatal conductance of the
seedlings. However, our results show that the long-term loss of
photosynthetic efficiency in the enriched seedlings cannot be
attributed solely to an increase in the resistance of the stomata,
since the internal CO2 concentration of the leaves remains very
high regardless of which method of CO2 enrichment is used.
Continuous CO2 enrichment improved the water uptake efficiency of
the seedlings. In French.

tomato/Lycopersicon esculentum

KEYWORDS: CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS,
INTERMITTENT ENRICHMENT, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, WUE

225  
Eamus, D. 1990. Carbon Dioxide and Plant Physiological Processes.
IN: The Greenhouse Effect and Terrestrial Ecosystems of the UK
(M.G.R. Cannell and M.D. Hooper, eds.), Institute of Terrestrial
Ecology, Natural Environment Research Council, Edinburgh Research
Station, Bush Estate, Penicuik.

KEYWORDS: CONDUCTANCE, ENVIRONMENTAL INTERACTIONS, GROWTH,
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, PHYSIOLOGICAL CO2
RESPONSES, RESPIRATION, REVIEW

226  
Eamus, D. 1992. Atmospheric CO2 and Trees, from Cellular to
Regional Responses. IN: Encyclopedia of Earth System Science, Vol.
1, Academic Press, Inc., New York, pp. 157-169.

KEYWORDS: ALLOCATION, CLIMATE, COMMUNITY LEVEL CO2 RESPONSES,
CONDUCTANCE, ENVIRONMENTAL INTERACTIONS, GROWTH, MODELING,
PHOTOSYNTHESIS, RESPIRATION, REVIEW, TREES, WUE

227  
Eamus, D. 1992. The Interaction of Rising CO2 and Temperatures with
Water Use Efficiency. Plant, Cell and Environment 14:843-852.

Recent data concerning the impact of elevated atmospheric CO2 upon
water use efficiency (WUE) and the related measure, instantaneous
transpiration efficiency (ITE), are reviewed. It is concluded from
both short and long-term studies that, at the scale of the
individual leaf or plant, an increase in WUE or ITE is generally
observed in response to increased atmospheric CO2 levels. However,
the magnitude of this increase may decline with time. The opinion
that elevated CO2 may substantially decrease transpiration at the
regional scale is discussed. The mechanisms by which elevated CO2
may cause a change in these measures are discussed in terms of
stomatal conductance, assimilation and respiration responses to
elevated CO2. Finally, recent experimental data and model outputs
concerning the impact of the interaction of increased temperature
with elevated CO2 on WUE, ITE and yield are reviewed. It is
concluded that substantially more data is required before reliable
predictions about the regional scale response of WUE and catchment
hydrology can be made.

KEYWORDS: MODELING, REVIEW, STOMATA, TEMPERATURE, TRANSPIRATION,
WUE

228  
Eamus, D., and G. Duff. 1992. Increased Atmospheric Carbon Dioxide
Levels and Vegetation Responses in the Tropics. IN: Conservation
and Development Issues in North Australia (I. Moffatt and A. Webb,
eds.), North Australia Research Unit, Australian National
University, Casuarina (Darwin), Northern Territory, Australia, pp.
145-154.

KEYWORDS: CARBOHYDRATES, CLIMATE, COMMUNITY LEVEL CO2 RESPONSES,
CONDUCTANCE, MODELING, RESPIRATION, REVIEW

229  
Eamus, D., and P.G. Jarvis. 1989. The Direct Effects of Increase in
the Global Atmospheric CO2 Concentration on Natural and Commercial
Temperate Trees and Forests. IN: Advances in Ecological Research,
Vol. 19 (M. Begon, A.H. Fitter, E.D. Ford, and A. Macfadyen, eds.),
Academic Press Ltd., New York, pp. 1-55.

KEYWORDS: ALLOCATION, CONDUCTANCE, FOREST, GROWTH, NITROGEN
FIXATION, NUTRITION, PHOTOSYNTHESIS, RESPIRATION, REVIEW, STRESS,
TREES, WUE

230  
Ehret, D.L., and P.A. Jolliffe. 1985. Leaf Injury to Bean Plants
Grown in Carbon Dioxide Enriched Atmospheres. Canadian Journal of
Botany 63:2015-2020.

Bush bean (Phaseolus vulgaris L.) plants grown in atmospheres
enriched with CO2 (1400 uL/L) showed marked reductions in
photosynthetic capacity and accelerated chlorosis of primary
leaves. Leaf injury was observed only in CO2 enriched plants, but
the degree of injury was regulated by secondary factors, light and
temperature. Conditions of relatively high light intensity (340-370
umol/m2/s photosynthetic photon flux density) or cool temperature
(20C) promoted leaf injury of CO2-enriched plants. Leaf starch
accumulation was highest under conditions that caused injury. The
enhanced chlorosis and corresponding decline in photosynthetic
activity, however, were not related to changes in stomatal
diffusive resistance or leaf water status. Contaminant gases, such
as ethylene, were not detectable in the CO2-enrichment chambers.

bean/Phaseolus vulgaris

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF INJURY, LEAF
PHOTOSYNTHESIS, LIGHT, PHOTOSYNTHETIC FEEDBACK INHIBITION,
TEMPERATURE

231  
Ehret, D.L., and P.A. Jolliffe. 1985. Photosynthetic Carbon Dioxide
Exchange of Bean Plants Grown at Elevated Carbon Dioxide
Concentrations. Canadian Journal of Botany 63:2026-2030.

Leaves of bean plants (Phaseolus vulgaris L. cv. Pure Gold Wax)
grown in atmospheres enriched in CO2 (1400 uL/L) showed a decrease
in CO2 exchange capacity when compared with unenriched plants (340
uL/L) measured at the same CO2 concentration. The decrease was not
associated with changes in chlorophyll concentration or
photorespiratory activity. The decrease was less evident in older
leaves, in leaves maintained at low light intensity, and in those
with reduced chlorophyll contents. Respiration rates in leaves of
CO2-enriched plants increased only under conditions that caused a
concurrent decrease in photosynthetic capacity. Enriched leaves had
higher starch contents than unenriched leaves. The results were
consistent with the idea that CO2 enrichment decreases
photosynthetic capacity when photoassimilate supply exceeds sink
demand.

Phaseolus vulgaris/bean

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, PHOTOSYNTHETIC FEEDBACK INHIBITION, RESPIRATION

232  
El Kohen, A., and M. Mousseau. 1990. Effet d'un Doublement de la
Teneur en CO2 Atmospherique sur le Bilan Carbone de Jeunes
Chataigniers. Bulletin de la Societe Ecophysiologique 15:135-147.

In French.

chestnut/Castanea sativa

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, OUTDOOR GROWTH
CHAMBERS, RESPIRATION, TREES

233  
El Kohen, A., J.-Y. Pontailler, and M. Mousseau. 1991. Effect of
Doubling of Atmospheric CO2 Concentration on Dark Respiration in
Aerial Parts of Young Chestnut Trees (Castanea sativa Mill.).
Comptes Rendus des Sciences (Paris) t. 312, Serie III:477-481.

Two-year-old sweet chestnut seedlings were grown in constantly
ventilated tunnels at ambient (350 vpm) or double (700 vpm) CO2
concentration during a full growing season. End-of-night dark
respiration of aerial parts was measured in each CO2 concentration
throughout the growing season. Dark respiration rate of enriched
plants showed a net decrease as compared to control plants during
the first half of the growing season. This difference decreased
with time and became negligible in the fall. Atmospheric CO2
concentration acted instantaneously on the respiration rate: when
doubled, it decreased control plant respiration and when decreased,
it enhanced CO2 enriched plant respiration. The explanation of
these findings remains hypothetical. It is concluded that the rise
in carbon dioxide level of the atmosphere will affect the carbon
balance of young trees not only through an increase in net
photosynthesis during the day, but also at night by reducing
respiratory losses. In French.

Castanea sativa/sweet chestnut

KEYWORDS: CARBON BUDGET, OUTDOOR GROWTH CHAMBERS, RESPIRATION,
TREES

234  
El Kohen, A., H. Rouhier, and M. Mousseau. 1992. Changes in Dry
Weight and Nitrogen Partitioning Induced by Elevated CO2 Depend on
Soil Nutrient Availability in Sweet Chestnut (Castanea sativa
Mill.). Annales des Sciences Forestieres 49:83-90.

The effect of 2 levels of atmospheric carbon dioxide (ambient, i.e.
350 ppm, and double, i.e. 700 ppm) and 2 contrasting levels of
mineral nutrition on dry weight, nitrogen accumulation and
partitioning were examined in 2-year-old chestnut seedlings
(Castanea sativa Mill.), grown in pots outdoors throughout the
vegetative season. Fertilization had a pronounced effect on dry
weight accumulation, tree height, leaf area, and plant nitrogen
content. Carbon dioxide enrichment significantly increased total
biomass by about 20%, both on fertilized and on unfertilized forest
soil, only the root biomass was increased, leading to an increase
in the root:shoot ratio. Contrastingly, on fertilized soil only
stem biomass and diameter but not height were increased. Carbon
dioxide enrichment significantly reduced the nitrogen concentration
in all organs, irrespective of the nutrient availability. However,
the biomass increase made up for this reduction in such a way that
the total nitrogen pool per tree remained unchanged.

Castanea sativa/sweet chestnut

KEYWORDS: ALLOCATION, GROWTH, LITTER QUALITY, NITROGEN, NUTRITION,
OUTDOOR GROWTH CHAMBERS, ROOT:SHOOT RATIO, TREES

235  
El Kohen, A., L. Venet, and M. Mousseau. 1993. Growth and
Photosynthesis of Two Deciduous Forest Species at Elevated Carbon
Dioxide. Functional Ecology 7:480-486.

Two-year-old sweet chestnut (Castanea sativa Mill) and beech (Fagus
sylvatica L.) seedlings were grown in large pots on the same forest
soil, at ambient (+/- 350 uL/L) and double (700 uL/L) atmospheric
CO2 concentration in constantly ventilated minigreenhouses during
the entire growing season. CO2 enrichment caused very different
changes in these two temperate deciduous species. A 20% dry weight
enhancement was obtained for sweet chestnut, while this increase
amounted to 60% in beech. This greater effect of an elevated CO2 in
beech was the result of a significant increase of net
photosynthesis of the seedlings occurring during the whole season.
On the contrary, this increase in photosynthesis lasted only a few
weeks in sweet chestnut and then an acclimation process took place.
No effect of an increased CO2 could be found on sweet chestnut leaf
area or leaf number, while a significant effect was found with
beech, in which total leaf area per plant increased, owing to a
greater number of growth flushes, each with larger leaves. The
partitioning of the biomass increase due to elevated CO2 was very
different in the two species. All additional dry matter was
allocated to the roots in sweet chestnut, while it was partitioned
equally amongst all organs of the beech seedling. The reactions to
elevated CO2 of different tree species is discussed in relation to
their specific growth strategy.

sweet chestnut/Castanea sativa/Fagus sylvatica/beech

KEYWORDS: ALLOCATION, GROWTH, OUTDOOR GROWTH CHAMBERS,
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, TREES

236  
Eng, R.Y.N., M.J. Tsujita, and B. Grodzinski. 1985. The Effects of
Supplementary HPS Lighting and Carbon Dioxide Enrichment on the
Vegetative Growth, Nutritional Status and Flowering Characteristics
of Chrysanthemum morifolium Ramat. Journal of Horticultural Science
60:389-395.

Supplementary high pressure sodium (HPS) lighting (140 umol/m2/s)
and CO2 enrichment (1375 uL/L) improved the vegetative growth of
Chrysanthemum morifolium cv Dramatic by increases in stem length,
stem diameter, root weight ratio, dry weight, relative growth and
net assimilation rates. Three-week-old chrysanthemums grown under
CO2 enrichment and HPS lighting had lower leaf weight and stem
weight ratios as well as lower foliar nutrient content than those
grown under ambient CO2 and natural light. Plants grown on to
maturity under CO2 enrichment and supplementary HPS lighting had
the longest stem lengths, the most flowers and greatest increase in
dry weight. The combination of both additional light and CO2 was
superior to either factor used alone. With 24 h HPS supplementary
lighting CO2 enrichment was most effective in improving vegetative
growth and flower quality when applied during the daytime. Night
CO2 enrichment was not commercially beneficial at the light levels
employed in this study.

Chrysanthemum morifolium/chrysanthemum

KEYWORDS: ALLOCATION, COMMERCIAL USE OF CO2, FLOWER PRODUCTION,
GREENHOUSE, LIGHT

237  
Enoch, H.Z. 1990. Crop Responses to Aerial Carbon Dioxide. Acta
Horticulturae 268:17-32.

Crops are subjected to a global bulk atmosphere that contains a
supra-optimal oxygen concentration and a sub-optimal carbon dioxide
concentration. It is expected that the present increase in
atmospheric CO2 concentration will continue, that a doubling will
occur during the next century and that eventually values of over
2500 ppm will be reached. Until then greenhouse crops should be CO2
enriched. The potential of intermittent CO2 enrichment (pulse CO2
enrichment) for yields enhancement and pollution avoidance will be
described. The main changes in crops due to elevated CO2 seem to be
secondary effects of enhanced photosynthesis but some morphogenetic
changes, for instance increased branching, are interpreted as
partial suppression of apical dominance and appear to show that CO2
concentration has additional hormone-like effects. Though over 1000
papers on CO2 enrichment have been published there is only an
incomplete understanding of whether other organs than leaves are
sensitive to CO2 concentration and whether elevated CO2 has a
trigger effect or a threshold effect on morphogenesis of crops.
Some of the research questions that should be asked in order to
improve our understanding of how CO2 enrichment influences plant
productivity will be discussed.

KEYWORDS: ALLOCATION, CO2 ENRICHMENT DURATION, CO2 PULSES,
COMMERCIAL USE OF CO2, GREENHOUSE, REVIEW

238  
Enoch, H.Z., and N. Zieslin. 1988. Growth and Development of Plants
in Response to Carbon Dioxide Concentrations. Applied Agricultural
Research 3:248-256.

Quality of protected crops can be improved by controlling the
aerial carbon dioxide (CO2) in the greenhouse. The influence of
atmosphere CO2 concentration on partitioning of dry matter, leaf
growth and development, stem growth, root formation, branching and
tillering, growth of the whole plant and on flowering is described
in this review. At elevated CO2 concentrations apical dominance in
C3 and C4 plants is weakened resulting in higher root-to-shoot
ratios and increased side shoot development (branching, tillering,
etc.). Most effects of elevated CO2 concentration appear to be
secondary effects of photosynthesis enhancement leading to higher
leaf weight per unit area, greater stem weight per unit length, and
an increase in absolute growth rate--but not always an increase in
relative growth rate. The influence of elevated CO2 concentration
on flowering is discussed in detail. Examples of organ development
that can be explained as secondary effects of enhanced
photosynthesis, as well as exceptions, are presented.

KEYWORDS: ALLOCATION, COMMERCIAL USE OF CO2, FLOWER PRODUCTION,
REVIEW, ROOT:SHOOT RATIO

239  
Evans, L.S., and G.R. Hendrey. 1992. Responses of Cotton Foliage to
Short-term Fluctuations in CO2 Partial Pressures. Critical Reviews
in Plant Sciences 11:203-212.

cotton/Gossypium hirsutum

KEYWORDS: 14C, CO2 PULSES, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS

240  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1989. The Effects of
Enriched Carbon Dioxide Atmospheres on Plant-Insect Herbivore
Interactions. Science 243:1198-1200.

Little is known about the effects of enriched CO2 atmospheres,
which may exist in the next century, on natural plant-insect
herbivore interactions. Larvae of a specialist insect herbivore,
Junonia coenia (Lepidoptera: Nymphalidae), were reared on one of
its host plants, Plantago lanceolata (Plantaginaceae), grown in
either current low (350 parts per million) or high (700 ppm) CO2-environments. Those larvae raised on high-CO2 foliage grew more
slowly and experienced greater mortality, especially in early
instars, than those raised on low-CO2 foliage. Poor larval
performance on high-CO2 foliage was probably due to the reduced
foliar water and nitrogen concentrations of those plants and not to
changes in the concentration of the defensive compounds, iridoid
glycosides. Adult pupal weight and female fecundity were not
affected by the CO2 environment of the host plant. These results
indicate that interactions between plants and herbivorous insects
will be modified under the predicted CO2 conditions of the 21st
century.

Plantago lanceolata

KEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS,
HERBIVORY, INSECTS, JUNONIA COENIA, NITROGEN

241  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1990. Performance and
Allocation Patterns of the Perennial Herb, Plantago lanceolata, in
Response to Simulated Herbivory and Elevated CO2 Environments.
Oecologia 87:37-42.

We tested the prediction that plants grown in elevated CO2
environments are better able to compensate for biomass lost to
herbivory than plants grown in ambient CO2 environments. The
herbaceous perennial Plantago lanceolata (Plantaginaceae) was grown
in either near ambient (380 ppm) or enriched (700 ppm) CO2
atmospheres, and then after 4 weeks, plants experienced either 1)
no defoliation; 2) every fourth leaf removed by cutting; or 3)
every other leaf removed by cutting. Plants were harvested at week
13 (9 weeks after simulated herbivory treatments). Vegetative and
reproductive weights were compared, and seeds were counted,
weighed, and germinated to assess viability. Plants grown in
enriched CO2 environments had significantly greater shoot weights,
leaf areas, and root weights, yet had significantly lower
reproductive weights (i.e. stalks + spikes + seeds) and produced
fewer seeds, than plants grown in ambient CO2 environments.
Relative biomass allocation patterns further illustrated
differences in plant responses to enriched CO2 atmospheres:
enriched CO2-grown plants only allocated 10% of their carbon
resources to reproduction whereas ambient CO2-grown plants
allocated over 20%. Effects of simulated herbivory on plant
performance were much less dramatic than those induced by enriched
CO2 atmospheres. Leaf area removal did not reduce shoot weights or
reproductive weights of plants in either CO2 treatment relative to
control plants. However, plants from both CO2 treatments
experienced reductions in root weights with leaf area removal,
indicating that plants compensated for lost above-ground tissues,
and maintained comparable levels of reproductive output and seed
viability, at the expense of root growth.

Plantago lanceolata

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY,
REPRODUCTION, SURVIVORSHIP

242  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1991. The Effects of
Enriched CO2 Atmospheres on the Buckeye Butterfly, Junonia coenia.
Ecology 72:751-754.

Plantago lanceolata

KEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS,
HERBIVORY, INSECTS, JUNONIA COENIA, NITROGEN

243  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1992. The Effect of
Nutrients and Enriched CO2 Environments on Production of Carbon-based Allelochemicals in Plantago: A Test of the Carbon/Nutrient
Balance Hypothesis. The American Naturalist 140:707-723.

In a test of the carbon/nutrient (C/N) balance hypothesis, we grew
the perennial herb Plantago lanceolata in different CO2 and
nutrient environments and then (1) measured the total allocation to
shoots, roots, and reproductive parts and (2) quantified aucobin,
catalpol, and verbascoside contents of replicate plants of six
genotypes. Plants grown under low-nutrient conditions do have
higher concentrations of carbon-based allelochemicals than plants
grown under high nutrient conditions. However, in contrast to the
C/N balance hypothesis, plants grown in elevated (700 uL/L) CO2
conditions had similar, or lower, concentrations of carbon-based
allelochemicals than plants grown in ambient (350 uL/L) CO2
conditions. We suggest that augmented substrate concentrations
(i.e., excess carbohydrates) are a necessary but insufficient
trigger for increased secondary metabolism; instead, hormonal
and/or direct physical cues (such as light) may be essential to
synthesize or activate the appropriate enzyme systems. Moreover,
although plant genotype significantly affected plant growth,
reproduction, and chemistry, we never observed significant
genotype-by-CO2 interactions for these factors, which suggests that
changing CO2 environments may not improve the fitness of certain
genotypes over others.

Plantago lanceolata

KEYWORDS: ALLELOCHEMICALS, ALLOCATION, CARBOHYDRATES, CARBON,
CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY,
NUTRITION

244  
Farrar, J.F., and M.L. Williams. 1991. The Effects of Increased
Atmospheric Carbon Dioxide and Temperature on Carbon Partitioning,
Source-sink Relations and Respiration. Plant, Cell and Environment
14:819-830.

Herbaceous C3 plants grown in elevated CO2 show increases in carbon
assimilation and carbohydrate accumulation (particularly starch)
within source leaves. Although changes in the partitioning of
biomass between root and shoot occur, the proportion of this extra
assimilate made available for sink growth is not known. Root:shoot
ratios tend to increase for CO2 enriched herbaceous plants and
decrease for CO2-enriched trees. Root:shoot ratios for cereals tend
to remain constant. In contrast, elevated temperatures decrease
carbohydrate accumulation within source and sink regions of a plant
and decrease root:shoot ratios. Allometric analysis of at least two
species showing changes in root:shoot ratios due to elevated CO2
show no alteration in the whole-plant partitioning of biomass.
Little information is available for interactions between
temperature and CO2. Cold-adapted plants show little response to
elevated levels of CO2, with some species showing a decline in
biomass accumulation. In general though, increasing temperature
will increase sucrose synthesis, transport and utilization for CO2-enriched plants and decrease carbohydrate accumulation within the
leaf. Literature reports are discussed in relation to the
hypothesis that sucrose is a major factor in the control of plant
carbon partitioning. A model is presented in support.

KEYWORDS: ALLOCATION, CARBOHYDRATES, MODELING, RESPIRATION, REVIEW,
SOURCE-SINK BALANCE, TEMPERATURE

245  
Ferguson, J.J., W.T. Avigne, L.H. Allen, and K.E. Koch. 1986.
Growth of CO2-enriched Sour Orange Seedlings Treated with
Gibberellins/Cytokinins. Proceedings of the Florida State
Horticultural Society 99:37-39.

Enriched CO2 atmospheres and specific plant growth regulators are
known to stimulate plant growth, but their combined effects on
citrus seedlings have not been studied. Sour orange (Citrus
aurantium L.) seedlings were treated with plant growth regulators
(6-benzyladenine <BA> [250 ul/l]; 6 benzyladenine and gibberellic
acid <BA + GA> [250 ul/l]; gibberellin 3 <GA3> [450 ul/l] and
gibberellin 4+7 <GA4+7> [250 ul/l]) and grown at either ambient or
elevated CO2 levels (330 or 660 ul/l). Seedlings treated with GA4+7
and grown at elevated CO2 levels were taller and had greater leaf
weight than plants given all other treatments. Leaf number
increased under elevated CO2 levels when BA or GA4+7 were applied.
Stem weight was unaffected by growth regulators except when GA4+7
was applied to plants grown under high CO2 levels. Stem caliper
increased slightly under high CO2 levels, especially when GA4+7 was
applied.

sour orange/Citrus aurantium

KEYWORDS: GROWTH, GROWTH REGULATORS, SPAR UNITS, TREES

246  
Fetcher, N., C.H. Jaeger, B.R. Strain, and N. Sionit. 1988. Long-term Elevation of Atmospheric CO2 Concentration and the Carbon
Exchange Rates of Saplings of Pinus taeda L. and Liquidambar
styraciflua L. Tree Physiology 4:255-262.

The relationship between carbon exchange rate (CER) and internal
CO2 concentration was measured in leaves of saplings of Liquidambar
styraciflua L. (sweetgum) and Pinus taeda L. (loblolly pine) grown
from seed for more than 14 months at atmospheric CO2 concentrations
of either 340 or 500 uL/L. An elevated concentration of CO2 during
growth reduced CER at any given internal CO2 concentration in
sweetgum, but not in loblolly pine. Stomatal limitation of CER
showed little response to concentration of CO2 during measurement,
but was higher in both species when grown at 500 than at 350 uL/L
CO2. The net effect of a long-term increase in CO2 concentration
from 350 to 500 uL/L was an increase in CER of loblolly pine, but
a slight decrease in CER of sweetgum. It is suggested that the
depression of CER in sweetgum resulted from a reduction in the
activity of ribulose-1,5-bisphosphate carboxylase-oxygenase.

sweetgum/Liquidambar styraciflua/loblolly pine/Pinus taeda

KEYWORDS: CONDUCTANCE, GREENHOUSE, LEAF PHOTOSYNTHESIS,
PHOTOSYNTHETIC ACCLIMATION, RIBULOSE BISPHOSPHATE CARBOXYLASE

247  
French, C.J. 1989. Propagation and Subsequent Growth of
Rhododendron Cuttings: Varied Response to CO2 Enrichment and
Supplementary Lighting. Journal of the American Society of
Horticultural Science 114:251-259.

CO2 mist (1100 uL CO2/L) during fall propagation inhibited rooting
of Rhododendron 'Anna Rose Whitney' (R. griersonianum x 'Countess
of Derby') and had no effect on R. 'Vulcan' ('Mars' x R.
griersonianum), R. 'Unique' (R. campylocarpum hybrid), R. 'Anah
Krushke' (R. ponticum seedling), or R. 'Pink Bountiful' (R.
williamsianum x 'Linswegeanum'). Supplementary lighting from high-pressure sodium lamps (HPS) for 16 hr/day (0400 to 2000 hr) had no
effect on rooting of any cultivar. There was an interaction between
CO2 mist and HPS exposure on rooting in R. 'Floriade' ('Britannia'
hybrid). CO2 mist inhibited and HPS stimulated shoot development
during propagation. CO2 mist during propagation inhibited
subsequent development of 'Anna Rose Whitney' and 'Vulcan'. HPS
during propagation inhibited subsequent growth of 'Floriade' and
'Vulcan'. CO2 enrichment of stock plants prior to propagation did
not affect rooting of R. 'Sonata', whereas CO2 mist during
propagation was inhibitory. In 'Anna Rose Whitney', there was an
interaction between CO2 enrichment before and during propagation.
Application of supplementary HPS for 16 hr/day following
propagation stimulated subsequent growth of both cultivars. CO2
mist during spring propagation stimulated rooting of 'Pink
Bountiful' and 'Vulcan' and had no effect on R. 'Matador' (R.
griersonianum x strigillosum), R. 'Martha Isaacson' (R. occidentale
x Ostbo seedling No. 70), or R. 'Elizabeth' (R. forestii var repens
x griersonianum). Supplementary HPS had no effect on rooting. A low
irradiance night break treatment from incandescent lamps (2000 to
0400 hr) had no effect on rooting of 'Vulcan'. There was an
interaction between night break lighting and CO2 mist on rooting in
'Unique'. CO2 mist and HPS during spring propagation had minor
effects on subsequent growth of 'Matador', 'Martha Isaacson', 'Pink
Bountiful', and 'Elizabeth'. CO2 mist and supplementary HPS have
little value in production of Rhododendron.

Rhododendron spp.

KEYWORDS: GREENHOUSE, HORTICULTURAL CROPS, LIGHT, ROOTING

248  
French, C.J. 1990. Rooting of Rhododendron 'Anna Rose Whitney'
Cuttings as Related to Stem Carbohydrate Concentration. HortScience
25:409-411.

Rooting of Rhododendron 'Anna Rose Whitney' (R. Griersonianum x
'Countess of Derby') was delayed in cuttings from stock plants
grown in full sun, compared to cuttings from plants grown in 80%
shade. In the outer stem (extracambium tissues), concentrations of
glucose, sucrose, soluble carbohydrate, and total nonstructural
carbohydrates were higher in cuttings from shaded stock plants. In
the inner stem (intracambium tissues), where rooting originates,
fructose, starch and nonstructural carbohydrates were lower in
cuttings from the shaded stock plants. Rooting percentage was
reduced by CO2 mist during propagation. At 7 days, during rooting
with a CO2 enrichment to 1100 uL/L, fructose in the inner stem was
3-fold higher than in cuttings rooted under atmospheric CO2 (340
uL/L). Under CO2 mist, total nonstructural carbohydrate
concentration was higher in the inner stem throughout the rooting
period. For both high stock plant irradiance and CO2 enrichment
during propagation, there was an inverse relationship between
fructose concentration in the inner stem and rooting. A possible
mechanism for inhibition by fructose is proposed.

Rhododendron spp.

KEYWORDS: CARBOHYDRATES, GREENHOUSE, HORTICULTURAL CROPS, ROOTING

249  
French, C.J., and J. Alsbury. 1989. Supplementary Lighting and CO2
Mist Influence Rooting of Camellia japonica. HortScience 24:452-454.

Supplementary irradiance from high-pressure sodium lamps (HPS) at
75 umol/s/m2 stimulated rooting of difficult-to-root Camellia
japonica 'Lady Clare' when applied from sunrise to sunset in a
heavily shaded greenhouse (20% light transmission). There was no
effect of HPS on the easy-to-root cultivar Blood of China.
Irradiance from HPS either at 45 umol/s/m2 for 16 hr/day or at 75
umol/s/m2 CO2 mist inhibited rooting of both cultivars when applied
in fall propagation. In spring, CO2 mist during the day simulated
root number of 'Lady Clare' when combined with a night-break
treatment from incandescent lamps (INC). Carbon dioxide mist had
little effect under a natural photoperiod, and CO2 mist was
ineffective when INC were used. The effects of supplementary CO2,
irradiance, and increased photoperiod on rooting varied with season
and cultivar.

Camellia japonica

KEYWORDS: CULTIVAR RESPONSES, ENVIRONMENTAL INTERACTIONS,
GREENHOUSE, HORTICULTURAL CROPS, LIGHT, PHOTOPERIOD, ROOTING

250  
Fried, J.S., K.A. Surano, P.F. Daley, J.H. Shinn, and P. Anderson.
1986. Biomass Production and Nutrient Responses of Ponderosa Pine
to Long-term Elevated CO2 Concentrations. IN: Proceedings of the
Ninth North American Forest Biology Workshop; 1986 June 15-18;
Stillwater, Oklahoma (C.G. Tauer and T.C. Hennessey, eds.), Society
of American Foresters, Department of Forestry, Oklahoma State
University, Stillwater, Oklahoma, pp. 11-18.

Ponderosa pine saplings and seedlings were continuously exposed to
elevated CO2 concentrations of ambient, and ambient +75, +150, and
+300 ppm in open-top chambers for 27 months. Saplings responded by
reducing above ground biomass production. Although potassium
concentration in both saplings and seedlings diminished as CO2
concentration increased, no nutrients appeared to become limiting
to growth as a result of elevated CO2. Concentrations of Ca, Mg and
Zn in the saplings at different concentrations of CO2 mirrored root
densities, indicating that an increase in root density at +150 ppm
may account for greater nutrient concentrations observed in that
tree.

Pinus ponderosa/ponderosa pine

KEYWORDS: CALCIUM, IRON, MAGNESIUM, MANGANESE, NITROGEN, NUTRITION,
OPEN-TOP CHAMBERS, PHOSPHORUS, POTASSIUM, ROOTS, SULFUR, TREES, X-RAY DENSITOMETRY, ZINC

251  
Fung, I.Y., C.J. Tucker, and K.C. Prentice. 1987. Application of
Advanced Very High Resolution Radiometer Vegetation Index to Study
Atmosphere-Biosphere Exchange of CO2. Journal of Geophysical
Research 92:2999-3015.

Normalized difference vegetation indices derived from radiances
measured by the Advanced Very High Resolution Radiometer aboard the
NOAA 7 polar-orbiting satellite were used to prescribe the phasing
of terrestrial photosynthesis. The satellite data were combined
with field data on soil respiration and a global map of net primary
productivity to obtain the seasonal exchange of CO2 between the
atmosphere and the terrestrial biosphere. The monthly fluxes of CO2
thus obtained were employed as source/sink functions in a global
three-dimensional atmospheric tracer transport model to simulate
the annual oscillations of CO2 in the atmosphere. Reasonable
agreement was found between the simulated and observed annual
cycles of atmospheric CO2 at the locations of the remote monitoring
stations. The results demonstrate that satellite data of high
spatial and temporal resolution can be used to provide quantitative
information about seasonal and longer-term variations of
photosynthetic activity on a global scale. Atmospheric CO2
observations and a three-dimensional atmospheric model have been
used to validate the translation of the nondimensional satellite
data into dimensional carbon fluxes. Direct calibration will
require extensive ground truth and field measurements at ecosystem
scales.

KEYWORDS: ADVANCED VERY HIGH RESOLUTION RADIOMETER, MODELING, NET
PRIMARY PRODUCTIVITY, NORMALIZED DIFFERENCE VEGETATION INDEX,
PHOTOSYNTHESIS, GLOBAL, RADIATION, REFLECTANCE, REMOTE SENSING

252  
Furbank, R.T., and D.A. Walker. 1986. Chlorophyll A Fluorescence as
a Quantitative Probe of Photosynthesis: Effects of CO2
Concentration during Gas Transients on Chlorophyll Fluorescence in
Spinach Leaves. New Phytologist 104:207-213.

The relationship between changes in chlorophyll a fluorescence and
changes in CO2 concentration in spinach leaves is analyzed. The
height of the fluorescence excursion, when plotted against the CO2
concentration during the transient, results in a hyperbola. When
these data are replotted on an inverse-reciprocal plot, an apparent
Km(CO2) for the fluorescence transient can be obtained which
closely approximates the Km(CO2) for carbon assimilation under
similar conditions. Transitions in CO2 concentration at 2% O2
result in deviation from this hyperbolic relationship, reducing the
apparent Km(CO2) for this process. The relationship between carbon
assimilation and chlorophyll fluorescence is discussed with
reference to the two components of fluorescence quenching. This
technique raises the possibility that chlorophyll fluorescence
could be used as a quantitative as well as a qualitative tool in
plant screening.

spinach/Spinacia oleracea

KEYWORDS: FLUORESCENCE, LEAF PHOTOSYNTHESIS

253  
Gale, J. 1986. Carbon Dioxide Enhancement of Tree Growth at High
Elevation. Science 231:859-860.

Technical comment.

KEYWORDS: ALTITUDE, PHOTOSYNTHESIS, TREE-RING ANALYSIS, TREES

254  
Garbutt, K., W.E. Williams, and F.A. Bazzaz. 1990. Analysis of the
Differential Response of Five Annuals to Elevated CO2 during
Growth. Ecology 71:1185-1194.

In order to investigate the effects, without competition, of CO2 on
germination, growth, physiological response, and reproduction, we
focused on co-occurring species that are prominent members of an
annual community in Illinois. Five species of old field annual
plants -- Abutilon theophrasti (C3), Amaranthus retroflexus (C4),
Ambrosia artemisiifolia (C3), Chenopodium album (C3) and Setaria
faberii (C4) -- were grown for their entire life cycle as
individuals at CO2 concentration of 350 uL/L, 500 uL/L, and 700
uL/L. Emergence time, growth rate, shoot water status,
photosynthesis, conductance, flowering time, nitrogen content, and
biomass and reproductive biomass were measured. There was no
detectable effect of enhanced CO2 on timing of emergence in any of
the species. Amaranthus relative growth rate (RGR) was always
higher at 700 uL/L CO2 than at 350 uL/L. In both Abutilon and
Ambrosia, RGR was greater at 700 uL/L than at 350 uL/L during the
first half of the experimental period, but during the second half
of the period the reverse was true. Shoot water potential
significantly increased (became less negative) with increasing CO2
in Amaranthus and Setaria. Similar but statistically nonsignificant
trends were found in Chenopodium and Abutilon. Overall rate of
photosynthesis increased with CO2 but there were no significant
effects, at the species level, of CO2 on photosynthetic rates.
Stomatal conductance decreased with increased CO2 at both high and
low light levels in C3 species but only at high light levels in C4
species. In all species, intercellular CO2 increased with external
CO2. Amaranthus flowered significantly earlier at 700 uL/L than at
350 uL/L, and Setaria flowered significantly later at 700 uL/L than
at either of the other CO2 levels. Both Abutilon and Ambrosia
showed a trend towards earlier flowering but this was not
statistically significant. Of the morphological characters measured
at the final harvest only specific leaf area (SLA) showed a
consistent response to CO2, decreasing with increasing CO2.
Significant CO2 x species interactions were also found for leaf
area, leaf biomass, biomass of reproductive parts, and seed biomass
indicating species-specific responses for these characters. The
proportion of nitrogen declined with increasing CO2; there was also
a significant CO2 x species interaction caused by the different
rates of decline in proportion of nitrogen among the species. The
response of most characters had a significant species x CO2
interaction. However, this was not simply caused by the C3/C4
dichotomy. Reproductive biomass (seed, fruits, and flowers)
increased with increasing CO2 in Amaranthus (C4) and in Chenopodium
and Ambrosia (both C3) but there was no change in Setaria (C4) and
Abutilon (C3) showed a peak at 500 uL/L. Species of the same
community differed in their response to CO2, and these differences
may help explain the outcome of competitive interactions among
these species above ambient CO2 levels.

Abutilon theophrasti/Amaranthus retroflexus/Ambrosia
artemisiifolia/Chenopodium album/Setaria faberii

KEYWORDS: C3, C4, COMPETITION, GROWTH ANALYSIS, LEAF
PHOTOSYNTHESIS, LIGHT, NITROGEN, OLD FIELD COMMUNITIES,
REPRODUCTION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

255  
Gardestrom, P. 1987. Adenylate Ratios in the Cytosol, Chloroplasts
and Mitochondria of Barley Leaf Protoplasts during Photosynthesis
at Different Carbon Dioxide Concentrations. FEBS Letters 212:114-118.

Barley (Hordeum vulgare) protoplasts were incubated in darkness and
in the light at saturating and limiting CO2 concentrations. The
protoplasts were fractioned by a membrane filtration technique
which allows quenching of the metabolism by acidification within
about 0.1 s and the ATP/ADP ratios in the cytosol, chloroplasts and
mitochondria were determined. It is concluded that the cytosolic
ATP/ADP ratio is considerably higher during photosynthesis at
limiting CO2 (which is the normal situation for a C3 plant in air)
compared to photosynthesis at saturating CO2 or darkness.

barley/Hordeum vulgare

KEYWORDS: ADENYLATES, LEAF PHOTOSYNTHESIS, METABOLITES

256  
Gastal, F., and B. Saugier. 1989. Relationships Between Nitrogen
Uptake and Carbon Assimilation in Whole Plants of Tall Fescue.
Plant, Cell and Environment 12:407-418.

tall fescue

KEYWORDS: GRASSES, NITROGEN, NUTRITION, PHOTOSYNTHESIS

257  
Gates, D.M. 1985. Global Biospheric Response to Increasing
Atmospheric Carbon Dioxide Concentration. IN: Direct Effects of
Increasing Carbon Dioxide on Vegetation, DOE/ER-0238 (B.R. Strain
and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research
Division, Washington, D.C., pp. 171-184.

KEYWORDS: BIOTIC GROWTH FACTOR, CARBON BUDGET, ECOSYSTEM LEVEL CO2
RESPONSES, NET PRIMARY PRODUCTIVITY, REVIEW, TREE-RING ANALYSIS

258  
Gaudillere, J.-P., and M. Mousseau. 1989. Short Term Effect of CO2
Enrichment on Leaf Development and Gas Exchange of Young Poplars
(Populus euramericana cv I 214). Acta Oecologica/Oecologia
Plantarum 10:95-105.

Fast growing young poplar trees bearing 25 to 30 leaves were placed
in a growth chamber. The air CO2 content was 330 uL/L during the
first 15 days and 660 uL/L the following 15 days. The leaves in 660
uL/L CO2 in air developed a greater area and specific weight and
contained more stomata, epidermal cells and chlorophyll per unit
area. Leaf developmental characteristics (Relative Leaf Expansion,
Leaf Plastochron Index, Leaf Expansion Duration) were modified by
the treatment. Leaves developed in normal CO2 atmosphere
demonstrated a significant regrowth, with increased cell and
stomatal number, when exposed to the elevated CO2 treatment. Whole
plant and single leaf gas exchange rates were measured at 330 and
660 uL/L. On single attached leaves, an increased CO2 level during
growth promoted a photosynthetic inhibition, shown by a lower g and
Pmax. Due to the greater leaf area, whole tree daily photosynthesis
and respiration increased with elevated CO2, enhancing growth
efficiency. Doubling the CO2 resulted in a threefold increase in
whole plant water use efficiency (WUE).

poplars/Populus euroamericana

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, LEAF
PHOTOSYNTHESIS, RESPIRATION, STOMATAL DENSITY, STOMATAL INDEX,
TREES, WUE

259  
Geethakumari, V.L., and K. Shivashankar. 1991. Studies on Organic
Amendment and CO2 Enrichment in Ragi/Soybean Intercropping Systems.
Indian Journal of Agronomy 36:202-206.

Organic amendment comprising of ragi husk and FYM mixed in 1:1
ratio by weight promoted organic carbon content and available P
status of the soil. A level of 4 t/ha of organic amendment promoted
the uptake of N significantly by both ragi and soybean.
Availability of P and K were also favourably influenced. Uptake of
nutrients by soybean was promoted by CO2 enrichment. Available P
status was higher in intercropped ragi and soybean as compared to
pure crops but nutrient uptake was higher by pure crops.

soybean/Glycine max/ragi/Eleusine coracana

KEYWORDS: ENZYMES, INTERCROPPING, NUTRITION, OPEN-TOP CHAMBERS,
ORGANIC AMENDMENTS

260  
Gifford, R.M. 1988. Direct Effects of Higher Carbon Dioxide
Concentrations on Vegetation. IN: Greenhouse: Planning for Climate
Change (G.I. Pearman, ed.), E.J. Brill, New York, pp. 506-519.

Higher atmospheric CO2 concentrations are potentially beneficial to
agriculture because they usually stimulate plant growth. The
typical magnitude of the 'CO2 fertilizing effect' is a 30-40%
increase in yield for a doubling of CO2 concentration to 700 ppmv.
Variation in responsiveness depends on plant species and
environmental conditions such as temperature and rainfall which may
be changing as a result of the greenhouse effect. The main
mechanisms of the 'CO2-fertilizing effect' involve several
physiological phenomena, some that are certainly primary
(stimulation of photosynthesis, suppression of photorespiration,
reduction in stomatal aperture) and others that seem so far to be
primary but may turn out not to be (greater leaf area development
and branching, reduced stomatal frequency, reduced dark
respiration, changes to reproductive development). It is often
assumed that the reduction in stomatal conductance at high CO2
concentration will lead to reduced evapotranspiration from
vegetated regions, all else being equal. There are both
physiological and boundary-layer meteorological considerations
which suggest that this effect might be small though there is some
argument about that. For annual crops like cereals, a warmer
climate will tend to reduce yield owing to the faster attainment of
physiological maturity. However, the size of the CO2-fertilizing
effect on yield for a currently adapted variety is similar to that
of the associated temperature-dependent reduction of yield. So the
net effect on cereal yield in a region will depend on the success
at introducing slower maturing and CO2-responsive varieties to
compensate for faster development in warm conditions, and on
whether the climate change involves more or less rainfall in the
region.

KEYWORDS: CLIMATE CHANGE, CONDUCTANCE, CROPS, PHOTOSYNTHESIS,
REVIEW, TRANSPIRATION, YIELD

261  
Gifford, R.M. 1988. Interactions with Vegetation. IN: Greenhouse:
Planning for Climate Change (G.I. Pearman, ed.), E.J. Brill, New
York, pp. 83-89.

Plant photosynthesis has transformed the pre-biotic anaerobic
atmosphere that was rich in CO2 to a modern atmosphere, fit for
advanced life, containing 21% O2 and only a trace concentration of
CO2. Modern vegetation also plays a significant part in determining
climate by affecting the partitioning of incoming solar energy over
land. This partitioning may change as a result of CO2 effects on
vegetation. In one way or another vegetation contributes to and/or
is affected by the other major changing components of the global
atmosphere -- O3, CH4, CFCs, N2O. Current best estimates of the
scale of net deforestation of the world indicate that it is
releasing about a quarter as much CO2 to atmosphere as fossil fuel
burning is. However, the increasing CO2 concentration in the
atmosphere is probably increasing the growth of vegetation. It is
estimated that the net annual storage of extra carbon in the form
of more standing biomass and soil organic matter than hitherto, may
approximately equal the carbon released by net deforestation.
Quantitative appraisal of the global carbon cycle reveals that to
attempt to permanently remove the fossil fuel-derived CO2 from the
atmosphere by massive re-afforestation or by storing felled timber
is unrealistic. Refraining from continued net deforestation would,
however, produce a probably detectable slowdown in the rate of
build-up of atmospheric CO2.

KEYWORDS: CARBON CYCLE, DEFORESTATION, REFORESTATION

262  
Gifford, R.M. 1989. The Effects of the Build-up of Carbon Dioxide
in the Atmosphere on Crop Productivity. IN: Proceedings of the 5th
Australian Agronomy Conference; 1989 Sept. 24-29; University of
Western Australia, Perth, Western Australia, Australian Society of
Agronomy.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, CROPS, PHOTOSYNTHESIS,
REVIEW, TEMPERATURE

263  
Gifford, R.M. 1989. Exploiting the Fertilizer Effect of Increasing
Atmospheric Carbon Dioxide. IN: Climate and Food Security,
International Symposium on Climate Variability and Food Security in
Developing Countries; 1987 Feb. 5-9; New Delhi, India,
International Rice Research Institute, Manila, and American
Association for the Advancement of Science, Washington, D.C., pp.
477-487.

High CO2 concentrations fertilize plants by stimulating
photosynthesis, suppressing photorespiration, and reducing
transpiration per unit leaf area. CO2 enhancement of growth occurs
at both optimal and nonoptimal levels of other environmental
variables (light, water, temperature, nitrogen nutrients,
salinity). Severely phosphate-deficient plants may not respond to
higher CO2 concentrations. The globally increasing CO2
concentration, therefore, represents an improving component of the
fitness of the environment for secure food production. This will
partially counter any deteriorating aspects of agricultural
environments (e.g. adverse climatic change, soil loss and
deterioration, acid precipitation). Because yield increase
percentages in response to high CO2 are larger for drought and
salt-stressed plants than for nonstressed plants, some marginal
cropping sites (e.g. on arid boundaries) may show less year-to-year
variation. This would be an improvement in the stability of food
production from such sites. Because C3 species will benefit more
than C4 species, substitution of C3 for C4 crops may become more
worthwhile. Communities with access to fertilizer may be better
able to exploit higher CO2 atmospheres. Cropping boundaries may
move onto more saline and drought-prone soils, although this would
probably be bad policy in the long term. Genetic variation in
within-species responsiveness to high CO2 may enable the breeding
of cultivars to take greater advantage of a high CO2 atmosphere.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, CULTIVAR RESPONSES,
ENVIRONMENTAL INTERACTIONS, REVIEW, YIELD

264  
Gifford, R.M. 1990. Photosynthesis and the Greenhouse Effect. IN:
Chemistry and the Environment, Proceedings of Regional Symposium,
1989, Brisbane (B.N. Noller and M.S. Chadha, eds.), Commonwealth
Science Council, London, pp. 59-71.

The greenhouse effect, whereby atmospheric CO2 and water vapour
prevent the Earth's surface from being totally frozen is likely to
be amplified by the anthropogenic emissions of fossil fuel CO2. The
global carbon cycle links photosynthesis to the greenhouse effect
on all timescales up to millions of years. Major characteristics of
the Earth's atmospheric composition, notably the low CO2 and the
high oxygen concentrations were created by the evolution of plant
photosynthesis. The low CO2 concentration in the atmosphere
probably came about by the substantial acceleration of rock
weathering that plants, especially angiosperms, cause. Calcium
released by weathering moves to the oceans where it paces the
formation of calcium carbonate rocks which are a massive carbon
pool that dwarfs all others combined. On a timescale of millions of
years the carbon from calcium carbonate is cycled back to the
atmosphere via volcanoes. On shorter timescales of sociopolitical
concern photosynthesis is involved with the current global change
in atmospheric CO2 increase. From what we know about plant
photosynthetic and growth responses to increasing CO2 concentration
interacting with other limiting environmental factors, it seems
very likely that the biosphere is absorbing, into standing biomass
and soil organic matter, some of the CO2 emitted from fossil fuel
burning and net deforestation thereby contributing to the 'missing
carbon' that does not appear as an increase in atmospheric CO2
concentration. However, the scope for accelerating this CO2
sequestering process by planting more trees is rather limited owing
to the large scale required relative to the land available and to
the fact that net carbon sequestration ceases when a forest
matures.

KEYWORDS: CARBON CYCLE, CARBON SEQUESTERING, CLIMATE CHANGE,
DEFORESTATION, PHOTOSYNTHESIS, REFORESTATION, REVIEW

265  
Gifford, R.M. 1992. Interaction of Carbon Dioxide with Growth-Limiting Environmental Factors in Vegetation Productivity:
Implications for the Global Carbon Cycle. IN:, Vol. I (R.L.
Desjardins, R.M. Gifford, T. Nilson, and E.A.N. Greenwood, eds.),
Advances in Bioclimatology, Springer Verlag, Berlin, pp. 24-58.

KEYWORDS: CARBON CYCLE, ENVIRONMENTAL INTERACTIONS, NET PRIMARY
PRODUCTIVITY, NUTRITION, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION,
REVIEW, SCALING, SOURCE-SINK BALANCE

266  
Gifford, R.M., H. Lambers, and J.I.L. Morison. 1985. Respiration of
Crop Species under CO2 Enrichment. Physiologia Plantarum 63:351-356.

Respiratory characteristics of wheat (Triticum aestivum L. cvs Gabo
and WW15), mung bean (Vigna radiata L. Wilczek cv. Celera) and
sunflower (Helianthus annuus L. cv. Sunfola) were studied in plants
grown under a normal CO2 concentration and in air containing an
additional 340 or 250 uL/L CO2. Such an increase in global
atmospheric CO2 concentration has been forecast for about the
middle of the next century. The aim was to measure the effect of
high CO2 on respiration and its components. Polarographic and, with
wheat, CO2 exchange techniques were used. The capacity of the
alternative pathway of respiration in roots was determined
polarographically in the presence of 0.1 mM KCN. The actual rate of
alternative pathway respiration was assessed by reduction in oxygen
consumption caused by 10 mM salicylhydroxamic acid. Each species
responded differently. In wheat, growth in high atmospheric CO2 was
associated with up to 45% reduction in respiration by both roots
and whole plants. Use of respiratory inhibitors in polarographic
measurements on wheat roots implicated reduction in the degree of
engagement of the alternative pathway as a major contributor to
this reduced respiratory activity of high-CO2 plants. No change was
found in the total sugar content per unit wheat root dry weight as
a result of high CO2. In none of the species was there an increase
in the absolute, or relative, contribution by the alternative
pathway to total respiration of the root system. Thus the improved
photosynthetic assimilate supply of plants grown in high CO2 did
not lead to increased diversion of carbon through the non-phosphorylating alternative pathway of respiration in the root. On
the contrary, in wheat grown in high CO2, the reduced loss of
carbon through that route must have contributed to their larger dry
weight.

wheat/Triticum aestivum/mung bean/Vigna
radiata/sunflower/Helianthus annuus

KEYWORDS: ALTERNATIVE RESPIRATORY PATHWAY, CANOPY PHOTOSYNTHESIS,
CARBOHYDRATES, CROPS, GREENHOUSE, RESPIRATION

267  
Gifford, R.M., and J.I.L. Morison. 1985. Photosynthesis, Water Use
and Growth of a C4 Grass Stand at High CO2 Concentration.
Photosynthesis Research 7:77-90.

Leaf photosynthesis rate of the C4 species Paspalum plicatulum
Michx was virtually CO2-saturated at normal atmospheric CO2
concentration but transpiration decreased as CO2 was increased
above normal concentrations, thereby increasing transpiration
efficiency. To test whether this leaf response led growth to be
CO2-sensitive when water supply was restricted, plants were grown
in sealed pots of soil as miniature swards. Water was supplied
either daily to maintain a constant water table, or at three growth
restricting levels on a 5-day drying cycle. Plants were either in
a cabinet with normal air (340 umol (CO2)/mol (air)) or with 250
umol/mol enrichment. Harvesting was by several cycles of
defoliation. With abundant water supply high CO2 concentration did
not cause increased growth, but it did not cause an increase in
growth over a wide range of growth-limiting water supplies either.
Only when water supply was less than 30-50% of the amount used by
the stand with a water-table was there evidence that dry weight
growth was enhanced by high CO2. In addition, with successive
regrowth, the enhancing effect under a regime of minimal water
allocations, became attenuated. Examination of leaf gas exchange,
growth and water use data showed that in the long term stomatal
conductance responses were of little significance in matching plant
water use to low water allocation; regulation of leaf area was the
mechanism through which consumption matched supply. Since high CO2
effects operate principally via stomatal conductance in C4 species,
we postulate that for this species higher CO2 concentrations
expected globally in future will not have much effect on long term
growth.

Paspalum plicatulum

KEYWORDS: C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
GRASSES, GROWTH, LEAF PHOTOSYNTHESIS, WATER STRESS, WUE

268  
Gislerod, H.R., and P.V. Nelson. 1989. The Interaction of Relative
Air Humidity and Carbon Dioxide Enrichment in the Growth of
Chrysanthemum morifolium Ramat. Scientia Horticulturae 38:305-313.

Plants of Chrysanthemum x morifolium cultivar 'Fiesta' were grown
hydroponically for 6 weeks in growth chambers at relative humidity
(RH) levels of 50 and 95% and CO2 levels of 340 and 940 uL/L in a
Latin square combination.  High RH as well as high CO2 resulted in
increased relative growth rate (RGR), increased dry weight of
leaves, stems and roots, and increased leaf area on main and
lateral stems during the first 2 weeks of growth.  During this
period, high CO2 levels interacted to stimulate the RH effects. 
During the third to sixth weeks of growth, the interaction of RH
and CO2 was either lost or, as in the case of RGR and root dry
weight, reversed in such a way that a negative effect of high CO2
at high RG was found.  At 6 weeks there were positive main effects
of RH and CO2, but no interaction on plant height, number of leaves
on lateral shoots, number of lateral shoots, and length of lateral
shoots.  The shoot to root dry weight ratio increased at high RH. 
Water consumption of plants decreased sharply at high RH and
moderately at the high CO2 level.  Stomatal aperture was larger at
high RH, but smaller at the high CO2 level.  It is concluded that
increased plant growth resulting from increased RH might be caused
by an increase in stomatal aperture which in turn facilitates CO2
absorption and utilization.

chrysanthemum/Chrysanthemum morifolium

KEYWORDS: ALLOCATION, CONDUCTANCE, FLOWER PRODUCTION, GROWTH
ANALYSIS, HORTICULTURAL CROPS, HUMIDITY, HYDROPONIC CULTURE,
ROOT:SHOOT RATIO, STOMATAL DENSITY, TRANSPIRATION

269  
Goudriaan, J. 1986. Simulation of Ecosystem Response to Rising CO2,
with Special Attention to Interfacing with the Atmosphere. IN:
Climate Vegetation Interactions, a NASA Workshop; 1986 January 27-29; Greenbelt, Maryland (C. Rosenzweig and R. Dickinson, eds.),
NASA Goddard Space Flight Center, Greenbelt, Maryland, pp. 68-75.

KEYWORDS: ECOSYSTEM LEVEL CO2 RESPONSES, MODELING, NET PRIMARY
PRODUCTIVITY, SIMULATION

270  
Goudriaan, J. 1990. Primary Productivity and CO2. IN: The
Greenhouse Effect and Primary Productivity in European Agro-ecosystems; 5-10 April 1990; Wageningen, The Netherlands (J.
Goudriaan, H. van Keulen, and H.H. van Laar, eds.), Pudoc,
Wageningen, pp. 23-25.

KEYWORDS: AGRICULTURE, BIOTIC GROWTH FACTOR, C3, C4, CO2
COMPENSATION POINT, CROP MODEL, PHOSPHOENOLPYRUVATE CARBOXYLASE,
PHOTOSYNTHETIC ACCLIMATION, REVIEW, RIBULOSE BISPHOSPHATE
CARBOXYLASE

271  
Goudriaan, J., and R.J. Bijlsma. 1987. Effect of CO2 Enrichment on
Growth of Faba Beans at Two Levels of Water Supply. Netherlands
Journal of Agricultural Science 35:189-191.

The occurrence of growth enhancement by increased CO2 levels is
well established under optimal conditions. A growth analysis study
of faba beans, grown under two CO2 levels (350 and 700 cm3/m3) in
combination with two levels of water supply, showed that the
beneficial CO2 effect is maintained when there is shortage of
water. The effects of additional CO2 and water were shown to be
multiplicative. (This is a short synopsis of M.S. Thesis (R.J.B.),
Dept. of Theoretical Production Ecology, Wageningen Agric. Univ.,
Wageningen, 1983.)

Vicia faba/broad bean

KEYWORDS: GREENHOUSE, GROWTH ANALYSIS, SENESCENCE, WATER STRESS,
WUE

272  
Goudriaan, J., H. van Keulen, and H.H. van Laar . 1990. The
Greenhouse Effect and Primary Productivity in European Agro-Ecosystems, Proceedings of the International Workshop on Primary
Productivity of European Agriculture and the Greenhouse Effect,
Wageningen, The Netherlands, 5-10 April 1990. Pudoc, Wageningen.

KEYWORDS: AGRICULTURE

273  
Goyal, A., and N.E. Tolbert. 1989. Variations in the Alternative
Oxidase in Chlamydomonas Grown in Air or High CO2. Plant Physiology
89:958-962.

Chlamydomonas in the resting phase of growth has an equal capacity
of about 15 micromole O2 uptake per hour per milligram of
chlorophyll for both the cytochrome c, CN-sensitive respiration,
and for the alternative, salicylhydroxamic acid-sensitive
respiration. Alternative respiration capacity was measured as
salicylhydroxamic acid inhibited O2 uptake in the presence of CN,
and cytochrome c respiration capacity as CN inhibition of O2 uptake
in the presence of salicylhydroxamic acid. Measured total
respiration was considerably less than the combined capacities for
respiration. During the log phase of growth on high (2-5%) CO2, the
alternative respiraiton capacity decreased about 90% but returned
as the culture entered the lag phase. When the alternative oxidase
capacity was low, addition of salicylic acid or cyanide induced its
reappearance. When cells were grown on low (air-level) CO2, which
induced a CO2 concentrating mechanism, the alternative oxidase
capacity did not decrease during the growth phase. Attempts to
measure in vivo distribution of respiration between the two
pathways with either CN or salicylhydroxamic acid alone were
inconclusive.

Chlamydomonas reinhardtii

KEYWORDS: ALGAE, ALTERNATIVE RESPIRATORY PATHWAY, CELL CULTURE

274  
Graham, R.L., M.G. Turner, and V.H. Dale. 1990. How Increasing CO2
and Climate Change Affect Forests. BioScience 40:575-587.

KEYWORDS: BIOME LEVEL CO2 RESPONSES, BIOSPHERE LEVEL CO2 RESPONSES,
CLIMATE CHANGE, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST, MODELING,
REVIEW, SPECIES RANGE

275  
Grant, W.J.R., H.M. Fan, W.J.S. Downton, and B.R. Loveys. 1992.
Effects of CO2 Enrichment on the Physiology and Propagation of Two
Australian Ornamental Plants, Chamelaucium uncinatum (Schauer) x
Chamelaucium floriferum (MS) and Correa schlechtendalii (Behr).
Scientia Horticulturae 52:337-342.

Root formation on both Chamelaucium and Correa cuttings maintained
at high humidity in an enclosed fog tunnel was significantly
enhanced when ambient CO2 was increased from 350 to 800 ubar. CO2
enrichment resulted in decreased transpiration and increased water
potential of cuttings implying an effect of CO2 on stomatal
conductance. CO2 enrichment led to increased starch levels in
cuttings of both species probably by raising the intercellular
partial pressure of CO2. Increased starch content with CO2
enrichment was able to account for 70-90% of the dry weight
increase in Correa, but only for 10-30% of the dry weight increase
in Chamelaucium. It is suggested that the stimulation of rooting
associated with CO2 enrichment probably derives from the improved
water relations of the cuttings rather than from increased
carbohydrate levels.

Chamelaucium uncinatum/Chamelaucium floriferum/Correa
schlechtendalii

KEYWORDS: CARBOHYDRATES, COMMERCIAL USE OF CO2, HORTICULTURAL
CROPS, ROOTING, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS,
TRANSPIRATION, WATER STATUS

276  
Graumlich, L.J. 1991. Subalpine Tree Growth, Climate, and
Increasing CO2: An Assessment of Recent Growth Trends. Ecology
72:1-11.

LaMarche et al. (Science 225: 1019-1021, 1984) hypothesized that
recent trends of increasing ring widths in subalpine conifers may
be due to the fertilizing effects of increased atmospheric CO2.
Five tree-ring series from foxtail pine (Pinus balfouriana),
lodgepole pine (P. murrayana), and western juniper (Juniperus
occidentalis) collected in the Sierra Nevada, California, were
analyzed to determine if the temporal and spatial patterns of
recent growth were consistent with the hypothesized CO2-induced
growth enhancement. Specifically, I address the following
questions: (1) Can growth trends be explained solely in terms of
climatic variation? (2) Are recent growth trends unusual with
respect to long-term growth records? For three of the five sites,
20th-century growth variation can be adequately modeled as a
function of climatic variation. For the remaining two sites, trends
in the residuals from the growth/climate models indicate systematic
underestimation of growth during the past decade that could be
interpreted as either CO2 fertilization or as a response to extreme
climatic events during the mid 1970s. At all five sites, current
growth levels have been equalled or exceeded during some
preindustrial periods. Taken together, these results do not
indicate that CO2-induced growth enhancement is occurring among
subalpine conifers in the Sierra Nevada. While the results
presented here offer no support for the hypothesized CO2
fertilization effect, they do provide insights into the response of
subalpine conifers to climatic variation. Response surfaces
demonstrate that precipitation during previous winter and
temperature during the current summer interact in controlling
growth and that the response can be nonlinear. Although maximum
growth rates occur under conditions of high winter precipitation
and warm summers for all three species, substantial species-to-species variation occurs in the response to these two variables.

Juniperus occidentalis/western juniper/Pinus balfouriana/foxtail
pine/Pinus murrayana/lodgepole pine

KEYWORDS: ALTITUDE, CLIMATE, DENDROCHRONOLOGY, TREE-RING ANALYSIS,
TREES

277  
Graybill, D.A. 1985. Western U.S. Tree-Ring Index Chronology Data
for Detection of Arboreal Response to Increasing Carbon Dioxide,
026 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C., and Environmental Sciences Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee.

Pinus longaeva/Pinus aristata/Pinus flexilis

KEYWORDS: ALTITUDE, TREE-RING ANALYSIS, TREES

278  
Graybill, D.A. 1987. A Network of High Elevation Conifers in the
Western U.S. for Detection of Tree-Ring Growth Response to
Increasing Atmospheric Carbon Dioxide. IN: Proceedings of the
International Symposium on Ecological Aspects of Tree-Ring
Analysis. U.S. Dept. of Energy Conference Report; DOE/CONF-8608144
(G.C. Jacoby and J.W. Hornbeck, eds.), NTIS, Springfield, Virginia,
pp. 463-474.

Tree-ring width growth at high elevation upper treeline sites in
the western U.S.A. evidences unparalleled increase during the past
century in comparison to growth records of the preceding 500 or
more years. Causes for this do not yet appear to be solely climatic
in origin because it remains unclear that crucial variables
affecting growth such as temperature or precipitation, have changed
correspondingly during their length of record. Given the recent
exponential rise of CO2, and its potential for affecting tree
growth at high elevations, it cannot yet be ruled out as an agent
of change. The rates of ring-width growth increase in some cases
appear to exceed the levels of known or estimated changes in
climatic parameters and also in CO2. This may in part be due to
changes in the growth potential of the organisms themselves,
providing an amplifying effect to environmental inputs. This could
include changes such as increasing needle mass that provides
increased photosynthetic capacity, increased root growth that
provides greater nutrient availability and increased water use
efficiency that is critical in the arid sites. The net effect may
not only be increasing growth but increasing persistence in growth
variation. Ongoing analysis of data from the current study should
permit further understanding of these changes.

Pinus aristata/Pinus longaeva

KEYWORDS: ALTITUDE, TREE-RING ANALYSIS, TREES

279  
Grodzinski, B. 1992. Plant Nutrition and Growth Regulation by CO2
Enrichment. BioScience 42:517-525.

KEYWORDS: ETHYLENE, GROWTH REGULATORS, LEAF PHOTOSYNTHESIS,
PARTITIONING, RESPIRATION, REVIEW, RIBULOSE BISPHOSPHATE
CARBOXYLASE, SOURCE-SINK BALANCE, STOMATA

280  
Grulke, N.E., G.H. Riechers, W.C. Oechel, U. Hjelm, and C. Jaeger.
1990. Carbon Balance in Tussock Tundra under Ambient and Elevated
Atmospheric CO2. Oecologia 83:485-494.

Whole ecosystem CO2 flux under ambient (340 uL/L) and elevated (680
uL/L) CO2 was measured in situ in Eriophorum tussock tundra on the
North Slope of Alaska. Elevated CO2 resulted in greater carbon
acquisition than control treatments and there was a net loss of CO2
under ambient conditions at this upland tundra site. These
measurements indicate a current loss of carbon from upland tundra,
possibly the result of recent climatic changes. Elevated CO2 for
the duration of one growing season appeared to delay the onset of
dormancy and resulted in approximately 10 additional days of
positive ecosystem flux. Homeostatic adjustment of ecosystem CO2
flux (sum of species' response) was apparent by the third week of
exposure to elevated CO2. Ecosystem dark respiration rates were not
significantly higher at elevated CO2 levels. Rapid homeostatic
adjustment to elevated CO2 may limit carbon uptake in upland
tundra. Abiotic factors were evaluated as predictors of ecosystem
CO2 flux. For chambers exposed to ambient and elevated CO2 levels
for the duration of the growing season, seasonality (Julian day)
was the best predictor of ecosystem CO2 flux at both ambient and
elevated CO2 levels. Light (PAR), soil temperature, and air
temperature were also predictive of seasonal ecosystem flux, but
only at elevated CO2 levels. At any combination of physical
conditions, flux of the elevated CO2 treatment was greater than
that at ambient. In short-term manipulations of CO2, tundra exposed
to elevated CO2 had threefold greater carbon gain, and had one half
the ecosystem level, light compensation point when compared to
ambient CO2 treatments. Elevated CO2-acclimated tundra had twofold
greater carbon gain compared to ambient treatments, but there was
no difference in ecosystem level, light compensation point between
elevated and ambient CO2 treatments. The predicted future increases
in cloudiness could substantially decrease the effect of elevated
atmospheric CO2 on net ecosystem carbon budget. These analyses
suggest little if any long-term stimulation of ecosystem carbon
acquisition by increases in atmospheric CO2.

Eriophorum vaginatum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, ECOSYSTEM LEVEL CO2
RESPONSES, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION, TRACKING
CHAMBERS, TUNDRA

281  
Gulyaev, B.I. 1986. Influence of CO2 Concentration on
Photosynthesis, Growth and Productivity of Plants. Physiology and
Biochemistry of Cultured Plants (Fiziologi i aibiokhimi i
akultumykh Rasteni) 18:574-591.

The works aimed at studying the responses of plants to higher (up
to 1000 uL/L) CO2 (Ca) concentrations are reviewed. An increase in
the productivity of C3-plants under the effect of carbon dioxide
enrichment (by 30-40%) of the atmosphere is, mainly, a result of
the photosynthesis intensification and leaf area growth. The
assimilates' pool level in plants depends on the determination
degree of vegetative growth, ability of the root system to utilize
an excess of assimilates and on the environmental conditions, which
explains why deep inhibition of photosynthesis under these
conditions is not always observed. Relative effect of CO2
enrichment on the productivity is higher with lower illuminations,
as the assimilates' deficiency is compensated by the photosynthesis
intensification. The rate of plant development slightly depends on
Ca while the total plants' resistance increased with Ca. Efficiency
of water utilization grows almost twice with Ca duplication. CO2
enrichment makes efficiency of symbiotic nitrogen-fixation in
leguminous plants higher. In Russian.

KEYWORDS: CO2 ENRICHMENT STUDIES, REVIEW

282  
Guy, M., G. Granoth, and J. Gale. 1990. Cultivation of Lemna gibba
under Desert Conditions. II: The Effect of Raised Winter
Temperature, CO2 Enrichment and Shading on Productivity. Biomass
23:1-11.

The aim of this work was to increase the productivity of Lemna
gibba ponds under desert conditions. In the winter season, the
ponds were covered with transparent plastic tents which raised
water temperature. This also allowed CO2 to be added to the air in
the tents to either the ambient, about 340 umol/mol, or to higher
concentrations. The plastic covers attenuated photosynthetically
active light by about 30%. Winter-season yields in the covered
ponds, maintained at ambient CO2 concentration, were 39% higher
than in the uncovered ponds. This could be ascribed to raised
temperatures. Enrichment of the atmosphere with CO2 further
increased yields by as much as 28%. The different treatments did
not affect protein content expressed as a percentage of dry weight.
Laboratory experiments indicated that the shorter the photoperiod
the larger is the growth response of Lemna gibba to CO2 enrichment.
Shading of the ponds during the June-August summer season reduced
pond temperatures at midday by about 5-6C and resulted in a 30-80%
increase in growth. It was concluded that under desert conditions
similar to those prevailing in this trial, high yields of Lemna
gibba can be achieved throughout a growing season of 12 months per
year by covering the ponds and raising ambient [CO2] during the
winter, and by shading in summer. Productivity of 7.4 +/- 1.0
g/m2/day can be maintained throughout the year. Whether or not it
is worthwhile to do so is a question of local economics

Lemna gibba/duckweed

KEYWORDS: ENVIRONMENTAL INTERACTIONS, GROWTH, GROWTH ANALYSIS,
LIGHT, OUTDOOR GROWTH CHAMBERS, TEMPERATURE

283  
Guy, R.D., and D.M. Reid. 1986. Photosynthesis and the Influence of
CO2-Enrichment on Delta-13 C Values in a C3 Halophyte. Plant, Cell
and Environment 9:65-72.

Shifts in [delta]-13C of the graminaceous C3 halophyte Puccinellia
nuttalliana (Schultes) Hitch. can be induced by salinization. To
investigate this phenomenon, three approaches were taken: assay of
carboxylases, CO2-enrichment studies, and gas exchange analysis.
Although ribulose-1,5-bisphosphate carboxylase activity decreased
with salinity, phosphoenolpyruvate carboxylase activity did not
increase and its levels were not atypical of C3 plants. When plants
were grown at four NaCl concentrations under atmospheres of 310 and
1300 cm3/m3 CO2, the CO2-enrichment enhanced the effects of
salinity on [delta]-13C. This is consistent with a biophysical
explanation for salt-induced shifts in [delta]-13C, whereby there
is a steepening of the CO2 diffusion gradient into the leaf. Gas
exchange analysis indicated that intercellular CO2 concentrations
were depressed in the leaves of salt-affected plants. This resulted
from a greatly decreased stomatal conductance coupled with only
small effects on intrinsic photosynthetic capacity. Water-use
efficiency was enhanced.

Puccinellia nuttalliana

KEYWORDS: C3, CI:CA, CONDUCTANCE, GRASSES, HALOPHYTES, ISOTOPE
DISCRIMINATION, PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE
BISPHOSPHATE CARBOXYLASE, SALT STRESS, WUE

284  
Hanan, J.J. 1986. CO2 Enrichment for Greenhouse Rose Production.
IN: Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 142-149.

The literature indicates that CO2 enrichment is a successful and
important adjunct to commercial plant production, the actual
practices being a function of climatic location and the particular
technological surroundings. For roses, there has been a hiatus
since the articles published by the Israelis and English in the
1970s. The North Europeans, particularly Danish and Dutch industry,
appear to have taken the lead in instrumentation and
computerization on a commercial scale, with actual use of CO2
monitors. However, there are some shortcomings in our practical
knowledge of CO2 enrichment and rose physiology. First, we need to
emphasize rates rather than simply CO2 concentration and irradiance
level in the photosynthetically active spectrum. Photosynthesis is
a rate process, dependent upon several other rates. Blackman's
contribution was the ability to open scientists' eyes to
significant interactions in the photosynthetic process in a manner
that allowed new investigative approaches. Second, we need to
emphasize the importance of plant water potential on rates if CO2
enrichment is to achieve maximum, efficient utilization. Any
student of practical plant physiology learns that the major portion
of radiation impinging upon a well-watered plant is converted to
latent heat. The importance of this major energy redistribution
supplies the rationale for a large portion of research at
agricultural research stations. Parenthetically, more than 90% of
total water withdrawals in the Southwestern U.S. is for irrigation.
Based upon this review, and some 30 years of observation, it seems
to me that manipulation of water potential to maximize CO2 uptake
offers the greatest opportunity for significant technological
advance in increasing rose yields in greenhouses. This will require
computers which can rapidly process information from a number of
instruments and recalculate settings of the implementation systems
to control irradiance, vapor pressure deficits, CO2 levels, as well
as plant temperature.

rose

KEYWORDS: COMMERCIAL USE OF CO2, ENVIRONMENTAL INTERACTIONS, FLOWER
PRODUCTION, GREENHOUSE, HORTICULTURAL CROPS, REVIEW, WATER STATUS

285  
Hand, D.W. 1986. CO2 Sources and Problems in Burning Hydrocarbon
Fuels for CO2 Enrichment. IN: Status and CO2 Sources, Vol. I (H.Z.
Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of
Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 99-121.

CO2 enrichment of the greenhouse atmosphere is an invaluable
technique for improving the performance of high-value salad and
flower crops during the difficult winter period when poor light
limits growth and development. According to government statistics
there are approximately 500 ha of heated glasshouses and film-plastic covered structures (greenhouses) in England and Wales
equipped specifically for CO2 enrichment. Additional areas of
glasshouses receive incidental enrichment when growers either use
direct-fired burners for warm-air heating or grow their crops in
raised beds of decomposing straw. CO2 for enrichment purposes can
be either supplied in liquid form or produced directly by burning
hydrocarbon fuels with a low-sulfur content in the atmosphere. Bulk
storage of liquid CO2 is difficult to justify economically on small
areas of glasshouses (i.e., less than 4000 m2) but handling liquid
CO2 in cylinders is laborious, time-consuming and expensive.
Natural gas, LPG propane, and low-sulfur grades of kerosene
(paraffin) are therefore favored by many growers because the CO2 is
produced comparatively cheaply and the heat of combustion can
provide a significant proportion of the daytime heat requirement in
winter. Government statistics show that low-sulfur hydrocarbon
fuels are used on 7 out of every 9 ha equipped for CO2 enrichment.
Generating CO2 from hydrocarbon fuels can give rise to several
gaseous air pollutants that are potentially damaging for crop
production. The risk to crops of injury from gaseous air pollutants
has also increased as growers have endeavored to reduce heating
costs by making their greenhouses more airtight. Gaseous air
pollutants, two groups account for most of the injuries to crops
growing in greenhouses enriched with CO2 produced from hydrocarbon
fuels. These are the nitrogen oxides such as NO and NO2 and unburnt
hydrocarbons such as ethylene and propylene. Inefficient fuel
combustion can also give rise to the formation of harmful aldehydes
like formaldehyde and acrolein. Nitrogen oxides are formed in the
burner flame of a CO2 producer by the heat-promoted combination of
atmospheric nitrogen and oxygen. The rate at which nitrogen oxides
are generated depends essentially on flame temperature, i.e., the
hotter the flame the greater the emission of nitrogen oxides.
Modern CO2 producers have a high flame temperature to ensure
efficient fuel combustion and the formation of nitrogen oxides is
an inevitable consequence of burner design. When threefold CO2
enrichment is practiced the concentration of nitrogen oxides in the
greenhouse atmosphere can be as high as 0.5 uL/L. Such a level may
cause injury to crops by reducing photosynthesis, inhibiting leaf
expansion, depressing growth, and decreasing yield. Ethylene
emissions from CO2 producers are the result of complex reactions
involved in the pyrolysis and oxidation of hydrocarbon fuels.
Burner design and operating variables such as the air-fuel ratio
are crucial in determining the amount of ethylene released into the
greenhouse atmosphere. In a well sealed greenhouse equipped for
three-fold CO2 enrichment the ethylene concentration can easily
rise to a level at which the pollutant has discernible effects on
crops, (i.e., between 0.01 and 0.1 uL/L). Ethylene differs from the
nitrogen oxides in that it is a naturally occurring plant growth
regulator and can affect many growth, developmental, and aging
processes. Escape of unburnt propylene gas (a major constituent of
LPG propane) from loose-fitting connections to fuel-supply lines
and faulty switching of gas-solenoid valves can cause injuries to
crops similar to those induced by ethylene. Propylene
concentrations of between 5 and 100 uL/L are commonly found in
greenhouse atmospheres polluted by a leak of fuel gases from
propane-fired CO2 producers. The pollutant mimics the action of
ethylene, albeit at a concentration 100 times that required for
injury by ethylene.

KEYWORDS: AIR POLLUTION, CO2 SOURCES, COMMERCIAL USE OF CO2,
EXPOSURE METHODS, GREENHOUSE, NITROGEN OXIDES, REVIEW

286  
Hand, D.W. 1989. The 'Greenhouse Effect': Is It Best Studied in
Greenhouses? Professional Horticulture 3:76-82.

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, HORTICULTURAL CROPS,
REVIEW

287  
Hand, D.W. 1990. CO2 Enrichment in Greenhouses: Problems of CO2
Acclimation and Gaseous Air Pollutants. Acta Horticulturae 268:81-97.

CO2 enrichment of the greenhouse atmosphere greatly improves the
output, quality and value of vegetables, cut-flowers and ornamental
plants. Raising the greenhouse CO2 concentration enhances
photosynthesis and growth by increasing the rate of CO2 fixation
concomitantly with a suppression of photo-respiration. Prolonged
exposure of plants to elevated CO2 concentrations can, however,
greatly accelerate the decline in the photosynthetic capacity of
individual leaves with age. Commercially, CO2 for enrichment is
normally obtained in liquid form or produced directly in the
greenhouse atmosphere by burning hydrocarbon fuels such as natural
gas, LPG propane, and premium kerosene (paraffin) which all contain
low and acceptable levels of sulphur. Plentiful supplies of natural
gas in both Britain and The Netherlands have also encouraged
growers in these countries to practise CO2 enrichment by ducting
flue-gases into their greenhouses from centralized, gas-fired
boiler installations. Generating CO2 from hydrocarbon fuels can
give rise to several gaseous air pollutants that are potentially
damaging for crop production. The pollutants that cause most of the
trouble in CO2-enriched greenhouses are nitrogen oxides such as
nitric oxide and nitrogen dioxide, and unburnt hydrocarbons such as
ethylene and propylene. Additionally, improvements to the
insulation of heated greenhouses restrict air exchange and increase
the hazard of certain plasticisers such as the alkyl esters of
phthalic acid which are used to give flexibility to PVC. The risk
of incurring losses in yield due to gaseous air pollutants can be
minimized by using low-sulphur fuels, avoiding leaks of fuel gases,
servicing burners regularly, limiting fuel consumption and
improving ventilation in near-airtight structures. Longer-term
measures to improve the productivity of crops grown in polluted
greenhouse atmospheres include the design of pollution-free
burners, and the development and use of cultivars that are tolerant
of gaseous air pollutants.

KEYWORDS: AIR POLLUTION, CO2 SOURCES, COMMERCIAL USE OF CO2,
GREENHOUSE, NITROGEN OXIDES, PHOTOSYNTHETIC ACCLIMATION

288  
Hand, D.W., J.W. Wilson, and B. Acock. 1993. Effects of Light and
CO2 on Net Photosynthetic Rates of Stands of Aubergine and
Amaranthus. Annals of Botany 71:209-216.

Net photosynthetic rates per unit ground area for plant stands of
Solanum melongena L. var. esculentum (aubergine) and Amaranthus
caudatus L. var. edulis (grain amaranth) were measured over 10 min
intervals in an airtight, glass, controlled-environment cabinet for
a range of light flux densities provided by the diurnal variation
in daylight. Light response curves for photosynthesis of stands,
grown at ambient CO2 concentration, were defined at 400, 800 and
1200 vpm CO2. Light compensation points for these stands were
around 20-30 J/m2/s and decreased slightly at higher CO2
concentrations. For aubergine, a C3 species, the short-term effects
of CO2 enrichment were to increase the initial slope as well as the
asymptote of the light response curve, reducing light saturation at
moderate to high light flux densities; but for amaranthus, a C4
species, saturation was less apparent and CO2 enrichment scarcely
increased photosynthesis except at light flux densities above 150
J/m2/s. The canopies intercepted 93-98% of incident light. The
efficiency of utilization of intercepted light in photosynthesis
(ug CO2/J) increased from zero at the light compensation point to
a maximum at an optimum light flux density of about 100 J/m2/s (the
optimum rose a little with CO2 enrichment) and decreased slightly
with further increase in light. Maximum utilization efficiencies at
500 vpom CO2 were 8-9 ug CO2/J. Enrichment to 1200 vpm did not
affect the peak utilization efficiency of the C4 amaranthus, but
increased that of aubergine to 12.2 ug CO2/J (equivalent to some
14% when using the heat of combustion of plant dry matter to
convert to the dimensionless form). This is among the highest
recorded efficiencies of light utilization for stands, and relates
to the exceptionally favourable environment, with optimal control
of CO2 concentration, humidity, temperature, water supply and
mineral nutrition.

Solanum melongena/aubergine/eggplant/Amaranthus caudatus/grain
amaranth

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
LIGHT, LIGHT UTILIZATION EFFICIENCY

289  
Hari, P., and H. Arovaara. 1988. Detecting CO2 Induced Enhancement
in the Radial Increment of Trees. Evidence from Northern Timber
Line. Scandinavian Journal of Forest Research 3:67-74.

Annual Ring data from northern Finland was analysed in order to
reveal possible trends in ring width development due to changes in
environmental factors. The data was analysed using a four component
multiplicative model. The components are: tree age, climatic
conditions, tree position and changes in environmental conditions.
Since the effect of tree age and position in the stand could be
easily eliminated the main problem was thus to eliminate the effect
of climatic conditions on ring width. This was based on the
dependence of the daily radial increment and daily maximum
temperature. The component associated with changing environmental
factors, especially to CO2 enrichment, was determined using the
model. The basal area development of the trees was calculated from
measured and estimated ring widths. Depending on the value of the
autocorrelation parameter, the effect of changes in environmental
factors on the basal area increment of the trees is between 15.5-43.3% during the period from 1950 to 1983.

Pinus sylvestris/Scots pine

KEYWORDS: MODELING, TREE-RING ANALYSIS, TREES

290  
Harley, P.C., and T.D. Sharkey. 1991. An Improved Model of C3
Photosynthesis at High CO2: Reversed O2 Sensitivity Explained by
Lack of Glycerate Reentry into the Chloroplast. Photosynthesis
Research 27:169-178.

Current models of C3 photosynthesis incorporate a phosphate
limitation to carboxylation which arises when the capacity for
starch and sucrose synthesis fails to match the capacity for the
production of triose phosphates in the Calvin cycle. As a result,
the release of inorganic phosphate in the chloroplast stroma fails
to keep pace with its rate of sequestration into triose phosphate,
and phosphate becomes limiting to photosynthesis. Such a model
predicts that when phosphate is limiting, assimilation becomes
insensitive to both CO2 and O2, and is thus incapable of explaining
the experimental observation that assimilation, under phosphate-limited conditions, frequently exhibits reversed sensitivity to
both CO2 and O2, i.e., increasing O2 stimulates assimilation and
increasing CO2 inhibits assimilation. We propose a model which
explains reversed sensitivity to CO2 and O2 by invoking the net
release of phosphate in the photorespiratory oxidation cycle. In
order for this to occur, some fraction of the glycollate carbon
which leaves the stroma and which is recycled to the chloroplast by
the photorespiratory pathway as glycerate must remain in the
cytosol, perhaps in the form of amino acids. In that case,
phosphate normally used in the stromal glycerate kinase reaction to
generate PGA from glycerate is made available for
photophosphorylation, stimulating RuBP regeneration and
assimilation. The model is parameterized for data obtained on
soybean and cotton, and model behavior in response to CO2, O2, and
light is demonstrated.

soybean/Glycine max/cotton/Gossypium hirsutum

KEYWORDS: LEAF PHOTOSYNTHESIS, MODELING, OXYGEN, PHOTOSYNTHESIS
MODEL, PHOTOSYNTHETIC FEEDBACK INHIBITION, RESPIRATION, SIMULATION

291  
Harley, P.C., R.B. Thomas, J.F. Reynolds, and B.R. Strain. 1992.
Modelling Photosynthesis of Cotton Grown in Elevated CO2. Plant,
Cell and Environment 15:271-282.

Cotton plants were grown in CO2-controlled growth chambers in
atmospheres of either 35 or 65 Pa CO2. A widely accepted model of
C3 leaf photosynthesis was parameterized for leaves from both CO2
treatments using non-linear least squares regression techniques,
but in order to achieve reasonable fits, it was necessary to
include a phosphate limitation resulting from inadequate triose
phosphate utilization. Despite the accumulation of large amounts of
starch (>50 g/m2) in the high CO2 plants, the photosynthetic
characteristics of leaves in both treatments were similar, although
the maximum rate of Rubisco activity (Vcmax), estimated from A
versus Ci response curves measured at 29C, was about 10% lower in
leaves from plants grown in high CO2. The relationship between key
model parameters and total leaf N was linear, the only difference
between CO2 treatments being a slight reduction in the slope of the
line relating Vcmax to leaf N in plants grown at high CO2. Stomatal
conductance of leaves of plants grown and measured at 65 Pa CO2 was
approximately 32% lower than that of plants grown and measured at
35 Pa. Because photosynthetic capacity of leaves grown in high CO2
was only slightly less than that of leaves grown in 35 Pa CO2, net
photosynthesis measured at the growth CO2, light and temperature
conditions was approximately 25% greater in leaves of plants grown
in high CO2, despite the reduction in leaf conductance. Greater
assimilation rate was one factor allowing plants grown in high CO2
to incorporate 30% more biomass during the first 36 d of growth.

cotton/Gossypium hirsutum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS,
MODELING, NITROGEN, PHOTOSYNTHESIS MODEL, RIBULOSE BISPHOSPHATE
CARBOXYLASE

292  
Harley, P.C., J.A. Weber, and D.M. Gates. 1985. Interactive Effects
of Light, Leaf Temperature, CO2 and O2 on Photosynthesis in
Soybean. Planta 165:249-263.

A biochemical model of C3 photosynthesis has been developed by G.D.
Farquhar et al. (1980, Planta 149, 78-90) based on Michaelis--Menten kinetics of ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase, with a potential RuBP limitation imposed via the Calvin
Cycle and rates of electron transport. The model presented here is
slightly modified so that parameters may be estimated from whole-leaf gas-exchange measurements. Carbon-dioxide response curves of
net photosynthesis obtained using soybean plants (Glycine max (L.)
Merr.) at four partial pressures of oxygen and five leaf
temperatures are presented, and a method for estimating the kinetic
parameters of RuBP carboxylase-oxygenase, as manifested in vivo, is
discussed. The kinetic parameters so obtained compare well with
kinetic parameters obtained in vitro, and the model fits to the
measured data give r2 values ranging from 0.87 to 0.98. In
addition, equations developed by J.D. Tenhunen et al. (1976,
Oecologia 26, 89-100, 101-109) to describe the light and
temperature responses of measured CO2-saturated photosynthetic
rates are applied to data collected on soybean. Combining these
equations with those describing the kinetics of RuBP carboxylase-oxygenase allows one to model successfully the interactive effects
of incident irradiance, leaf temperature, CO2 and O2 on whole-leaf
photosynthesis. This analytical model may become a useful tool for
plant ecologists interested in comparing photosynthetic responses
of different C3 plants or of a single species grown in contrasting
environments.

soybean/Glycine max

KEYWORDS: ENVIRONMENTAL INTERACTIONS, LEAF PHOTOSYNTHESIS, LIGHT,
MODELING, OXYGEN, PHOTOSYNTHESIS MODEL, RESPIRATION, RIBULOSE
BISPHOSPHATE CARBOXYLASE, TEMPERATURE

293  
Hartz, T.K., A. Baameur, and D.B. Holt. 1991. Carbon Dioxide
Enrichment of High-value Crops under Tunnel Culture. Journal of the
American Society of Horticultural Science 116:970-973.

The feasibility of field-scale CO2 enrichment of vegetable crops
grown under tunnel culture was studied with cucumber (Cucumis
sativus L. cv. Dasher II), summer squash (Cucurbita pepo L. cv.
Gold Bar), and tomato (Lycopersicon esculentum Mill. cv. Bingo)
grown under polyethylene tunnels. The drip irrigation system was
used to uniformly deliver a CO2-enriched air stream independent of
irrigation. Carbon dioxide was maintained between 700 and 1000 uL/L
during daylight hours. Enrichment began immediately after crop
establishment and continued for about 4 weeks. At the end of the
treatment phase, enrichment had significantly increased plant dry
weight in the 2 years of tests. This growth advantage continued
through harvest, with enriched cucumber, squash, and tomato plots
yielding 30%, 20%, and 32% more fruit, respectively, in 1989. In
1990, cucumber and squash yields were increased 20%, and 16%,
respectively. As performed, the expense of CO2 enrichment
represented less than a 10% increase in total preharvest costs. A
similar test was conducted on fall-planted strawberries (Fragaria
x ananassa Duch. cvs. Irvine and Chandler). Carbon dioxide
enrichment under tunnel culture modestly increased 'Irvine' yields
but did not affect 'Chandler'.

Cucumis sativus/cucumber/Cucurbita pepo/squash/Lycopersicon
esculentum/tomato/Fragaria ananassa/strawberry

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, HORTICULTURAL CROPS,
YIELD

294  
Hartz, T.K., and D.B. Holt. 1991. Root-zone Carbon Dioxide
Enrichment in Field Does Not Improve Tomato or Cucumber Yield.
HortScience 26:1423.

tomato/Lycopersicon esculentum/cucumber/Cucumis sativus

KEYWORDS: COMMERCIAL USE OF CO2, FIZZ IRRIGATION, SOIL CO2
CONCENTRATION, YIELD

295  
Harvey, L.D.D. 1989. Effect of Model Structure on the Response of
Terrestrial Biosphere Models to CO2 and Temperature Increase.
Global Biogeochemical Cycles 3:137-153.

The sensitivity of a number of different globally aggregated models
of the terrestrial biosphere to changes of atmospheric CO2 and
temperature is investigated. Net primary production (NPP) or net
photosynthesis (NP) is modeled as a logistic function, with
enhancement due to increased CO2 using the beta factor widely used
in global carbon cycle models. NPP also increases with temperature
using a Q10 of 1.4, while respiration and coefficients for
translocation and for detritus to soil, and soil to soil, carbon
transfers increase with a Q10 of 2.0. The pathway of carbon flow to
the slowly overturning soil reservoir has a significant effect on
equilibrium sensitivity of total carbon mass to temperature
increases if the transfer coefficient from the rapidly to slowly
overturning reservoir is fixed; maximum sensitivity occurs if all
the carbon entering the slowly overturning reservoir first passes
through the rapidly overturning reservoir. If the transfer
coefficient increases in parallel with the increase of soil
respiration coefficient, the carbon pathway has no effect on
equilibrium sensitivity, although the transient response depends
strongly on the subdivision of the soil reservoir. Allowing the
detritus to soil transfer coefficient to increase in parallel with
the coefficient for detrital respiration reduces the equilibrium
sensitivity of the total carbon mass to temperature increases by
about half. The variation in model response to CO2 and temperature
increase using different model structures is generally comparable
to the variation resulting from uncertainty in feedback parameters.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, MODELING, NET PRIMARY
PRODUCTIVITY, TEMPERATURE

296  
Hatton, T.J., J. Walker, W.R. Dawes, and F.X. Dunin. 1992.
Simulations of Hydroecological Responses to Elevate CO2 at the
Catchment Scale. Australian Journal of Botany 40:679-696.

A spatially explicit hydroecological landscape model of water,
carbon and energy balances (Topog-IRM) is described. The landscape
is envisaged as a catchment forested with a single stratum
comprising Eucalyptus maculata trees. The model was used to
simulate the direct effects of a 2x elevation in atmospheric carbon
dioxide at two levels of nitrogen on catchment water yield, soil
moisture status and tree growth. Experimental results used to
parameterise the model are detailed. Key features of the model are
(1) an ability to scale hydrological processes at the catchment
scale in three dimensions, and (2) a means to integrate multiple
factors/stresses on plant growth. The effects of CO2 on catchment
hydrology (water yield or soil moisture content) and forest growth
(expressed as leaf area index, LAI) were modelled for a 2-year
period, and contrasted with the effects of added nitrogen. Results
were expressed as totals for the catchment or spatially distributed
across the catchment. For the total catchment, water yield
increased in the order: high CO2 with low N, high CO2 with high N,
ambient CO2 with low N, ambient CO2 with high N. LAI increased from
3.3 to 5.76 in the order: ambient CO2 with low N, ambient CO2 with
high N, high CO2 with low N, high CO2 with high N. These results
agree with previous data. New findings are: (1) with elevated CO2
a new equilibrium in transpiration is established in which leaf
area increases offset decreases in stomatal conductance; (2) the
addition of nitrogen increases transpiration without any indication
of a new equilibrium being reached during the simulated period; (3)
the spatial distribution of soil moisture changes, presenting a new
resource base for spatial changes to species composition and growth
rates. The major hydroecological responses to elevated CO2 are seen
as increased maximum upper canopy leaf area, increased litter
inputs, especially at times of drought (hence changed fire
regimes), changes in the composition of the understory (hence
litter composition, soil microfauna, and the spatial expression of
biological diversity) and a slight increase in water yield.

Eucalyptus maculata

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION,
FOREST, HYDROLOGIC MODEL, MODELING, NITROGEN, SOIL CO2
CONCENTRATION

297  
Havir, E.A., and N.A. McHale. 1989. Regulation of Catalase Activity
in Leaves of Nicotiana sylvestris by High CO2. Plant Physiology
89:952-957.

The effect of high CO2 (1% CO2/21% O2) on the activity of specific
forms of catalase (CAT-1, -2, and -3) (EA Havir, NA McHale [987]
Plant Physiol 84: 450-455) in seedling leaves of tobacco (Nicotiana
sylvestris, Nicotiana tabacum) was examined. In high CO2, total
catalase activity decreased by 50% in the first 2 days, followed by
a more gradual decline in the next 4 days. The loss of total
activity resulted primarily from a decrease in CAT-1 catalase. In
contrast, the activity of CAT-3 catalase, a form with enhanced
peroxidatic activity, increased 3-fold in high CO2 relative to air
controls after 4 days. Short-term exposure to high CO2 indicated
that the 50% loss of total activity occurs in the first 12 hours.
Catalase levels increased to normal within 23 hours after seedlings
were returned to air. When seedlings were transferred to air after
prolonged exposure to high CO2 (13 days), the levels of CAT-1
catalase were partially restored while CAT-3 remained at its
elevated level. Levels of superoxide dismutase activity and those
of several peroxisomal enzymes were not affected by high CO2. Total
catalase levels did not decline when seedlings were exposed to
atmospheres of 0.04% CO2/5% O2 or 0.04% CO2/1% O2, indicating that
regulation of catalase in high CO2 is not related directly to
suppression of photorespiration. Antibodies prepared against CAT-1
catalase from N. tabacum reacted strongly against CAT-1 catalase
from both N. sylvestris and N. tabacum but not against CAT-3
catalase from either species. This observation, along with the
rapid changes in CAT-1 and the much slower changes in CAT-3 suggest
that one form is not directly derived from the other.

Nicotiana sylvestris/Nicotiana tabacum/tobacco

KEYWORDS: CATALASE, ENZYMES, PEROXIDASE, PROTEINS, SUPEROXIDE
DISMUTASE

298  
He, H., M.B. Kirkham, D.J. Lawlor, and E.T. Kanemasu. 1992.
Photosynthesis and Water Relations of Big Bluestem (C4) and
Kentucky Bluegrass (C3) under High Concentration of Carbon Dioxide.
Transactions of the Kansas Academy of Science 95:139-152.

As the carbon dioxide (CO2) concentration in the atmosphere
increases, comparing how C3 and C4 plants will respond is
important. The objective of this study was to determine the
photosynthetic rate, intercellular CO2 concentration, transpiration
rate, stomatal resistance, leaf temperature, water potential, and
water requirement of a C3 grass (Kentucky bluegrass, Poa pratensis
L.) and a C4 grass (big bluestem, Andropogon gerardii Vitman)
growing in a fall in a tallgrass prairie in Kansas under two levels
of CO2 (ambient and two-times ambient). Elevated CO2 increased the
photosynthetic rate of Kentucky bluegrass by 151% but did not
affect the photosynthetic rate of big bluestem. Intercellular CO2
concentrations of both grasses were increased by about the same
amount, which was about half the increase in the atmospheric CO2
concentration. Doubled CO2 reduced the transpiration rates and
increased stomatal resistance of both grasses, but big bluestem was
affected more than Kentucky bluegrass. The twice-ambient level of
CO2 increased (between 0.2 and 0.3 MPa) the water potential of both
grasses. Doubled CO2 decreased the water requirements of big
bluestem and Kentucky bluegrass by 41.6% and 158%, respectively.

Kentucky bluegrass/Poa pratensis/big bluestem/Andropogon gerardii

KEYWORDS: C3, C4, CI:CA, CONDUCTANCE, LEAF PHOTOSYNTHESIS, OUTDOOR
GROWTH CHAMBERS, TALLGRASS PRAIRIE, TRANSPIRATION, WATER STATUS,
WUE

299  
Hendrey, G.R. 1992. The DOE/USDA FACE Program: Goal, Objectives,
and Results Through 1989. Critical Reviews in Plant Sciences 11:75-83.

The FACE system is a tool for studying the effects of CO2
enrichment on vegetation and natural ecosystems and the exchange of
carbon between the biosphere and the atmosphere. FACE experiments
are conducted in a true field setting without any chamber effect.
FACE studies were conducted in an agronomic setting using cotton
because the plant and field conditions are relatively uniform, thus
permitting an evaluation of FACE performance. Cotton is a woody
perennial with well-known physiological characteristics and a high
level of response to CO2 enrichment. It is therefore a convenient
subject for experimentation. The BNL FACE system was shown to be
reliable in field experiments conducted in 1987-1989, providing
effective control of CO2 concentrations in an open field setting
without any type of confinement of ambient air. The system operates
effectively over plant canopies ranging in stature from bare ground
to 200 cm with both open and closed canopies. Control of CO2
concentrations over large plots is within the criterion range +/-
20% of set point for 1-min averages at least 80% of the time in all
of these situations over both vertical and horizontal profiles. The
area under effective control is described, approximately, by the
diameter of the FACE array minus 4 m and is as large as 380 m2 in
the largest configuration tested to date (Hendrey 1992). In 1989 a
12-m diameter 'sweet spot' in the center of the FACE array had
season-long average CO2 concentrations throughout the volume from
ground level to the top of the canopy that were within the range of
94% to 104% of the target concentration. Operating costs for a
four-array FACE system are approximately $450-650/m2 of usable plot
area under effective CO2 control. Cotton grown under CO2 enrichment
showed significant increases in biomass accumulation, both above
ground and below ground. Soil respiration also increased in CO2
enriched plots. Enriched plants matured earlier and, in general,
had greater agronomic yields. Water use efficiency increased with
CO2 enrichment. The FACE system as reported here has had two years
of successful biological experimentation. Results from these
experiments are intended for use in evaluating both the effects of
CO2 on plants and ecosystems, and on the feedback processes
operating between the biosphere and atmosphere that are the
primary, short-term regulators of atmospheric CO2 concentration.

KEYWORDS: EXPOSURE METHODS, FACE

300  
Hendrey, G.R. (ed.). 1992. FACE: Free Air CO2 Enrichment for Plant
Research in the Field (Vol. 11 in Critical Reviews in Plant
Sciences, B.V. Conger, ed.). CRC Press, Inc., Boca Raton, Florida.

KEYWORDS: EXPOSURE METHODS, FACE, REVIEW

301  
Hendrey, G.R. 1992. Global Greenhouse Studies: Need for a New
Approach to Ecosystem Manipulation. Critical Reviews in Plant
Sciences 11:61-74.

KEYWORDS: CARBON CYCLE, CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2
RESPONSES, ECOSYSTEM LEVEL CO2 RESPONSES, EXPOSURE METHODS, REVIEW,
SCALING

302  
Hendrey, G.R., K.F. Lewin, F. Lipfert, Z. Kolber, and M. Daum.
1988. Free-Air Carbon Dioxide Enrichment (FACE) Facility
Development: I. Concept, Prototype Design and Performance, 045 in
Green Report Series, Response of Vegetation to Carbon Dioxide. U.S.
Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C.

KEYWORDS: EXPOSURE METHODS, FACE

303  
Hendrey, G.R., K.F. Lewin, and J. Nagy. 1993. Free Air Carbon
Dioxide Enrichment: Development, Progress, Results. Vegetatio
104/105:17-31.

Credible predictions of climate change depend in part on
predictions of future CO2 concentrations in the atmosphere.
Terrestrial plants are a large sink for atmospheric CO2 and the
sink rate is influenced by the atmospheric CO2 concentration.
Reliable field experiments are needed to evaluate how terrestrial
plants will adjust to increasing CO2 and thereby influence the rate
of change of atmospheric CO2. Brookhaven National Laboratory (BNL)
has developed a unique Free-Air CO2 Enrichment (FACE) system for a
cooperative research program sponsored by the U.S. Department of
Energy and U.S. Department of Agriculture, currently operating as
the FACE User Facility at the Maricopa Agricultural Center (MAC) of
the University of Arizona. The BNL FACE system is a tool for
studying the effects of CO2 enrichment on vegetation and natural
ecosystems, and the exchange of carbon between biosphere and the
atmosphere, in open-air settings without any containment. The FACE
system provides stable control of CO2 at 550 ppm +/- 10%, based on
1-min averages, over 90% of the time. In 1990, this level of
control was achieved over an area as large as 380 m2, at an annual
operating cost of 668/m2. During two field seasons of enrichment
with cotton (Gossypium hirsutum) as the test plant, enrichment to
550 ppm CO2 resulted in significant increases in photosynthesis and
biomass of leaves, stems and roots, reduced evapotranspiration, and
changes in root morphology., In addition, soil respiration
increased and evapotranspiration decreased.

Gossypium hirsutum/cotton

KEYWORDS: CARBON:NITROGEN RATIO, EVAPOTRANSPIRATION, EXPOSURE
METHODS, FACE, PHOTOSYNTHESIS, ROOTS, SOIL RESPIRATION, WATER
STRESS

304  
Hendrey, G.R., F.W. Lipfert, B.A. Kimball, D.R. Hileman, and N.C.
Bhattacharya. 1988. Free Air Carbon Dioxide Enrichment (FACE)
Facility Development: II. Field Tests at Yazoo City, MS, 1987, 046
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington,
D.C.

cotton/Gossypium hirsutum

KEYWORDS: CONDUCTANCE, EXPOSURE METHODS, FACE, GROWTH MODEL, LEAF
PHOTOSYNTHESIS, MODELING, OPEN-TOP CHAMBERS

305  
Hendrix, D.L. 1992. Influence of Elevated CO2 on Leaf Starch of
Field-Grown Cotton. Critical Reviews in Plant Sciences 11:223-226.

cotton/Gossypium hirsutum

KEYWORDS: CARBOHYDRATES, FACE

306  
Higginbotham, K.O., J.M. Mayo, S. L'Hirondelle, and D.K.
Krystofiak. 1985. Physiological Ecology of Lodgepole Pine (Pinus
contorta) in an Enriched CO2 Environment. Canadian Journal of
Forest Research 15:417-421.

Relatively little work has been done to evaluate the effects of
chronically high levels of carbon dioxide on growth and physiology
of woody plants. In this study, seedlings of lodgepole pine (Pinus
contorta Dougl. var. latifolia Engelm.) were grown for 5-month
periods at 330, 1000, or 2000 uL CO2/L. Height growth; leaf area
production; biomass of leaves, stems, and roots; and photosynthetic
responses to changing light, moisture, and CO2 concentration were
measured. Significant differences between treatments were found in
mean seedling height on all measurement dates. Seedlings grown at
1000 uL CO2/L were tallest, with seedlings grown in 2000 uL/L
intermediate between the control (330 uL/L) and 1000 uL/L
treatments. The same relationship was found in production of total
leaf surface area. Increased leaf surface area yields a productive
advantage to seedlings grown at concentrations of CO2 up to 2000
uL/L even if no increase in net photosynthesis is assumed. Biomass
of stems, roots, and secondary leaves was increased in both
elevated CO2 conditions, with root biomass approximately 15 times
greater in seedlings grown at 1000 uL/L than in those grown at 330
uL CO2/L. Stomatal resistances were essentially the same for all
treatments, indicating no CO2-induced stomatal closure to at least
2000 uL/L. Photosynthetic Vmax (milligrams per square decimetre per
hour) for light response curves varied with CO2 concentration. If
results are extrapolated beyond a 5-month period and into field
conditions, it appears that size of trees, interactions with
competitors, and ecological role of the species might be altered.

lodgepole pine/Pinus contorta

KEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH, LIGHT, PHOTOSYNTHESIS, ROOTS, TREES, WATER STRESS

307  
Highsmith, M. 1989. Two Aspects of Starch Formation in Mature
Soybean Leaves. IN: Current Topics in Plant Biochemistry and
Physiology: Proceedings of the Plant Biochemistry and Physiology
Symposium, Vol. 8, The Interdisciplinary Plant Biochemistry and
Physiology Program, University of Missouri, Columbia, p. 267.

soybean/Glycine max

KEYWORDS: CARBOHYDRATES, CARBON BUDGET, DIURNAL CYCLE

308  
Hilbert, D.W., A. Larigauderie, and J.F. Reynolds. 1991. The
Influence of Carbon Dioxide and Daily Photon-flux Density on
Optimal Leaf Nitrogen Concentration and Root:Shoot Ratio. Annals of
Botany 68:365-376.

Using a cost-benefit model, the leaf nitrogen concentration and
root:shoot ratio that maximize whole-plant relative growth rate are
determined as a function of the above-ground environment
(integrated daily photon flux density and the concentration of
carbon dioxide at the site of fixation within the leaf). The major
advantage of this approach is that it determines the adaptive
significance of leaf physiology by considering the functional
integration of leaves and roots. The predicted response to
increasing daily photon flux densities is an increase in optimal
leaf N concentration (Nopt) and a concomitant increase in
root:shoot ratio. Increased carbon dioxide concentration, on the
other hand, reduce Nopt and only slightly change root:shoot ratio.
The observed increase in leaf nitrogen concentration found in
plants growing at high altitudes (low CO2 partial pressure) is also
predicted. Since these responses to light and CO2 maximize the
whole-plant relative growth rate, the observed adjustments that
plants make to light and carbon dioxide concentration appear to be
adaptive. We show that the relationship between photosynthesis and
leaf nitrogen concentration is complex and depends on the light and
CO2 levels at which photosynthesis is measured. The shape of this
function is important in determining Nopt and the opposite response
of leaf nitrogen to light and carbon dioxide is shown to be the
result of the different effects of light and CO2 on the
photosynthesis-leaf nitrogen curve.

KEYWORDS: ALLOCATION, GROWTH MODEL, MODELING, NITROGEN, ROOT:SHOOT
RATIO

309  
Hilbert, D.W., T.I. Prudhomme, and W.C. Oechel. 1987. Response of
Tussock Tundra to Elevated Carbon Dioxide Regimes: Analysis of
Ecosystem CO2 Flux through Nonlinear Modeling. Oecologia 72:466-472.

The response of tussock tundra to elevated atmospheric
concentrations of CO2 was measured at Toolik Lake, Alaska in the
summer of 1983. Computer-controlled greenhouses were used to
determine diurnal ecosystem flux of CO2 under four treatments: 340
ppm, 500 ppm, and 680 ppm CO2, as well as 680 ppm CO2 with a four
degree centigrade increase in temperature. For the seven days of
data analyzed, net daily CO2 flux was significantly different
between treatments. Net uptake was positively correlated with CO2
concentration in the chamber and negatively correlated with
temperature. A nonlinear model was used to analyze this data set
and to determine some of the reasons for different net CO2 flux.
This model allowed an estimation of light utilization efficiency,
total conductance of CO2, and a comparable measure of total
respiration. From this analysis we conclude that nutrient
limitations in the arctic decrease the capacity of tundra plants to
make use of elevated CO2 concentrations. The plants respond by
decreasing conductance in the presence of elevated CO2, which
results in approximately equal gross uptake rates for the three CO2
treatments. Apparent changes in system respiration result in higher
net uptake under elevated CO2 but this may be due to biases in the
data. The treatment with increased temperature exhibited higher
conductances and, consequently, higher gross uptake of CO2 than the
other treatments. Higher temperatures, however, also increase
respiration with the result being lower net uptake than would be
expected in the absence of temperature increases.

KEYWORDS: ECOSYSTEM LEVEL CO2 RESPONSES, PHOTOSYNTHESIS MODEL,
RESPIRATION, TEMPERATURE, TRACKING CHAMBERS, TUNDRA

310  
Hildmann, H., K. Windisch, A. Heissner, W. Weber, J. Domroese, S.
Weber, and A. Markert. 1989. Testing a Strategy of Growth and Yield
Control in Greenhouse Cucumbers in a Specialized Vegetable Growing
Farm. Acta Horticulturae 260:123-136.

Cucumis sativus

KEYWORDS: HORTICULTURAL CROPS, YIELD

311  
Hileman, D.R., N.C. Bhattacharya, P.P. Ghosh, P.K. Biswas, L.H.
Allen Jr., K.F. Lewin, and G.R. Hendrey. 1992. Distribution of
Carbon Dioxide within and above a Cotton Canopy Growing in the FACE
System. Critical Reviews in Plant Sciences 11:187-194.

KEYWORDS: EXPOSURE METHODS, FACE

312  
Hileman, D.R., N.C. Bhattacharya, P.P. Ghosh, P.K. Biswas, K.F.
Lewin, and G.R. Hendrey. 1992. Responses of Photosynthesis and
Stomatal Conductance to Elevated Carbon Dioxide in Field-Grown
Cotton. Critical Reviews in Plant Sciences 11:227-231.

cotton/Gossypium hirsutum

KEYWORDS: CONDUCTANCE, FACE, LEAF PHOTOSYNTHESIS

313  
Hileman, D.R., P.P. Ghosh, N.C. Bhattacharya, P.K. Biswas, L.H.
Allen Jr., G. Peresta, and B.A. Kimball. 1992. A Comparison of the
Uniformity of an Elevated CO2 Environment in Three Different Types
of Open-top Chambers. Critical Reviews in Plant Sciences 11:195-202.

Carbon dioxide levels were determined at various points inside
three different types of open-top chambers (square, round without
frustum and round with frustum), to compare the variability in CO2
concentrations among the different types of chambers. At similar
rates of injection of CO2 into the fan housings of the three
chambers, CO2 levels were highest in the round chamber with a
frustum and lowest in the square chamber. The lower enrichment
levels in the square chamber were most likely due to greater air
movement by the fan. Variability in CO2 concentration was lowest in
the round chamber with a frustum. Variability was similar in the
round (without frustum) and square chambers, except at the upper
heights, where variability was somewhat greater in the shorter,
square chamber. These trends were true both for variability from
point to point within chambers and for variability over time. In
both the square chamber and the round chamber without a frustum,
CO2 levels were frequently lower and more variable in the downwind
side of the chamber than in the upwind side. The round chamber with
the frustum showed no evidence of a wind direction effect.

KEYWORDS: EXPOSURE METHODS, OPEN-TOP CHAMBERS

314  
Hocking, P.J., and C.P. Meyer. 1985. Responses of Noogoora Burr
(Xanthium occidentale Bertol.) to Nitrogen Supply and Carbon
Dioxide Enrichment. Annals of Botany 55:835-844.

We studied the responses of Xanthium occidentale (Bertol.)
(cocklebur or Noogoora burr), a noxious weed, to atmospheric CO2
enrichment and nitrate-N concentrations in the root zone ranging
from 0.5 to 25 mM. CO2 enrichment (1500 cm3/m3) increased dry-matter production to about the same extent (18 per cent) at all
levels of supplied N: most of the increment in dry matter was
distributed equally between leaves and roots so that there was
little effect on shoot-to-root dry-weight ratios. Growth was
stimulated greatly by N and plateaued at 12 mM supplied N. Shoot-to-root dry-weight and total N ratios increased with increasing N
supply. CO2 enrichment had no effect on the total amount of N
accumulated by plants, but increased the N-use efficiency of
leaves. Enriched plants had lower concentrations and quantities of
N in their leaves than controls, and therefore lower shoot-to-root
total N ratios. Little free NO3 accumulated in organs of control or
enriched plants. NO3 was a major form of N in xylem sap from
detopped plants at low supplied NO3-N, but amino N was equal in
importance at high supplied NO3-N in control and enriched plants.
Concentrations of NO3 were lower in the xylem sap of CO2 enriched
plants. It was concluded that the better N-use efficiency of CO2
enriched plants could result in increased growth of X. occidentale
in regions of marginal soil fertility as atmospheric levels of CO2
increase.

Xanthium occidentale/cocklebur

KEYWORDS: ALLOCATION, GREENHOUSE, GROWTH, NITROGEN, NUTRITION,
ROOT:SHOOT RATIO

315  
Hocking, P.J., and C.P. Meyer. 1991. Carbon Dioxide Enrichment
Decreases Critical Nitrate and Nitrogen Concentrations in Wheat.
Journal of Plant Nutrition 14:571-584.

Atmospheric carbon dioxide (CO2) levels are increasing, In a
glasshouse experiment with wheat grown at 5 levels of nitrate (NO3)
supply, CO2 enrichment (1500 cm3/m3) substantially decreased
critical concentrations of NO3-N and total-N in stem bases and
leaves. For example, critical NO3-N concentrations in stem bases at
Feekes Stages 1.5, 5, and 10.3, were 4.5, 2.0, and 2.0 mg/g dry wt,
respectively, for CO2-enriched plants, compared with 7.5, 6.2 and
6.4 mg/g dry wt, respectively, for control plants grown at the
ambient level of CO2. However, concentrations of NO3-N in the
rooting medium required to produce maximum dry matter accumulation
by CO2-enriched plants were similar to those of control plants at
the three growth stages. Critical concentrations of NO3-N and
total-N declined with time in stem bases and leaves of plants grown
at both ambient and elevated CO2 levels, but the decline was
greater for CO2-enriched plants. It was concluded that diagnostic
criteria based on current critical N concentrations may become
invalid as the atmospheric level of CO2 increases.

wheat/Triticum aestivum

KEYWORDS: GREENHOUSE, GROWTH, GROWTH STAGES, NITROGEN, NUTRITION

316  
Hocking, P.J., and C.P. Meyer. 1991. Effects of CO2 Enrichment and
Nitrogen Stress on Growth, and Partitioning of Dry Matter and
Nitrogen in Wheat and Maize. Australian Journal of Plant Physiology
18:339-356.

Atmospheric CO2 levels are increasing, but little is known about
how this will affect tissue concentrations and the partitioning of
agriculturally important nutrients such as nitrogen (N) within crop
plants. To investigate this, a glasshouse experiment was conducted
in which wheat, a C3 species, and maize, a C4 species, were grown
for 8 weeks at high CO2 (1500 cm3/m3) on N supplies ranging from
deficient (0.5 mol/m3) to more than adequate for maximum growth (25
mol/m3). Wheat responded to both CO2 enrichment and N supply; maize
responded only to N supply. CO2-enriched wheat produced about twice
the dry matter of control plants at all levels of N supply. Tiller
and ear numbers were increased by CO2 enrichment irrespective of N
supply. Enriched wheat plants had lower Leaf Area Ratio but higher
Net Assimilation Rate and Relative Growth Rate than control plants.
There was no effect of CO2 enrichment on specific leaf weight. The
enriched plants had lower shoot to root dry matter ratios than the
controls at 6 mol/m3 N and higher. Shoot to root dry matter ratios
of both wheat and maize increased with increasing N supply. CO2-enriched wheat plants accumulated more N than the controls but the
proportional increase in N content was not as great as that in dry
matter, with the result that concentrations of total-N and nitrate-N were lower in all organs of enriched plants, including ears.
Nitrate reductase activity was lower in enriched than in control
wheat plants. N-use efficiency by wheat was increased by CO2
enrichment. From a practical point of view, the study indicates
that critical total-N and NO3-N concentrations used to diagnose the
N status of wheat will need to be reassessed as global CO2 levels
increase. Elevated CO2 may also reduce the protein content of grain
and thus the baking quality of hard wheats.

wheat/Triticum aestivum/maize/Zea mays

KEYWORDS: ALLOCATION, C3, C4, CROPS, GREENHOUSE, GROWTH ANALYSIS,
NITRATE REDUCTASE, NITROGEN, NUTRITION, ROOT:SHOOT RATIO

317  
Hoddinott, J., and P. Jolliffe. 1988. The Influence of Elevated
Carbon Dioxide Concentrations on the Partitioning of Carbon in
Source Leaves of Phaseolus vulgaris. Canadian Journal of Botany
66:2396-2401.

Plants may alter their growth pattern in response to being grown in
elevated CO2 concentrations. The nature of the change in carbon
partitioning underlying those alterations was investigated in
Phaseolus vulgaris cv. Gold Crop grown to the third trifoliate leaf
stage in CO2 concentrations of 380, 800, and 1400 ppm. There was no
effect of the CO2 concentration on plant height, leaf area, or dry
weight, but the specific leaf weight increased significantly with
the CO2 concentration, indicating a denser leaf structure. The
starch content of the leaves also increased significantly as the
CO2 level increased. A primary leaf was pulse labelled with 14-CO2
and the depletion of label from that source leaf was monitored with
a GM tube. The depletion of the count rate with time was described
by a nonlinear curve fitting procedure that allowed the derivation
of rate constants to describe the partitioning of carbon in a two-compartment model. Rates of carbon storage decreased in the light
with increasing CO2 concentrations with no effect on the rates of
export or remobilization. Both export and storage were reduced in
the dark at all CO2 levels, with an increase in the residence time
of carbon in the export pool. Reducing the CO2 concentration around
the source leaf just after labelling did not change carbon
partitioning compared to controls. Increasing the CO2 concentration
around the source leaf just after labelling increased all carbon
flux rates and reduced the residence times in the leaf pools.

Phaseolus vulgaris/bean

KEYWORDS: 14C, ASSIMILATE PARTITIONING, CARBOHYDRATES, CARBON
BUDGET, REMOBILIZATION

318  
Hogan, K.P., A.P. Smith, and L.H. Ziska. 1991. Potential Effects of
Elevated CO2 and Changes in Temperature on Tropical Plants. Plant,
Cell and Environment 14:763-778.

Very little attention has been directed at the responses of
tropical plants to increases in global atmospheric CO2
concentrations and the potential climatic changes. The available
data, from greenhouse and laboratory studies, indicate that the
photosynthesis, growth and water use efficiency of tropical plants
can increase at higher CO2 concentrations. However, under field
conditions abiotic (light, water or nutrients) or biotic
(competition or herbivory) factors might limit these responses. In
general, elevated atmospheric CO2 concentrations seem to increase
plant tolerance to stress, including low water availability, high
or low temperature, and photoinhibition. Thus, some species may be
able to extend their ranges into physically less favourable sites,
and biological interactions may become relatively more important in
determining the distribution and abundance of species. Tropical
plants may be more narrowly adapted to prevailing temperature
regimes than are temperate plants, so expected changes in
temperature might be relatively more important in the tropics.
Reduced transpiration due to decreased stomatal conductance could
modify the effects of water stress as a cue for vegetative or
reproductive phenology of plants of seasonal tropical areas. The
available information suggests that changes in atmospheric CO2
concentrations could affect processes as varied as plant/herbivore
interactions, decomposition and nutrient cycling, local and
geographic distributions of species and community types, and
ecosystem productivity. However, data on tropical plants are few,
and there seem to be no published tropical studies carried out in
the field. Immediate steps should be undertaken to reduce our
ignorance of this critical area.

KEYWORDS: ALLOCATION, COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL
INTERACTIONS, HERBIVORY, PHENOLOGY, POPULATION LEVEL CO2 RESPONSES,
REVIEW, SOIL MICROORGANISMS, SPECIES RANGE, TEMPERATURE, TROPICAL
PLANTS

319  
Hollinger, D.Y. 1987. Gas Exchange and Dry Matter Allocation
Responses to Elevation of Atmospheric CO2 Concentration in
Seedlings of Three Tree Species. Tree Physiology 3:193-202.

Photosynthetic rates of 13-month-old Pinus radiata D. Don,
Nothofagus fusca (Hook f.) Orst. and Pseudotsuga menziesii (Mirb.)
Franco seedlings grown and measured at elevated atmospheric
concentrations of CO2 (about 620 uL/L) were 32 to 55% greater than
those of seedlings grown and measured at ambient (about 310 uL/L)
concentrations of CO2. Seedlings grown in ambient and elevated
concentrations of CO2 had similar rates of photosynthesis when
measured at 620 uL/L CO2, but when measured at 310 uL/L CO2 the P.
radiata and N. fusca seedlings which were grown at elevated CO2 had
lower rates of photosynthesis than the seedlings grown at an
ambient concentration of CO2. Stomatal conductances in general were
lower when measured at 620 uL/L CO2 than at 310 uL/L CO2.

Pinus radiata/Nothofagus fusca/Pseudotsuga menziesii/Monterey
pine/New Zealand red beech/Douglas-fir

KEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, TREES, VPD

320  
Houghton, R.A. 1987. Biotic Changes Consistent with the Increased
Seasonal Amplitude of Atmospheric CO2 Concentrations. Journal of
Geophysical Research 92:4223-4230.

Monthly estimates of gross primary production (gross uptake of CO2
by plants) and ecosystem respiration (gross release of CO2 from the
ecosystem) in an oak-pine forest in the northeastern United States
were used in this study to examine the types of metabolic changes
in terrestrial systems that might yield the increased seasonal
amplitude of CO2 concentrations observed at several monitoring
stations in recent years. In this study, increases in either
photosynthesis or respiration increased the amplitude of the
seasonal oscillation of CO2 concentrations if the increases were
predominantly in the northern hemispheric summer and winter,
respectively. The quantitative changes in metabolism required to
produce the observed increase in amplitude, however, were too large
to be explained by CO2 fertilization or by a temperature-induced
increase in winter respiration. Investigations of the role of the
biota in causing seasonal and year-to-year variations in
atmospheric CO2 concentrations are limited by the lack of stations
monitoring CO2 in continental air.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX,
ECOSYSTEM LEVEL CO2 RESPONSES, FOREST, MODELING, NET PRIMARY
PRODUCTIVITY, RESPIRATION, TERRESTRIAL METABOLISM

321  
Houghton, R.A. 1987. Terrestrial Metabolism and Atmospheric CO2
Concentrations. BioScience 37:672-678.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX,
ECOSYSTEM LEVEL CO2 RESPONSES, MODELING, NET PRIMARY PRODUCTIVITY,
RESPIRATION, REVIEW, TERRESTRIAL METABOLISM

322  
Houpis, J.L.J., K.A. Surano, S. Cowles, and J.H. Shinn. 1988.
Chlorophyll and Carotenoid Concentrations in Two Varieties of Pinus
ponderosa Seedlings Subjected to Long-term Elevated Carbon Dioxide.
Tree Physiology 4:187-193.

Two varieties of ponderosa pine (Pinus ponderosa Dougl. var.
scopulorum (Rocky Mountain variety) and P. ponderosa var. ponderosa
(Sierran variety)) seedlings were subjected to elevated atmospheric
CO2 for two and a half years. The CO2 concentrations were ambient,
ambient + 75 uL/L, ambient + 150 uL/L and ambient + 300 uL/L, or
approximately 350, 425, 500 and 650 uL/L CO2. After one and a half
years of exposure to elevated CO2 and until the end of the study,
seedlings of both varieties showed symptoms of stress including
mottling, mid-needle abscission and early senescence. In both
varieties, exposure to CO2 concentrations greater than ambient + 75
uL/L resulted in lower chlorophyll a, chlorophyll b and carotenoid
concentrations. At elevated CO2 concentrations, the concentration
of pigments in needles of the Sierran variety were lower than those
in the Rocky Mountain variety. Also, at elevated CO2
concentrations, the pigment concentrations in the 1-year-old
needles of both P. ponderosa varieties were lower than those in
current-season needles.

Pinus ponderosa/ponderosa pine

KEYWORDS: OPEN-TOP CHAMBERS, PIGMENTS, SENESCENCE, TREES

323  
Houpis, J.L.J., K.A. Surano, P.F. Daley, and J.H. Shinn. 1986.
Growth and Morphology of Pinus ponderosa Seedlings Exposed to Long-term Elevated Atmospheric Carbon Dioxide Concentration. IN:
Proceedings of the Ninth North American Forest Biology Workshop;
1986 June 15-18; Stillwater, Oklahoma (C.G. Tauer and T.C.
Hennessey, eds.), Society of American Foresters, and Department of
Forestry, Oklahoma State University, pp. 19-26.

The growth and morphology of two varieties of Pinus ponderosa were
measured after two years of continuous fumigation with carbon
dioxide. After two years of treatment, the seedlings of the Rocky
Mountain variety showed no significant difference in total stem
height or volume, but the basal diameters of those grown at +300
ppm CO2 were significantly greater than those grown at +0 ppm and
+75 ppm. The response of the seedlings of the Sierran variety in
these parameters was quite different, with those at +150 ppm and
+300 ppm significantly greater in height than those at +75 ppm and
those at +150 ppm and +300 ppm significantly greater than those at
+0 ppm and +75 ppm in basal diameter and stem volume. However,
using a combined analysis based on percent change in height,
diameter, or volume, seedlings at +150 ppm responded to a
significantly greater degree than all other levels. Thus, the
beneficial effects of elevated carbon dioxide increase up to +150
ppm and begin to decrease between +150 ppm and +300 ppm.

ponderosa pine/Pinus ponderosa

KEYWORDS: GROWTH, LEAF AREA DEVELOPMENT, MORPHOLOGY, OPEN-TOP
CHAMBERS, TREES

324  
Houter, G., H. Gijzen, E.M. Nederhoff, and P.C.M. Vermeulen. 1989.
Simulation of CO2 Consumption in Greenhouses. Acta Horticulturae
248:315-320.

In order to calculate the CO2 and heat demand in greenhouses, a
simulation model is composed of a greenhouse climate submodel and
a crop submodel. The purpose of the model is to use it as a
management system, which can be consulted for decisions on
investments in CO2 and heating equipment. The greenhouse climate
submodel calculates the conditions inside the greenhouse on the
basis of outside weather data and specific setpoints for the
greenhouse climate. It also calculates the demand for heat and the
necessity for ventilation. Both these factors are related to the
CO2 fluxes to the greenhouse. The crop submodel calculates leaf
photosynthesis, crop photosynthesis, dry matter production and
fresh weight production. As yet, the production of a tomato and of
a cucumber can be simulated.

KEYWORDS: CANOPY PHOTOSYNTHESIS, CO2 MEASUREMENT AND CONTROL,
COMMERCIAL USE OF CO2, MODELING, SIMULATION

325  
Hrubec, T.C., J.M. Robinson, and R.P. Donaldson. 1985. Effects of
CO2 Enrichment and Carbohydrate Content on the Dark Respiration of
Soybeans. Plant Physiology 79:684-689.

During the period of most active leaf expansion, the foliar dark
respiration rate of soybeans (Glycine max cv Williams), grown for
2 weeks in 1000 microliters CO2 per liter air, was 1.45 milligrams
CO2 evolved per hour leaf density thickness, and this was twice the
rate displayed by leaves of control plants (350 microliters CO2 per
liter air). There was a higher foliar nonstructural carbohydrate
level (e.g. sucrose and starch) in the CO2 enriched compared with
CO2 normal plants. For example, leaves of enriched plants displayed
levels of nonstructural carbohydrate equivalent to 174 milligrams
glucose per gram dry weight compared to the 84 milligrams glucose
per gram dry weight found in control plant leaves. As the leaves of
CO2 enriched plants approached full expansion, both the foliar
respiration rate and carbohydrate content of the CO2 enriched
leaves decreased until they were equivalent with those same
parameters in the leaves of control plants. A strong positive
correlation between respiration rate and carbohydrate content was
seen in high CO2 adapted plants, but not in the control plants.
Mitochondria, isolated simultaneously from the leaves of CO2
enriched and control plants, showed no difference in NADH or
malate-glutamate dependent O2 uptake, and there were no observed
differences in the specific activities of NAD+ linked isocitrate
dehydrogenase and cytochrome c oxidase. Since the mitochondrial O2
uptake and total enzyme activities were not greater in young
enriched leaves, the increase in leaf respiration rate was not
caused by metabolic adaptations in the leaf mitochondria as a
response to long term CO2 enrichment. It was concluded, that the
higher respiration rate in the enriched plant's foliage was
attributable, in part, to a higher carbohydrate status.

Glycine max/soybean

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES,
GROWTH, LEAF AREA DEVELOPMENT, RESPIRATION

326  
Huerta, A.J., and I.P. Ting. 1988. Effects of Various Levels of CO2
on the Induction of Crassulacean Acid Metabolism in Portulacaria
afra (L.) Jacq. Plant Physiology 88:183-188.

In response to water stress, Portulacaria afra (L.) Jacq.
(Portulacaceae) shifts its photosynthetic carbon metabolism from
the Calvin-Benson cycle for CO2 fixation (C3) photosynthesis or
Crassulacean acid metabolism (CAM)-cycling, during which organic
acids fluctuate with a C3-type of gas exchange, to CAM. During the
CAM induction, various attributes of CAM appear, such as stomatal
closure during the day, increase in diurnal fluctuation of organic
acids, and an increase in phosphoenolpyruvate carboxylase activity.
It was hypothesized that stomatal closure due to water stress may
induce changes in internal CO2 concentration and that these changes
in CO2 could be a factor in CAM induction. Experiments were
conducted to test this hypothesis. Well-watered plants and plants
from which water was withheld starting at the beginning of the
experiment were subjected to low (40 ppm), normal (ca. 330 ppm),
and high (950 ppm) CO2 during the day with normal concentrations of
CO2 during the night for 16 days. In water-stressed and in well-watered plants, CAM induction as ascertained by fluctuation of
total titratable acidity, fluctuation of malic acid, stomatal
conductance, CO2 uptake, and phosphoenolpyruvate carboxylase
activity, remained unaffected by low, normal or high CO2
treatments. In well-watered plants, however, both low and high
ambient concentrations of CO2 tended to reduce organic acid
concentrations, low concentrations of CO2 reducing the organic
acids more than high CO2. It was concluded that exposing the plants
to the CO2 concentrations mentioned had no effect on inducing or
reducing the induction of CAM and that the effect of water stress
on CAM induction is probably mediated by its effects on biochemical
components of leaf metabolism.

Portulacaria afra

KEYWORDS: CAM, CONDUCTANCE, LEAF PHOTOSYNTHESIS, METABOLITES,
PHOSPHOENOLPYRUVATE CARBOXYLASE, SUNLIT CONTROLLED ENVIRONMENT
CHAMBERS, WATER STRESS

327  
Hunt, R., D.W. Hand, M.A. Hannah, and A.M. Neal. 1991. Response to
CO2 Enrichment in 27 Herbaceous Species. Functional Ecology 5:410-421.

CO2-enrichment experiments were performed on 25 British native
species of widely differing ecology. Two crops, one C3
(sunflower)and one C4 (maize), were also included. The background
regime involved full-light, glasshouse conditions, non-limiting
supplies of water and mineral nutrients and a daytime mean
temperature of 18C. Four CO2 treatments were maintained at nominal
concentrations of 350, 500, 650 or 800 v.p.m. over a 56-day period.
Hyperbolic functions were fitted to yield vs CO2 concentration. The
functions were then used to generate predictions of Q-540/350 (the
quotient of present yield under the CO2 regime predicted for the
year 2050) and Q-700/350 (the quotient of present yield predicted
for a doubling of ambient CO2 concentration). Values of Q-540/350
for whole-plant dry weight ranged from below 1.01 to 1.49, the
upper values being at least similar in magnitude to those already
observed in C3 crops. The mean value of whole-plant Q-700/350 for
11 species of near-competitive strategy was 1.43. Four species of
stress-tolerant or ruderal strategy had a mean Q-700/350 of only
1.05. High CO2 responsiveness was common only within the
competitive strategy and its close relations. The fitted Q-540/350
for species of the pure strategy was 1.38. In the centre of the
strategic range the fitted value was 1.12, and at the far extreme,
the value for species of ruderal or stress-tolerant strategy was
only 1.03.

Agrostis capillaris/Arrhenatherum elatius/Brachypodium
pinnatum/Bromus erectus/Bromus sterilis/Cerastium
fontanum/Chamerion angustifolium/Chenopodium album/Dactylis
glomerata/Deschampsia flexuosa/Desmazeria rigida/Digitalis
purpurea/Epilobium hirsutum/Festuca ovina/Festuca
rubra/Helianthemum nummularium/Holcus lanatus/Koeleria
macrantha/Plantago lanceolata/Poa annua/Poa trivialis/Rumex
acetosella/Urtica dioica/Zea mays/Plantago lanceolata/Lolium
perenne/Helianthus annuus/Eriophorum vaginatum

KEYWORDS: GROWTH, MODELING, PLANT STRATEGIES, SPECIES COMPETITION,
SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

328  
Idso, S.B. 1986. Industrial Age Leading to the Greening of the
Earth? Nature 320:22.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX,
TEMPERATURE

329  
Idso, S.B. 1988. Three Phases of Plant Response to Atmospheric CO2
Enrichment. Plant Physiology 87:5-7.

Several years of research on seven different plants (five
terrestrial and two aquatic species) suggest that the beneficial
effects of atmospheric CO2 enrichment may be divided into three
distinct growth response phases. First is a well-watered optimum-growth-rate phase where a 300 parts per million increase in the CO2
content of the air generally increases plant productivity by
approximately 30%. Next comes a nonlethal water-stressed phase
where the same increase in atmospheric CO2 is more than half again
as effective in increasing plant productivity. Finally, there is a
water-stressed phase normally indicative of impending death, where
atmospheric CO2 enrichment may actually prevent plants from
succumbing to the rigors of the environment and enable them to
maintain essential life processes, as life ebbs from corresponding
ambient-treatment plants.

Agave vilmoriniana/Daucus carota/carrot/cotton/Gossypium
hirsutum/radish/Raphanus sativus/soybean/Glycine max/water
fern/Azolla pinnata/water hyacinth/Eichhornia crassipes

KEYWORDS: AQUATIC PLANTS, GROWTH, OPEN-TOP CHAMBERS, WATER STRESS

330  
Idso, S.B. 1989. Carbon Dioxide, Soil Moisture, and Future Crop
Production. Soil Science 147:305-307.

Model simulations of the effects of increases in atmospheric carbon
dioxide on air temperature, precipitation, and soil moisture
suggest that the resultant 'greenhouse effect' will be bad for
agriculture. Experimental evidence, however, indicates otherwise,
demonstrating that plants can more than compensate for the
predicted adverse climatic changes. Indeed, recent evidence from
around the globe suggests that a carbon-dioxide-induced stimulation
of the biosphere is already in progress.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, MODELING, REVIEW,
SIMULATION, WUE

331  
Idso, S.B. 1989. Three Stages of Plant Response to Atmospheric CO2
Enrichment. Plant Physiology and Biochemistry 27:131-134.

Weekly assessments of biomass production in water hyacinths
(Eichhornia crassipes) and daily assessments of new-leaf production
in water lilies (Nymphaea marliac carnea) demonstrate that the
positive effects of atmospheric CO2 enrichment on the growth rates
of these plants are considerably greater both before (I) and after
(III) the primary maximum-growth-rate stage (II) characteristic of
the middle portion of a plants' life cycle. For these two
particular aquatic macrophytes, the growth enhancement factor for
a 300 uL/L increase in the atmospheric CO2 concentration went from
a mean of 1.54 in stage I, to 1.33 in stage II, to actually
approach infinity in stage III.

Eichhornia crassipes/water hyacinth/water lily/Nymphaea marliac

KEYWORDS: AQUATIC PLANTS, GROWTH, OPEN-TOP CHAMBERS

332  
Idso, S.B. 1990. Interactive Effects of Carbon Dioxide and Climate
Variables on Plant Growth. IN: Impact of Carbon Dioxide, Trace
Gases, and Climate Change on Global Agriculture, ASA Special
Publication No. 53, American Society of Agronomy, Madison,
Wisconsin.

The climate variables predicted to experience major modification as
a result of future increases in atmospheric CO2 and other
radiatively active trace gases are temperature and precipitation.
Predicted changes in these two parameters should intensify the
hydrologic cycle over the globe, but could produce opposite trends
in certain regions. A 'worst-case' scenario of consequent local
reductions in summer soil moisture is evaluated in terms of the
beneficial effects of atmospheric CO2 enrichment on plant water use
efficiency and the interactive effect of air temperature increase
on the growth-enhancing effects of atmospheric CO2 enrichment. It
is demonstrated that the direct biological impacts of concomitant
increases in CO2 and air temperature are probably sufficient to
offset the adverse effects of summer soil moisture reductions
predicted by state-of-the-art climate/water balance models. It is
also noted that the worst-case climate scenario is unrealistic.
Consequently, plant growth the world over should be significantly
stimulated by atmospheric CO2 enrichment, a phenomenon that many
people feel is already evident in a number of ecological
indicators.

KEYWORDS: CLIMATE CHANGE, ENVIRONMENTAL INTERACTIONS, GROWTH,
HYDROLOGIC MODEL, LEAF PHOTOSYNTHESIS, TEMPERATURE, WATER STRESS,
WUE

333  
Idso, S.B. 1990. A Role for Soil Microbes in Moderating the Carbon
Dioxide Greenhouse Effect. Soil Science 149:179-180.

KEYWORDS: CARBON IN SOILS, CARBON SEQUESTERING, SOIL MICROORGANISMS

334  
Idso, S.B. 1991. The Aerial Fertilization Effect of CO2 and Its
Implications for Global Carbon Cycling and Maximum Greenhouse
Warming. Bulletin of the American Meteorological Society 72:962-965.

Citrus aurantium

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CARBON CYCLE, CO2 SEASONAL
FLUX, GROWTH, OPEN-TOP CHAMBERS, TEMPERATURE, TREES

335  
Idso, S.B. 1991. Comment on 'Modelling the Seasonal Contribution of
a CO2 Fertilization Effect of the Terrestrial Vegetation to the
Amplitude Increase in Atmospheric CO2 at Mauna Loa Observatory' by
G.H. Kohlmaier et al. Tellus 43B:338-341.

KEYWORDS: BIOTIC GROWTH FACTOR, CO2 SEASONAL FLUX, RHIZOSPHERE

336  
Idso, S.B. 1991. A General Relationship between CO2-induced
Increases in Net Photosynthesis and Concomitant Reductions in
Stomatal Conductance. Environmental and Experimental Botany 31:381-383.

Simultaneous measurements of net photosynthesis and stomatal
conductance of leaves of sour orange trees growing in normal and
CO2-enriched air, together with similar data for cotton, soybeans
and water hyacinth, suggest that a plant's photosynthetic response
to atmospheric CO2 enrichment is inversely proportional to its
degree of CO2-induced stomatal closure.

Citrus aurantium/sour orange

KEYWORDS: CONDUCTANCE, LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
TREES

337  
Idso, S.B., S.G. Allen, M.G. Anderson, and B.A. Kimball. 1989.
Atmospheric CO2 Enrichment Enhances Survival of Azolla at High
Temperatures. Environmental and Experimental Botany 29:337-341.

In 2 years of experimentation with Azolla pinnata var. pinnata at
Phoenix, Arizona, growth rates of this floating aquatic fern first
decreased, then stagnated, and finally became negative when the
mean air temperature rose above 30C. When the atmospheric CO2
content above the plants was increased from the mean ambient
concentration of 340 umol CO2/mol air to 640 umol CO2/mol air,
however, the debilitating effects of high temperatures were
reduced: in one case to a much less severe negative growth rate, in
another case to merely a short period of zero growth rate, and in
a third case to no discernible ill effects whatsoever -- in spite
of the fact that the ambient treatment plants in this instance all
died. With the double verification of this phenomenon provided by
both weekly biomass and periodic net photosynthesis determinations,
it would appear that atmospheric CO2 enrichment may be capable of
preventing the deaths of some plant species in situations where
their demise is normally brought about by either the direct effects
of unduly high temperatures or by associated debilitating diseases.

Azolla pinnata/water fern

KEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
TEMPERATURE

338  
Idso, S.B., S.G. Allen, and B.A. Kimball. 1990. Growth Response of
Water Lily to Atmospheric CO2 Enrichment. Aquatic Botany 37:87-92.

Hardy water lilies (Nymphaea cultivar 'Marliacea carnea') were
grown out-of-doors at Phoenix, Arizona in sunken metal stock tanks
located within open-top, clear plastic-wall, CO2-enrichment
chambers; two were maintained at a CO2 concentration of 650 ppm and
two were maintained at the ambient CO2 concentration of about 350
ppm. Over a 5-month period, 25 different plant properties were
evaluated, each one of which showed some degree of stimulation or
enhancement under CO2-enriched conditions. In particular, net
photosynthesis was increased by about 49%, leaf size by 18%, and
integrated leaf number x life span by 16%, which resulted in a
whole-plant biomass enhancement of 270%. After 21 months,
differences between treatments were not quite as dramatic; but at
the conclusion of the experiment, the rhizomes in the CO2-enriched
treatment were still more than two-and-a-half times greater in
total biomass than their ambient-grown counterparts.

water lily/Nymphaea

KEYWORDS: ALLOCATION, AQUATIC PLANTS, GROWTH, LEAF AREA
DEVELOPMENT, OPEN-TOP CHAMBERS

339  
Idso, S.B., K.L. Clawson, and M.G. Anderson. 1986. Foliage
Temperature: Effects of Environmental Factors with Implications for
Plant Water Stress Assessment and the CO2/Climate Connection. Water
Resources Research 22:1702-1706.

Throughout the summer and fall of 1985, several day-long sets of
foliage temperature measurements were obtained for healthy and
potentially transpiring water hyacinth, cotton, and alfalfa plants
growing in a sealed and unventilated greenhouse at Phoenix,
Arizona, along with concurrent measurements of air temperature,
vapor pressure and net radiation, plus in the case of water
hyacinths, leaf diffusion resistance measurements. Some data for
these plants were additionally obtained out of doors under natural
conditions, while dead, nontranspiring stands of alfalfa and water
hyacinth were also monitored, both out of doors and within the
greenhouse. Analyses of the data revealed that plant nonwater-stressed baselines, i.e., plots of foliage-air temperature
differential versus air vapor pressure deficit for potentially
transpiring vegetation, were (1) curvilinear, as opposed to the
straight lines which have so often appeared to be the case with
much smaller and restricted data sets, and (2) that these baselines
are accurately described by basic theory, utilizing independently
measured values of plant foliage and aerodynamic resistances to
water vapor transport. These findings lead to some slight
adjustments in the procedure for calculating the Idso-Jackson plant
water stress index and they suggest that plants can adequately
respond to much greater atmospheric demands for evaporation than
what has been believed possible in the past. In addition, they
demonstrate that the likely net radiation enhancement due to a
doubling of the atmospheric carbon dioxide concentration will have
little direct effect on vegetation temperatures, but that the
antitranspirant effect of atmospheric CO2 enrichment on foliage
temperature may be substantial.

water hyacinth/Eichhornia crassipes/cotton/Gossypium
hirsutum/alfalfa/Medicago sativa

KEYWORDS: AQUATIC PLANTS, CONDUCTANCE, CROPS, TEMPERATURE,
TRANSPIRATION, VPD

340  
Idso, S.B., and B.A. Kimball. 1989. Growth Response of Carrot and
Radish to Atmospheric CO2 Enrichment. Environmental and
Experimental Botany 29:135-139.

Seven crops of carrots and 11 crops of radishes were grown from
seed in open-top, clear-plastic-wall, CO2-enrichment chambers
throughout the entire year at Phoenix, AZ. Cumulative dry matter
production at weekly intervals was significantly increased by a 300
ppm increase in the CO2 content of the air at all temperatures
encountered, but with progressively greater effects being
registered at higher and higher temperatures. At 25C, the
productivity enhancement factor for radish was about 1.5, while for
carrot it was approximately 2.0. When regressed upon air
temperature, the productivity enhancement factors of both species
decreased to a null value of 1.0 in the vicinity of 12C. The slope
of the carrot relationship was nearly 250% greater than that of the
radish relationship.

carrot/Daucus carota/radish/Raphanus sativus

KEYWORDS: CROPS, GROWTH, OPEN-TOP CHAMBERS, TEMPERATURE

341  
Idso, S.B., and B.A. Kimball. 1991. Downward Regulation of
Photosynthesis and Growth at High CO2 Levels. Plant Physiology
96:990-992.

Numerous photosynthesis and growth measurements of sour orange
(Citrus aurantium L.) trees maintained in ambient air and air
enriched with an extra 300 microliters per liter of CO2 have
revealed the CO2-enriched trees to have consistently sequestered
approximately 2.8 times more carbon than the control trees over a
period of three full years. Under field conditions in the natural
environment, plants may not experience the downward regulation of
photosynthetic capacity typically observed in long-term CO2
enrichment experiments with plants growing in pots.

sour orange/Citrus aurantium

KEYWORDS: GROWTH, OPEN-TOP CHAMBERS, TREES

342  
Idso, S.B., and B.A. Kimball. 1991. Effects of Two and a Half Years
of Atmospheric CO2 Enrichment on the Root Density Distribution of
Three-year-old Sour Orange Trees. Agricultural and Forest
Meteorology 55:345-349.

Eight sour orange trees planted directly into the ground at
Phoenix, Arizona, as small seedlings in July 1987 have been
enclosed by four clear-plastic-wall, open-top chambers since
November of that year, half of which have been continuously
supplied with a CO2 enriched atmosphere consisting of an extra 300
cm3 CO2/m3 of air. Extensive soil coring of the trees' root zones
conducted in July 1990 indicated that two and a half years of
growth under these conditions produced a fine root biomass
enhancement of 175% in the CO2 enriched trees. This growth
enhancement is of the same order of magnitude as our previously
reported results for net photosynthesis and trunk and branch
volumes for these trees.

Citrus aurantium/sour orange

KEYWORDS: GROWTH, OPEN-TOP CHAMBERS, ROOTS, TREES

343  
Idso, S.B., and B.A. Kimball. 1992. Season Fine-root Biomass
Development of Sour Orange Trees Grown in Atmospheres of Ambient
and Elevated CO2 Concentration. Plant, Cell and Environment 15:337-341.

Sour orange trees have been grown from the seedling stage out-of-doors at Phoenix, Arizona, USA, in open-top enclosures with clear
plastic walls for 3.5 years. For the last 3 years of this period,
half of the trees have been continuously exposed to air enriched
with CO2 to 300 umol/mol above the ambient concentation. At 2-month
intervals over the last 12 months, we have determined the fine-root
biomass in the top 0.4 m of the soil profile beneath the trees.
Results from both treatments define a single relationship between
fine-root biomass and trunk cross-sectional area. The data also
show the CO2-enriched trees to have approximately 2-3 times more
fine-root biomass in this soil layer than the trees grown in
ambient air.

Citrus aurantium/sour orange

KEYWORDS: OPEN-TOP CHAMBERS, ROOTS, TREES

344  
Idso, S.B., and B.A. Kimball. 1993. Effects of Atmospheric CO2
Enrichment on Net Photosynthesis and Dark Respiration Rates of
Three Australian Tree Species. Journal of Plant Physiology 141:166-171.

Net photosynthesis and dark respiration rates of leaves of three
Australian tree species exposed to a range of atmospheric CO2
concentrations were measured throughout the summer of 1991. For all
three species - the Australian bottle tree (Brachychiton populneum
(Schott.) R. Br.) and two eucalyptus (Eucalyptus microtheca F.
Muell. and E. polyanthemus Schauer) - dark respiration dropped by
approximately 50% for a 360 to 720 uL/L doubling of the air's CO2
concentration, while net photosynthesis rose by a factor of two.
These results were not significantly different from results
obtained previously for the common orange tree (Citrus aurantium
L.).

Australian bottle tree/Brachychiton populneum/sour orange/Citrus
aurantium/Eucalyptus microtheca/Eucalyptus polyanthemus

KEYWORDS: LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, RESPIRATION,
TREES

345  
Idso, S.B., B.A. Kimball, and S.G. Allen. 1991. CO2 Enrichment of
Sour Orange Trees: 2.5 Years into a Long-term Experiment. Plant,
Cell and Environment 14:351-353.

Eight sour orange trees have been grown from seedling stage in the
field at Phoenix, Arizona, U.S.A., in four identically-vented,
open-top, clear-plastic-wall chambers for close to 2.5 years. Half
of the chambers have been maintained at ambient atmospheric CO2
concentrations over this period, while half of them have been
maintained at 300 ppm (300 umol CO2 per mol air) above ambient.
Initially, the trees in each treatment were essentially identical;
but in less than 2 years, the trunks of the CO2 enriched trees had
become twice as large as their ambient-treatment counterparts.
After 2 full years of growth, the enriched trees had 79% more
leaves, 56% more primary branches with 72% more volume, 70% more
secondary branches with 90% more volume, and 250% more tertiary
branches with 855% more volume. In addition, the CO2-enriched trees
also had fourth-, fifth- and sixth-order branches, while the
ambient treatment trees had no branches above third order. Total
trunk plus branch volume of the CO2-enriched trees was 2.79 times
that of the ambient-treatment trees after 2 full years of growth.

sour orange/Citrus aurantium

KEYWORDS: GROWTH, OPEN-TOP CHAMBERS, TREES

346  
Idso, S.B., B.A. Kimball, and S.G. Allen. 1991. Net Photosynthesis
of Sour Orange Trees Maintained in Atmospheres of Ambient and
Elevated CO2 Concentration. Agricultural and Forest Meteorology
54:95-101.

Eight sour orange trees planted directly into the ground at
Phoenix, Arizona, as small seedlings in July 1987 have been
enclosed by four clear-plastic-wall, open-top chambers since
November of that year. Half of the trees have been continuously
supplied with a CO2-enriched atmosphere consisting of an extra 300
cm3 of CO2 per m3 of air. Data from a comprehensive inventory of
all above-ground plant parts at the conclusion of two full years of
growth under these conditions have revealed that the net effect of
the CO2-enriched air was to more than double the normal production
of biomass over the time interval. Here we report net
photosynthesis measurements made throughout the last summer of the
period, which suggest that the primary impetus for this large
growth response was an equivalent enhancement of the net
photosynthetic rates of the CO2-enriched trees.

sour orange/Citrus aurantium

KEYWORDS: GROWTH, OPEN-TOP CHAMBERS, PHOTOSYNTHESIS, TREES

347  
Idso, S.B., B.A. Kimball, and M.G. Anderson. 1985. Atmospheric CO2
Enrichment of Water Hyacinths: Effects on Transpiration and Water
Use Efficiency. Water Resources Research 21:1787-1790.

Open-top clear plastic wall chambers enclosing pairs of sunken
metal stock tanks, one of each pair of which contained a full cover
of water hyacinths, were maintained out-of-doors at Phoenix,
Arizona for several weeks during the summer of 1984. One of these
chambers represented ambient conditions, while the other three were
continuously enriched with carbon dioxide to approximate target
concentrations of 500, 650, and 900 ppm. During a 4-week period
when plant growth was at its maximum, water hyacinth biomass
production increased by 36% for a 300-600 ppm doubling of the
atmospheric CO2 content, while water use efficiency, or the biomass
produced per unit of water transpired, actually doubled. These
results are similar to hat has been observed in several terrestrial
plants and they indicate the general trend which may be expected to
occur as atmospheric CO2 continues to rise in the years ahead.

water hyacinth/Eichhornia crassipes

KEYWORDS: AQUATIC PLANTS, GROWTH, OPEN-TOP CHAMBERS, TRANSPIRATION,
WUE

348  
Idso, S.B., B.A. Kimball, and M.G. Anderson. 1986. Foliage
Temperature Increases in Water Hyacinth Caused by Atmospheric CO2
Enrichment. Archives for Meteorology, Geophysics and Bioclimatology
Ser. B 36:365-370.

Atmospheric CO2 enrichment tends to induce partial stomatal closure
in most higher plants. This phenomenon reduces per-unit-leaf-area
plant transpirational water loss rates, which in turn leads to
higher plant temperatures. Working in the field with water
hyacinths maintained in open-top, clear-plastic wall, CO2-enrichment chambers at Phoenix, Arizona, we have quantified this
relationship for a plant species which has been shown previously to
react like most land plants in this regard. Our results indicate
that in some parts of the world this non-greenhouse mechanism for
surface temperature change may play an important role in
determining future climate. Under sunlit and well-watered
conditions conducive to active growth, for instance, we found water
hyacinth foliage temperatures to increase by 2.7 K in response to
a 300 to 600 ppm doubling of the atmospheric CO2 concentration.

water hyacinth/Eichhornia crassipes

KEYWORDS: AQUATIC PLANTS, OPEN-TOP CHAMBERS, TEMPERATURE,
TRANSPIRATION

349  
Idso, S.B., B.A. Kimball, M.G. Anderson, and J.R. Mauney. 1987.
Effects of Atmospheric CO2 Enrichment on Plant Growth: the
Interactive Role of Air Temperature. Agriculture, Ecosystems and
Environment 20:1-10.

Comprehensive reviews of the plant science literature indicate that
a 300 part per million (ppm) increase in atmospheric carbon dioxide
(CO2) concentration generally increases plant growth by
approximately 30%. Working with two species of floating aquatic
plants and three terrestrial species, we demonstrate that this
stimulatory effect of atmospheric CO2 enrichment is strongly
temperature dependent. Indeed, our results suggest that for a 3C
increase in mean surface air temperature (as is generally predicted
to result from the 'greenhouse effect' of such an increase in the
CO2 content of the air), the growth enhancement factor for such a
CO2 increase rises from 1.30 to 1.56. If the non-CO2 trace gas
greenhouse effect is equally as strong, as recent model studies
suggest, the growth enhancement factor rises still higher to a
value of 1.85. On the other hand, our results also indicate that
atmospheric CO2 enrichment tends to reduce plant growth at
relatively cold air temperatures, i.e. below a daily mean air
temperature of approximately 18.5C. As a result, predicting the
ultimate biospheric consequences of a doubling of the Earth's
atmospheric CO2 concentration may prove to be much more complex
than originally anticipated.

carrot/Daucus carota/radish/Raphanus sativus/water
hyacinth/Eichhornia crassipes/water fern/Azolla pinnata

KEYWORDS: AQUATIC PLANTS, CROPS, GROWTH, OPEN-TOP CHAMBERS,
TEMPERATURE

350  
Idso, S.B., B.A. Kimball, M.G. Anderson, and S.R. Szarek. 1986.
Growth Response of a Succulent Plant, Agave vilmoriniana, to
Elevated CO2. Plant Physiology 80:796-797.

Large (about 200 grams dry weight) and small (about 5 grams dry
weight) specimens of the leaf succulent Agave vilmoriniana Berger
were grown outdoors at Phoenix, Arizona. Potted plants were
maintained in open-top chambers constructed with clear, plastic
wall material. Four CO2 concentrations of 350, 560, 675, and 885
microliters per liter were used during two growth periods and two
water treatments. Small and large plants were grown for 6 months,
while a few large plants were grown for 1 year. Wet-treatment
plants received water twice weekly, whereas dry-treatment plants
received slightly more water than they would under natural
conditions. Plant growth rates in all treatments were significantly
different between small and large specimens, but not between 6
month and 1 year large plants. Only the dry-treatment plants
exhibited statistically different growth rates between the CO2
treatments. This productivity response was equivalent to a 28% and
3-fold increase when mathematically interpolated between CO2
concentrations of 300 and 600 microliters per liter for large and
small plants, respectively.

Agave vilmoriniana

KEYWORDS: CAM, GROWTH, GROWTH ANALYSIS, OPEN-TOP CHAMBERS, WATER
STRESS

351  
Idso, S.B., B.A. Kimball, and J.R. Mauney. 1987. Atmospheric Carbon
Dioxide Enrichment Effects on Cotton Midday Foliage Temperature:
Implications for Plant Water Use and Crop Yield. Agronomy Journal
79:667-672.

In an experiment designed to determine the likely consequences of
the steadily rising carbon dioxide (CO2) concentration of Earth's
atmosphere for the foliage temperature, water use, and yield of
cotton (Gossypium hirsutum L. var. Deltapine-61) plants, cotton was
grown out-of-doors at Phoenix, AZ, in open-top, clear-polyethylene-wall, CO2-enrichment chambers for three summers under mean daylight
CO2 concentrations of 340, 500 and 640 umol CO2/mol air on an
Avondale clay loam soil [fine-loamy, mixed (calcareous),
hyperthermic Anthropic Torrifluvent]. Infrared thermometer
measurements of the cotton foliage temperature (Tf) indicated that
a 330 to 660 umol CO2/mol air doubling of the atmospheric CO2
content results in a midday Tf increase of 1.1C for well-watered
cotton at Phoenix in the summer. This temperature increase was
predicted to produce a 9% reduction in per-unit-leaf-area plant
transpiration rate and an 85% increase in crop biomass production,
which compared favorably with the measured crop biomass increase of
82% for such a doubling of the air's CO2 content. These findings,
together with similar findings for a second plant species -- water
hyacinth [Eichhornia cassipes (Mart.) Solms] -- allowed us to
develop a technique for assessing the effects of a 330 umol CO2/mol
air CO2 concentration increase on the percentage yield increase (Y)
of a crop via infrared thermometry by means of the equation Y =
7.6% x (IJ), where IJ represents the Idso-Jackson plant water
stress index. If this equation holds up under further scrutiny, it
could provide a rapid and efficient means for assessing the yield
response of crops to atmospheric CO2 enrichment.

cotton/Gossypium hirsutum

KEYWORDS: CROPS, OPEN-TOP CHAMBERS, TEMPERATURE, TRANSPIRATION,
VPD, WUE

352  
Idso, S.B., B.A. Kimball, and J.R. Mauney. 1988. Effects of
Atmospheric CO2 Enrichment on Root:Shoot Ratios of Carrots, Radish,
Cotton and Soybean. Agriculture, Ecosystems and Environment 22:293-299.

Detailed analyses of root:shoot ratios, determined at weekly
intervals during a succession of cropping cycles, show that the
responses of root crops, such as radish and carrot, differ from
those of cotton and soybean. Whereas the root:shoot ratios of the
latter crops were not affected by atmospheric CO2 enrichment,
increasing the CO2 concentration of the air from 340 (ambient) to
650 umol CO2/mol air significantly increased the proportions of
assimilates allocated to the roots of radish and carrot. This
effect increased the root:shoot ratios of both root crops by
approximately 36% at all stages of plant growth, suggesting a
response to atmospheric CO2 enrichment that is independent of plant
size and not caused by a progressive reduction in nitrogen
availability.

soybean/Glycine max/cotton/Gossypium hirsutum/radish/Raphanus
sativus/carrot/Daucus carota

KEYWORDS: ALLOCATION, CROPS, GROWTH, OPEN-TOP CHAMBERS, ROOT:SHOOT
RATIO

353  
Idso, S.B., B.A. Kimball, and J.R. Mauney. 1988. Atmospheric CO2
Enrichment and Plant Dry Matter Content. Agricultural and Forest
Meteorology 43:171-181.

Fresh and dry plant weights were measured throughout a number of
different CO2 enrichment experiments with six terrestrial plants
and two aquatic species. Similar data were also extracted from the
literature for 18 additional plants. In general, CO2 enrichment had
little effect on plant percentage dry matter content, except under
conditions conducive to starch accumulation in leaves, and then it
caused an increase in percentage dry matter content.

carrot/Daucus carota/cotton/Gossypium hirsutum/radish/Raphanus
sativus/soybean/Glycine max/water fern/Azolla pinnata/water
hyacinth/Eichhornia crassipes/Agave
vilmoriniana/tomato/Lycopersicon esculentum

KEYWORDS: DRY MATTER CONTENT, OPEN-TOP CHAMBERS, REVIEW

354  
Israel, D.W., T.W. Rufty Jr., and J.D. Cure. 1990. Nitrogen and
Phosphorus Nutritional Interactions in a CO2 Enriched Environment.
Journal of Plant Nutrition 13:1419-1433.

Nonnodulated soybean plants (Glycine max [L.] Merr. 'Lee') were
supplied with nutrient solutions containing growth limiting
concentrations of N or P to examine effects on N- and P- uptake
efficiencies (mg nutrient accumulated/gdw root) and utilization
efficiencies in dry matter production (gdw2/mg nutrient).
Nutritional treatments were imposed in aerial environments
containing either 350 or 700 uL/L atmospheric CO2 to determine
whether the nutrient interactions were modified when growth rates
were altered. Nutrient-stress treatments decreased growth and N-
and P- uptake and utilization efficiencies at 27 days after
transplanting (DAT) and seed yield at maturity (98 DAT).
Atmospheric CO2 enrichment increased growth and N- and P-utilization efficiencies at 27 DAT and seed yield in all
nutritional treatments and did not affect N- and P-uptake
efficiencies at 27 DAT. Parameter responses to nutrient stress at
27 DAT were not altered by atmospheric CO2 enrichment and vice
versa. Nutrient-stress treatments lowered the relative seed yield
response to atmospheric CO2 enrichment.

soybean/Glycine max

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
NITROGEN, NUTRITION, PHOSPHORUS, YIELD

355  
Ito, T. 1989. More Intensive Production of Lettuce under
Artificially Controlled Conditions. Acta Horticulturae 260:381-389.

lettuce/Lactuca sativa

KEYWORDS: COMMERCIAL USE OF CO2, HORTICULTURAL CROPS

356  
Jansen, C.M., S. Pot, and H. Lambers. 1986. The Influence of CO2
Enrichment of the Atmosphere and NaCl on Growth and Metabolism of
Urtica dioica L. IN: Biological Control of Photosynthesis (R.
Marcelle, H. Clijsters, and M. Van Poucke, eds.), Martinus Nijhoff
Publishers, Dordrecht, The Netherlands, pp. 143-146.

Urtica dioica plants were grown at 0 and 25 mM NaCl at two
concentrations to determine the effect of CO2 enrichment on their
response to NaCl. Their relative growth rate was stimulated by CO2
enrichment, which can be explained by their enhanced photosynthetic
rate. The relative growth rate was reduced by NaCl at both CO2
concentrations. This reduction was associated with a reduction of
their photosynthetic rate. The leaf area ratio was negatively
correlated with the photosynthetic rate and counteracted both the
response to CO2 enrichment and to NaCl.

Urtica dioica

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH ANALYSIS, RESPIRATION, SALT STRESS

357  
Jarvis, P.G. 1989. Atmospheric Carbon Dioxide and Forests.
Philosophical Transactions of the Royal Society, London (Series B)
324:369-392.

Knowledge about the effects of the rise in atmospheric CO2
concentration on trees and forest is assessed and, the converse,
the possible impact of forests on the atmospheric CO2 concentration
is discussed. At the cellular scale, much is known about the role
of CO2 as a substrate in photosynthesis, but only little about its
role as an activator and regulator. At the leaf scale, the response
of CO2 assimilation to CO2 concentration has been described often
and is well represented by biochemically based models, but there is
inadequate information to parameterize the models of CO2-acclimated
leaves. Growth and partitioning to the roots of seedlings and young
trees generally increases in response to a doubling in atmospheric
CO2 concentration. Experimental results are very variable, because
of the differing length of the experiments, the artificial
conditions and the artefactual constraints. At larger scales,
direct measurements of responses to increase in atmospheric CO2 are
impractical but models of canopy processes suggest that significant
increases in CO2 assimilation will result from the rise in
atmospheric concentration. Inferences from the increase in
amplitude of the seasonal oscillation in the global atmospheric CO2
concentration at different latitudes suggest that forest is having
a significant impact on the global atmospheric concentration, but
it seems unlikely that expansion of the forest resource could
effectively reduce the increase in atmospheric CO2.

KEYWORDS: CARBON SEQUESTERING, CO2 SEASONAL FLUX, FOREST, LEAF
PHOTOSYNTHESIS, MODELING, PHOTOSYNTHETIC ACCLIMATION, REVIEW, TREES

358  
Jiao, J. 1989. Predicting the Growth Response of Greenhouse Roses
to Aerial Environments Based on Carbon Dioxide Exchange Studies.
Doctoral Dissertation, University of Guelph, Canada, Dissertation
Abstracts Vol. 50:04-B, p.1187.

The influence of aerial environment (i.e. irradiance, CO2
concentration, and temperature) on net CO2 exchange of single-stemmed 'Samantha' roses at different stages of flowering shoot
development was studied. Photosynthesis and photorespiration in
leaves of different ages were similar, except in the young
expanding leaves, which had lower net assimilation rates due to
their lower leaf conductance and carboxylation efficiency. Long-term CO2 enrichment did not reduce photosynthetic efficiency. Leaf
photosynthesis was saturated at 500 umol/m2/s photosynthetically
active radiation (PAR). At saturation irradiance and ambient CO2
concentration, photosynthesis and photorespiration of mature leaves
were insensitive to temperature change from 15 to 30C. Whole plant
net photosynthetic rates were similar on a leaf area basis at
different stages of shoot development. Whole plants had higher
saturation irradiance (1000 umol/m2/s) but lower net photosynthetic
rates than those of single leaves due to mutual shading and
respiration of sink organs. Second-order polynomial functions were
used to predict whole plant net photosynthesis at various aerial
environments. Irradiance, CO2 concentration, and temperature
attributed 70%, 20%, and 5%, respectively, to the total variance
explained by the model (R2=0.86). The predicted optimal
temperatures for whole plant net photosynthesis increased from 19
to 25C with increasing irradiance and CO2 concentration. The
Arrhenius equation described dark respiration temperature response
well. Although night respiration increased with day-time carbon (C)
gain, plant daily growth was still proportional to day-time CO2
assimilation. A whole plant daily growth model was developed by
combining a dark respiration model with a day-time C gain model.
The use of net CO2 exchange as a nondestructive estimation of
biomass production under various irradiance, CO2 concentration, and
temperature conditions provided physiological basis of
environmental control of plant growth and productivity. The data
and models presented can be served as a guideline for setting and
controlling the greenhouse environment for rose production.

rose/Rosa hybrida

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOXYLATION EFFICIENCY,
COMMERCIAL USE OF CO2, FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL
CROPS, LEAF PHOTOSYNTHESIS, LIGHT, MODELING, RESPIRATION,
TEMPERATURE

359  
Jiao, J., M.J. Tsujita, and B. Grodzinski. 1991. Influence of
Temperature on Net CO2 Exchange in Roses. Canadian Journal of Plant
Science 71:235-243.

The effect of temperature on net CO2 exchange of source and sink
tissues of the flowering shoots and of whole plants was examined
using single-stemmed Samantha roses. At all stages of shoot
development, the optimal temperature range for whole-plant carbon
(C) gain at saturating irradiance and ambient CO2 level was between
20 and 25C, narrower than the temperature range for optimal leaf
net photosynthesis. Dark respiration increased more dramatically
than photosynthesis with temperatures between 15 and 35C. At 25C,
C loss due to respiration from the flower bud at colour bud stage
accounted for 45% of the C loss of the flowering shoot. At low
irradiance levels (e.g. 200 umol/m2/s) whole-plant net
photosynthesis was greater at 16 than at 22C because of a greater
reduction in respiration. Lowering the night temperature from 27
to 17C also increased daily C gain due to a reduction in the C
lost at night. Whole-plant net photosynthesis of plants grown and
measured at enriched (1000 +/- 100 uL/L) CO2 was greater than that
of plants grown and measured at ambient (350 +/- 50 uL/L) level at
temperatures between 15 and 35C. Furthermore, the optimal
temperatures for whole-plant net photosynthesis in CO2 enrichment
was higher than at ambient CO2 level.

rose/Rosa hybrida

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, GREENHOUSE, LIGHT,
MODELING, RESPIRATION, SOURCE-SINK BALANCE, TEMPERATURE

360  
Jiao, J., M.J. Tsujita, and B. Grodzinski. 1991. Influence of
Radiation and CO2 Enrichment on Whole Plant Net CO2 Exchange in
Roses. Canadian Journal of Plant Science 71:245-252.

At three stages of flowering shoot development, varying the
irradiance and CO2 levels had a similar effect on the whole-plant
net CO2 exchange rate (NCER) of Samantha rose plants. At 22C, the
NCER was saturated at 1000 umol/m2/s photosynthetically active
radiation (PAR). The duration of the light period was also
important in determining daily carbon (C) gain. When roses were
exposed to a constant daily radiant energy dose of 17.6 umol/m2
provided either as a 12-h irradiation interval at 410 umol/m2/s PAR
or 24 h of irradiation at 204 umol/m2/s PAR, the plants exposed to
24 h of continuous irradiation at the lower photon flux density
retained 80% more C. Under saturating irradiance, the net
photosynthetic rate at an enriched (1000 uL/L) CO2 level was almost
double that at ambient (350 uL/L) CO2. However, plants grown at
ambient and enriched CO2 levels had similar whole-plant NCERs when
compared at the same assay CO2 level. Under CO2 enrichment the
flower stem was longer and thicker but the flower bud size at
harvest was not significantly different to that of roses grown at
the ambient CO2 level.

rose/Rosa hybrida

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, GREENHOUSE, LIGHT,
TEMPERATURE

361  
Jiao, J., M.J. Tsujita, and B. Grodzinski. 1991. Optimizing Aerial
Environments for Greenhouse Rose Production Utilizing Whole-plant
Net CO2 Exchange. Canadian Journal of Plant Science 71:253-261.

A daily growth model was developed for Samantha roses based on
nondestructive measurements of whole-plant net CO2 exchange rate
(NCER) under various aerial environmental conditions. Irradiance,
CO2 concentration, and temperature accounted for 70, 20, and 5%,
respectively, of the variance in whole-plant net photosynthesis
explainable by a second-order polynomial model (R2=0.86). The
predicted optimal temperatures for whole-plant net photosynthesis
increased from 19 to 24C with increasing irradiance from 100 to
1200 umol/m2/s and CO2 concentration from 350 to 1500 uL/L. Dark
respiration rate increased exponentially with temperature and could
be predicted by the Arrhenius equation. Even though respiratory
carbon (C) loss at night increased linearly with daytime C gain,
daily C gain (delta C) was still proportional to daytime net
photosynthesis. The relative contribution of irradiance (100-1200
umol/m2/s), day length (8-16 h), CO2 concentration (350-1500 uL/L),
day temperature (15-30C), and night temperature (15-25C) to plant
daily growth was 64, 31, 4, 0.3, and 0.7%, respectively.

rose/Rosa hybrida

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, DAYLENGTH,
ENVIRONMENTAL INTERACTIONS, FLOWER PRODUCTION, GREENHOUSE, GROWTH
MODEL, HORTICULTURAL CROPS, LIGHT, MODELING, RESPIRATION,
TEMPERATURE

362  
Johnson, H.B., H.W. Polley, and H.S. Mayeux. 1993. Increasing CO2
and Plant-plant Interactions: Effects on Natural Vegetation.
Vegetatio 104/105:157-170.

Plant species and functional groups of species show marked
differences in photosynthesis and growth in relation to rising
atmospheric CO2 concentrations through the range of the 30%
increase of the recent past and the 100% increase since the last
glaciation. A large shift was found in the compositional mix of 26
species of C3's and 17 species of C4's grown from a native soil
seed bank in a competitive mode along a CO2 gradient that
approximated the CO2 increase of the past 150 years and before. The
biomass of C3's increased from near zero to 50% of the total while
that of the C4's was reduced 25% as CO2 levels approached current
ambient. The proposition that acclimation to rising CO2 will
largely negate the fertilization effect of higher CO2 levels on
C3's is not supported. No signs of photosynthetic acclimation were
evident for Avena sativa, Prosopis glandulosa, and Schizachyrium
scoparium plants grown in subambient CO2. The effects of changing
CO2 levels on vegetation since the last glaciation are thought to
have been at least as great, if not greater, than those which
should be expected for a doubling of current CO2 levels.
Atmospheric CO2 concentrations below 200 ppm are thought to have
been instrumental in the rise of the C4 grasslands of North America
and other extensive C4 grasslands and savannas of the world.
Dramatic invasion of these areas by woody C3 species are
accompanying the historical increase in atmospheric CO2
concentration now in progress.

Prosopis glandulosa/mesquite/Schizachyrium scoparium/little
bluestem/Brassica kaber/field mustard/Avena sativa/oat/Cenchrus
incertus/Paspalum setaceum/Panicum cappillare/Digitaria
ciliaris/Eragrostis spectabilis/Cyperus globulosus/Mollugo
verticillata/Sporobolus neglectus/Euphorbia prostrata/Setaria
sp./Echinochloa crus-galli/Amaranthus sp./Croton glandulosa/Verbena
hastata/Verbena halei/Oenothera sp./Ratibida columnaris/Ambrosia
artemisiifolia/Lesquerella sp./Gaillardia pulchella/Gaura
sp./Solanum sp./Gutierrezia dracunculoides/Rudbeckia
hirta/Commelina erecta/Panicum angustifolium/Croton
capitatum/Monarda punctata/Croton monanthogynus/Oxalis dillenii

KEYWORDS: C3, C4, GRADIENT EXPOSURE TUNNEL, GRASSES, PLANT-PLANT
INTERACTIONS, PRE-INDUSTRIAL CO2 CONCENTRATION, SPECIES
COMPETITION, TREES, WEEDS

363  
Johnson, R.H., and D.E. Lincoln. 1990. Sagebrush and Grasshopper
Responses to Atmospheric Carbon Dioxide Concentration. Oecologia
84:103-110.

Seed- and clonally-propagated plants of Big Sagebrush (Artemisia
tridentata var. tridentata) were grown under atmospheric carbon
dioxide regimes of 270, 350 and 650 uL/L and fed to Melanoplus
differentialis and M. sanguinipes grasshoppers. Total shrub biomass
significantly increased as carbon dioxide levels increased, as did
the weight and area of individual leaves. Plants grown from seed
collected in a single population exhibited a 3-5 fold variation in
the concentration of leaf volatile mono- and sesquiterpenes,
guaianolide sesquiterpene lactones, coumarins and flavones within
each CO2 treatment. The concentration of leaf allelochemicals did
not differ significantly among CO2 treatments for these seed-propagated plants. Further, when genotypic variation was controlled
by vegetative propagation, allelochemical concentrations also did
not differ among carbon dioxide treatments. On the other hand,
overall leaf nitrogen concentration declined significantly with
elevated CO2. Carbon accumulation was seen to dilute leaf nitrogen
as the balance of leaf carbon versus nitrogen progressively
increased as CO2 growth concentration increased. Grasshopper
feeding was highest on sagebrush leaves grown under 270 and 650
uL/L CO2, but varied widely within treatments. Leaf nitrogen
concentration was an important positive factor in grasshopper
relative growth but had no overall effect on consumption. Potential
compensatory consumption by these generalist grasshoppers was
apparently limited by the sagebrush allelochemicals. Insects with
a greater ability to feed on chemically defended host plants under
carbon dioxide enrichment may ultimately consume leaves with a
lower nitrogen concentration but the same concentration of
allelochemicals. Compensatory feeding may potentially increase the
amount of dietary allelochemicals ingested for each unit of
nitrogen consumed.

Artemisia tridentata/sagebrush

KEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS,
HERBIVORY, INSECTS, MELANOPLUS DIFFERENTIALIS, MELANOPLUS
SANGUINIPES, NITROGEN

364  
Johnson, R.H., and D.E. Lincoln. 1991. Sagebrush Carbon Allocation
Patterns and Grasshopper Nutrition: The Influence of CO2 Enrichment
and Soil Mineral Limitation. Oecologia 87:127-134.

Artemisia tridentata seedlings were grown under carbon dioxide
concentrations of 350 and 650 uL/L and two levels of soil
nutrition. In the high nutrient treatment, increasing CO2 led to a
doubling of shoot mass, whereas nutrient limitation completely
constrained the response to elevated CO2. Root biomass was
unaffected by any treatment. Plant root/shoot ratios declined under
carbon dioxide enrichment but increased under low nutrient
availability, thus the ratio was apparently controlled by changes
in carbon allocation to shoot mass alone. Growth under CO2
enrichment increased the starch concentrations of leaves grown
under both nutrient regimes, while increased CO2 and low nutrient
availability acted in concert to reduce leaf nitrogen concentration
and water content. Carbon dioxide enrichment and soil nutrient
limitation both acted to increase the balance of leaf storage
carbohydrate versus nitrogen (C/N). The two treatment effects were
significantly interactive in that nutrient limitation slightly
reduced the C/N balance among the high-CO2 plants. Leaf volatile
terpene concentration increased only in the nutrient limited plants
and did not follow the overall increase in leaf C/N ratio.
Grasshopper consumption was significantly greater on host leaves
grown under CO2 enrichment but was reduced on leaves grown under
low nutrient availability. An overall negative relationship of
consumption versus leaf volatile concentration suggests that
terpenes may have been one of several important leaf
characteristics limiting consumption of the low nutrient hosts.
Digestibility of host leaves grown under the high CO2 treatment was
significantly increased and was related to high leaf starch
content. Grasshopper growth efficiency (ECI) was significantly
reduced by the nutrient limitation treatment but co-varied with
leaf water content.

sagebrush/Artemisia tridentata

KEYWORDS: ALLELOCHEMICALS, CARBOHYDRATES, CARBON:NITROGEN RATIO,
CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, INSECTS, LEAF
PHOTOSYNTHESIS, NITROGEN, NUTRITION, ROOT:SHOOT RATIO, TERPENES

365  
Jolliffe, P.A., and D.L. Ehret. 1985. Growth of Bean Plants at
Elevated Carbon Dioxide Concentrations. Canadian Journal of Botany
63:2021-2025.

Plants of Phaseolus vulgaris L. cv. Pure Gold Wax were grown in
controlled environment chambers at six CO2 concentrations ranging
from 340 to 3000 uL/L. Data for plant growth analysis were obtained
from five harvests from 11 to 55 days after planting. Growth curves
were fitted to the data using a cubic spline regression procedure.
CO2 enrichment caused large and rapid increases in leaf dry weight,
unit leaf rate, and specific leaf weight. Smaller responses
included a decrease in leaf area ratio and an increase in leaf
weight ratio. Root dry weight and leaf area were not significantly
affected by CO2 treatments. Relative growth rate was initially
higher in CO2 enriched plants and later declined; it may not be a
suitable index for the evaluation of CO2 effects during long
periods of growth. The results indicate that leaf formation and
expansion were not limited by assimilate supply. Maximum growth and
pod yield were obtained in plants grown at 1200 uL/L CO2.

bean/Phaseolus vulgaris

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, YIELD

366  
Jones, J.W., E. Dayan, H. van Keulen, and H. Challa. 1989. Modeling
Tomato Growth for Optimizing Greenhouse Temperatures and Carbon
Dioxide Concentrations. Acta Horticulturae 248:285-294.

Predictions of crop yield response to a dynamic environment are
essential to the development of optimal control strategies for
greenhouses. A dynamic tomato growth and yield model (TOMGRO) was
developed specifically for coupling to physical models of the
greenhouse environment for optimizing temperature and carbon
dioxide concentrations for tomato production. The model is based on
development and growth components. Experiments were conducted in
outdoor, computer-controlled plant growth chambers to parameterize
the development, carbon exchange, and growth submodels under
combinations of two CO2 (350 and 950 vpm) and three night
temperatures (12, 16, and 20 C). Daytime temperatures were held to
28 for all treatments. The model successfully described
development, growth, and yield for all combinations of temperature
and CO2 in this experiment.

tomato/Lycopersicon esculentum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CO2 MEASUREMENT AND CONTROL,
COMMERCIAL USE OF CO2, GREENHOUSE, GROWTH STAGES, HORTICULTURAL
CROPS, MODELING, SPAR UNITS, TEMPERATURE, YIELD

367  
Jones, P., B.L. Roy, and J.W. Jones. 1989. Coupling Expert Systems
and Models for the Real-time Control of Plant Environments. Acta
Horticulturae 248:445-452.

A control system, to regulate CO2 in a plant growth chamber, based
on distributed processing and a multi-tasking operating system is
described. CO2 controls are based on a model of plant
photosynthetic light response. Parameters in the model that change
through time are automatically evaluated and updated on a 'daily'
basis. The system demonstrates how separation of the processing
tasks facilitates sophisticated programming. Results in terms of
the quality of controls achieved are favorable. The importance of
distributed processing and multi-tasking to the application of data
analysis, simulation models, and expert systems in 'real-time'
environmental controls is discussed. Low cost hardware and
supporting software is quickly becoming available and the challenge
will become practical implementation of straightforward ideas. The
general conclusion is that practical application of such systems
can be expected in the near term.

KEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2,
MODELING

368  
Kano, A. 1985. Growth Model of Greenhouse Tomatoes with Carbon
Dioxide Enrichment: Development and Experimental Tests (Simulation,
Modelling). Doctoral Dissertation, Texas A&M University,
Dissertation Abstracts Vol. 46:10-B, p.3272 (147 pp.).

A deterministic, compartmental growth model of greenhouse tomato
plants, written in Pascal computer language, was developed based on
a leaf assimilation model and a model of a theory that the
photosynthesis rate is controlled both by the environmental
conditions and by the internal carbohydrate level in the leaf. The
model was tested with data obtained from two experiments conducted
in 1983 through 1984 at College Station, Texas. Three 2m x 2m x 10m
chambers were built in a plastic-covered greenhouse, and tomato
plants were grown in the chambers at three different CO2
concentrations: 340, 700, and 1000 um3/m3. Inputs to the model were
the light and CO2 levels and the air temperature. The outputs
included the CO2 assimilation rate, dry-mass accumulation rate, and
tomato yield, which were compared with the results from the
measurements. The model underestimated the CO2 assimilation rate
and dry-mass accumulation rate of tomatoes for all CO2 levels;
however, it predicted the fruit growth and yield rather accurately.
For a growth model with parameters taken not from the measurements,
but from earlier published results, the magnitude and trend of the
results of the simulation were reasonably acceptable. A potential
use of the model is to predict the effects of environmental factors
or to estimate the benefit from CO2 enrichment under different
environmental conditions. It also can be a part of an integrated
greenhouse model which predicts growth and yield of the crop in the
greenhouse using the environmental conditions outside the
greenhouse and the greenhouse control mechanisms and strategies.

tomato/Lycopersicon esculentum

KEYWORDS: GREENHOUSE, GROWTH MODEL, GROWTH RATE, HORTICULTURAL
CROPS, LIGHT, MODELING, TEMPERATURE, YIELD

369  
Karvonen, T., and P. Peltonen-Sainio. 1990. The Influence of CO2
and Air Temperature on Agricultural Productivity in Northern
Latitudes. IN: The Greenhouse Effect and Primary Productivity in
European Agro-ecosystems; 5-10 April 1990; Wageningen, The
Netherlands (J. Goudriaan, H. van Keulen, and H.H. van Laar, eds.),
Pudoc, Wageningen, p. 61.

KEYWORDS: AGRICULTURE, MODELING, TEMPERATURE

370  
Kats, G., D.M. Olszyk, and C.R. Thompson. 1985. Open Top
Experimental Chambers for Trees. Journal of the Air Pollution
Control Association 35:1298-1301.

KEYWORDS: EXPOSURE METHODS, OPEN-TOP CHAMBERS, TREES

371  
Kaushal, P., J.M. Guehl, and G. Aussenac. 1989. Differential Growth
Response to Atmospheric Carbon Dioxide Enrichment in Seedlings of
Cedrus atlantica and Pinus nigra ssp. Laricio var. Corsicana.
Canadian Journal of Forest Research 19:1351-1358.

Nine-month-old seedlings of Cedrus atlantica Manetti and Pinus
nigra Arn. ssp. Laricio var. Corsicana were transplanted in
parallelepipedal containers permitting root growth observations
(minirhizotrons) and in 6 L pots and were then transferred into two
polyethylene tunnels in a greenhouse, where they were submitted to
atmospheric CO2 concentrations of 350 (normal) and 800 umol/mol
(enriched) for their 2nd growth year. At the end of the enrichment
period, the biomass of the enriched plants was 66 (C. atlantica)
and 30% (P. nigra) higher than those of the plants grown at normal
CO2 concentrations. The root:shoot biomass ratio remained
unaffected by enrichment in both species. Height and diameter
growth were 20 (C. atlantica) and 10% (P. nigra) higher in the
enriched treatment. At the end of the enrichment period, the CO2
assimilation rate was no longer stimulated in the enriched C.
atlantica plants as compared with the normal treatment, but
remained slightly stimulated in the P. nigra seedlings. The
differential growth response to elevated CO2 appears to be related
to the distinct genetic growth pattern of the two species, namely
to their different patterns of root growth before bud break and
during the early aerial growth.

Cedrus atlantica/Pinus nigra

KEYWORDS: ALLOCATION, CARBOHYDRATES, GREENHOUSE, GROWTH, LEAF
PHOTOSYNTHESIS, RHIZOTRON, ROOT:SHOOT RATIO, ROOTS, TRANSPIRATION,
TREES, WUE

372  
Ke, D., and M.E. Saltveit Jr. 1989. Carbon Dioxide-induced Brown
Stain Development as Related to Phenolic Metabolism in Iceberg
Lettuce. Journal of the American Society of Horticultural Science
114:789-794.

Controlled atmospheres containing air + 11% CO2 caused tissue
injury and induced phenylalanine ammonia-lyase (PAL, EC 4.3.1.5)
activity in iceberg lettuce (Lactuca sativa L.) midrib tissue.
Injury symptoms included brown stain (browning of epidermal tissue)
and sunken epidermal areas (pitting) a few millimeters in diameter.
Pitting occurred in high-CO2 atmospheres at 5C with no increase in
phenolic content, but browning did not develop until the tissue had
been transferred to air at 25C. Browning developed within several
hours of transfer to air and the degree of browning was correlated
with the soluble phenolic content. The oxidation of soluble
phenolic compounds to brown substances by polyphenol oxidase (PPO,
EC 1.10.3.2) could account for tissue browning. Lignification was
associated with cell wall thickening in discolored tissue and was
accompanied by an increase in ionically bound and soluble
peroxidase (POD, EC 1.11.1.7) activities. Exposure of tissue to
elevated CO2 increased ionically bound indoleacetic acid (IAA)
oxidase activity, but reduced soluble IAA oxidase activity.
Application of an aqueous solution of 1.0 mM IAA to the tissue
before treatment did not significantly reduce browning. Lettuce
tissue exposed to 1.5% O2 + 1% CO2 had reduced PAL activity and
lower soluble phenolic content than lettuce exposed to air + 11%
CO2. Depending on the sensitivity of the lettuce tissue to CO2
injury, low-O2 atmospheres either reduced or slightly retarded
browning induced by 11% CO2.

Lactuca sativa/lettuce

KEYWORDS: ENZYMES, GROWTH REGULATORS, HORTICULTURAL CROPS, PHENOLIC
METABOLISM

373  
Kelly, D.W., P.R. Hicklenton, and E.G. Reekie. 1991. Photosynthetic
Response of Geranium to Elevated CO2 as Affected by Leaf Age and
Time of CO2 Exposure. Canadian Journal of Botany 69:2482-2488.

Geranium plants were grown from seed in chambers maintained at 350
or 1000 uL/L CO2. Photosynthesis as affected by leaf age and by
leaf position was determined. Elevated CO2 enhanced photosynthesis
to the greatest extent in middle-aged leaves; very young leaves
exhibited little enhancement, and net photosynthesis in the oldest
leaves was depressed by elevated CO2. Temporary increases in net
photosynthesis (relative to leaves developed at high CO2) resulted
when young leaves grown at 350 uL/L CO2 were switched to 1000 uL/L
CO2. Leaves switched later in development exhibited permanent
enhancement. Middle-aged leaves exhibited a temporary depression
followed by permanent enhancement. Leaves developed at high CO2 and
switched to low CO2 did not exhibit any photosynthetic depression
relative to plants grown continuously at low CO2. Similarly, leaves
developed at low CO2, switched to high CO2 for various lengths of
time, and returned to low CO2 showed no photosynthetic depression.
Leaves developed at low CO2 and switched to high CO2 exhibited
increases in specific leaf weight and leaf thickness. The increase
in leaf thickness was proportional to length of time spent at high
CO2. High CO2 depressed the rate at which stomata developed but did
not affect final stomatal density. Results suggest that
photosynthesis at low CO2 was limited by CO2 regardless of
developmental environment, whereas photosynthesis at high CO2 was
limited by the developmental characteristics of the leaf. Further,
both biochemical and structural modifications appear to be involved
in this response. Because of the very different responses of young
versus old leaves, future studies should be careful to consider
leaf age in assessing response to elevated CO2.

geranium/Pelargonium hortorum

KEYWORDS: ANATOMY, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, SENESCENCE, STOMATAL
DENSITY

374  
Kendall, A.C., J.C. Turner, and S.M. Thomas. 1985. Effects of CO2
Enrichment at Different Irradiances on Growth and Yield of Wheat.
Journal of Experimental Botany 36:252-260.

Wheat, Triticum aestivum L., the winter cultivars Hobbit and
Cappelle-Desprez, and the spring cultivars Sicco and Kleiber, were
grown in normal air or air enriched with CO2 either outdoors in a
glass-roofed cage or in controlled environment rooms. In neither
the winter nor the spring wheat was growth increased due to
enrichment with CO2 before anthesis. Enrichment of the two winter
wheat cultivars increased shoot dry weight significantly at 15 d
after anthesis but produced no significant increase in grain yield.
With the spring cultivars there was a significant increase in shoot
dry weight by 18 d after anthesis and the grain yield was also
larger due to an increase in grain size. Shoot weight increased
because the stems were larger, and there was a diversion of
assimilate from grain growth to late tiller production. Root tissue
comprised less than 20% of the total dry matter at anthesis (for
all cultivars); effects of CO2 enrichment on root growth appeared
to be less important than effects on shoot and ear growth. Growth
and yield responses to CO2 enrichment were observed (for the spring
cultivars) at irradiances of both 250 and 635 uE/m2/s, but the
effects were greater at the lower irradiance.

wheat/Triticum aestivum

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR
RESPONSES, GRASSES, LIGHT, OPEN-TOP CHAMBERS, REPRODUCTION, YIELD

375  
Kendall, A.C., J.C. Turner, S.M. Thomas, and A.J. Keys. 1985.
Effects of CO2 Enrichment at Different Irradiances on Growth and
Yield of Wheat. II. Effects on Kleiber Spring Wheat Treated from
Anthesis in Controlled Environments in Relation to Effects on
Photosynthesis and Photorespiration. Journal of Experimental Botany
36:261-273.

Spring wheat plants were grown in a cage with a glass roof until
three days after anthesis and then subjected to treatments in
constant environment rooms with any one of all combinations of four
irradiances and two concentrations of carbon dioxide. The
photoperiod was 16 h and day/night temperatures 19C/14C. Growth
and yield of grain were saturated at the two brightest irradiances.
Carbon dioxide enrichment from 350 to 1200 mm3/dm3 increased shoot
dry weight and grain yield at final harvest at all irradiances, by
averages of 10.5 (not significant) and 23.5 (significant) percent
respectively. However, increasing the irradiance from 150 to 613
uE/m2/s caused much larger yield increases (approximately 3-fold).
Increased grain production by increased light was caused by both
increases in dry weight per grain and by increases in grain number
per spikelet. The increase caused by CO2 enrichment was mainly
because of increased dry weight per grain. Increase in ear dry
weight caused by CO2 enrichment took place between 30 and 60 d
after anthesis. The increase in shoot dry weight took place
immediately after exposure to increased CO2 from 3 to 15 d after
anthesis. Net photosynthesis by flag leaves on the main shoots was
almost doubled 16 d after anthesis by the CO2 enrichment even
though stomatal resistance was also doubled. However, this increase
was not reflected by a proportional increase in yield, probably
because increased mutual shading by bigger stems and by late
tillers reduced total assimilation and because of increased
respiration by the shoots. The increase in photosynthesis was not
due to a decrease in photorespiration but to an increase in gross
photosynthesis.

wheat/Triticum aestivum

KEYWORDS: 14C, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LEAF
PHOTOSYNTHESIS, LIGHT, RESPIRATION, SEED PRODUCTION, YIELD

376  
Khan, M.A.H., and A. Madsen. 1986. Leaf Diffusive Resistance and
Water Economy in Carbon Dioxide-Enriched Rice Plants. New
Phytologist 104:215-223.

The leaf diffusive resistance to the transfer of water vapour and
CO2 exchange in rice plants (Oryza sativa L., cv. IR-20) measured
from the late vegetative stage to maturity, varied in response to
differing CO2 enrichments. The leaf diffusive resistance of plants
treated with 900 uL/L CO2 ranged from one-half to twice that of the
control plants (330 uL/L CO2). This difference was more pronounced
during the heading and ripening stages. In plants treated with 600
uL/L CO2, the diffusive resistances appeared to be smaller than in
the control plants for most of the day. In the diurnal cycles,
resistances were highest during the early morning and before
sunset, the maximum again occurring in the plants treated with 900
uL/L CO2. The rate of transpiration was inversely related to the
diffusive resistance, and was 20 to 100% lower in the plants
treated with 900 uL/L CO2 than in the controls, both in the
seasonal and diurnal cycles. In plants treated with 600 uL/L CO2,
the rate of transpiration was lower than in the controls in the
morning but distinctly higher during the afternoon. However, the
integrated total daily transpiration in 600 uL/L CO2 did not exceed
that of the controls. In all cases, CO2-treated plants, through
their increased biomass production and economic yield, appeared to
have a higher water use efficiency than the control plants.

rice/Oryza sativa

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, DIURNAL
CYCLE, GROWTH STAGES, SEED PRODUCTION, TRANSPIRATION, YIELD

377  
Kienast, F., and R.J. Luxmoore. 1988. Tree-ring Analysis and
Conifer Growth Responses to Increased Atmospheric CO2 Levels.
Oecologia 76:487-495.

Tree-ring analysis data of naturally grown conifers were analyzed
to evaluate the possibility of enhanced tree growth due to
increased atmospheric CO2. Tree cores were obtained from 34 sites
in four different climatic regions in the northern hemisphere. In
each of the four regions, the sampling sites were located along
ecological gradients between the subalpine treeline and low
elevations and, sometimes, the arid forest border. Growth trends
after 1950, when the atmospheric CO2 concentration increased by
more than 30 uL/L indicate an increase in ring-widths at eight of
the 34 sites. These chronologies were from sites which moderate
temperature or water stress. In four cases the growth increase in
the post-1950 period coincided with favorable climatic conditions.
In the remaining four cases, the growth increase exceeded the upper
bound response expected from CO2 enrichment experiments with
seedling conifer species. Therefore, increased growth in any of the
tree-ring chronologies examined could not be solely attributed to
higher atmospheric CO2 concentrations.

KEYWORDS: BIOTIC GROWTH FACTOR, REVIEW, TREE-RING ANALYSIS, TREES,
X-RAY DENSITOMETRY

378  
Kimball, B.A. 1985. Adaptation of Vegetation and Management
Practices to a Higher Carbon Dioxide World. IN: Direct Effects of
Increasing Carbon Dioxide on Vegetation, DOE/ER-0238 (B.R. Strain
and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research
Division, Washington, D.C., pp. 185-204.

KEYWORDS: AGRICULTURE, REVIEW

379  
Kimball, B.A. 1986. CO2 Stimulation of Growth and Yield under
Environmental Restraints. IN: Physiology, Yield, and Economics,
Vol. II (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide
Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton,
Florida, pp. 55-67.

The stimulation of growth of C3 plants by CO2 enrichment as
affected by several environmental restraints is discussed. Based on
the interacting effects of CO2 concentration and light intensity on
photosynthesis of C3 plants, it was hypothesized that huge relative
increases in growth could occur at very low light intensities due
to shifts in the light compensation point. Large relative and
absolute increases could also occur at high light intensities due
to saturation effects. Actual observations by many previous workers
of growth and yield with CO2 enrichment at various light
intensities exhibited much scatter, and it is concluded that to a
first approximation, relative CO2 growth stimulation is rather
constant with light intensity. A similar conclusion was reached
with respect to temperature over the temperature range that plants
are normally grown. It is reasonable to expect that greater growth
with CO2 enrichment will require greater amounts of fertilizer
nutrients, and this hypothesis is supported by the available data.
CO2 enrichment causes partial closure of stomates, which has been
shown to restrict the loss of water from leaves and to restrict the
intake of air pollutants into leaves. The former effect gives
plants greater ability to withstand or avoid water (and possibly
salinity) stress, while the second effect gives plants (C3) greater
ability to withstand air pollutant injury.

KEYWORDS: AIR POLLUTION, ENVIRONMENTAL INTERACTIONS, LIGHT,
NUTRITION, REVIEW, SALT STRESS, TEMPERATURE, WATER STRESS

380  
Kimball, B.A. 1986. Influence of Elevated CO2 on Crop Yield. IN:
Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 105-115.

The prior literature on the effects of CO2 enrichment on plant
growth and yield were examined. More than 770 observations of the
yields or biomass production of 38 crops and 8 other species grown
at elevated CO2 were extracted from more than 40 reports, published
during the last 66 years. The percentage increase in yield of the
CO2 enriched plants to their respective controls were computed and
statistically analyzed. CO2 enrichment increased the economic yield
of mature agricultural crops by 26% with a 95% confidence interval
from 18 to 36%. Excluding flower crops, whose yield was measured by
number of blooms, the mean yield increase of C3 crops with CO2
enrichment was 36%. Plotting yield increase against CO2
concentration revealed that 1000 uL/L is about the optimum
concentration with relatively little increase occurring at higher
values. Further analysis of 147 experiments which had controlled
CO2 concentrations for their duration showed that yields probably
will increase by 32% (with a 95% confidence interval from 27 to
38%) with the future doubling of atmospheric CO2 concentration. How
to use these data to estimate grower's yield responses to CO2
enrichment is also discussed, and an example is presented.

KEYWORDS: C3, C4, CROPS, FLOWER PRODUCTION, GREENHOUSE,
HORTICULTURAL CROPS, REVIEW, TREES

381  
Kimball, B.A. 1992. Cost Comparisons among Free-Air CO2 Enrichment,
Open-Top Chamber, and Sunlit Controlled-Environment Chamber Methods
of CO2 Exposure. Critical Reviews in Plant Sciences 11:265-270.

The costs associated with producing high-CO2-grown plants were
compared for three experimental techniques--free-air CO2 enrichment
(FACE), open-top chambers (OTC), and sunlit controlled environment
chambers (Soil, Plant, Atmosphere Research units, SPAR). The
operating costs for treated plant production were estimated to be
about $149,000/year and $128,000/year for SPAR and OTC,
respectively. For FACE they were about $438,000/year, with the CO2
cost amounting to about $288,000/year for continuous enrichment by
300 umol/mol above ambient for a 6 month growing season.
Substantial savings in FACE CO2 expense can be realized where lower
concentrations or shorter enrichment duration can be used.
Nevertheless, the FACE plots are much larger so there is a huge
economy of scale. The cost per enriched area for plant growth was
about $500/m/year for FACE compared to about $9,300 and
$1,800/m/year for SPAR and OTC, respectively. When the additional
costs of making scientific measurements was addressed, the cost of
scientific labor was seen to be the largest expense of conducting
research, and the costs of producing treated plants were seen to be
only about 26, 18, and 28% of the total costs of SPAR, OTC, and
FACE projects, respectively.

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, EXPOSURE METHODS, FACE,
SPAR UNITS

382  
Kimball, B.A., D.H. Akey, J.R. Mauney, S.B. Idso, S.G. Allen, D.L.
Hendrix, and J.W. Radin. 1988. Elevated CO2: Modeling Crop
Responses, Interaction with Temperature, Effects on Trees and
Insects, 052 in Green Report Series, Response of Vegetation to
Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.,
Washington, D.C.

cotton/Gossypium hirsutum/Agave vilmoriniana/Citrus
aurantium/orange trees/sorghum/Sorghum bicolor

KEYWORDS: BEET ARMYWORM, CAM, CROP MODEL, FACE, FIZZ IRRIGATION,
HERBIVORY, INSECTS, MODELING, OPEN-TOP CHAMBERS, SPODOPTERA EXIGUA,
TEMPERATURE, TREES

383  
Kimball, B.A., R.L. La Morte, G.J. Peresta, J.R. Mauney, K.F.
Lewin, and G.R. Hendrey. 1992. Weather, Soils, Cultural Practices,
and Cotton Growth Data from the 1989 FACE Experiment in IBSNAT
Format. Critical Reviews in Plant Sciences 11:271-308.

cotton/Gossypium hirsutum

KEYWORDS: FACE, MODELING

384  
Kimball, B.A., J.R. Mauney, D.H. Akey, D.L. Hendrix, S.G. Allen,
S.B. Idso, J.W. Radin, and E.A. Lakatos. 1987. Effects of
Increasing Atmospheric CO2 on the Growth, Water Relations, and
Physiology of Plants Grown under Optimal and Limiting Levels of
Water and Nitrogen, 049 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division and U.S. Dept. of Agriculture, Agric. Res. Serv.,
Washington, D.C.

cotton/Gossypium hirsutum

KEYWORDS: BEET ARMYWORM, EXPOSURE METHODS, FACE, FIZZ IRRIGATION,
GROWTH MODEL, LEAF PHOTOSYNTHESIS, NITROGEN, OPEN-TOP CHAMBERS,
STOMATA, WATER STRESS

385  
Kimball, B.A., J.R. Mauney, G. Guinn, F.S. Nakayama, S.B. Idso,
J.W. Radin, D.L. Hendrix, G.D. Butler, T.I. Zarembinski, and P.E.
Nixon. 1985. Effect of Increasing Atmospheric CO2 on the Yield and
Water Use of Crops, 027 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, and U.S. Dept. of Agriculture, Agric. Res.
Serv., Washington, D.C.

cotton/Gossypium hirsutum

KEYWORDS: CARBOHYDRATES, CONDUCTANCE, EXPOSURE METHODS, LEAF
PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, SOIL
RESPIRATION, WATER STATUS, YIELD

386  
Kimball, B.A., J.R. Mauney, G. Guinn, F.S. Nakayama, P.J. Pinter
Jr., K.L. Clawson, S.B. Idso, G.D. Butler, and J.R. Radin. 1984.
Effects of Increasing Atmospheric CO2 on the Yield and Water Use of
Crops, 023 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C.

cotton/Gossypium hirsutum

KEYWORDS: CONDUCTANCE, CROPS, LEAF PHOTOSYNTHESIS, OPEN-TOP
CHAMBERS, WATER, WATER STRESS, WUE, YIELD

387  
Kimball, B.A., J.R. Mauney, G. Guinn, F.S. Nakayama, P.J. Pinter
Jr., K.L. Clawson, R.J. Reginato, and S.B. Idso. 1983. Effects of
Increasing Atmospheric CO2 on the Yield and Water Use of Crops, 021
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C.

cotton/Gossypium hirsutum

KEYWORDS: CROPS, EVAPOTRANSPIRATION, EXPOSURE METHODS, GROWTH,
OPEN-TOP CHAMBERS, YIELD

388  
Kimball, B.A., J.R. Mauney, F.S. Nakayama, and S.B. Idso. 1993.
Effects of Increasing Atmospheric CO2 on Vegetation. Vegetatio
104/105:65-75.

The increasing atmospheric CO2 concentration probably will have
significant direct effects on vegetation whether predicted changes
in climate occur or not. Averaging over many prior greenhouse and
growth chamber studies, plant growth and yield have typically
increased more than 30% with a doubling of CO2 concentration. Such
a doubling also causes stomatal conductance to decrease about 37%,
which typically increases leaf temperatures more than 1C, and
which may decrease evapotranspiration, although increases in leaf
area counteract the latter effect. Interactions between CO2 and
climate variables also appear important. In one study the growth
increase from near-doubled CO2 ranged from minus 60% at 12C to 1%
at 19C to plus 130% at 34C, suggesting that if the climate warms,
the average growth response to doubled CO2 could be consistently
higher than the 30% mentioned above. Even when growing in nutrient-poor soil, the growth response to elevated CO2 has been large, in
contrast to nutrient solution studies which showed little response.
Several studies have suggested that under water-stress, the CO2
growth stimulation is as large or larger than under well-watered
conditions. Therefore, the direct CO2 effect will compensate
somewhat, if not completely, for a hotter drier climate. And if any
climate change is small, then plant growth and crop yields will
probably be significantly higher in the future high-CO2 world.

KEYWORDS: CLIMATE CHANGE, ENVIRONMENTAL INTERACTIONS, NUTRITION,
REVIEW, TEMPERATURE, WATER STRESS

389  
Kimball, B.A., J.R. Mauney, J.W. Radin, F.S. Nakayama, S.B. Idso,
D.L. Hendrix, D.H. Akey, S.G. Allen, M.G. Anderson, and W. Hartung.
1986. Effects of Increasing Atmospheric CO2 on the Growth, Water
Relations, and Physiology of Plants Grown under Optimal and
Limiting Levels of Water and Nitrogen, 039 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, and U.S. Dept. of Agriculture,
Agric. Res. Serv., Washington, D.C.

cotton/Gossypium hirsutum

KEYWORDS: ABA, CARBOHYDRATES, EXPOSURE METHODS, FACE, FIZZ
IRRIGATION, GROWTH, HERBIVORY, INSECTS, ISOTOPE DISCRIMINATION,
LEAF PHOTOSYNTHESIS, NITROGEN, OPEN-TOP CHAMBERS, PECTINOPHORA
GOSSYPIELLA, PINK BOLLWORM, WATER STATUS, WATER STRESS, YIELD

390  
Kimball, B.A., P.J. Pinter Jr., and J.R. Mauney. 1992. Cotton Leaf
and Boll Temperatures in the 1989 FACE Experiment. Critical Reviews
in Plant Sciences 11:233-240.

cotton/Gossypium hirsutum

KEYWORDS: EXPOSURE METHODS, FACE, TEMPERATURE

391  
King, K.M., and D.H. Greer. 1986. Effects of Carbon Dioxide
Enrichment and Soil Water on Maize. Agronomy Journal 78:515-521.

The current global rise in atmospheric CO2 concentration may lead
to changes in yield and water use of crops. This study was done to
determine the effects of increased CO2 in combination with soil
water levels on the growth, yield, transpiration, and water use
efficiency of maize (Zea mays L.). Corn plants (cv. PX74) were
grown in Opiki humic silty clay loam (fine, illitic, mesic Histic
Humaquepts) soil in 22-L pots from emergence to maturity (111 days)
in controlled environment rooms at CO2 concentrations of 350/360,
600/650/, and 850/900 uL/L (day/night). Within each room, at a
given CO2 concentration, the plants were subjected to one of three
soil water treatments: complete replacement of weekly transpiration
(control) and 75 and 50% replacement of the control transpiration.
The 350 uL/L treated plants produced an average of 401 g dry matter
across all water treatments and the 600 and 850 uL/L treated plants
produced an average of 431 and 436 g dry matter per plant,
respectively. The differences in total dry matter between the 600
and 850 uL/L treated plants remained nonsignificant throughout the
experiment. There were significant differences between all soil
water treatments in dry matter production with the low soil water
level averaging 284 g and the medium and high water level averaging
440 and 544 g/plant, respectively. Transpiration was reduced with
increased CO2 concentration and was 80.5 and 70.4% at 600 and 850
uL/L, respectively, of that at 350 uL/L averaged across water
treatments. The water use efficiency (WUE) increased markedly with
increased CO2 concentration. At 600 and 850 uL/L the WUE was 34 and
55% greater, respectively, than at 350 uL/L. Further work is needed
on the applicability of this controlled environment experiment to
the real world.

corn/Zea mays

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, TRANSPIRATION,
WATER STRESS, WUE

392  
Kirkham, M.B., H. He, T.P. Bolger, D.J. Lawlor, and E.T. Kanemasu.
1991. Leaf Photosynthesis and Water Use of Big Bluestem under
Elevated Carbon Dioxide. Crop Science 31:1589-1594.

With the atmospheric concentration of CO2 increasing, it is
important to know how this will affect crop growth. The objective
of the study was to determine the effect of elevated CO2 on big
bluestem (Andropogon gerardii Vitman) growing in a tallgrass
prairie on a Tully silty clay loam (fine, mixed, mesic Pachic
Argiustoll) kept at a high water level (field capacity) or a low
water level (half field capacity). Sixteen cylindrical plastic
chambers were placed on the prairie to maintain the two levels of
CO2 (mean +/- SD: 337 +/- 32 and 658 +/- 81 umol/mol) over a full
growing season. Soil-water content was measured weekly with a
neutron probe. Photosynthesis, transpiration, stomatal resistance,
and intercellular CO2 concentration were determined with a portable
leaf photosynthetic system. Canopy temperature was monitored with
an infrared thermometer. Elevated (doubled) CO2 reduced
transpiration rate of big bluestem by 25 and 35 % under the high-
and low-water treatments, respectively. Under both watering
regimes, stomatal resistance was greater by about 1.6 s/cm with
doubled CO2 than with ambient CO2. Plants grown with doubled CO2 at
high- and low-water levels had warmer canopy temperatures (average
1.15 and 0.70C warmer, respectively) than plants grown at ambient
CO2. Carbon-dioxide concentration did not affect the rate of
photosynthesis, even though intercellular CO2 concentration was
increased under high CO2. Elevated CO2 did not increase the height
of plants grown at the high water level, but it did increase the
height at the low water level by an average of 9 cm.

Andropogon gerardii/big bluestem

KEYWORDS: C4, LEAF PHOTOSYNTHESIS, OUTDOOR GROWTH CHAMBERS,
TALLGRASS PRAIRIE, TEMPERATURE, TRANSPIRATION, WATER STRESS

393  
Kirkham, M.B., E.T. Kanemasu, G.W. Harbers, D.W. Reed, H. He, R.D.
Theisen, T.P. Bolger, D.E. Goodrum, L.K. Ballou, D.J. Lawlor, D.
Nie, and W.P. Lu. 1990. Rangeland-Plant Response to Elevated CO2,
056 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C.

Andropogon gerardii/big bluestem

KEYWORDS: CONDUCTANCE, FORBS, GRASSES, GROWTH, LEAF PHOTOSYNTHESIS,
OUTDOOR GROWTH CHAMBERS, RANGELAND, SEDGES, TALLGRASS PRAIRIE,
TRANSPIRATION

394  
Kirschbaum, M.U.F., and G.D. Farquhar. 1987. Investigation of the
CO2 Dependence of Quantum Yield and Respiration in Eucalyptus
pauciflora. Plant Physiology 83:1032-1036.

In leaves of C3 plants, the rate of nonphotorespiratory respiration
appears to be higher in darkness than in the light. This change
from a high to a low rate of carbon loss with increasing photon
flux density leads to an increase in the apparent quantum yield of
photosynthetic CO2 assimilation at low photon flux densities (Kok
effect). The mechanism of this suppression of nonphotorespiratory
respiration is not understood, but biochemical evidence and the
observation that a Kok effect is often not observed under low O2,
has led to the suggestion that photorespiration might be involved
in some way. This hypothesis was tested with snowgum (Eucalyptus
pauciflora Sieb. ex Spreng.) using gas exchange methods. The test
was based on the assumption that if photorespiration were involved,
then it would also have an influence on the Kok effect. Under
normal atmospheric levels of CO2 and O2, a Kok effect was found.
Changing the intercellular partial pressure of CO2, however, did
not affect the estimate of nonphotorespiratory respiration, and it
was concluded that its decrease with increasing photon flux density
did not involve photorespiration. Concurrent measurements showed
that the quantum yield of net assimilation of CO2 increased with
increasing intercellular partial pressure of CO2, and this increase
agreed closely with predictions based on recent models of
photosynthesis.

Eucalyptus pauciflora/snowgum

KEYWORDS: LEAF PHOTOSYNTHESIS, MODELING, QUANTUM REQUIREMENT,
RESPIRATION

395  
Knight, S.L., and C.A. Mitchell. 1988. Effects of CO2 and
Photosynthetic Photon Flux on Yield, Gas Exchange and Growth Rate
of Lactuca sativa L. 'Waldmann's Green'. Journal of Experimental
Botany 39:317-328.

Enrichment of CO2 to 46 mmol/m3 (1000 mm3/dm3) at a moderate
photosynthetic photon flux (PPF) of 450 umol/m2/s stimulated fresh
and dry weight gain of lettuce leaves 39% and 75% relative to
plants at 16 mmol/m3 CO2 (350 mm3/dm3). Relative growth rate (RGR)
was stimulated only during the first several days of exponential
growth. Elevating CO2 above 46 mmol/m3 at moderate PPF had no
further benefit. However, high PPF of 880-900 umol/m2/s gave
further, substantial increases in growth, RGR, net assimilation
rate (NAR) and photosynthetic rate (Pn), but a decrease in leaf
area ratio (LAR), at 46 or 69 mmol/m3 (1000 or 1500 mm3/dm3) CO2,
the differences being greater at the higher CO2 level. Enrichment
of CO2 to a supraoptimal level of 92 mmol/m3 (2000 mm3/dm3) at high
PPF increased leaf area and LAR, decreased specific leaf weight,
NAR and Pn and had no effect on leaf, stem and root dry weight or
RGR relative to plants grown at 69 mmol/m3 CO2 after 8 d of
treatment. The results of the study indicate that leaf lettuce
growth is most responsive to a combination of high PPF and CO2
enrichment to 69 mmol/m3 for several days at the onset of
exponential growth, after which optimizing resources might be
conserved.

lettuce/Lactuca sativa

KEYWORDS: ALLOCATION, CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH ANALYSIS, LIGHT, RESPIRATION

396  
Knoppik, D., H. Selinger, and A. Ziegler-Jons. 1986. Differences
between the Flag Leaf and the Ear of a Spring Wheat Cultivar
(Triticum aestivum cv. Arkas) with Respect to the CO2 Response of
Assimilation, Respiration and Stomatal Conductance. Physiologia
Plantarum 68:451-457.

The CO2- and H2O-exchanges in the flag leaf and the ear of a spring
wheat cultivar (Triticum aestivum cv. Arkas) were measured at CO2
partial pressures, pi(CO2), between 8 and 400 Pa under high
photosynthetic photon flux densities (2000 umol/m2/s). The
experiments were carried out on each organ separately while
attached to the intact plant, from the time of early emergence
through senescence. To study the contribution of the kernels to the
gas exchange of ears, experiments were also carried out on
sterilized ears (treatment A) and on ears from which the kernels
were removed (treatment B). Flag leaves and ears differed
considerably with regard to CO2-dependence of assimilation,
response of stomata to varying pa(CO2), CO2 compensation point (and
its temperature dependence), dark respiration, and dissimilation in
the light (i.e. CO2 production which is not due to oxygenation of
ribulose 1,5-bisphosphate). The higher dark respiration of the ear
originated mainly from the kernels and continued to some extent in
the light. Thus, the CO2 compensation point was attained at higher
CO2 partial pressures for the ear than for the flag leaf. The CO2
uptake of the ear was not saturated at intercellular CO2 partial
pressures below 180 Pa CO2, while that of the flag leaf reached
saturation at about 80 Pa CO2. CO2-saturated rates of CO2 uptake
were 2.5 and 1.5 times the rates at natural CO2 partial pressure
for ear and flag leaf, respectively. The stomatal conductance
decreased with rising CO2 partial pressure above 35 Pa, in a more
pronounced manner for the flag leaf than for the ear.

wheat/Triticum aestivum

KEYWORDS: CO2 COMPENSATION POINT, CONDUCTANCE, LEAF PHOTOSYNTHESIS,
RESPIRATION

397  
Koch, K.E., L.H. Allen Jr., P. Jones, and W.T. Avigne. 1987. Growth
of Citrus Rootstock (Carrizo Citrange) Seedlings During and After
Long-term CO2 Enrichment. Journal of the American Society of
Horticultural Science 112:77-82.

Carrizo citrange seedlings [Citrus sinensis (L.) Osbeck x Poncirus
trifoliata (L.) Raf.] were grown in field enclosures for 17 weeks
during 1984 at 330, 660, or 990 uL/L CO2 and then transferred to
ambient air for 10 weeks to examine growth during and after these
treatments. Immediately, after the CO2 treatment period, plants
grown at the highest CO2 level had accumulated about 120% more
total dry matter than those at 330 uL/L CO2, compared to a mean
increase of 67% at 660 uL/L. Shoot length, leaf area, and leaf
number were also increased 71%, 55%, and 39%, respectively, at 990
uL/L CO2 and somewhat less at 660 uL/L. Percentage gains from CO2
enrichment decreased during the posttreatment period, but absolute
differences were maintained or increased for at least 10 more
weeks. During the treatment period, dry matter partitioning among
leaves, stems, and roots did not vary with CO2 level, but root
growth after transplanting and transfer to ambient air occurred at
the expense of shoot growth in plants that had been grown at
ambient CO2 levels. Plant growth, in terms of dry weight, shoot
length, leaf area, and leaf number, was advanced 1.0 to 3.5 weeks
after 17 weeks at elevated CO2 levels, and fresh weight per
centimeter of stem length was about 1 month ahead. This last
parameter can be used as an approximate indicator of readiness for
scion budding, suggesting that CO2 enrichment could represent a
considerable value to the citrus nursery industry. Data are also
consistent with the hypothesis that a greater response to elevated
CO2 is likely to occur where a high sink demand and/or low levels
of leaf starch are maintained. Both such demand and low leaf starch
occur in citrus seedlings, which have a pronounced juvenility
period and capacity for continuous flush-type growth.

Citrus sinensis/Poncirus trifoliata/Carrizo citrange

KEYWORDS: ALLOCATION, COMMERCIAL USE OF CO2, GROWTH, HORTICULTURAL
CROPS, LEAF AREA DEVELOPMENT, POSTENRICHMENT RESPONSES, SOURCE-SINK
BALANCE, SPAR UNITS, TREES

398  
Koch, K.E., P. Jones, W.T. Avigne, and L.H. Allen Jr. 1986. Growth,
Dry Matter Partitioning, and Diurnal Activities of RuBP Carboxylase
in Citrus Seedlings Maintained at Two Levels of CO2. Physiologia
Plantarum 67:477-484.

The long term response of citrus rootstock seedlings to CO2
enrichment was examined in Carrizo citrange [Poncirus trifoliata
(L.) Raf. x Citrus sinensis (L.) Osbeck] and Swingle citrumelo [P.
trifoliata x C. paradisi Macf.]. Plantlets 14 weeks old were
transferred to outdoor controlled environment chambers and
maintained for 5 months from Feb. 14 to July 21. During this
period, new growth (cm) of citrange and citrumelo shoots at 660
uL/L was 94 and 69% greater, respectively, than at 330 uL/L. Total
dry weight of both rootstock shoots had increased by over 100%.
Growth of few species is affected this markedly by elevated CO2
levels. More carbon was partitioned to above-ground organs in CO2-enriched citrus seedlings. Stem dry matter per unit length was also
32 and 44 % greater in citrange and citrumelo, respectively. Total
leaf area was increased by 24% in citrange and 85% in citrumelo due
to greater leaf number and size. Variations in overall relative
growth rate appeared to be related to the rapid, sequential, flush-type growth in citrus, in which an entire shoot segment with its
associated leaves remains an active sink until fully expanded. RuBP
carboxylase (EC 4.1.1.39) activity in leaves of recently-expanded
flushes was higher in citrumelo plants grown at 660 vs. 330 uL/L
CO2 and changed diurnally for citrange (but not citrumelo) leaves
at both CO2 levels. The results are consistent with the hypothesis
that positive long-term effects of CO2 enrichment may be greater in
species or during growth periods where sink capacity for carbon
utilization is high.

Carrizo citrange/Citrus sinensis/Poncirus trifoliata/Swingle
citrumelo/Citrus paradisi/Poncirus trifoliata

KEYWORDS: ALLOCATION, DIURNAL CYCLE, GROWTH, HORTICULTURAL CROPS,
LEAF AREA DEVELOPMENT, RIBULOSE BISPHOSPHATE CARBOXYLASE, SOURCE-SINK BALANCE, SPAR UNITS, TREES

399  
Kondracka, A., and S. Maleszewski. 1986. Effect of Oxygen on
Photosynthesis in Bean (Phaseolus vulgaris L.) Leaves at Elevated
Carbon Dioxide Concentration. IN: Biological Control of
Photosynthesis (R. Marcelle, H. Clijsters, and M. Van Poucke,
eds.), Martinus Nijhoff Publishers, Dordrecht, The Netherlands, pp.
127-134.

Phaseolus vulgaris/bean

KEYWORDS: 14C, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, METABOLITES, OXYGEN

400  
Korner, C. 1988. Does Global Increase of CO2 Alter Stomatal
Density? Flora 181:253-257.

The hypothesis is tested that global increases of CO2-concentration
reduce stomatal density. Historical and recent data for leaves of
over 200 plant species are compared. Statistically significant
differences in stomatal density occur neither in lowland, nor in
alpine plants over the 7 to 12 decades spanning of this comparison.

KEYWORDS: STOMATAL DENSITY

401  
Korner, C. 1992. CO2 Fertilization: The Great Uncertainty in Future
Vegetation Development. IN: Vegetation Dynamics and Global Change
(H.H. Shugart and A.M. Solomon, eds.), Chapman and Hall Publishers,
New York.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, ECOSYSTEM LEVEL CO2
RESPONSES, REVIEW

402  
Korner, C. 1992. Responses to Elevated Carbon Dioxide in Artificial
Tropical Ecosystems. Science 257:1672-1675.

Carbon, nutrient, and water balance as well as key plant and soil
processes were simultaneously monitored for humid tropical plant
communities treated with CO2-enriched atmospheres. Despite vigorous
growth, no significant differences in stand biomass (of both the
understory and overstory), leaf area index, nitrogen or water
consumption, or leaf stomatal behavior were detected between
ambient and elevated CO2 treatments. Major responses under elevated
CO2 included massive starch accumulation in the tops of canopies,
increased fine-root production, and a doubling of CO2 evolution
from the soil. Stimulated rhizosphere activity was accompanied by
increased loss of soil carbon and increased mineral nutrient
leaching. This study points at the inadequacy of scaling-up from
physiological baselines to ecosystems without accounting for
interactions among components, and it emphasizes the urgent need
for whole-system experimental approaches in global-change research.

KEYWORDS: ALLOCATION, CARBOHYDRATES, CARBON IN SOILS, ECOSYSTEM
LEVEL CO2 RESPONSES, MAGNESIUM, NITROGEN, NUTRITION, PHOSPHORUS,
POTASSIUM, RHIZOSPHERE, ROOTS, SCALING, SOIL RESPIRATION, SUNLIT
CONTROLLED ENVIRONMENT CHAMBERS, TROPICAL PLANTS

403  
Korner, C., and M. Diemer. 1987. In situ Photosynthetic Responses
to Light, Temperature and Carbon Dioxide in Herbaceous Plants from
Low and High Altitude. Functional Ecology 1:179-194.

Net CO2 assimilation (A) was analysed in situ in 112 pairs of
altitudinally separated, herbaceous plant species in the Austrian
Alps at 600 and 2600 m. Both groups of species show a similar
average response to light, saturating at quantum flux densities
(400--700 mm) QFD) of more than 1200 umol/m2/s. Temperature optimum
of QFD-saturated A differs little (3 K) and corresponds to the
median of air temperature at leaf level for hours with rate-saturating light conditions and not to mean air temperature which
differs by 10 K. Species with an exclusive high altitude
distribution show steeper initial slopes and higher levels of
saturation of the response of A to internal partial pressure of CO2
(CPI) than low elevation species. Mean A at local ambient partial
pressure (CPA) does not differ between sites (c. 18 umol/m2/s),
despite the 21% decrease in atmospheric pressure. Plants at high
altitude operate at mean CPI of 177 ubar as compared to 250 ubar at
low altitude. The higher ECU (efficiency of carbon dioxide uptake
[linear slope of A/CPI curve]) as well as the steeper CO2 gradient
between mesophyll and ambient air of alpine plants are explained by
(1) greater leaf and palisade layer thickness and (2) greater
nitrogen (protein) content per unit leaf area. We hypothesize that
alpine plants profit more from enhanced CO2 levels than lowland
plants (Fig. 7).

KEYWORDS: ALTITUDE, ENVIRONMENTAL INTERACTIONS, LEAF
PHOTOSYNTHESIS, LIGHT, REVIEW, TEMPERATURE

404  
Korner, C., G.D. Farquhar, and Z. Roksandic. 1988. A Global Survey
of Carbon Isotope Discrimination in Plants from High Altitude.
Oecologia 74:623-632.

Carbon 13/12 isotope ratios have been determined from leaves of a
hundred C3 plant species (or ecotypes) from all major mountain
ranges of the globe, avoiding drought stressed areas. A general
increase in 13C content was found with increasing altitude, i.e.,
overall discrimination against the heavy isotope is reduced at high
elevation. The steepest decline of discrimination is observed in
taxa typically ranging to highest elevation (e.g. the genus
Ranunculus). Mean [delta] 13C for all samples collected between
2500 and 5600 m altitude is -26.15 per mil compared to the lowland
average of -18.80 per mil (P < 0.001). Forbs from highest
elevations reach -24 per mil. According to theory of 13C
discrimination this indicates decreasing relative limitation of
carbon uptake by carboxylation. In other words, we estimate that
the ratio of internal to external partial pressure of CO2 (pi/pa)
in leaves of high elevation plants is lower than in leaves of low
altitude. These results confirm recent gas exchange analyses in
high and low elevation plants.

KEYWORDS: ALTITUDE, C3, CI:CA, ISOTOPE DISCRIMINATION, LEAF
PHOTOSYNTHESIS, REVIEW

405  
Kramer, P.J., and N. Sionit. 1987. Effects of Increasing Carbon
Dioxide Concentration on the Physiology and Growth of Forest Trees.
IN: The Greenhouse Effect, Climate Change, and U.S. Forests (W.E.
Shands and J.S. Hoffman, eds.), The Conservation Foundation,
Washington, D.C., pp. 219-246.

KEYWORDS: CONDUCTANCE, ENVIRONMENTAL INTERACTIONS, FOREST,
PARTITIONING, PHOTOSYNTHESIS, REVIEW, TREES, WATER STATUS

406  
Krizek, D.T. 1986. Photosynthesis, Dry Matter Production and Growth
in CO2-Enriched Atmospheres. IN: Number One, Cotton Physiology
(J.R. Mauney and J.McD. Stewart, eds.), The Cotton Foundation
Reference Book Series, The Cotton Foundation, Memphis, Tennessee,
pp. 193-225.

Most studies on CO2 enrichment under greenhouse and growth chamber
conditions have demonstrated the stimulatory effects of elevated
CO2 levels on the growth and development of cotton and other
economically important plants. Recent tests involving CO2
enrichment of cotton and other crops in the field are encouraging,
but further studies are needed to determine whether or not the
practice is economically feasible. One of the most pronounced
effects of CO2 enrichment in cotton, tomato and other species is a
large build-up in sugars and starches stored in the leaves.
Increasing the CO2 level from 330 uL/L to 630-1000 uL/L under
controlled environments lowered the node number of the first
flower, doubled boll production and delayed abscission of squares
and bolls. The metabolic consequences of CO2 enrichment of cotton
plants need to be examined in greater detail. Since CO2 utilization
can be influenced by a myriad of genetic, physiological,
biochemical and morphological factors, careful studies are required
to determine the interaction of CO2 with these factors. Because of
the marked influence of CO2 enrichment on water-use-efficiency
through its effect on CO2 assimilation, transpiration and stomatal
regulation, special attention should be given to this area of
research.

cotton/Gossypium hirsutum

KEYWORDS: CARBOHYDRATES, ENVIRONMENTAL INTERACTIONS, GROWTH, GROWTH
STAGES, LEAF AREA DEVELOPMENT, NUTRITION, PHOTOSYNTHESIS,
PHOTOSYNTHETIC FEEDBACK INHIBITION, REPRODUCTION, REVIEW,
SENESCENCE, WUE

407  
Krupa, S.V., and R.N. Kickert. 1989. The Greenhouse Effect: Impacts
of Ultraviolet-B (UV-B) Radiation, Carbon Dioxide (CO2), and Ozone
(O3) on Vegetation. Environmental Pollution 61:263-393.

There is a fast growing and an extremely serious international
scientific, public and political concern regarding man's influence
on the global climate. The decrease in stratospheric ozone (O3) and
the consequent possible increase in ultraviolet-B (UV-B) is a
critical issue. In addition, tropospheric concentrations of
'greenhouse gases' such as carbon dioxide (CO2), nitrous oxide
(N2O) and methane (CH4) are increasing. These phenomena, coupled
with man's use of chlorofluorocarbons (CFCs), chlorocarbons (CCs),
and organo-bromines (OBs) are considered to result in the
modification of the earth's O3 column and altered interactions
between the stratosphere and the troposphere. A result of such
interactions could be the global warming. As opposed to these
processes, tropospheric O3 concentrations appear to be increasing
in some parts of the world (e.g. North America). Such tropospheric
increases in O3 and particulate matter may offset any predicted
increases in UV-B at those locations. The effects of UV-B, CO2 and
O3 on plants have been studied under growth chamber, greenhouse and
field conditions. Few studies, if any, have examined the joint
effects of more than one variable on plant response. There are
methodological problems associated with many of these experiments.
Thus, while results obtained from these studies can assist in our
understanding, they must be viewed with caution in the context of
the real world and predictions into the future. Historically, plant
biologists have studied the effects of CO2 on plants for many
decades. Evidence is presented for various plant species in the
form of relative yield increases due to CO2 enrichment. Sensitivity
rankings (biomass response) are again provided for crops and native
plant species. However, most publications on the numerical analysis
of cause-effect relationships do not consider sensitivity analysis
of the models used. The joint effects of UV-B, CO2 and O3 are
poorly understood. Based on the literature of plant response to
individual stress factors and chemical and physical climatology of
North America, we conclude that nine different crops may be
sensitive to the joint effects: three grain and six vegetable crops
(sorghum, oat, rice, pea, bean, potato, lettuce, cucumber and
tomato). In North America, we consider Ponderosa and loblolly pine
as vulnerable among tree species. This conclusion should be
moderated by the fact that there are few, if any, data on hardwood
species. Note: This abstract has been abridged.

KEYWORDS: AIR POLLUTION, CROPS, ENVIRONMENTAL INTERACTIONS, GROWTH,
OZONE, REVIEW, TREES, UV-B RADIATION

408  
Krupa, S.V., and R.N. Kickert. 1993. The Greenhouse Effect: The
Impacts of Carbon Dioxide (CO2), Ultraviolet-B (UV-B) Radiation and
Ozone (O3) on Vegetation (Crops). Vegetatio 104/105:223-238.

Man's influence on the 'greenhouse effect', the heating of the
atmosphere due to increasing concentrations of tropospheric trace
gases, is of much international concern. Among the climatic
variables, elevated levels of carbon dioxide (CO2), ultraviolet-B
(UV-B) radiation and ozone (O3) are known to have a direct effect
on vegetation. Our current knowledge of these effects is mainly
based on studies involving single stress mode. Thus, the joint
effects of CO2, UV-B and O3 on vegetation are poorly understood.
Nevertheless, based on the literature analysis of plant response to
individual stress factors, it can be concluded that sorghum, pea,
bean, potato, oat, lettuce, cucumber, rice and tomato are among the
crop species potentially sensitive to the joint effects of the
aforementioned three variables. Similar information for tree
species is essentially lacking. At least with some climatic
variables such as O3, present modeling efforts of cause-effect
relationships have proven to be controversial. While at a regional
geographic scale ambient CO2 concentrations appear to be relatively
homogeneous, ambient concentrations of O3 exhibit significant
temporal and spatial variability. Because of the protective action
of O3 against UV-B, similar but inverse temporal and spatial
variability is expected in the surface levels of UV-B. Thus, future
experimental designs should consider these exposure dynamics and
modeling cause-effect relationships should be directed to
stochastic processes.

KEYWORDS: AIR POLLUTION, CROPS, ENVIRONMENTAL INTERACTIONS,
MODELING, OZONE, REVIEW, UV-B RADIATION

409  
Kuehny, J.S., M.M. Peet, P.V. Nelson, and D.H. Willits. 1991.
Nutrient Dilution by Starch in CO2-enriched Chrysanthemum. Journal
of Experimental Botany 42:711-716.

Increasing growth irradiance and CO2 generally decreases foliar
nutrient concentration on a dry weight basis and increases foliar
starch concentration. However, the extent to which starch
concentrations 'dilute' foliar nutrient concentrations when the
latter are expressed on a dry weight basis is not known. To
determine the importance of differential starch accumulation in
calculating nutrient concentrations on a dry weight basis, leaf
nutrient and starch concentrations were measured in Chrysanthemum
x morifolium 'Fiesta' (Ramat.) cuttings grown at three irradiance
levels and two CO2 levels for eight weeks in both winter and
spring. On a dry weight basis, foliar concentrations of most
nutrients were lower in both seasons as a result of the elevated
CO2 and irradiance levels, and total dry weights were higher. Per
cent starch was greater at the high CO2 level in both seasons but
was only greater at higher irradiances in the winter experiment.
When starch was subtracted from the leaf dry weights, the
differences between CO2 and irradiance treatments disappeared with
respect to N, P, K, Ca, Mg, S, and B but not for Fe, Mn, Zn, and
Cu.

Chrysanthemum morifolium/chrysanthemum

KEYWORDS: BORON, CALCIUM, CARBOHYDRATES, COPPER, GREENHOUSE, IRON,
LIGHT, MAGNESIUM, MANGANESE, NITROGEN, NUTRITION, PHOSPHORUS,
POTASSIUM, SULFUR, ZINC

410  
Kurooka, H., S. Fukunaga, E. Yuda, S. Nakagawa, and S. Horiuchi.
1990. Effect of Carbon Dioxide Enrichment on Vine Growth and Berry
Quality of Kyoho Grapes. Journal of the Japanese Society of
Horticultural Science 59:463-470.

Although ambient temperature is kept adequate, grape cultivation
under covered facilities during winter months in Japan gives rise
to low yields of poor quality berries because of low light
intensities. This investigation was conducted in leaf chamber,
using Vitis labruscana Bailey cv. Kyoho, to determine the influence
of leaf age, light intensity, and CO2 concentrations on
photosynthesis. The effects of CO2 enrichment on vine growth and
fruit quality were also investigated in growth chambers. 1. The
rate of photosynthesis per unit leaf area (Pn) between May 28 and
September 19 rapidly increased with leaf growth, reaching a maximum
of 18.9 mg CO2/dm2/hr, 37 days after the unfolding of a leaf. Pn
then gradually decreased with leaf age. In young leaves, higher CO2
concentrations and stronger light intensities resulted in a
significant increase in Pn. Older leaves exhibited a similar
enhancement of Pn upon exposure to high light intensity. Pn was
saturated at 828 ppm CO2. 2. Administration of 1,000 to 1,100 ppm
CO2 to vines for an 8 hr/day at a late stage of berry development
until harvest had no effect on berry size but resulted in an
increase in sugar and anthocyanin contents but a decrease in
organic acid content. Dry weight of newly developed roots doubled
as a result of CO2 enrichment. 3. Application of CO2 under a long-day photoperiod at an early stage of berry development to a week
before veraison markedly promoted shoot elongation. Furthermore,
CO2 enrichment gave a 36% increase in both berry and cluster
weights and also a higher sugar-acid ratio at harvest. In Japanese.

grapes/Vitis labruscana

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
STAGES, HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS, PHOTOPERIOD,
SENESCENCE

411  
Laitat, E., and P. Loosveldt. 1992. Open-top Chambers for Study of
the Physiology of Acclimated Trees under Enhanced CO2 in Natural
Pollution Climate. IN: Responses of Forest Ecosystems to
Environmental Changes (A. Teller, P. Mathy, and J.N.R. Jeffers,
eds.), Elsevier Applied Science, London, pp. 653-654.

Norway spruce/Picea abies/sycamore/Acer pseudoplatanus/beech/Fagus
sylvatica

KEYWORDS: AIR POLLUTION, EXPOSURE METHODS, OPEN-TOP CHAMBERS,
TEMPERATE FOREST, TREES

412  
LaMarche, V.C., Jr., D.A. Graybill, H.C. Fritts, and M.R. Rose.
1986. Carbon Dioxide Enhancement of Tree Growth at High Elevations.
Science 231:860.

Technical comment.

KEYWORDS: ALTITUDE, PHOTOSYNTHESIS, TREE-RING ANALYSIS, TREES

413  
Lambers, H. 1993. Rising CO2, Secondary Plant Metabolism, Plant-herbivore Interactions and Litter Decomposition. Theoretical
Considerations. Vegetatio 104-105:263-271.

A brief account is given of the ecological significance of
quantitatively important secondary plant compounds, mainly those of
a phenolic nature, in herbivory and decomposition. Phenolic
compounds accumulate to a greater extent in slow-growing species
than in fast-growing ones, particularly when soil conditions
(nutrients, water) restrict growth. Two hypotheses to explain the
increased concentration of phenolics when soil conditions are
unfavorable are presented. The first hypothesis (the 'carbon supply
model of secondary plant metabolism') considers the increased
levels of non-structural carbohydrates as the major trigger. The
second hypothesis (the 'amino acid diversion model of secondary
plant metabolism') states that increased accumulation of phenolics
stems from a decreased use of a common precursor (phenylalanine or
tyrosine) for protein synthesis. Current experimental evidence,
though still fairly limited, supports the second hypothesis, but
further testing is required before the first model can be rejected.
So far, there is very little evidence for a direct effect of
atmospheric CO2 on the concentration of secondary compounds in
higher plants. However, there are likely to be indirect effects,
due to a stronger limitation by the nitrogen supply in plants whose
growth has been promoted by atmospheric CO2. It is concluded that
it is very likely that phenolic compounds accumulate to a greater
extent in plants exposed to elevated CO2, due to a greater
limitation of nutrients, rather than as a direct effect of elevated
CO2.

KEYWORDS: CARBON:NITROGEN RATIO, ENVIRONMENTAL INTERACTIONS,
HERBIVORY, PHENOLIC METABOLISM, REVIEW, SECONDARY METABOLITES

414  
Landsberg, J., and M.S. Smith. 1992. A Functional Scheme for
Predicting the Outbreak Potential of Herbivorous Insects under
Global Atmospheric Change. Australian Journal of Botany 40:565-577.

There are many possible ways in which changes in the global
atmosphere could influence the outbreak potential of herbivorous
insects; we clarify these by developing a scheme for analysing
insect populations in terms of functional attributes that are both
important in population regulation and responsive to global change.
This analysis shows that elevated CO2 is not likely to have a major
influence on probability of insect outbreak, except possibly in
systems in which nitrogen-based defensive compounds are produced by
plants in response to herbivory. Systems that will have high
potential to outbreak, if climatic conditions become more
favourable for plant growth and responses are not constrained by
other resources, include those in which both herbivorous insects
and host plants have highly flexible growth patterns and activity
cues. Global changes that increase environmental stress on host
plants are most likely to favour sap-feeding insects. Critical
enemy (predator or parasitoid) control of the dormant phase of
herbivorous insects may be very important in preventing or allowing
outbreaks, but is often poorly understood.

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, GLOBAL CHANGE, HERBIVORY,
INSECTS, REVIEW

415  
Larigauderie, A., D.W. Hilbert, and W.C. Oechel. 1988. Effect of
CO2 Enrichment and Nitrogen Availability on Resource Acquisition
and Resource Allocation in a Grass, Bromus mollis. Oecologia
77:544-549.

The effects of CO2 enrichment on the growth, biomass partitioning,
photosynthetic rates, and leaf nitrogen concentration of a grass,
Bromus mollis (C3), were investigated at a favorable and a low
level of nitrogen availability. Despite increases in root:shoot
ratios, leaf nitrogen concentrations were decreased under CO2
enrichment at both nitrogen levels. For the low-nitrogen treatment,
this resulted in lower photosynthetic rates measured at 675 uL/L
for the CO2-enriched plants, compared to photosynthetic rates
measured at 350 uL/L for the non-enriched plants. At higher
nitrogen availability, photosynthetic rates of plants grown and
measured at 675 uL/L were greater than photosynthetic rates of the
non-enriched plants measured at 350 uL/L. Water use efficiency,
however, was increased in enriched plants at both nitrogen levels.
CO2 enrichment stimulated vegetative growth at both high and low
nitrogen during most of the vegetative growth phase but, at the end
of the experiment, total biomass of the high and low CO2 treatments
did not differ for plants grown at low nitrogen availability. While
not statistically significant, CO2 tended to stimulate seed
production at high nitrogen and decrease it at low nitrogen.

Bromus mollis

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES,
LEAF AREA DEVELOPMENT, LEAF PHOTOSYNTHESIS, NITROGEN, NUTRITION,
ROOT:SHOOT RATIO, WUE

416  
Larigauderie, A., J. Roy, and A. Berber. 1986. Long Term Effects of
High CO2 Concentration on Photosynthesis of Water Hyacinth
(Eichhornia crassipes (Mart.) Solms). Journal of Experimental
Botany 37:1303-1312.

The photosynthetic response to CO2 concentration, light intensity
and temperature was investigated in water hyacinth plants
(Eichhornia crassipes (Mart.) Solms) grown in summer at ambient CO2
or at 10,000 umol (CO2)/mol and in winter at 6,000 umol (CO2)/mol.
Plants grown and measured at ambient CO2 had high photosynthetic
rate (35 umol (CO2)/m2/s), high saturating photon flux density
(1,500-2,000 umol/m2/s) and low sensitivity to temperature in the
range 20-40C. Maximum photosynthetic rate (63 umol (CO2)/m2/s) was
reached at an internal CO2 concentration of 800 umol/mol. Plants
grown at high CO2 in summer had photosynthetic capacities at
ambient CO2 which were 15% less than for plants grown at ambient
CO2, but maximum photosynthetic rates were similar. Photosynthesis
by plants grown at high CO2 and high light intensity had typical
response curves to internal CO2 concentration with saturation at
high CO2, but for plants grown under high CO2 and low light and
plants grown under low CO2 and high light intensity photosynthetic
rates decreased sharply at internal CO2 concentrations above 1,000
umol/mol.

water hyacinth/Eichhornia crassipes

KEYWORDS: AQUATIC PLANTS, GREENHOUSE, LEAF PHOTOSYNTHESIS, LIGHT,
PHOTOSYNTHETIC ACCLIMATION

417  
Lasceve, G., H. Gautier, J. Jappe, and A. Vavasseur. 1993.
Modulation of the Blue Light Response of Stomata of Commelina
communis by CO2. Physiologia Plantarum 88:453-459.

Effects of CO2 on stomatal movements of Commelina communis L. were
studied with plants, epidermal strips and guard cell protoplasts.
With plants, the stomatal response induced by a blue light pulse
was studied for different ambient CO2 concentration ranging from
CO2-deprived air to 100 Pa in darkness or under red light. It was
observed that the blue light response could be obtained not only
under a red light background but also in darkness and CO2-free air,
the two responses being quite similar. With epidermal strips, the
effect of CO2 on ferricyanide reductase activity at the guard cell
plasmalemma was studied by transmission electron microscopy. In the
presence of ferric ions, reduced ferricyanide gives an electron
dense precipitate of Prussian Blue. In darkness and CO2-free air as
well as under light and normal air, a precipitate was found along
the plasmalemma of the guard cells, indicating a ferricyanide
reductase activity. With guard cell protoplasts suspended in a
medium either in equilibrium with air or in a CO2 free medium the
H+ extrusion induced by a blue light pulse added to a red light
background was measured. A low CO2 content was obtained by adding
photosynthetic algae to the suspension of guard cell protoplasts.
In a CO2-free medium the rate of H+ extrusion was enhanced. The
results are discussed on the basis of a possible competition for
reducing power between CO2 fixation and a putative blue light
dependent redox chain located on the plasma membrane.

Commelina communis

KEYWORDS: BLUE LIGHT RESPONSE, STOMATA

418  
Lawlor, D.W., and R.A.C. Mitchell. 1991. The Effects of Increasing
CO2 on Crop Photosynthesis and Productivity: a Review of Field
Studies. Plant, Cell and Environment 14:807-818.

Only a small proportion of elevated CO2 studies on crops have taken
place in the field. They generally confirm results obtained in
controlled environments: CO2 increases photosynthesis, dry matter
production and yield, substantially in C3 species, but less in C4,
it decreases stomatal conductance and transpiration in C3 and C4
species and greatly improves water-use efficiency in all plants.
The increased productivity of crops with CO2 enrichment is also
related to the greater leaf area produced. Stimulation of yield is
due more to an increase in the number of yield-forming structures
than in their size. There is little evidence of a consistent effect
of CO2 on partitioning of dry matter between organs or on their
chemical composition, except for tubers. Work has concentrated on
a few crops (largely soybean) and more is needed on crops for which
there are few data (e.g. rice). Field studies on the effects of
elevated CO2 in combination with temperature, water and nutrition
are essential; they should be related to the development and
improvement of mechanistic crop models, and designed to test their
predictions.

KEYWORDS: AGRICULTURE, ALLOCATION, CONDUCTANCE, CONTROLLED
ENVIRONMENT CHAMBERS, CROPS, MODELING, OPEN-TOP CHAMBERS, REVIEW,
WUE, YIELD

419  
Leadley, P.W., and B.G. Drake. 1993. Open Top Chambers for Exposing
Plant Canopies to Elevated CO2 Concentration and for Measuring Net
Gas Exchange. Vegetatio 104/105:3-15.

Open top chamber design and function are reviewed. All of the
chambers described maintain CO2 concentration measured at a central
location within +/- 30 ppm of a desired target when averaged over
the growing season, but the spatial and temporal range within any
chamber may be closer to 100 ppm. Compared with unchambered
companion plots, open top chambers modify the microenvironment in
the following ways: temperatures are increased up to 3C depending
on the chamber design and location of the measurement; light
intensity is typically diminished by as much as 20%; wind velocity
is lower and constant; and relative humidity is higher. The chamber
environment may significantly alter plant growth when compared with
unchambered controls, but the chamber effect on growth has not been
clearly attributed to a single or even a few environmental factors.
A method for modifying an open top chamber for tracking gas
exchange between natural vegetation and the ambient air is
described. This modification consists of the addition of a top with
exit chimney to reduce dilution of chamber CO2 by external ambient
air, is quickly made and permits estimation of the effects of
elevated CO2 and water vapor exchange. The relatively simple design
and construction of open top chambers make them the most likely
method to be used in the near future for long-term elevated CO2
exposure of small trees, crops and grassland ecosystems.
Improvements in the basic geometry to improve control of
temperature, reduce the variation of CO2 concentrations, and
increase the turbulence and wind speed in the canopy boundary layer
are desirable objectives. Similarly, modifications for measuring
water vapor and carbon dioxide exchange will extend the usefulness
of open top chambers to include non-destructive monitoring of the
responses of ecosystems to rising atmospheric CO2.

KEYWORDS: CANOPY PHOTOSYNTHESIS, EXPOSURE METHODS, REVIEW

420  
Leadley, P.W., J.A. Reynolds, J.F. Thomas, and J.F. Reynolds. 1987.
Effects of CO2 Enrichment on Internal Leaf Surface Area in
Soybeans. Botanical Gazette 148:137-140.

Internal cell surface areas were measured on fully expanded leaves
of soybean seedlings that had been continuously exposed to 348 or
645 ppm CO2 environments. Plants grown in the high CO2 treatment
had thicker leaves but less palisade cell surface area per unit
leaf area. Surface area of the mesophyll per unit leaf area was
unaffected by CO2. The potential ramifications of these CO2-induced
changes in leaf anatomy on photosynthesis and water-use efficiency
are explored.

soybean/Glycine max

KEYWORDS: ANATOMY, LEAF AREA DEVELOPMENT, OPEN-TOP CHAMBERS

421  
Leadley, P.W., and J.F. Reynolds. 1988. Effects of Elevated Carbon
Dioxide on Estimation of Leaf Area and Leaf Dry Weight of Soybean.
American Journal of Botany 75:1771-1774.

The objectives of this study were to determine the effects of
elevated CO2 on relationships between leaf area (A) and linear leaf
dimensions (length [L] and width [W]) and leaf dry weight (M) in
soybeans (Glycine max (L.) Merr. cv. Bragg). Based on dimensional
measurements made on trifoliolates 1-6 for plants grown under three
CO2 levels (348, 502 and 645 uL/L), the best predictor for both
trifoliolate leaf area and for fully expanded central leaflets of
the trifoliolates was an equation of the form A = B0 + B1 (L x W);
these relationships were unaffected by CO2, although there was a
small effect of leaf position. For expanding central leaflets of
the fifth trifoliolate, no CO2, leaf size (age) or CO2 x leaf size
effect was found. Specific leaf weight (i.e., M/A) was
significantly affected by CO2, increasing with increasing CO2.
Hence, trifoliolate dry weight can be nondestructively estimated
from trifoliolate area using the equation M = 0.097 + (6.71 x 10 [-3] + 1.04 x 10 [-6] x [CO2]) A, where [CO2] is mean daytime CO2
concentration of the growth environment.

soybean/Glycine max

KEYWORDS: LEAF AREA DEVELOPMENT, MODELING, OPEN-TOP CHAMBERS

422  
Leadley, P.W., and J.F. Reynolds. 1989. Effect of Carbon Dioxide
Enrichment on Development of the First Six Mainstem Leaves in
Soybean. American Journal of Botany 76:1551-1555.

Many conclusions concerning plant responses to CO2 enrichment have
been based on assumptions of increased leaf size derived from
observations of average leaf area measured at some time well into
the growth period. The objectives of this study were to study the
effect of elevated CO2 on 1) the timing of mainstem leaflet
appearance, 2) the rate and duration of leaflet expansion, and 3)
the final area of individual leaflets of soybeans (Glycine max (L.)
Merr. cv. Bragg) grown from seed at 348, 502, and 645 uL/L CO2
concentrations. Central leaflet areas from mainstem trifoliolates
1-6 were measured every two days from time of appearance to full
expansion. Leaflets tended to appear earlier in elevated CO2
treatments; leaflets 2 through 6 appeared an average of 0.4 days
earlier in the 502 uL/L treatment and 1.2 days earlier in the 645
uL/L treatment than in the 349 uL/L treatment. Relative rates of
expansion were different among leaflets in their response to
elevated CO2; expansion rates of leaflets 1 and 4 were
significantly higher at the highest CO2 concentration. However,
final area of leaflets was not affected by CO2 or (in leaflet 5
only) was slightly smaller at the highest CO2 treatment.
Apparently, higher expansion rates of leaflets 1 and 4 at high CO2
were offset by a tendency for decreased duration of expansion. It
appears that there are morphological constraints on final leaflet
area in soybean seedlings which limit the effects of elevated CO2
on the early development of mainstem leaf area.

Glycine max/soybean

KEYWORDS: LEAF AREA DEVELOPMENT, OPEN-TOP CHAMBERS

423  
Leadley, P.W., and J.F. Reynolds. 1992. Long-term Response of an
Arctic Sedge to Climate Change: A Simulation Study. Ecological
Applications 2:323-340.

It appears that polar regions of the Earth will bear the brunt of
global temperature increases. Because of the ecological importance
of the sedge Eriophorum vaginatum in the arctic and the large
amount of data available on its growth and physiology, we chose
this species as a test case to model the potential long-term
response of arctic plants to global climate change. Our simulation
model utilizes a mechanistic framework and includes the effects of
light, temperature, season length, nitrogen availability, and CO2
concentration on E. vaginatum growth dynamics. The model was
parameterized based on a series of published studies of the growth
responses of E. vaginatum to nutrients and validated using (1)
field studies on the growth responses of E. vaginatum to
temperature and shading, and (2) the effects of elevated CO2 and
temperature on E. vaginatum photosynthesis. The effect of a 50-yr
period of climate change on peak biomass (overwintering biomass
plus seasonal production) in E. vaginatum was explored. We use
climate change here to refer to linear increases over a 50-yr
period in temperature (from 8 to 13C), season length (from 100 to
120 d), and atmospheric CO2 (from 340 to 680 uL/L). Similarly, a
wide range of nitrogen availabilities (from 9 to 18 g/m2/y) was
also examined because of its importance in productivity. The model
predicts that a simultaneous increase in the direct effects of
temperature, season length, and CO2, with no change in nitrogen
availability, will result in a slight decrease in peak biomass. A
simulated long-term doubling of nitrogen availability results in an
(about) 70% increase in peak biomass, whereas with concurrent
changes in climate and nitrogen availability, the model predicts a
slight decline in peak biomass compared to increases in nitrogen
alone. In essence, the model predicts that climate change will have
substantial effects on E. vaginatum only indirectly through changes
in nitrogen availability. Simulated peak biomass responds linearly
up to a doubling of current nitrogen availabilities. Therefore, at
low-to-moderate increases in nitrogen availability, the predicted
response of E. vaginatum to climate change is linearly (and almost
exclusively) dependent on our ability to predict the effects of
climate change on nitrogen cycling. At nitrogen availabilities > 2x
current availabilities, the relationship flattens out very rapidly
because the plant becomes limited by carbon uptake. Thus, if
nitrogen availabilities more than double in the future, E.
vaginatum may shift from being a nutrient-limited to a carbon-limited system and, consequently, increased season length and
elevated CO2 concentrations may play an important role in
controlling E. vaginatum productivity.

Eriophorum vaginatum

KEYWORDS: CLIMATE CHANGE, ENVIRONMENTAL INTERACTIONS, GROWTH,
MODELING, NITROGEN, SIMULATION, TUNDRA

424  
Leavitt, S.W., E.A. Paul, B.A. Kimball, G.R. Hendrey, J.R. Mauney,
R. Rauschkolb, H. Rogers, K.F. Lewin, J. Nagy, P.J. Pinter Jr., and
H.B. Johnson. 1994. Carbon Isotope Dynamics of Free-Air CO2-Enriched Cotton and Soils. Agricultural and Forest Meteorology (in
press):.

A role for soils as global carbon sink or source under increasing
atmospheric CO2 concentrations has been speculative. Free-air
carbon dioxide enrichment (FACE) experiments with cotton, conducted
from 1989 to 1991 at the Maricopa Agricultural Center in Arizona,
maintained circular plots at 550 umol/mol CO2 with tank CO2 while
adjacent ambient control plots averaged about 370 umol/mol CO2.
This provided an exceptional test for entry of carbon into soils
because the petrochemically-derived tank CO2 used to enrich the air
above the FACE plots was depleted in both radiocarbon (14C content
was 0% modern carbon [pmC] and 13C ([delta] 13C = about -36 per
mil) relative to background air, thus serving as a potent isotopic
tracer. Flask air samples, and plant and soil samples were
collected in conjunction with the 1991 experiment. Most of the
isotopic analyses on plants were performed on the holocellulose
component. Soil organic carbon was obtained by first removing
carbonate with HCl, floating off plant fragments with a NaCl
solution, and picking out remaining plant fragments under
magnification. The [delta] 13C of the air above the FACE plots was
approximately -15 to -19 per mil, i.e., much more 13C depleted than
the background air of approximately -7.5 per mil. The [delta] 13C
values of plants and soils in the FACE plots were 10-12 per mil and
2 per mil [delta] 13C-depleted, respectively, compared with their
control counterparts. The 14C content of the FACE cotton plants was
approximately 40 pmC lower than the control cotton, but the 14C
results from soils were conflicting and therefore not as revealing
as the [delta] 13C of soils. Soil stable-carbon isotope patterns
were consistent, and mass balance calculations indicate that about
10% of the present organic carbon content in the FACE soil derived
from the 3 year FACE experiment. At a minimum, this is an important
quantitative measure of carbon turnover, but the presence of 13C-depleted carbon, even in the recalcitrant 6N HCl resistant soil
organic fraction (average age 2200 years before present [BP]),
suggests that at least some portion of this 10% is an actual
increase in carbon accumulation. Similar isotopic studies on FACE
experiments in different ecosystems should permit more definitive
assessment of carbon turnover rates and perhaps provide insight
into the extent to which soil organic matter can accommodate the
'missing' carbon in the global carbon cycle.

cotton/Gossypium hirsutum

KEYWORDS: 14C, CARBON IN SOILS, FACE, ISOTOPE DISCRIMINATION

425  
Lekkerkerk, L.J.A., S.C. van de Geijn, and J.A. van Veen. 1990.
Effects of Elevated Atmospheric CO2-levels on the Carbon Economy of
a Soil Planted with Wheat. IN: Soils and the Greenhouse Effect
(A.F. Bouwman, ed.), John Wiley & Sons, New York, pp. 423-429.

wheat/Triticum aestivum

KEYWORDS: AGRICULTURE, LITTER DECOMPOSITION, SOIL MICROORGANISMS,
SOIL RESPIRATION

426  
Lekkerkerk, L.J.A., J.A. van Veen, and S.C. van de Geijn. 1990.
Influence of Climatic Change on Soil Quality; Consequences of
Increased Atmospheric CO2-concentration on Carbon Input and
Turnover in Agro-ecosystems. IN: The Greenhouse Effect and Primary
Productivity in European Agro-ecosystems; 5-10 April 1990;
Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H.
van Laar, eds.), Pudoc, Wageningen, pp. 46-47.

KEYWORDS: AGRICULTURE, CARBON:NITROGEN RATIO, LITTER DECOMPOSITION,
REVIEW

427  
Lenssen, G.M., J. Lamers, M. Stroetenga, and J. Rozema. 1993.
Interactive Effects of Atmospheric CO2 Enrichment, Salinity and
Flooding on Growth of C3 (Elymus athericus) and C4 (Spartina
anglica) Salt Marsh Species. Vegetatio 104/105:379-388.

The growth response of Dutch salt marsh species (C3 and C4) to
atmospheric CO2 enrichment was investigated. Tillers of the C3
species Elymus athericus were grown in combinations of 380 and 720
uL/L CO2 and low (0) and high (300 mM NaCl) soil salinity. CO2
enrichment increased dry matter production and leaf area
development while both parameters were reduced at high salinity.
The relative growth response to CO2 enrichment was high under
saline conditions. Growth increase at elevated CO2 was higher after
34 than 71 days. A lower response to CO2 enrichment after 71 days
was associated with a decreased specific leaf area (SLA). In two
other experiments the effect of CO2 (380 and 720 uL/L) on growth of
the C4 species Spartina anglica was studied. In the first
experiment total plant dry weight was reduced by 20% at elevated
CO2. SLA also decreased at high CO2. The effect of elevated CO2 was
also studied in combination with soil salinity (50 and 400 mM NaCl)
and flooding. Again plant weight was reduced (10%) at elevated CO2,
except under the combined treatment high salinity/non-flooded. But
these effects were not significant. High salinity reduced total
plant weight while flooding had no effect. Causes of the salinity
dependent effect of CO2 enrichment on growth and consequences of
elevated CO2 for competition between C3 and C4 species are
discussed.

Spartina anglica/Elymus athericus

KEYWORDS: C3, C4, GREENHOUSE, GROWTH ANALYSIS, SALT MARSH, SALT
STRESS, SPECIES COMPETITION

428  
Lenssen, G.M., and J. Rozema. 1990. The Effect of Atmospheric CO2-enrichment and Salinity on Growth, Photosynthesis and Water
Relations of Salt Marsh Species. IN: The Greenhouse Effect and
Primary Productivity in European Agro-ecosystems; 5-10 April 1990;
Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H.
van Laar, eds.), Pudoc, Wageningen, pp. 64-67.

Aster tripolium/Elymus pycnanthus/Spartina anglica

KEYWORDS: AGRICULTURE, ALLOCATION, AQUATIC PLANTS, C3, C4,
GREENHOUSE, HALOPHYTES, LEAF PHOTOSYNTHESIS, SALT MARSH,
TRANSPIRATION, WATER STATUS

429  
Levanon, D., B. Motro, and U. Marchaim. 1986. Organic Materials
Degradation for CO2 Enrichment of Greenhouse Crops. IN: Status and
CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.), Carbon
Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca
Raton, Florida, pp. 123-145.

Carbon comprises approximately 50% of the dry matter in all
organisms. Photoautotrophs (plants and algae) fix atmospheric CO2
into organic materials. These organic materials serve as a source
of energy and carbon for the heterotrophs (a large group of
organisms, including all animals). This utilization of organic
materials in the respiration process causes the essential return of
CO2 to the atmospheric pool. This natural process could be
manipulated for CO2 enrichment of greenhouse crops. Organic waste
materials of agricultural or urban origin can serve as sources of
CO2 enrichment. For practical use they must be cheap and available
in the vicinity of the greenhouse. Animal manures mixed with
vegetative wastes are probably the most suitable raw materials for
this purpose. The recommended methods for application of CO2 from
biodegradation of organic materials to greenhouses are: composting,
anaerobic digestion, and spreading the organic matter on the
greenhouse ground or incorporating it in the upper soil layer. The
use of each of the above methods must be based on knowledge of the
ecology of aerobic and anaerobic degradation. The decision as to
which one of these methods is the most suitable must be based on a
feasibility study where local conditions, such as the availability
of raw materials, climate, labor, and construction costs, etc. are
taken into consideration.

KEYWORDS: CO2 SOURCES, COMMERCIAL USE OF CO2, GREENHOUSE

430  
Leverenz, J.W. 1988. The Effects of Illumination Sequence, CO2
Concentration, Temperature and Acclimation on the Convexity of the
Photosynthetic Light Response Curve. Physiologia Plantarum 74:332-341.

It was shown previously that the convexity (curvature or rate of
bending) of the photosynthetic light response curve was strongly
correlated with chlorophyll content in shade acclimated conifer
needles (Leverenz 1987, Physiol. Plant. 71: 20-29) in agreement
with an hypothesis that gradients of light within leaves affect the
convexity. In the present study it is shown that the convexity at
any given chlorophyll content can be altered when leaves of Pinus
sylvestris L. Picea glauca (Muench), Picea mariana (M.II.) BS.P.
and Picea abies (L.) Karst pre-treated with less shade. This
probably induced a differential acclimation of cells on the top and
bottom side of the leaves to their local light environment. Leaves
were illuminated on i) their top surface, ii) their bottom surface,
or iii) uniformly in a light integrating sphere during measurements
of photosynthesis. After shoots had been transferred from the
growth environment to a new measuring environment, the convexity
increased from the first to the second day towards a maximum of
0.97. The rate of increase towards this maximum was 55 to 62% per
day and probably is the result of re-acclimation of cells within
the leaves. The data show that the act of measuring photosynthesis
induces a significant alteration in the experimental material when
measurements are made for more than one day. The convexity of the
light response curve of photosynthesis, was independent of whether
the steady state measurements were made beginning in the dark and
sequentially increasing photon flux density or beginning at high
light and sequentially lowering photon flux density. Neither
variation of CO2 concentration from 35 to 200 Pa, nor of
temperature from 5 to 32C affected the convexity.

Pinus sylvestris/Scots pine/Picea glauca/white spruce/Picea
mariana/Picea abies/Norway spruce/Abies lasiocarpa

KEYWORDS: LEAF PHOTOSYNTHESIS, LIGHT, MODELING, PHOTOSYNTHESIS
MODEL

431  
Lewin, K.F., G.R. Hendrey, and Z. Kolber. 1992. Brookhaven National
Laboratory Free-Air Carbon Dioxide Enrichment Facility. Critical
Reviews in Plant Sciences 11:135-141.

KEYWORDS: EXPOSURE METHODS, FACE

432  
Lieth, J.H., J.F. Reynolds, and H.H. Rogers. 1986. Estimation of
Leaf Area of Soybeans Grown under Elevated Carbon Dioxide Levels.
Field Crops Research 13:193-203.

Leaf area (LA) data are required for describing numerous canopy
processes. However, determining LA for a crop is both time
consuming and labor intensive, requiring a substantial investment
of resources. The objectives of this study were (1) to develop
statistical models for estimating LA of field-grown soybean
(Glycine max) plants grown in open-top field chambers from
measurements of destructive (leaf and top dry weight) and non-destructive (leaf number, plant height, and branch length)
variables, (2) to examine the effects of CO2 concentration on these
statistical relationships, and (3) to test the applicability of
such models to independent data collected under different
experimental conditions. Predictive models of LA based on either
branch length (LA = 147.6 BRL (exp 0.635), CV = 11%) or top dry
weight (LA = 328.8 x TDW (exp 0.731), CV = 12%) were found to have
the lowest coefficient of variation about the regression line, to
be unaffected by increasing CO2, and to be reasonable predictors of
LA under different growth conditions. Both leaf area per leaf and
specific leaf area ratios changed with increasing CO2 and growth
conditions. Plant height was a poor predictor of LA.

Glycine max/soybean

KEYWORDS: LEAF AREA DEVELOPMENT, MODELING, OPEN-TOP CHAMBERS

433  
Lincoln, D.E. 1993. The Influence of Plant Carbon Dioxide and
Nutrient Supply on Susceptibility to Insect Herbivores. Vegetatio
104/105:273-280.

The carbon/nutrient ratio of plants has been hypothesized to be a
significant regulator of plant susceptibility of leaf-eating
insects. As rising atmospheric carbon dioxide stimulates
photosynthesis, host plant carbon supply is increased and the
accompanying higher levels of carbohydrates, especially starch,
apparently 'dilute' the protein content of the leaf. When host
plant nitrogen supply is limited, plant responses include increased
carbohydrate accumulation, reduced leaf protein content, but also
increased carbon-based defensive chemicals. No change, however, has
been observed in the concentration of leaf defensive
allelochemicals with elevated carbon dioxide during host plant
growth. Insect responses to carbon-fertilized leaves include
increased consumption with little change in growth, or
alternatively, little change in consumption with decreased growth,
as well as enhanced leaf digestibility, reduced nitrogen use
efficiency, and reduced fecundity. The effects of plant carbon and
nutrient supply on herbivores appear to result, at least in part,
from independent processes affecting secondary metabolism.

KEYWORDS: ALLELOCHEMICALS, CARBON:NITROGEN RATIO, HERBIVORY,
NITROGEN, REVIEW, SECONDARY METABOLITES

434  
Lincoln, D.E., and D. Couvet. 1989. The Effect of Carbon Supply on
Allocation to Allelochemicals and Caterpillar Consumption of
Peppermint. Oecologia 78:112-114.

The carbon supply of peppermint plants was manipulated by growing
clonal propagules under three carbon dioxide regimes (350, 500 and
650 uL/L). Feeding by fourth instar caterpillars of Spodoptera
eridania increased with elevated CO2 hostplant regime, as well as
with low leaf nitrogen content and by a high proportion of leaf
volatile terpenoids. Leaf weight increased significantly with the
increased carbon supply, but the amount of nitrogen per leaf did
not change. The amount of volatile leaf mono- and sesquiterpenes
increased proportionately with total leaf dry weight and hence was
not influenced by CO2 supply. These results are consistent with
ecological hypotheses which assume that allocation to defense is
closely regulated and not sensitive to carbon supply per se.

Mentha piperita/peppermint

KEYWORDS: ALLELOCHEMICALS, ALLOCATION, CONTROLLED ENVIRONMENT
CHAMBERS, HERBIVORY, NITROGEN, SPODOPTERA ERIDANIA

435  
Lincoln, D.E., D. Couvet, and N. Sionit. 1986. Response of an
Insect Herbivore to Host Plants Grown in Carbon Dioxide Enriched
Atmospheres. Oecologia 69:556-560.

Rising atmospheric carbon dioxide concentration is expected to
increase plant productivity but little evidence is available
regarding effects on insect feeding or growth. Larvae of the
soybean looper, a noctuid moth, were fed leaves of soybean plants
grown under three carbon dioxide regimes (350, 500 and 650 uL/L).
Larvae fed at increasingly higher rates on plants from elevated
carbon dioxide atmospheres: 30% greater on leaves from the 650 uL/L
treatment than on leaves from the 350 uL/L treatment. When
variation in larval feeding was related to the leaf content of
nitrogen and water, there was no significant remaining effect of
carbon dioxide treatment. The principal effect on herbivores of
increasing the carbon supply of leaves appeared to be reduction of
leaf nutrient concentration. This study suggests that feeding by
herbivores on the leaves of C3 plants may increase as the level of
atmospheric carbon dioxide rises.

soybean/Glycine max

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, NITROGEN,
PSEUDOPLUSIA INCLUDENS, WATER STATUS

436  
Lindhout, P., and G. Pet. 1990. Effects of CO2 Enrichment on Young
Plant Growth of 96 Genotypes of Tomato (Lycopersicon esculentum).
Euphytica 51:191-196.

The early growth of 96 genotypes of tomato was studied at 320 ppm
CO2 and at 750 ppm CO2 in separate climate rooms. Plants were
harvested at 40 and 55 days after sowing. Fresh and dry weights
were determined. Large differences between genotypes were found for
average plant fresh weight and dry weights and for relative growth
rates. The average overall growth enhancement by CO2 enrichment was
2.3. Two genotypes showed significant genotype x CO2 interaction.
The consequences of these results for tomato breeding are
discussed.

tomato/Lycopersicon esculentum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES,
GROWTH ANALYSIS, HORTICULTURAL CROPS

437  
Lipfert, F.W., Y. Alexander, G.R. Hendrey, K.F. Lewin, and J. Nagy.
1992. Performance Analysis of the BNL FACE Gas Injection System.
Critical Reviews in Plant Sciences 11:143-163.

KEYWORDS: EXPOSURE METHODS, FACE

438  
Long, S.P. 1991. Modification of the Response of Photosynthetic
Productivity to Rising Temperature by Atmospheric CO2
Concentrations: Has its Importance Been Underestimated? Plant, Cell
and Environment 14:729-739.

Climate change will include correlated increases in temperature and
atmospheric CO2 concentration (Ca). Rising temperatures will
increase the ratio of photorespiratory loss of carbon to
photosynthetic gain, whilst rising Ca will have an opposing effect.
The mechanism of these effects at the level of carboxylation in C3
photosynthesis are quantitatively well understood and provide a
basis for models of the response of leaf and canopy carbon exchange
to climate change. The principles of such a model are referred to
here and used to quantitatively examine the implications of
concurrent increase in temperature and Ca. Simulations of leaf
photosynthesis show the increase, with elevation of Ca from 350 to
650 umol/mol, in light saturated rates of CO2 uptake (Asat) and
maximum quantum yields (phi) to rise with temperature. An increase
in Ca from 350 to 650 umol/mol can increase Asat by 20% at 10C and
by 105% at 35C, and can raise the temperature optimum of Asat by
5C. This pattern of change agrees closely with experimental data.
At the canopy level, simulations also suggest a strong interaction
of increased temperature and CO2 concentration. Predictions are
compared with the findings of long-term field studies. The
principles used here suggest that elevated Ca will alter both the
magnitude of the response of leaf and canopy carbon gain to rising
temperature, and sometimes, the direction of response. Findings
question the value of models for predicting plant production in
response to climate change which ignore the direct effects of
rising Ca and the modifications that rising Ca imposes on the
temperature response of net CO2 exchange.

KEYWORDS: CLIMATE CHANGE, MODELING, PHOTOSYNTHESIS, REVIEW,
RIBULOSE BISPHOSPHATE CARBOXYLASE, TEMPERATURE

439  
Long, S.P., N.R. Baker, and C.A. Raines. 1993. Analysing the
Responses of Photosynthetic CO2 Assimilation to Long-term Elevation
of Atmospheric CO2 Concentration. Vegetatio 103/104:33-45.

Understanding how photosynthetic capacity acclimatises when plants
are grown in an atmosphere of rising CO2 concentrations will be
vital to the development of mechanistic models of the response of
plant productivity to global environmental change. A limitation to
the study of acclimatisation is the small amount of material that
may be destructively harvested from long-term studies of the
effects of elevation of CO2 concentration. Technological
developments in the measurement of gas exchange, fluorescence and
absorption spectroscopy, coupled with theoretical developments in
the interpretation of measured values now allow detailed analyses
of limitations to photosynthesis in vivo. The use of leaf chambers
with Ulbricht integrating spheres allows separation of change in
the maximum efficiency of energy transduction in the assimilation
of CO2 from changes in tissue absorptance. Analysis of the response
of CO2 assimilation to intercellular CO2 concentration allows
quantitative determination of the limitation imposed by stomata,
carboxylation efficiency, and the rate of regeneration of ribulose
1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method
for detecting photoinhibition in heterogeneously illuminated leaves
within canopies in the field. Modulated fluorescence and absorption
spectroscopy allow parallel measurements of the efficiency of light
utilisation in electron transport through photosystems I and II in
situ.

KEYWORDS: ABSORPTION SPECTROSCOPY, FLUORESCENCE, PHOTOSYNTHESIS,
PHOTOSYNTHETIC ACCLIMATION, QUANTUM REQUIREMENT, REVIEW, RIBULOSE
BISPHOSPHATE CARBOXYLASE

440  
Long, S.P., and B.G. Drake. 1991. Effect of the Long-Term Elevation
of CO2 Concentration in the Field on the Quantum Yield of
Photosynthesis of the C3 Sedge, Scirpus olneyi. Plant Physiology
96:221-226.

CO2 concentration was elevated throughout 3 years around stands of
the C3 sedge Scirpus olneyi on a tidal marsh of the Chesapeake Bay.
The hypothesis that tissues developed in an elevated CO2 atmosphere
will show an acclimatory decrease in photosynthetic capacity under
light-limiting conditions was examined. The absorbed light quantum
yield of CO2 uptake (phi-abs) and the efficiency of photosystem II
photochemistry were determined for plants which had developed in
open top chambers with CO2 concentrations in air of 680 micromoles
per mole, and of 351 micromoles per mole as controls. An Ulbricht
sphere cuvette incorporated into an open gas exchange system was
used to determine phi-abs and a portable chlorophyll fluorimeter
was used to estimate the photochemical efficiency of photosystem
II. When measured in an atmosphere with 10 millimoles per mole O2
to suppress photorespiration, shoots showed a phi-abs of 0.093 +/-
0.003, with no statistically significant difference between shoots
grown in elevated or control CO2 concentrations. Efficiency of
photosystem II photochemistry was also unchanged by development in
an elevated CO2 atmosphere. Shoots grown and measured in 680
micromoles per mole of CO2 in air showed a phi-abs of 0.078 +/-
0.004 compared with 0.065 +/-0.003 for leaves grown and measured in
351 micromoles per mole CO2 in air; a highly significant increase.
In accordance with the change in phi-abs, the light compensation
point of photosynthesis decreased from 51 +/- 3 to 31 +/- 3
micromoles per square meter per second for stems grown and measured
in 351 and 680 micromoles per mole of CO2 in air, respectively. The
results suggest that even after 3 years of growth in elevated CO2,
there is no evidence of acclimation in capacity for photosynthesis
under light-limited conditions which would counteract the
stimulation of photosynthetic CO2 uptake otherwise expected through
decreased photorespiration.

Scirpus olneyi

KEYWORDS: AQUATIC PLANTS, LEAF PHOTOSYNTHESIS, LIGHT, OPEN-TOP
CHAMBERS, PHOTOSYNTHESIS MODEL, PHOTOSYNTHETIC ACCLIMATION, QUANTUM
REQUIREMENT, SALT MARSH

441  
Long, S.P., and P.R. Hutchin. 1991. Primary Production in
Grasslands and Coniferous Forests with Climate Change: An Overview.
Ecological Applications 2:139-156.

In energy terms primary production is the driving step of the
global carbon cycle. To predict the interaction of ecosystems with
the 'greenhouse' effect, it is necessary to understand how primary
production, consumption, and decomposition will respond to climate
change. Most estimates of primary production have been made by
extrapolation from measured standing crops. For grasslands we show
this approach to be seriously in error. Even where detailed studies
of turnover and belowground production have been undertaken, errors
are invariably high, severely limiting the value of models based on
correlation of climate with measured production. Detailed
information is available on the responses of individual plant
processes to individual climate variables at the leaf, plant, and
stand level, giving potential for a more mechanistic approach in
modelling. This approach is limited by lack of information on
multivariate interactions and on some key physiological processes,
and by uncertainties in scaling up to populations and communities.
Despite this, some important insights to possible community
responses, particularly those of C3 and C4 types, may be gained
from knowledge of responses at the plant level and below. This
review outlines the expected character of climate change in
grasslands and coniferous forests. Knowledge of the responses of
different physiological processes underlying production to
individual aspects of climate change is considered, and its
implications for higher levels of organization are discussed.
Although feasible, mechanistic models of production compound the
errors associated with individual process responses with
uncertainties surrounding interaction and scaling up, and result in
very large errors in any prediction of response to climate change.
We conclude that there is insufficient information to predict
accurately the response of primary production to climate change.
The key processes for which information is inadequate and the
parameters that have meaning at different scales need to be
identfied. Of particular promise is the approach of predicting
production from light interception and conversion efficiency.

KEYWORDS: ALLOCATION, C3, C4, CLIMATE CHANGE, CONIFEROUS FOREST,
ECOSYSTEM LEVEL CO2 RESPONSES, GCM'S, GRASSES, MODELING, NET
PRIMARY PRODUCTIVITY, PHOTOSYNTHESIS MODEL, REVIEW, SCALING,
SELECTION PRESSURE, TEMPERATURE

442  
Long, S.P., G.Y. Nie, B.G. Drake, G. Hendrey, and K. Lewin. 1992.
The Implications of Concurrent Increases in Temperature and CO2
Concentration for Terrestrial C3 Photosynthesis. IN: Proceedings of
the IXth International Congress on Photosynthesis; 30 August-4
September 1992; Nagoya, Japan (N. Murata, ed.), Kluwer Academic,
Dordrecht.

KEYWORDS: PHOTOSYNTHESIS, TEMPERATURE

443  
Longuenesse, J.J. 1990. Influence of CO2 Enrichment Regime on
Photosynthesis and Yield of a Tomato Crop. Acta Horticulturae
268:63-70.

Tomato plants var. Melody were grown in two greenhouses at the
Centre de Recherches d'Avignon, in the South of France, where two
CO2 enrichment regimes were compared: - Standard regime with
setpoint at 1000 ppm, 6 hours per day (treatment C1000) -
Simulation of a CO2 enrichment technique using the smoke exhausts
from the boiler used to heat the greenhouse (treatment Cs). We
measured in situ photosynthesis of leaves at different periods
during the experiment, first before enrichment was applied, then
during the CO2 enrichment period. These measurements were analyzed
by fitting a leaf photosynthesis model to the data for each period;
this curve fitting showed that when the amount of CO2 feeded to the
plants is low (setpoint at 1000-1500 ppm; less than 2 hours per
day) there is no acclimation effect on leaf assimilation; but when
the enrichment is stronger (6 hours per day at 1000 ppm or 2 hours
at 2500-3500 ppm) the acclimation effect reduces significantly the
assimilation during the non-enriched hours of the day. The number
and weight of fruits produced was measured for each of the three
trusses; the analysis of these results shows that the C2 treatment
can give the same yield as the standard regime C1000, provided the
maximum CO2 concentration in the greenhouse is maintained below a
limit of 2000-2500 ppm.

Lycopersicon esculentum/tomato

KEYWORDS: CO2 ENRICHMENT DURATION, GREENHOUSE, HORTICULTURAL CROPS,
LEAF PHOTOSYNTHESIS, MODELING, PHOTOSYNTHETIC ACCLIMATION, YIELD

444  
Loomis, R.S., and H.R. Lafitte. 1987. The Carbon Economy of a Maize
Crop Exposed to Elevated CO2 Concentrations and Water Stress, as
Determined from Elemental Analyses. Field Crops Research 17:63-74.

Maize crops grown in open fumigation chambers under field
conditions were exposed to four levels of water supply.
Photosynthetic and respiratory activities were assessed from
elemental analyses of above-ground biomass. Elemental composition
varied little with CO2 or water treatment. The mean elemental
composition of organic materials per 100 g biomass at a harvest
during grain filling was C: 3.63, H:6.04, N: 0.093 O: 2.87, S:
0.002. (The balance of the mass, 2.08 g, was due to minerals). That
material had more C and H and less N and was more reduced
chemically than pre-anthesis biomass. While crop growth rates were
affected by CO2 and water, the growth respiration factor (0.11 g
C/g biomass) and the fraction of estimated gross photosynthesis
used in growth respiration were small and unaffected by treatment.
It is estimated that net carbon storage amounted to 53% of gross
photosynthesis, while 14% went to growth respiration and 33% went
to maintenance.

corn/Zea mays

KEYWORDS: CARBON BUDGET, GROWTH ANALYSIS, HYDROGEN, NITROGEN,
NUTRITION, OPEN-TOP CHAMBERS, OXYGEN, RESPIRATION, SULFUR, WATER
STATUS

445  
Lord, D., S. Morissette, and J. Allaire. 1993. Influence de
l'intensite lumineuse, de la temperature nocturne de l'air et de la
concentration en CO2 sur la croissance de semis d'epinette noire
(Picea mariana) produits en recipients en serres. Canadian Journal
of Forest Research 23:101-110.

Growth of containerized black spruce seedlings grown in greenhouses
was studied in relation to factors known to influence plant growth.
Artificial light intensity (3.80 and 72.04 umol/m2/s) and night air
temperature (5, 10, 12.5, 15 and 20C) were considered in a first
experiment and artificial light intensity (4.24 and 59.57
umol/m2/s) and CO2 air concentration (ambient and 1000 uL/L) in a
second one. Higher light intensity and CO2 enrichment increased dry
biomass of seedlings as well as growth in height and stem diameter.
Both factors similarly enhanced the last two parameters since
height/diameter ratios showed little variation among treatments.
Reducing night air temperature down to 10C did not significantly
influence height growth nor biomass increase when high intensity
light was provided. Lower light intensity raised the threshold to
12.5C. Shoot height, diameter, and dry biomass as well as the
number of branches and buds per millimeter were strongly reduced by
a 5C night air temperature. High intensity light enhanced growth
of containerized black spruce seedlings more than CO2 enrichment or
a 5C night air temperature. When used simultaneously, these growth
enhancing factors had a synergistic effect during most of the
treatment period; thereafter, the effect became partially additive.
The relative growth rate peaked at the onset of exponential shoot
growth and decreased after this point. However, the enhancing
factors were still efficient since absolute growth differences
between seedlings grown under the most favorable conditions and
controls kept increasing. The faster growing pace imposed by these
growth enhancing conditions during the treatment period was
maintained over the entire first growing season. In French.

Picea mariana/black spruce

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS,
ENVIRONMENTAL INTERACTIONS, GROWTH ANALYSIS, LIGHT, TEMPERATURE,
TREES

446  
Lu, J.Y., P.K. Biswas, and R.D. Pace. 1986. Effect of Elevated CO2
Growth Conditions on the Nutritive Composition and Acceptability of
Baked Sweet Potato. Journal of Food Science 51:358-359 & 539.

'Georgia Jet' sweet potatoes were grown at CO2 concentrations of
354, 431, 506 and 659 ppm for 90 days. Elevated CO2 concentrations
decreased protein, total carotenoids and insoluble dietary fiber.
An increase in dry matter and reddish-orange color was observed at
506 and 659 ppm CO2 concentrations. Sensory evaluation scores for
flavor and moistness indicated that sweet potatoes grown under high
CO2 concentrations were acceptable and not different from the
control.

Ipomoea batatas/sweet potato

KEYWORDS: CARBOHYDRATES, FOOD QUALITY, OPEN-TOP CHAMBERS, PROTEINS,
TUBERS

447  
Luo, Y., and P.S. Nobel. 1993. Growth Characteristics of Newly
Initiated Cladodes of Opuntia ficus-indica as Affected by Shading,
Drought and Elevated CO2. Physiologia Plantarum 87:467-474.

Biomass accumulation and area expansion of newly initiated cladodes
of Opuntia ficus-indica were studied to help understand the high
productivity of this Crassulacean acid metabolism species. In a
glasshouse, both dry weight and area increased more and more
rapidly for about 30 days and then increased linearly with time up
to 63 days. The relative growth rate averaged 0.12/day, comparable
to values for productive C3 and C4 plants. New cladodes initiated
on basal cladodes with 2-fold higher initial dry weight grew twice
as fast. Drought reduced biomass accumulation and area expansion of
new cladodes by 62 and 52%, respectively. A 70% reduction in
irradiation decreased biomass accumulation of new cladodes by 17%
and their thickness by 11%. In a growth chamber containing 720 umol
CO2/mol air, biomass of newly initiated cladodes was 7% higher,
area was 8% less, specific mass was 16% higher and less
carbohydrate was translocated from basal cladodes than for 360 umol
CO2/mol. The large capacity for storage of carbohydrate and water
in basal cladodes of O. ficus-indica apparently buffered
environmental stresses, thereby reducing their effects on growth of
daughter cladodes.

Opuntia ficus-indica/prickly pear cactus

KEYWORDS: CAM, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS,
LEAF AREA DEVELOPMENT, LIGHT, WATER STRESS

448  
Luo, Y., and B.R. Strain. 1992. Leaf Water Status in Velvetleaf
under Long-term Interactions of Water Stress, Atmospheric Humidity,
and Carbon Dioxide. Journal of Plant Physiology 139:600-604.

Well watered and water-stressed Abutilon theophrasti, were grown
with relative humidity of 45% or 85% at 30C and CO2 concentrations
of 350 or 650 umol/mol. Elevated leaf water potentials of the
water-stressed plants grown in both high and low humidities were
caused by CO2 enrichment. Elevated water content (kg/m2 leaf area)
caused by CO2 enrichment, higher water content at a given water
potential, and notably lower rate in desiccation from detached
leaves all occurred only in the plants grown in low humidity. These
results may be related to enhanced dehydration resistance of the
plants that experienced long-term low humidity.

Abutilon theophrasti

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, HUMIDITY, VPD, WATER
STATUS

449  
Luxmoore, R.J., R.J. Norby, and E.G. O'Neill. 1986. Seedling Tree
Responses to Nutrient Stress under Atmospheric CO2 Enrichment. IN:
Forest Plants and Forest Protection, Vol. I (Edwin Donaubauer,
ed.), 18th IUFRO World Congress, Division 2, Yugoslav IUFRO World
Congress Organizing Committee, Vienna, pp. 178-183.

Three species of seedling trees were grown in pots containing low-nutrient soil for periods of up to 40 weeks under a range of
atmospheric CO2 concentrations. In all cases, total dry weight
increased with CO2 enrichment, with a greater relative increase in
root weight than shoot weight. In an experiment with Pinus
virginiana in open-top field chambers, phosphorus and potassium
uptake did not increase with an increase in CO2 from 365 to 690
uL/L, even though dry matter gain increased by 37% during the
exposure period. In experiments with Quercus alba and Liriodendron
tulipifera under controlled environment conditions there were
obvious symptoms of nitrogen deficiency and total nitrogen uptake
did not increase with CO2 enrichment. However, dry weight gain was
more than 90% higher at 690 uL/L CO2. The three experiments with
CO2 enrichment demonstrate that increases in plant dry weight can
occur without increased uptake of some nutrients from the low-nutrient soil. A mechanism for these responses may involve
increased mobilization of nutrients in association with increased
sucrose transport under elevated CO2 conditions.

Pinus virginiana/Quercus alba/Liriodendron tulipifera

KEYWORDS: CALCIUM, GROWTH, NITROGEN, NUTRITION, OPEN-TOP CHAMBERS,
PHOSPHORUS, POTASSIUM, RHIZOSPHERE, ROOTS, TREES, ZINC

450  
Luxmoore, R.J., E.G. O'Neill, J.M. Ells, and H.H. Rogers. 1986.
Nutrient Uptake and Growth Responses of Virginia Pine to Elevated
Atmospheric CO2. Journal of Environmental Quality 15:244-251.

One-year-old Virginia pine (Pinus virginiana Mill.) seedlings with
native or Pisolithus tinctorius mycorrhizal associations were grown
in pots with soil low in organic matter and in cation exchange
capacity and were exposed to one of five atmospheric CO2 levels in
the range of 340 to 940 uL/L in open-top field chambers. The mean
dry weight of the seedlings increased from 4.4 to 11.0 g/plant
during the 122-d exposure period. Significant increases in dry
weight and uptake of N, Ca, Al, Fe, Zn, and Sr occurred with CO2
enrichment. Greater chemical uptake was associated with greater
root weight. Specific absorption rates for chemicals (uptake per
gram of root per day) were generally not affected by CO2
enrichment. The uptake of P and K was not increased with elevated
CO2, and these elements showed the greater nutrient-use efficiency
(C gain per element uptake). The nutrient-use efficiency for N and
Ca were not influenced by atmospheric CO2 enrichment. Large
increases in Zn uptake at high CO2 suggested an increase in
rhizosphere acidification, which may have resulted from the release
of protons from the roots, since it was estimated that cation
uptake increasingly exceeded anion uptake with CO2 enrichment.
Potassium, P, and NO3 concentrations in the pot leachate decreased
with higher CO2 levels, and a similar trend was found for Al and
Mg. These results suggest that soil-plant systems may exhibit
increased nutrient and chemical retention at elevated atmospheric
CO2.

Pinus virginiana/Virginia pine

KEYWORDS: ALLOCATION, ALUMINUM, BARIUM, BORON, CALCIUM, COPPER,
IRON, MAGNESIUM, MANGANESE, MYCORRHIZAE, NITROGEN, NUTRITION, OPEN-TOP CHAMBERS, PHOSPHORUS, POTASSIUM, ROOTS, STRONTIUM, TREES, ZINC

451  
Luxmoore, R.J., M.L. Tharp, and D.C. West. 1990. Simulating the
Physiological Basis of Tree-Ring Responses to Environmental
Changes. IN: Process Modeling of Forest Growth Responses to
Environmental Stress (R.K. Dixon, R.S. Meldahl, G.A. Ruark, and
W.G. Warren, eds.), Timber Press, Portland, Oregon, pp. 393-401.

The detection of possible forest growth responses to changes in
atmospheric CO2 or air pollutants is very difficult by statistical
analysis of tree-ring chronologies, and a complementary modeling
approach has been initially tested. In this new approach, a linked
set of mechanistic unified transport models (UTM) of carbon, water,
and chemical dynamics in soil-plant-litter systems is used to
generate a matrix of simulated annual stemwood increment and winter
carbon storage values for a range of degree day, water stress, and
atmospheric CO2 concentrations. These values represent potential
tree growth responses as determined by hourly time-step
physiological processes. The matrix is accessed by a forest
succession model (Forests of East Tennessee, FORET) according to
selected degree day and water stress values or by use of actual
site data. These potential growth responses are modified to
realized annual increments according to the competition algorithms
of the succession simulator using yearly time-steps. A 12% increase
in stemwood production was predicted for an oak-hickory (Quercus-Carya sp.) forest in eastern Tennessee by the UTM for a change in
atmospheric CO2 both from 260 to 340 and from 340 to 600 ppmv
(uL/L). A signal of +/- 12% was incorporated into the diameter
growth algorithms for the species represented in Forests of East
Tennessee (FORET), and simulations were conducted for 32 plots with
slightly different initial species composition representative of
the oak-hickory forest (Shugart and West, 1977). Preliminary
results suggest that the spatial variation in the species
complement for the 32 plots masked the detection of the CO2 signal
in 200-year simulations. In a repeat analysis eliminating spatial
variability, 24 replicate simulations were conducted for a single
plot, and again there were no simulation responses that could be
attributed to CO2 enrichment for the five plots evaluated in this
manner. Temporal variability due to establishment and mortality
algorithms in FORET probably masked the CO2 signal from the Unified
Transport Model (UTM). Spatial and/or temporal variability in
forest-stand dynamics may mask the detection of tree response to
atmospheric CO2 enrichment. A backcast simulation procedure that
largely eliminates spatial and temporal effects is recommended for
further testing of the linked-modeling method of tree-ring
chronology analysis.

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, MODELING, SIMULATION,
TEMPERATE FOREST, TREE-RING ANALYSIS, TREES

452  
Madsen, T.V. 1987. The Effect of Different Growth Conditions on
Dark and Light Carbon Assimilation in Littorella uniflora.
Physiologia Plantarum 70:183-188.

The effect of long-term exposure to different inorganic carbon,
nutrient and light regimes on CAM activity and photosynthetic
performance in the submerged aquatic plant, Littorella uniflora
(L.) Aschers was investigated. The potential CAM activity of
Littorella was highly plastic and was reduced upon exposure to low
light intensities (43 umol/m2/s), high CO2 concentrations (5.5 mM,
pH 6.0) or low levels of inorganic nutrients, which caused a 25-80%
decline in the potential maximum CAM activity relative to the
activity in the control experiments (light: 45 umol/m2/s; free CO2:
1.5 mM). The CAM activity was regulated more by light than by CO2,
while nutrient levels only affected the activity to a minor extent.
The minor effect of low nutrient regimes may be due to a general
adaptation of isoetic species to low nutrient levels. The
photosynthetic capacity and CO2 affinity was unaffected or
increased by exposure to low CO2, irrespective of nutrient levels.
High CO2, low nutrient and low light, however, reduced the capacity
by 22-40% and the CO2 affinity by 35-45%, relative to control. The
parallel effect of growth conditions on CAM activity and
photosynthetic performance of Littorella suggest that light and
dark carbon assimilation are interrelated and constitute an
integrated part of the carbon assimilation physiology of the plant.
The results are consistent with the hypothesis that CAM is a
carbon-conserving mechanism in certain aquatic plants. The
investment in the CAM enzyme system is beneficial to the plants
during growth at high light and low CO2 conditions.

Littorella uniflora

KEYWORDS: AQUATIC PLANTS, CAM, PHOTOSYNTHESIS

453  
Maevskaya, S.N., T.F. Andreeva, S.Y. Voevudskaya, and N.N.
Cherkanova. 1990. Effect of Elevated CO2 Concentration on
Photosynthesis and Nitrogen Metabolism of Mustard Plants.
Fiziologiya Rastenii 37:921-927.

We investigated the effect of prolonged (8- to 10-day) influence of
elevated atmospheric CO2 content (0.14%) on the photosynthetic rate
and nitrogen metabolism in mustard plants (Brassica juncea L.). The
photosynthetic rate and intensity of nitrogen metabolism in leaves
of mustard plants in the vegetative phase of growth are higher
under conditions of elevated atmospheric CO2 concentration than in
leaves of plants that developed under conditions of normal CO2
content in the atmosphere. Intensification of nitrogen metabolism
occurred mainly due to increase of NR activity. Activity of GS and
GO increased to a lesser extent. Significant changes were detected
in the rates of synthesis of separate amino acids. Thus, formation
of alanine and aspartic acid increased by 84 and 40%, respectively,
but the rates of glycine and serine synthesis declined. The excess
of amino acids (alanine and aspartic acid) is evacuated from the
metabolic pool into vacuoles, with the result that a normal
metabolic pool of amino acids is preserved. A state of homeostasis
is preserved, protein and chlorophyll synthesis is not disturbed,
and growth and biomass accumulation intensify in plants under
conditions of elevated CO2 concentration.

Brassica juncea/mustard

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES, METABOLITES,
NITRATE REDUCTASE, NITROGEN

454  
Maleszewski, S., Z. Kaminska, A. Kondracka, and M. Mikulska. 1988.
Response of Net Photosynthesis in Bean (Phaseolus vulgaris) Leaves
to the Elevation of the Partial Pressures of Oxygen and Carbon
Dioxide. Physiologia Plantarum 74:221-224.

Bean (Phaseolus vulgaris L. cv. Golden Saxa) plants were grown
under low artificial light or under natural daylight. The rate of
net photosynthesis (Pn) was measured at: CO2 partial pressure,
p(CO2), of 0.03, 0.09 or 0.15 kPa; O2 partial pressure, p(O2), of
2, 21 or 31 kPa and at light intensities of 350 or 1000 umol/m2/s
(photosynthetically active radiation). In plants which had been
grown under natural light, stimulation of Pn at 2 kPa p(O2) was
found only at elevated p(CO2) and high light. It is proposed that
this phenomenon is dependent on a high capacity of the
photosynthetic apparatus to regenerate ribulose 1,5-bis-phosphate.

bean/Phaseolus vulgaris

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GREENHOUSE, LEAF
PHOTOSYNTHESIS, LIGHT, OXYGEN, RIBULOSE 1,5-BISPHOSPHATE

455  
Mandl, R.H., J.A. Laurence, and R.J. Kohut. 1989. Development and
Testing of Open-Top Chambers for Exposing Large, Perennial Plants
to Air Pollutants. Journal of Environmental Quality 18:534-540.

To study the effects of air pollutants on large perennial plants,
two designs of large, open-top chambers were tested in wind tunnel
studies and subsequent field trials. Flow visualization of air
patterns in the wind tunnel showed that a frustum and inner baffle
plate covering 50% of the top surface provided the best exclusion
capabilities. This was quantified by measurement of pollutant
distribution in scale models. Prototype chambers were erected
around grape (Vitus sp.) vines in a commercial vineyard and
evaluated over two growing seasons. Exclusion efficiencies of 80 to
95% were found during the test period. The rain shadow caused by
the frustum was significant with losses greatest near the walls.
The average increase in leaf temperature between ambient and within
the chamber was 2.5C. Light intensity was reduced 14 and 22% in
the circular and rectangular chamber, respectively. Although there
is some modification of the plant environment, the chambers provide
a suitable environment during the growing season for air pollution
studies with large perennial plants.

KEYWORDS: EXPOSURE METHODS, OPEN-TOP CHAMBERS, OUTDOOR GROWTH
CHAMBERS

456  
Mann, W., and H. Krug. 1989. Production Planning -- CO2 Enrichment.
Acta Horticulturae 248:201-206.

Following the approach of Krug and Liebig the CO2 factor was
integrated into the planning model for radiation and temperature.
The response surface for autumn plantings of lettuce, graphs for
the growth periods (100 g) as a function of temperature set point
and CO2 concentration as well as corresponding input factor costs,
are presented. CO2 enrichment results in remarkable increases of
growth rates, particularly in combination with high irradiances and
favourable temperatures. Therewith the growth period will be
shortened, especially if due to better growth in favourable
environments unfavourable conditions will be avoided. This can be
achieved in autumn by enhancing growth to finish the crop before
winter, in spring by later plantings and enhancing growth to finish
at the time scheduled.

kohlrabi/Brassica oleracea/radish/Raphanus sativus/lambs lettuce

KEYWORDS: GREENHOUSE, HORTICULTURAL CROPS, LIGHT, TEMPERATURE

457  
Marek, L.F., and M.H. Spalding. 1991. Changes in Photorespiratory
Enzyme Activity in Response to Limiting CO2 in Chlamydomonas
reinhardtii. Plant Physiology 97:420-425.

The activity of two photorespiratory enzymes, phosphoglycolate
phosphatase (PGPase) and glycolate dehydrogenase (glycolate DH),
changes when CO2-enriched wild-type (WT) Chlamydomonas reinhardtii
cells are transferred to air levels of CO2.  Adaptation to air
levels of CO2 by Chlamydomonas involves induction of a CO2-concentrating mechanism (CCM) which increases the internal
inorganic carbon concentration and suppresses oxygenase activity of
ribulose-1, 5-bisphosphate carboxylase oxygenase. PGPase in cell
extracts shows a transient increase in activity that reaches a
maximum 3 to 5 hours after transfer and then declines to the
original level within 48 hours.  The decline in PGPase activity
begins at about the time that physiological evidence indicates the
CCM is approaching maximal activity.  Glycolate DH activity in 24
hour air-adapted WT cells is double that seen in CO2-enriched
cells.  Unlike WT, the high-CO2-requiring mutant, cia-5, does not
respond to limiting CO2 conditions:  it does not induce any known
aspects of the CCM and it does not show changes in PGPase or
glycolate DH activities. Other known mutants of the CCM show
patterns of PGPase and glycolate DH activity after transfer to
limiting CO2 which are different from WT and cia-5 but which are
consistent with changes in activity being initiated by the same
factor that induces the CCM, although secondary regulation must
also be involved.

Chlamydomonas reinhardtii

KEYWORDS: ALGAE, AQUATIC PLANTS, CELL CULTURE, ENZYMES,
RESPIRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE

458  
Margolis, H.A., and L.P. Vezina. 1990. Atmospheric CO2 Enrichment
and the Development of Frost Hardiness in Containerized Black
Spruce Seedlings. Canadian Journal of Forest Research 20:1392-1398.

The hypothesis that a relatively brief exposure to elevated
atmospheric CO2 could increase the frost resistance of shoots was
tested on containerized black spruce seedlings (Picea mariana
(Mill.) B.S.P.). Seedlings were exposed to 1000 ppm CO2 toward the
end of their second growing season in an unheated production tunnel
and in a heated greenhouse.  In 1987, continuous 10-week CO2
exposures were applied in conjunction with mineral nutrient
fertilization, and freezing tests were conducted each week.  In
1988, a series of shorter 2-week CO2 exposures was applied to
different groups of seedlings and no mineral nutrients were added. 
Controlled freezing tests were conducted at -10xC and were followed
by electrolytic conductivity measurements to assess frost injury. 
Under all experimental conditions, freezing tests on seedlings from
both the production tunnel and the greenhouse indicated
significantly greater frost damage for the CO2-enriched seedlings
than for the controls.  Late-growing season CO2 enrichment
negatively affected the bud initiation - bud development stage of
frost-hardiness development.

Picea mariana/black spruce

KEYWORDS: FROST HARDINESS

459  
Marino, B.D., and M.B. McElroy. 1991. Isotopic Composition of
Atmospheric CO2 Inferred from Carbon in C4 Plant Cellulose. Nature
349:127-131.

The isotopic composition of atmospheric carbon dioxide provides an
important constraint for models of the global carbon cycle. It is
shown that carbon in C4 plants preserves an isotopic record of the
CO2 used in photosynthesis. Data for the maize plant Zea mays yield
results for the isotopic composition of atmospheric CO2 consistent
with measurements of modern air and air trapped in polar ice. Data
from C4 plants may thus be used to extend the isotopic record of
atmospheric CO2 into the past, complementing data from other
sources.

corn/Zea mays

KEYWORDS: C4, CARBON CYCLE, ISOTOPE DISCRIMINATION, PRE-INDUSTRIAL
CO2 CONCENTRATION

460  
Mari Torres, J. 1989. Influence of Carbon Dioxide Dosing on the
Photosynthetic Response and Its Relationship with the Production of
Different Light Saturation Plants. Doctoral Dissertation,
University of Barcelona, Dissertation Abstracts Vol. 51:01-C, p.29
(297 pp.).

In plants of Fatsia japonica and Pelargonium x hortorum cv.
Silipen, grown in controlled environment conditions, three growth
treatments with CO2 were carried out: (a) control (constant normal
CO2 at 340 vpm), (b) selective enrichment (CO2 constant at 800 vpm
during the first two and last two hours of the day, maintaining it
at 340 vpm during the rest of the day), and (c) constant CO2
enrichment (800 vpm). After three weeks of growth, experiments were
carried out on daily courses (gas exchange, water potential, etc.)
in nine different treatments (each growth treatment was measured in
its CO2 conditions and in those of the other two), in two
populations of leaves of both species; and dry-matter production
analysis of different initial LAI plants, as well as other
observations (cellular and chloroplastic ultrastructure). The
growth treatments with CO2 enrichment gave rise to increases in
dry-matter production in both species. The percentage increases in
comparison with the control being, 34% and 45% in Pelargonium x
hortorum of medium LAI, 49% and 76% in Pelargonium x hortorum of
low LAI, and 77% and 77% in Fatsia japonica of medium LAI, in the
treatments with selective and constant CO2 enrichment respectively.
These increases were due to the effect of CO2 on the physiological
determinants of crop growth (Charles-Edwards). The most direct
effect is felt on the second determinant (the efficiency of the
conversion of light intercepted by vegetal material), on increasing
the net photosynthesis in an important way which reverts on the
first determinant (the quantity of intercepted radiation by the
crop) with the effect of autoacceleration and also additivity due
to the better water relations. The most relative efficiency of the
treatment with selective enrichment in relation to the continued
one was related to the mechanisms implied in the acclimatization
(photosynthetic and stomatic), each depending on the type of light
saturation of the plant, as well as on a negative effect of
autoshading in the continued CO2 enrichment treatment. In Spanish.

Fatsia japonica/Pelargonium hortorum

KEYWORDS: ANATOMY, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LIGHT
UTILIZATION EFFICIENCY, PHOTOSYNTHETIC ACCLIMATION, STOMATA

461  
Marks, S., and K. Clay. 1990. Effects of CO2 Enrichment, Nutrient
Addition, and Fungal Endophyte-Infection on the Growth of Two
Grasses. Oecologia 84:207-214.

Increasing atmospheric carbon dioxide (CO2) concentration is
expected to increase plant productivity and alter plant/plant
interactions, but little is known about its effects on symbiotic
interactions with microorganisms. Interactions between perennial
ryegrass, Lolium perenne (a C3 plant), and purpletop grass, Tridens
flavus (a C4 plant), and their clavicipitaceous fungal endophytes
(Acremonium lolii and Balansia epichloe, respectively) were
investigated by growing the grasses under 350 and 750 uL/L CO2 at
two nutrient levels. Infected and uninfected perennial ryegrass
responded with increased growth to both CO2 enrichment and nutrient
addition. Biomass and leaf area of infected and uninfected plants
responded similarly to CO2 enrichment. When growth analysis
parameters were calculated, there were significant increases in
relative growth rate and net assimilation rate of infected plants
compared to uninfected plants, although the differences remained
constant across CO2 and nutrient treatments. Growth of purpletop
grass did not increase with CO2 enrichment or nutrient addition and
there were no significant differences between infected and
uninfected plants. CO2 enrichment did not alter the interactions
between these two host grasses and their endophytic-fungal
symbionts.

Lolium perenne/perennial ryegrass/Tridens flavus/purpletop grass

KEYWORDS: ACREMONIUM LOLII, BALANSIA EPICHLOE, C3, C4, CONTROLLED
ENVIRONMENT CHAMBERS, GRASSES, GROWTH ANALYSIS, NUTRITION, PLANT-FUNGUS INTERACTIONS, SOIL MICROORGANISMS

462  
Marks, S., and B.R. Strain. 1989. Effects of Drought and CO2
Enrichment on Competition between Two Old Field Perennials. New
Phytologist 111:181-186.

We studied the effects of drought stress and CO2 enrichment on the
competition between Aster pilosus Willd. (aster, C3) and Andropogon
virginicus L. (broomsedge, C4) under two CO2 concentrations (350
and 650 uL/L CO2) and two water treatments (well-watered and water-limited). Although broomsedge is the more drought-tolerant species,
this did not increase its competitive ability against aster under
drought conditions. With CO2 enrichment, aster was a stronger
competitor than broomsedge and comprised 75% of above-ground pot
biomass in both water treatments. CO2 enrichment also increased
aster survival when competing with broomsedge under extreme drought
conditions. Although drought stress and CO2 enrichment interacted
to affect the two species in different ways, there was no
interaction of drought stress and competition; aster was a stronger
competitor than broomsedge under CO2 enrichment in both well-watered and water-limited conditions. With future increases in the
atmospheric CO2 concentration, aster may delay broomsedge dominance
in old-field communities.

Aster pilosus/aster/broomsedge/Andropogon virginicus

KEYWORDS: C3, C4, CONTROLLED ENVIRONMENT CHAMBERS, OLD FIELD
COMMUNITIES, SPECIES COMPETITION, SUCCESSIONAL COMMUNITIES,
SURVIVORSHIP, TRANSPIRATION, WATER STRESS, WUE

463  
Martin, P. 1992. EXE: a Climatically Sensitive Model to Study
Climate Change and CO2 Enhancement Effects on Forests. Australian
Journal of Botany 40:717-735.

Vegetation plays a significant role in determining the local and
regional hydrology of ice-free continental surfaces and the
dynamics of the atmosphere above it. Vegetation also influences the
global climate directly by affecting atmospheric chemistry. In
particular, it partially controls the carbon cycle. In turn,
vegetation is influenced by climate and changes in the ambient
concentration of CO2. This may have important consequences for
agriculture and natural resource exploitation. A formal recognition
of atmosphere/biosphere interrelationships is crucial but
insufficient. Systematic investigations of the interactions between
climate, plant physiology and ecology are badly needed. In this
spirit, this paper presents the results of numerical simulations
performed with the Energy, water and momentum eXchange, and
Ecological dynamics (EXE) model at a local scale over periods of
400-800 (simulation) years. EXE constitutes a first attempt to
couple a physiologically based water budget and an explicit
atmospheric general circulation model (GCM). Within this context,
the paper demonstrates through the examples it analyses that both
potential stomatal response to CO2 and the possible range of
changes in atmospheric relative humidity are likely major factors
in determining the ecosystem response to greenhouse warming.
Consequently, they should be considered in future studies of this
kind. The paper also provides explanations regarding the movements
of ecotones, defined as the transition zones between different
vegetation assemblages. Taking the North American forest/prairie
boundary as a case study, the analysis of the results shows how, in
the greenhouse warmed world, St Paul, MN, might look like North
Platte, NE. Finally, building on the previous example by using two
different models, this study illustrates that results can be
strongly model dependent and encourages extreme caution in their
interpretation.

KEYWORDS: CLIMATE CHANGE, CONDUCTANCE, ECOSYSTEM LEVEL CO2
RESPONSES, ECOSYSTEM MODEL, EVAPOTRANSPIRATION, FOREST, GCM'S,
HUMIDITY, MODELING, SIMULATION

464  
Martin, P., N.J. Rosenberg, and M.S. McKenney. 1989. Sensitivity of
Evapotranspiration in a Wheat Field, a Forest, and a Grassland to
Changes in Climate and Direct Effects of Carbon Dioxide. Climatic
Change 14:117-151.

Micrometeorological and physiological measurements were used to
develop Penman-Monteith models of evapotranspiration for a wheat
field in eastern Nebraska, a forest in Tennessee, and a grassland
in east-central Kansas. The model fit the measurements well over
the periods of observation. Model sensitivities to changes in
climatic and physiological parameters were then analyzed. The range
of changes considered was established from recent general
circulation model output and from review of recent plant
physiological research. Finally, climate change scenarios produced
by general circulation models for the locations and seasons
matching the observed data were applied to the micrometeorological
models. Simulation studies show that when all climatic and plant
factors are considered, evapotranspiration estimates can differ
greatly from those that consider only temperature. Depending on
ecosystem and on climate and plant input used, evapotranspiration
can differ from the control (no climate or plant change) by about
-20 to +40%.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, EVAPOTRANSPIRATION, FOREST,
GCM'S, GRASSES, MODELING, SIMULATION

465  
Masle, J. 1992. Will Plant Performance on Soils Prone to Drought or
With High Mechanical Impedance to Root Penetration Be Improved
under Elevated Atmospheric CO2 Concentration? Australian Journal of
Botany 40:491-500.

Plants growing on dry soils or on soils with high mechanical
resistance to root penetration grow more slowly and exhibit lower
stomatal conductance than those growing on moist and loose soils.
In most situations in nature where edaphic stresses develop rather
slowly (compared to stresses imposed in most pot experiments
conducted under controlled conditions), photosynthesis is mainly
reduced via stomatal effects rather than via changes in mesophyll
capacity for photosynthesis. Elevated CO2 will induce an increase
in the internal partial pressure of CO2, despite stomatal
conductance being lowered even further. Photosynthesis will
therefore be improved, and leaf turgor will be increased. It is
widely thought that growth on dry or hard soils is not carbon
limited because levels of soluble carbohydrates in the leaves and
root cells are increased. It is shown in this paper than growth on
soil with high mechanical resistance does respond to elevated CO2.
However, this response is smaller than expected from the increase
of carbon assimilation rate because: (a) carbon partitioning is
altered so that supplementary carbohydrates are preferentially
allocated to the roots; (b) leaf growth sensitivity to internal
availability of sugars is lower than in plants growing on loose
soils. These alterations of 'sink activity' and carbon partitioning
are mediated by unknown signalling factor(s) induced in the roots.
It is not known whether the root factors acting in droughted plants
are of the same nature. In both droughted and impeded plants the
interacting effects of these factors and of ambient CO2 levels are
likely to result in improved transpiration efficiency. More
experiments are needed in this area, however, especially to
ascertain the relative contribution of changes in growth patterns
versus changes in the patterns of water use. In conclusion, the
importance of identifying the nature of the sink limitations
induced by root signals is emphasized. It is a fundamental area of
research to be developed not only for assessing growh responses to
rising CO2 under edaphic stress, but likely also for reconciling
conflicting responses of field-grown and pot-grown plants.

wheat/Triticum aestivum

KEYWORDS: ALLOCATION, CONDUCTANCE, REVIEW, ROOTS, SOIL RESISTANCE,
SOURCE-SINK BALANCE, WATER STRESS

466  
Masle, J., G.D. Farquhar, and R.M. Gifford. 1990. Growth and Carbon
Economy of Wheat Seedlings as Affected by Soil Resistance to
Penetration and Ambient Partial Pressure of CO2. Australian Journal
of Plant Physiology 17:465-487.

Wheat seedlings were grown on soils with different resistances to
root penetration and at various ambient partial pressures of CO2,
pa. The partial pressure pa was varied either (a) as soon as
seedlings emerged and until the end of the experiment (i.e., until
c. 2 weeks after sowing, until the three leaf stage) or (b) only
after the effects of high soil resistance were well established,
and then for two days. In the first week after emergence, a higher
soil resistance induced slower growth of both roots and shoot. This
effect was independent of pa. We conclude that at this stage, with
much of the plant's carbon being supplied from hydrolysis of seed
reserves, growth at high soil resistance was not C-source limited.
There was, however, a positive relationship between shoot growth
rate and the carbohydrate concentration in that tissue, the degree
of which varied with soil resistance. A given carbohydrate
concentration was associated with a lower growth rate at high,
compared with low, soil resistance. We deduced that this reduced
sensitivity of growth to internal availability of substrate
carbohydrate may be one manifestation of a sink limitation.
Subsequent to the first week following emergence, roots grew faster
on soil with higher resistance, while the shoot continued to grow
more slowly. As seed reserves were becoming exhausted, growth
became sensitive to pa, i.e. somewhat source-limited. This response
to partial pressure of CO2 was mainly seen in the roots. The
correlation between growth rate and carbohydrate levels was
maintained. We conclude that increased soil resistance induces a
factor which retards shoot growth, partly by decreasing its
sensitivity to carbohydrate levels, making more carbon available
for root growth. It is unclear whether or not this factor also
directly affects the physiology of the roots. A higher soil
resistance resulted in greater respiratory losses as a proportion,
phi, of carbon fixation. Reduced pa also induced greater phi.
Theory is developed relating phi to carbon assimilation, allocation
and maintenance. It leads to the prediction that respiratory
losses, as a proportion, phi, should be increased under most
environmental conditions which reduce relative growth rate.

wheat/Triticum aestivum

KEYWORDS: ALLOCATION, CARBOHYDRATES, CARBON BUDGET, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, ISOTOPE DISCRIMINATION,
NITROGEN, RESPIRATION, ROOTS, SOIL RESISTANCE, SOURCE-SINK BALANCE,
TRANSPIRATION

467  
Masuda, T., K. Fujita, K. Kogure, and S. Ogata. 1989. Effect of CO2
Enrichment and Nitrate Application on Vegetative Growth and
Dinitrogen Fixation of Wild and Cultivated Soybean Varieties. Soil
Science and Plant Nutrition 35:357-366.

A wild soybean variety (Glycine soja Sieb. and Zucc. line Nakei-No.
1) and a cultivated soybean variety (Glycine max L. Merr. cv.
Tamahomare) were subjected to CO2 enrichment and/or NO3-N
application (50 and 300 ppm), and the growth and dinitrogen
fixation in the vegetative growth stage were examined. 1. The whole
plant weight of the cultivated soybean variety was more promoted by
CO2 enrichment than by NO3-N application, while that of the wild
one was enhanced by NO3-N application compared with CO2 enrichment.
2. The dinitrogen-fixing activity which was lower in wild soybean
variety than in the cultivated one increased by CO2 enrichment in
both soybean varieties, when nitrate was not applied to the plants. 
The increase by CO2 enrichment was remarkable in the cultivated
soybean variety and was negligible in the wild one.  In both
soybean varieties, the dinitrogen-fixing activity decreased by the
application of 50 ppm NO3-N as a result of CO2 enrichment. 3. The
increment of whole plant N in the cultivated soybean variety was
markedly enhanced by either CO2 enrichment or NO3-N application,
while that in the wild soybean variety was slightly enhanced by
NO3-N application and did not change by CO2 enrichment.  However,
the simultaneous supply of CO2 and NO3-N enhanced remarkably the
increment of whole plant N in both soybean varieties. These results
indicate that the CO2 enrichment increased the dry matter
production in the cultivated soybean variety along with the
increase of dinitrogen-fixing activity, while in the wild one dry
matter production increased slightly.  On the other hand, the
increase of dry matter production by NO3-N application was less
appreciable in the cultivated soybean variety but larger in the
wild one compared with the increase by CO2 enrichment,
respectively.  The simultaneous supply of CO2 and NO3-N increased
remarkably the dry matter production in both soybean varieties. 
Therefore, it is assumed that the vegetative growth of the
cultivated soybean variety in predominantly limited by the
insufficient supply of photosynthates, whereas that of the wild one
is mainly limited by the insufficient supply of N due to lower
dinitrogen fixation by nodules.

soybean/Glycine max/Glycine soja

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN,
NITROGEN FIXATION, NITROGENASE ACTIVITY, NUTRITION

468  
Mauney, J.R., and D.L. Hendrix. 1988. Responses of Glasshouse Grown
Cotton to Irrigation with Carbon Dioxide-saturated Water. Crop
Science 28:835-838.

cotton/Gossypium hirsutum

KEYWORDS: FIZZ IRRIGATION, SOIL CO2 CONCENTRATION

469  
Mauney, J.R., K.F. Lewin, G.R. Hendrey, and B.A. Kimball. 1992.
Growth and Yield of Cotton Exposed to Free-Air CO2 Enrichment.
Critical Reviews in Plant Sciences 11:213-222.

This experiment successfully grew a cotton crop from germination to
maturity with controlled CO2 enrichment to 550 umol/mol using a
vertical vent pipe array to control the CO2 concentration. Four
replications were sufficient to obtain statistically significant
results. On Day Of Year (DOY) 220, 112 days after planting, the
FACE plots had 45% greater dry weight than controls. Thereafter,
the FACE plots added weight at a slower rate than the controls, so
that at the final harvest the difference was only 20%. The crop
allocated a greater proportion of its dry weight to roots in the
FACE plots than in the controls. On DOY235 when the total dry
weight increase was 39%, the root dry weight increase in the FACE
plots was 85%. The uniformity of the crop response within the plots
and between replications will allow a greater area to be used in
future experiments. The area for sampling crop responses can be
enlarged from the 12 m used in this experiment. It appears that 18
and perhaps 20 m of the 22-m diameter of the plots can be used for
sampling crop response.

cotton/Gossypium hirsutum

KEYWORDS: ALLOCATION, FACE, GROWTH, YIELD

470  
Mbikayi, N.T., D.R. Hileman, N.C. Bhattacharya, P.P. Ghosh, and
P.K. Biswas. 1988. Effects of CO2 Enrichment on the Physiology and
Biomass Production in Cowpeas (Vigna unguiculata L.) Grown in Open
Top Chambers. IN: Proceedings of the International Congress of
Plant Physiology, 15-20 February 1988, Vol. Vol.II (S.K. Sinha,
P.V. Sane, S.C. Bhargava, and P.K. Agrawal, eds.), Society for
Plant Physiology and Biochemistry, New Delhi, India, pp. 640-645.

This study was undertaken to investigate the effects of increased
concentrations of carbon dioxide on growth, physiology and biomass
production in cowpeas subjected to 354, 354 (ambient CO2 in open
chamber), 506 and 655 uL/L CO2. The CO2 enriched environment
increased plant height, fresh and dry weights of whole plant,
nodule numbers and mass, and protein-nitrogen in seeds. The effects
were most pronounced at 655 uL/L CO2. In contrast, stomatal
density, stomatal conductance and protein-nitrogen in roots
decreased at 655 as compared to 354 and 506 uL CO2/L.

Vigna unguiculata/cowpea

KEYWORDS: AGRICULTURE, CROPS, NODULATION, OPEN-TOP CHAMBERS,
PROTEINS, STOMATAL DENSITY, YIELD

471  
McLaughlin, S.B., and R.J. Norby. 1991. Atmospheric Pollution and
Terrestrial Vegetation: Evidence of Changes, Linkages, and
Significance to Selection Processes. IN: Ecological Genetics and
Air Pollution (G.E. Taylor Jr., L.F. Pitelka, and M.T. Clegg,
eds.), Springer Verlag, Inc., New York, pp. 61-101.

KEYWORDS: AIR POLLUTION, FOREST, REPRODUCTION, REVIEW, SELECTION
PRESSURE, SPECIES COMPETITION

472  
McMurtrie, R.E. 1991. Relationship of Forest Productivity to
Nutrient and Carbon Supply--a Modeling Analysis. Tree Physiology
9:87-99.

A simple model of photosynthetic and nutritional controls over
foliar dynamics is analyzed to compare the magnitude of the growth
response of forest stands to increased rates of photosynthesis and
nutrient supply. According to the model, productivity achieved at
canopy closure is sensitive to nutrient supply, except where
nutrient availability exceeds the plants' uptake capacity. Plants
growing under nutrient-limited conditions can only respond
positively to enhanced photosynthetic rates if they simultaneously
increase their nutrient uptake, or reduce nutrient concentrations
in stem, branch, root or senescing leaf tissue, or shift their
carbon allocation in favor of biomass components with low nutrient
concentrations. In particular, a response is more likely where
considerable internal cycling of nitrogen occurs before leaf
senescence, or where foliar allocation decreases with decreasing
leaf nutrient concentrations.

KEYWORDS: ALLOCATION, ECOSYSTEM LEVEL CO2 RESPONSES, MODELING,
NUTRITION

473  
McMurtrie, R.E., H.N. Comins, M.U.F. Kirschbaum, and Y.-P. Wang.
1992. Modifying Existing Forest Growth Models to Take Account of
Effects of Elevated CO2. Australian Journal of Botany 40:657-677.

Most published process models of the growth of forest stands are
concerned predominantly with either tree physiology or nutrient
cycling, concentrating respectively on photosynthetic carbon gain
and allocation, or on decomposition and nutrient uptake processes.
Mechanistic formulations of direct CO2 effects on photosynthesis
have been incorporated in some physiology-based models, whereas
modifications incorporating direct CO2 effect in nutrient-driven
models have usually been more empirical. Physiology-based models
predict considerable CO2-fertiliser effects, while nutrient driven
models tend to be less sensitive to elevated ambient CO2
concentration (Ca). This paper describes how effects of elevated Ca
can be incorporated in these various types of forest growth models.
The magnitude of the simulated response to elevated Ca varies
markedly depending on a particular model's spatial and temporal
resolution and on which processes are incorporated. Two physiology-based models of forest canopy processes (MAESTRO and BIOMASS) and
a plant-soil model (G'DAY) are considered here. MAESTRO and BIOMASS
incorporate mechanistic descriptions of the biochemical basis of
photosynthesis by C3 plants, while G'DAY contains a simplified
formulation but includes soil processes. All three models are used
to simulate the response to an instantaneous doubling of Ca.
Simulations of MAESTRO and BIOMASS show that on a clear day total
canopy photosynthesis is temperature-dependent with increases of
approximately 10, 45 and 70% at 10.25 and 40C respectively. A
simulation for a stand of Pinus radiata growing with abundant water
and nutrients and mean annual day-time temperature of 14.8C shows
an increase of 25% in annual canopy photosynthesis. On nutrient-limited sites plant responses to elevated Ca are constrained by
feedbacks associated with rates of decomposition and nutrient
cycling. According to the G'DAY model, which incorporates these
feedbacks, an instantaneous doubling of Ca leads to a 27% initial
productivity increase lasting less than a decade and a more modest
increase of 8% sustained in the long term.

KEYWORDS: CANOPY PHOTOSYNTHESIS, COMMUNITY LEVEL CO2 RESPONSES,
FOREST, LEAF PHOTOSYNTHESIS, MODELING, NITROGEN, NUTRIENT CYCLING,
QUANTUM REQUIREMENT, SOIL, TEMPERATURE

474  
McMurtrie, R.E., and Y.-P. Wang. 1993. Mathematical Models of the
Photosynthetic Response of Tree Stands to Rising CO2 Concentrations
and Temperatures. Plant, Cell and Environment 16:1-13.

Two published models of canopy photosynthesis, MAESTRO and BIOMASS,
are simulated to examine the response of tree stands to increasing
ambient concentrations of carbon dioxide (Ca) and temperatures. The
models employ the same equations to described leaf gas exchange,
but differ considerably in the level of detail employed to
represent canopy structure and radiation environment. Daily rates
of canopy photosynthesis simulated by the two models agree to
within 10% across a range of CO2 concentrations and temperatures.
A doubling of Ca leads to modest increases of simulated daily
canopy photosynthesis at low temperatures (10% increase at 10C),
but larger increases at higher temperatures (60% increase at 30C).
The temperature and CO2 dependencies of canopy photosynthesis are
interpreted in terms of simulated contributions by quantum-saturated and non-saturated foliage. Simulations are presented for
periods ranging from a diurnal cycle to several years. Annual
canopy photosynthesis simulated by BIOMASS for trees experiencing
no water stress is linearly related to simulated annual absorbed
photosynthetically active radiation, with light utilization
coefficients for carbon of epsilon = 1.66 and 2.07 g/MJ derived for
Ca of 350 and 700 umol/mol, respectively.

KEYWORDS: CANOPY PHOTOSYNTHESIS, FOREST, MODELING, RADIATION,
SIMULATION, TEMPERATURE, TREES

475  
Miao, S.L., P.M. Wayne, and F.A. Bazzaz. 1992. Elevated CO2
Differentially Alters the Responses of Co-ocurring Birch and Maple
Seedlings to a Moisture Gradient. Oecologia 90:300-304.

To determine the effects of elevated CO2 and soil moisture status
on growth and niche characteristics of birch and maple seedlings,
gray birch (Betula populifolia) and red maple (Acer rubrum) were
experimentally raised along a soil moisture gradient ranging from
extreme drought to flooded conditions at both ambient and elevated
atmospheric CO2 levels. The magnitude of growth enhancement due to
CO2 was largely contingent on soil moisture conditions, but
differently so for maple than for birch seedlings. Red maple showed
greatest CO2 enhancement under moderately moist soil conditions,
whereas gray birch showed greatest enhancements under moderately
dry soil conditions. Additionally, CO2 had a relatively greater
ameliorating effect in flooded conditions for red maple than for
gray birch, whereas the reverse pattern was true for these species
under extreme drought conditions. For both species, elevated CO2
resulted in a reduction in niche breadths on the moisture gradient;
5% for gray birch and 23% for red maple. Species niche overlap
(proportional overall) was also lower at elevated CO2 (0.98 to:
0.88:11%). This study highlights the utility of experiments
crossing CO2 levels with gradients of other resources as effective
tools for elucidating the potential consequences of elevated CO2 on
species distributions and potential interactions in natural
communities.

Betula populifolia/Acer rubrum/red maple/grey birch

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, WATER STRESS

476  
Miglietta, F., and A. Raschi. 1993. Studying the Effect of Elevated
CO2 in the Open in a Naturally Enriched Environment in Central
Italy. Vegetatio 104/105:391-400.

A gas vents area was recently localized in Central Italy. The gas
emitted from the vents is composed by 92% of carbon dioxide and
this produces an anomaly in the composition of the atmosphere over
an area of about 2 ha. Atmospheric carbon dioxide concentration was
measured by means of an infrared gas analyzer and diffusion tubes
in several points and for some days within the area. Measurements
revealed that the site can be at least divided into three sub-areas
having increasing CO2 concentration in the air. A preliminary
analysis of natural vegetation in the area was conducted by
counting stomatal and epidermal cells number and measuring guard
cell size on leaves of several oak trees growing both near and far
away from the vents. This analysis suggested that elevated CO2 may
have reduced the size of guard cells leaving stomatal density and
stomatal index unaltered.

KEYWORDS: AIR POLLUTION, STOMATAL DENSITY, STOMATAL INDEX

477  
Miller, W.F., P.M. Dougherty, and G.L. Switzer. 1987. Effect of
Rising Carbon Dioxide and Potential Climate Change on Loblolly Pine
Distribution, Growth, Survival, and Productivity. IN: The
Greenhouse Effect, Climate Change, and U.S. Forests (W.E. Shands
and J.S. Hoffman, eds.), The Conservation Foundation, Washington,
D.C., pp. 157-187.

An appreciable northward and northeastward shift in the range of
loblolly pine is forecast by the year 2080. The projected southern
boundary of the range may extend from the central Louisiana through
central Mississippi and central Alabama, and then through northern
Georgia, northern South Carolina, and eastern North Carolina. An
increase in the probability of summer drought, with durations of up
to three months, is also projected throughout the southern portion
of the adjusted range. Yields are expected to be reduced over much
of the range because of reduced soil water and changes in the
edaphic substrates in the adjusted range. Regeneration practices
probably will have to be modified to ameliorate the effects of the
anticipated climatic change. Ripping, the use of containerized
seedlings, and increased herbaceous weed control probably will be
necessary under the expected changed conditions to assure
satisfactory regeneration success. Tree-breeding programs should be
dynamic, anticipating the possibility of range shift and reduced
productive potential. Predictions of reduced productive potentials
may be overly pessimistic in view of the possibility of increased
water-use efficiency related to elevated carbon dioxide levels.

Pinus taeda/loblolly pine

KEYWORDS: CLIMATE CHANGE, GCM'S, REVIEW, SPECIES RANGE, TREES,
WATER STRESS, WUE, YIELD

478  
Miszalski, Z., and J. Mydlarz. 1990. SO2 Influence on
Photosynthesis of Tomato Plants (Lycopersicon esculentum L.) at
Different CO2 Concentrations. Photosynthetica 24:2-8.

The net photosynthetic rate (Pn) decrease after SO2 fumigation of
tomato plants (Lycopersicon esculentum L. cv. Gem) was strongly
dependent on the CO2 level in the plants' atmosphere, especially in
the post-fumigation period. Differences in SO2 action mode at
different CO2 concentrations did not depend directly on Pn.

tomato/Lycopersicon esculentum

KEYWORDS: AIR POLLUTION, HORTICULTURAL CROPS, PHOTOSYNTHESIS

479  
Miszalski, Z., and H. Ziegler. 1989. Sulfite Sensitivity of Oat
(Avena sativa L.) Protoplasts. Biochemie und Physiologie der
Pflanzen 185:233-243.

Determination of the efflux of K+ and 14C fixation products showed
isolated oat protoplasts to be in good condition after 1 h
incubation in 10 mM sulfide. Evolution of O2 in light by
protoplasts incubated in darkness for up to 90 min at 25C did not
change significantly, but after incubation in light the
photosynthesis rate slowly decreased. The decrease in the
photosynthesis rate after incubation in the presence of 10 mM
sulfite when measured with the 14C fixation method is much smaller
than when measured by O2 evolution. This suggests strong sulfite
oxidation. Using both methods it was found that protoplasts
incubated in a medium with sulfite and 1 mM bicarbonate at pH 7.0
were more sensitive than when incubated with 5 mM bicarbonate at pH
7.6. Data presented here show that the lower sensitivity to SO2 of
plants at high CO2 concentration is not only due to higher stomatal
resistance but also to differences in sensitivity of mesophyll
cells.

oat/Avena sativa

KEYWORDS: AIR POLLUTION, PHOTOSYNTHESIS

480  
Mitchell, R. 1990. Uncertainty in Prediction of Effects of
Environmental Change on Wheat Yields. IN: The Greenhouse Effect and
Primary Productivity in European Agro-ecosystems; 5-10 April 1990;
Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H.
van Laar, eds.), Pudoc, Wageningen, pp. 51-52.

wheat/Triticum aestivum

KEYWORDS: AGRICULTURE, CROP MODEL, LEAF AREA DEVELOPMENT, MODELING,
SIMULATION, TEMPERATURE, YIELD

481  
Mo, G., D. Nie, M.B. Kirkham, H. He, L.K. Ballou, F.W. Caldwell,
and E.T. Kanemasu. 1992. Root and Shoot Weight in a Tallgrass
Prairie under Elevated Carbon Dioxide. Environmental and
Experimental Botany 32:193-201.

The atmospheric concentration of carbon dioxide (CO2) is increasing
and knowing how this will affect native vegetation is important.
The objective of this study was to determine the effect of elevated
CO2 on root growth in a tallgrass prairie kept at a high water
level (73 cm of water in a 200 cm soil profile) and a low water
level (66 cm of water in 200 cm). Sixteen cylindrical plastic
chambers were placed on the prairie to maintain two levels of CO2
(ambient or twice ambient). At the end of two seasons' exposure to
the different treatments, dry weight and length of roots in the 0-40 cm depth were determined. Shoot growth also was measured to
determine shoot:root ratios. The CO2 and water treatments had no
significant effect on root dry weight in the 0-40 cm depth. In the
0-10 cm depth, doubled CO2 reduced dry weight and length of roots
of plants grown under the high water level by 47 and 31%,
respectively. Warm-season, C4 grasses had the highest shoot dry
weight, which was greatest under the high water, ambient CO2
treatment. The shoot:root ratio did not change with treatment.

Andropogon gerardii/big bluestem/Andropogon scoparius/little
bluestem/Sorghastrum nutans/Indiangrass/Sporobolus asper/tall
dropseed/Panicum virgatum/switchgrass/Bouteloua
curtipendula/sideoats grama/Dichanthelium oligosanthes/Scribner
panicum/Poa pratensis/Kentucky bluegrass/Carex spp./Artemisia
ludoviciana/Louisiana sagewort/Ambrosia spp./ragweed/Aster
spp./aster/Amorpha canescens/lead plant/Asclepias
spp./milkweed/Kuhnia eupatorioides/false boneset/Salva
pitcheri/pitcher's sage/Solidago spp./golden rod/Rosa
arkansana/Arkansas rose

KEYWORDS: ALLOCATION, C3, C4, FORBS, GRASSES, ROOT:SHOOT RATIO,
ROOTS, SEDGES, TALLGRASS PRAIRIE, WATER STRESS

482  
Moe, R., and L.M. Mortensen. 1986. CO2 Enrichment in Norway. IN:
Status and CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.),
Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc.,
Boca Raton, Florida, pp. 59-73.

In the last years it has been a great upsurge in the interest for
CO2 enrichment of greenhouse crops in Norway. The sources of CO2
are mainly pure liquid CO2 from containers, followed by kerosene
and propane burning. Due to risk of air pollution (CO, C2H4, SO2,
NOx) by use of kerosene and propane, pure CO2 is recommended to
sensitive crops (for example, tomato, cucumber, and flowering
plants). Kerosene burning is mainly used in lettuce crops in
Norway. Equipment for control of CO2 supply and measurement of the
CO2 concentration in the greenhouse atmosphere is available. The
cause of increasing interest in CO2 application in Scandinavia is
better knowledge about the effects of CO2 enrichment on different
crops, more knowledgeable growers, tighter greenhouses, and reduced
CO2 flux from decomposition of organic material. Results from
research are presented as well as practical experiences in
Norwegian greenhouse operations. In the research some of the most
important greenhouse species have been studied. The overall effects
of CO2 enrichment are fast growth rate, increased yields, and
improved plant quality. An important observation is the beneficial
effect of CO2 application at low light levels during the winter
months (October to March) in Scandinavia. CO2 enrichment lowers the
light compensation point and makes artificial lighting more
profitable. On basis of the results, a CO2 level of 800 to 1000
uL/L is recommended for most species. Intermittent CO2 enrichment
showed promising results in chrysanthemums and further research is
following up the idea that intermittent CO2 application might be as
beneficial as continuous CO2 application. CO2 enrichment seems to
increase the optimum temperature for photosynthesis and growth.
More research on intermittent CO2 enrichment and temperature/CO2
interaction studies is needed before final conclusions can be made.

KEYWORDS: CO2 SOURCES, COMMERCIAL USE OF CO2, ENVIRONMENTAL
INTERACTIONS, EXPOSURE METHODS, GREENHOUSE, HORTICULTURAL CROPS,
INTERMITTENT ENRICHMENT, OXYGEN, PHOTOSYNTHESIS, REVIEW

483  
Mohapatra, P.K. 1990. CO2 Enrichment and Physiology of
Inflorescence Development in Wheat. Photosynthetica 24:9-15.

The effect of CO2 fertilization on growth, development and sucrose
concentration of the shoot apex of wheat plants (Triticum aestivum
L. cv. Warimba) growing in a controlled environment growth cabinet
(photoperiod 16h, irradiance 375 umol/m2/s, and temperature 20 +/-
1C) was observed. CO2 enrichment from germination onwards
stimulated shoot growth, but did not affect the growth, morphology
and sugar concentration of the inflorescence on the main shoot.

wheat/Triticum aestivum

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES,
GROWTH STAGES, REPRODUCTION

484  
Mooney, H.A., B.G. Drake, R.J. Luxmoore, W.C. Oechel, and L.F.
Pitelka. 1991. Predicting Ecosystem Responses to Elevated CO2
Concentrations. BioScience 41:96-104.

KEYWORDS: C3, C4, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST, OPEN-TOP
CHAMBERS, PHOTOSYNTHESIS, REVIEW, SALT MARSH, TRACKING CHAMBERS,
TUNDRA

485  
Morin, F., M. Andre, and T. Betsche. 1992. Growth Kinetics,
Carbohydrate, and Leaf Phosphate Content of Clover (Trifolium
subterraneum L.) after Transfer to a High CO2 Atmosphere or to High
Light and Ambient Air. Plant Physiology 99:89-95.

Intact air-grown (photosynthetic photon flux density, 400
microeinsteins per square meter per second) clover plants
(Trifolium subterraneum L.) were transferred to high CO2 (4000
microliters CO2 per liter; photosynthetic photon flux density, 400
microeinsteins per square meter per second) or to high light (340
microliters CO2 per liter; photosynthetic photon flux density, 800
microeinsteins per square meter per second) to similarly stimulate
photosynthetic net CO2 uptake. The daily increment of net CO2
uptake declined transiently in high CO2, but not in high light,
below the values in air/standard light. After about 3 days in high
CO2, the daily increment of net CO2 uptake increased but did not
reach the high light values. Nightly CO2 release increased
immediately in high light, whereas there was a 3-day lag phase in
high CO2. During this time, starch accumulated to a high level, and
leaf deterioration was observed only in high CO2. After 12 days,
starch was two- to threefold higher in high CO2 than in high light,
whereas sucrose was similar. Leaf carbohydrates were determined
during the first and fourth day in high CO2. Starch increased
rapidly throughout the day. Early in the day, sucrose was low and
similar in high CO2 and ambient air (same light). Later, sucrose
increased considerably in high CO2. The findings that (a) much more
photosynthetic carbon was partitioned into the leaf starch pool in
high CO2 than in high light, although net CO2 uptake was similar,
and that (b) rapid starch formation occurred in high CO2 even when
leaf sucrose was only slightly elevated suggest that low sink
capacity was not the main constraint in high CO2. It is proposed
that carbon partitioning between starch (chloroplast) and sucrose
(cytosol) was perturbed by high CO2 because of the lack of
photorespiration. Total phosphate pools were determined in leaves.
Concentrations based on fresh weight of orthophosphate, soluble
esterified phosphate, and total phosphate markedly declined during
13 days of exposure of the plants to high CO2 but changed little in
high light/ambient air. During this time, the ratio of
orthophosphate to soluble esterified phosphate decreased
considerably in high CO2 and increased slightly in high
light/ambient air. It appears that phosphate uptake and growth were
similarly stimulated by high light, whereas the coordination was
weak in high CO2.

clover/Trifolium subterraneum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, CONTROLLED
ENVIRONMENT CHAMBERS, LIGHT, PHOSPHORUS, RESPIRATION, SOURCE-SINK
BALANCE

486  
Morison, J.I.L. 1987. Intercellular CO2 Concentration and Stomatal
Response to CO2. IN: Stomatal Function (E. Zeiger, G.D. Farquhar,
and I.R. Cowan, eds.), Stanford University Press, Stanford,
California, pp. 229-251.

KEYWORDS: C3, C4, CAM, CI:CA, CONDUCTANCE, LIGHT, REVIEW, STOMATA,
TEMPERATURE, VPD, WUE

487  
Morison, J.I.L. 1987. Plant Growth and CO2 History. Nature 327:560.

KEYWORDS: PRE-INDUSTRIAL CO2 CONCENTRATION, STOMATAL DENSITY, WUE

488  
Morison, J.I.L. 1988. Effect of Increasing Atmospheric CO2 on
Plants and Their Responses to Other Pollutants, Climatic and Soil
Factors. Aspects of Applied Biology 17:113-122.

The profound effects of increased atmospheric CO2 on plant growth
are described. The interactions of increased CO2 with low light,
water supply, low temperature and other pollutants are shown to be
substantial. It is suggested that for the quantitative prediction
of plant growth in future atmospheres the traditional physiological
research needs to be accompanied by more studies at the crop and
community level of organisation.

KEYWORDS: AIR POLLUTION, COMMUNITY LEVEL CO2 RESPONSES,
ENVIRONMENTAL INTERACTIONS, LIGHT, REVIEW, TEMPERATURE, WATER
STRESS

489  
Morison, J.I.L. 1989. Plant Growth in Increased Atmospheric CO2.
IN: Proceedings of the Community of European Communities Symposium,
Carbon Dioxide and Other Greenhouse Gases: Climatic and Associated
Impacts; 3-5 November 1986; Brussels, Belgium (R. Fantechi and A.
Ghazi, eds.), Kluwer Academic Publishers, Dordrecht, The
Netherlands, pp. 228-244.

The major direct and indirect effects of increasing atmospheric CO2
concentration on plant growth are discussed. The physiological
processes likely to be affected include net photosynthesis,
partitioning and development and stomatal conductance. Attention is
drawn to problems in extrapolating from short term experiments and
measurements at low scales of organisation to likely effects of CO2
in the field. In particular, it is argued that the likely
magnitudes of the negative feedbacks between canopy evaporation,
canopy temperature, soil evaporation and local and regional vapour
pressure deficit are such that many predictions have overestimated
the decrease of evaporation from crops. The increasing
contributions that mechanistic crop-weather models formulated at
the level of whole canopies will make to exploring the sensitivity
of plant growth to increased CO2 is highlighted.

KEYWORDS: ALLOCATION, CONDUCTANCE, EVAPOTRANSPIRATION, MODELING,
PHOTOSYNTHETIC ACCLIMATION, PHYSIOLOGICAL CO2 RESPONSES, REVIEW,
SCALING, WATER STATUS

490  
Morison, J.I.L. 1990. Plant and Ecosystem Responses to Increasing
Atmospheric CO2. Tree 5:69-70.

KEYWORDS: C3, C4, CLIMATE CHANGE, ECOSYSTEM LEVEL CO2 RESPONSES,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, REVIEW, SALT MARSH, TUNDRA

491  
Morison, J.I.L. 1993. Response of Plants to CO2 under Water Limited
Conditions. Vegetatio 104/105:193-209.

The influence of increased atmospheric CO2 on the interaction
between plant growth and water use is proving to be one of the most
profound impacts of the anthropogenic 'Greenhouse Effect'. This
paper illustrates the interaction between CO2 and water in plant
growth at a range of scales. Most published work has concentrated
on water use efficiency, especially at shorter time scales, and has
shown large increases of leaf water use efficiency with increased
CO2. However, the magnitude of the effect is variable, and does not
consistently agree with predictions from simple leaf gas exchange
considerations. The longer the time scales considered, the less the
information and the more the uncertainty in the response to CO2,
because of the additional factors that have to be considered, such
as changes in leaf area, respiration of non-photosynthetic tissues
and soil evaporation. The need for more detailed studies of the
interactions between plant evaporation, water supply, water status
and growth is stressed, as increased CO2 can affect all of these
either directly, or indirectly through feedbacks with leaf gas
exchange, carbon partitioning, leaf growth, canopy development and
root growth.

KEYWORDS: EVAPOTRANSPIRATION, MODELING, REVIEW, WUE

492  
Moroney, J.V., R.K. Togasaki, H.D. Husic, and N.E. Tolbert. 1987.
Evidence That an Internal Carbonic Anhydrase Is Present in 5% CO2-Grown and Air-Grown Chlamydomonas. Plant Physiology 84:757-761.

Inorganic carbon (Ci) uptake was measured in wild-type cells of
Chlamydomonas reinhardtii and in cia-3, a mutant strain of C.
reinhardtii that cannot grow with air levels of CO2. Both air-grown
cells, that have a CO2 concentrating system, and 5% CO2-grown cells
that do not have this system, were used. When the external pH was
5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon
(Ci) and this accumulation was enhanced when the permeant carbonic
anhydrase inhibitor, ethoxyzolamide, was added. When the external
pH was 5.1, 5% CO2-grown cells also accumulated some Ci, although
not as much as air-grown cells and this accumulation was stimulated
by the addition of ethoxyzolamide. At the same time, ethoxyzolamide
inhibited CO2 fixation by high CO2-grown, wild-type cells at both
pH 5.1 and 7.3. These observations imply that 5% CO2-grown, wild-type cells, have a physiologically important internal carbonic
anhydrase, although the major carbonic anhydrase located in the
periplasmic space is only present in air-grown cells. Inorganic
carbon uptake by cia-3 resemble those of wild-type cells that have
been treated with ethoxyzolamide. It is concluded that an internal
carbonic anhydrase is under different regulatory control than
periplasmic carbonic anhydrase.

Chlamydomonas reinhardtii

KEYWORDS: ALGAE, AQUATIC PLANTS, CARBONIC ANHYDRASE, CELL CULTURE

493  
Mortensen, L.M. 1985. Nitrogen Oxides Produced during CO2
Enrichment. I. Effects on Different Greenhouse Plants. New
Phytologist 101:103-108.

Plants were grown in chambers with CO2 enrichment (1000 uL/L) and
with or without the addition of 0.85 uL/L nitrogen oxides (NOx).
The following species were tested: Lactuca sativa (lettuce),
Cucumis sativus (cucumber), Lycopersicon esculentum (tomato),
Saintpaulia ionantha, Rosa, Kalanchoe blossfeldiana, Chrysanthemum
x morifolium, Helxine soleirolii, Hedera helix, and Nephrolepis
exaltata. All species responded positively to an increase in CO2
level from 330 to 1000 uL/L. The dry weights of tomato, roses and
Saintpaulia responded negatively to the addition of NOx. In tomato,
the reduced dry weight was due to reduction in shoot length and
leaf area. In roses the stem was shorter and in Saintpaulia the
leaves smaller when NOx was added. Furthermore, the time to
flowering increased and number of flowers/flower buds decreased in
Saintpaulia.

Lactuca sativa/lettuce/Cucumis sativus/cucumber/Lycopersicon
esculentum/tomato/Saintpaulia ionantha/Rosa/Kalanchoe
blossfeldiana/Chrysanthemum morifolium/Helxine soleirolii/Hedera
helix/English ivy/Nephrolepis exaltata

KEYWORDS: AIR POLLUTION, CONTROLLED ENVIRONMENT CHAMBERS,
FLOWERING, GROWTH, HORTICULTURAL CROPS

494  
Mortensen, L.M. 1985. Nitrogen Oxides Produced during CO2
Enrichment. II. Effects on Different Tomato and Lettuce Cultivars.
New Phytologist 101:411-415.

Eight cultivars of Lycopersicon esculentum (tomato) and six
cultivars of Lactuca sativa (lettuce) were subjected to CO2-enriched air (1000 uL/L) containing 0.7 or 0.9 uL/L nitrogen oxides
(NOx). CO2 enrichment without NOx significantly increased the dry
weight of all tomato (35-81%) and lettuce cultivars (25-101%). In
six of the eight tomato cultivars the dry weight was reduced by the
addition of NOx. The mean relative growth rate (RGR) decreased by
4-19% depending on the cultivar. This meant that the benefit of CO2
enrichment was almost completely eliminated in most of the
cultivars. Marginal leaf necrosis appeared in some of the
cultivars, while in others no visible injury developed. None of the
lettuce cultivars was significantly affected by the addition of
NOx.

Lycopersicon esculentum/tomato/Lactuca sativa/lettuce

KEYWORDS: AIR POLLUTION, CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR
RESPONSES, GROWTH, GROWTH ANALYSIS, HORTICULTURAL CROPS

495  
Mortensen, L.M. 1986. Effect of Intermittent as Compared to
Continuous CO2 Enrichment on Growth and Flowering of Chrysanthemum
x morifolium Ramat. and Saintpaulia ionantha H. Wendl. Scientia
Horticulturae 29:283-289.

Plants of three cultivars of Saintpaulia ionantha and Chrysanthemum
x morifolium were grown until flowering at 335 (normal) or 900 uL/L
CO2 (high). Continuous high CO2 concentration increased the final
dry weights from 76 to 126% in Saintpaulia and from 15 to 32% in
Chrysanthemum compared to the normal concentration. Changing the
CO2 concentration from normal to high (intermittent) in intervals
of 1 h resulted in dry weights intermediate to that of constant
normal or constant high CO2 concentrations in both species. Morning
and evening enrichment gave the same effect as 1-h intermittent
enrichment in Saintpaulia. High CO2 concentration given every other
day gave the same effect as 1-h intermittent CO2 in Chrysanthemum.
Increased dry weights were accompanied by more and larger leaves in
Saintpaulia, and mainly by thicker and longer stem and more lateral
breaks in Chrysanthemum. Time to flowering was significantly
reduced by CO2 enrichment in Saintpaulia, but was generally not
affected in Chrysanthemum. Number of flowers and flowerbuds was
increased by CO2 application in both species. Constant high CO2
concentration generally had effects superior to that of the
intermittent treatments.

chrysanthemum/Saintpaulia ionantha

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES,
FLOWERING, GROWTH ANALYSIS, HORTICULTURAL CROPS, INTERMITTENT
ENRICHMENT

496  
Mortensen, L.M. 1986. Nitrogen Oxides Produced during CO2
Enrichment. III. Effects on Tomato at Different Photon Flux
Densities. New Phytologist 104:653-660.

Seedlings of Lycopersicon esculentum (tomato) were subjected to
CO2-enriched air (1000 uL/L) containing 1.5 uL/L nitrogen oxides
(NOx) for 25 d at four photon flux densities (30, 95, 175, and 250
umol/m2/s PAR). CO2 enrichment without NOx significantly increased
the dry weights (47 to 93%) at all light levels. Addition of NOx
strongly reduced the mean dry weight at the lowest light level even
below that of the unenriched control. At the two highest light
levels, NOx reduced the dry weight, but much less than at the
lowest level. NOx caused severe leaf injury at the lowest light
level, but this effect disappeared with increased photon flux
density. A system was constructed for measurement of the net CO2
exchange rate (CER) for single plants. Short-term measurements
showed significant reductions of CER when the NO concentration was
increased from 0 to 9 uL/L at 550 umol/m2/s but almost no effect at
150 to 200 umol/m2/s. NO caused similar percentage reductions of
CER at 335 and 1000 uL/L CO2. The absorption of NO was not
significantly affected by increasing the photon flux density from
150 to 550 umol/m2/s.

Lycopersicon esculentum/tomato

KEYWORDS: AIR POLLUTION, CANOPY PHOTOSYNTHESIS, CONTROLLED
ENVIRONMENT CHAMBERS, HORTICULTURAL CROPS, LIGHT, TRANSPIRATION

497  
Mortensen, L.M. 1987. Review: CO2 Enrichment in Greenhouses. Crop
Responses. Scientia Horticulturae 33:1-25.

The interest in CO2 enrichment has risen and declined several times
throughout this century. During the last few years the interest of
CO2 enrichment has strongly increased, mainly due to a better
scientific understanding of how CO2 affects plants and due to the
introduction of non-polluting CO2 sources. CO2 enrichment decreases
the oxygen inhibition of photosynthesis and increases the net
photosynthesis in plants. This is the basis for increased growth
rates caused by CO2 at low as well as at high light levels.
Elevated CO2 concentrations also increase the optimal temperature
for growth. Pot plants, cut flowers, vegetables and forest plants
show very positive effects from CO2 enrichment by increased dry
weight, plant height, number of leaves and lateral branching. Plant
quality expressed by growth habit and number of flowers is often
enhanced by CO2 enrichment. The rooting of cuttings is often
stimulated by high CO2 levels. The optimal CO2 concentration for
growth and yield seems to lie between 700 and 900 uL/L and this CO2
level is generally recommended in greenhouses. CO2 concentrations
higher than 1000 uL/L might cause growth reductions and leaf
injuries, and certainly do increase the loss of CO2 due to leakage
from the greenhouse. Continuous CO2 enrichment during the light
period seems to be superior to intermittent CO2 application. CO2
enrichment during periods of ventilation of the greenhouse increase
the yield of cucumber, while some other species seem to be less
affected. Air pollution in connection with the burning of
hydrocarbons for CO2 enrichment might cause visible or invisible
injuries to plants. The safest source of CO2 is pure liquid CO2
from containers, which is recommended for general use for
greenhouse crops. Further research with the CO2 factor should
mainly be concentrated on how CO2 enrichment affects the optimal
levels of temperature and air humidity for plant growth and
quality.

KEYWORDS: CO2 SOURCES, COMMERCIAL USE OF CO2, CROPS, GROWTH,
INTERMITTENT ENRICHMENT, REVIEW, ROOTING, TREES

498  
Mortensen, L.M. 1991. Effects of Temperature, Light and CO2 Level
on Growth and Flowering of Miniature Roses. Norwegian Journal of
Agricultural Sciences 5:295-300.

The effect of different temperatures (18, 21, 24, 27 and 30C),
supplementary photosynthetic photon flux densities (2, 60 and 120
umol/m2/s PPFD) and CO2 concentrations (345 and 900 uL/L) on growth
and flowering of the miniature rose cultivar Orange Meillandina
were studied at 60N latitude during winter. Growth rate was very
low and few flowers developed at the lowest PPFD level irrespective
of temperature. When the PPFD level was increased to 60 umol/m2/s
plant dry weight and number of flowers increased significantly. A
further increase in PPFD level to 190 umol/m2/s gave a significant,
but smaller effect. Increasing the temperature from 18 to 30C at
the two highest PPFD caused an almost linear decrease in days until
sale (five open flowers), plant dry weight and plant height. The
effect of CO2 concentration (345 and 900 uL/L) was studied at 24C.
CO2 enrichment increased plant dry weight (15-25%) while there was
only a small effect or no effect at all on the other growth
parameters.

rose/Rosa

KEYWORDS: FLOWERING, GREENHOUSE, GROWTH, HORTICULTURAL CROPS,
LIGHT, TEMPERATURE

499  
Mortensen, L.M. 1992. Diurnal Photosynthesis and Transpiration of
Ficus benjamina L. as Affected by Length of Photoperiod, CO2
Concentration and Light Level. Acta Agriculturae Scandinavica,
Section B, Soil and Plant Sciences 42:100-105.

The diurnal net photosynthesis of Ficus benjamina L., cultivar
Cleo, was studied at different daylengths (12, 18 and 24 h/day),
photosynthetic photon flux densities (40 and 120 umol/m2/s PPFD)
and CO2 concentrations (350 and 700 umol/mol). Net photosynthesis
increased to a maximum after 5-6 and 6-7 h of light at 12 and 18
h/day photoperiods, respectively, followed by a decrease towards
the end of the photoperiod. At a photoperiod of 18 h/day similar
diurnal curves were found at 350 and 700 umol/mol CO2, and at 40
and 120 umol/m2/s PPFD. Five days after the photoperiod was changed
from 18 to 24 h/day the diurnal rhythm disappeared. Transpiration
followed the same diurnal rhythm as that for photosynthesis. The
water-use efficiency was enhanced by raising the CO2 concentration.
A decrease in the CO2 concentration from 700 to 350 umol/mol after
six days at high CO2 first significantly decreased the
photosynthesis, but three days later it reached the same level as
that at high CO2.

Ficus benjamina

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
DAYLENGTH, DIURNAL CYCLE, PHOTOSYNTHETIC ACCLIMATION, TRANSPIRATION

500  
Mortensen, L.M. 1992. Effects of Ozone Concentration on Growth of
Tomato at Various Light, Air Humidity and Carbon Dioxide Levels.
Scientia Horticulturae 49:17-24.

The effect of ozone (O3) concentration on the growth of
Lycopersicon esculentum was studied at different photosynthetic
photon flux densities (PPFD), relative air humidities (RH) and
carbon dioxide (CO2) concentrations. Increasing the O3
concentration from <10 to 85 nL/L for 6 h per day reduced the shoot
dry weight 35% at 70% RH and 62% at 90% RH. Increasing the PPFD
from 100 to 350 umol/m2/s significantly reduced the effect of O3 in
one of two experiments. The most pronounced interaction between RH,
PPFD and O3 was found on plant height. High O3 levels generally
decreased plant height at low PPFD and had no, or a stimulating,
effect on high PPFD. Raising the RH from 70 to 90% significantly
increased the negative effect of O3 on height. Increasing the O3
concentration from <10 to 65 nL/L significantly decreased plant
height at low CO2 concentration (300-340 uL/L), but small effects
were found at high CO2 concentration (700-800 uL/L).

tomato/Lycopersicon esculentum

KEYWORDS: AIR POLLUTION, GROWTH, HORTICULTURAL CROPS, LIGHT, OZONE,
RELATIVE HUMIDITY, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

501  
Mortensen, L.M., and H.R. Gislerod. 1989. Effect of CO2, Air
Humidity, and Nutrient Solution Concentration on Growth and
Transpiration of Begonia x hiemalis Fotsch. Gartenbauwissenschaft
54:184-189.

The effects of CO2 concentration, relative air humidity (RH), and
concentration of the nutrient solution (NC) were studied on Begonia
x hiemalis plants in growth rooms. The plants were grown from
rooted cuttings until flowering at a photon flux density of 110
umol/m2/s. Plant dry weight was significantly increased by
increasing the CO2 concentrations from 340 to 900 uL/L at normal
(2.0 mS/cm) and high NC (4.0 mS/cm), but not at the low level (1.0
mS/cm). Number of leaves and flowers were enhanced by CO2
enrichment at normal and high NC, but no effects were found at low
NC. The effect of CO2 enrichmewnt on dry weight was larger at 60
than at 85% RH. Increasing the RH-level from 60 to 85% particularly
increased the dry weight at 340 uL/L CO2 at normal and high NC. A
normal NC generally gave the best growth of the plants. A high NC,
however, counteracted the negative effects of high RH on plant
quality (large leaves and voluminous plants). Transpiration or
water consumption of the plants was strongly decreased by either
increasing the CO2 or RH level.

Begonia hiemalis

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, HORTICULTURAL CROPS,
HUMIDITY, NUTRITION

502  
Mortensen, L.M., and R. Moe. 1992. Effects of CO2 Enrichment and
Different Day/Night Temperature Combinations on Growth and
Flowering of Rosa L. and Kalanchoe blossfeldiana v. Poelln.
Scientia Horticulturae 5:145-153.

The effects of increasing the CO2 concentration from 350 to 700
uL/L on growth and flowering of Rosa L. and Kalanchoe blossfeldiana
at four different day/night temperature combinations (20/20C,
23/14C and 17/26C day/night, and 20/20C with 2 h at 14C in the
morning) were studied in 6 growth chambers. An increase in the CO2
concentration resulted in enhanced total dry weight, stem:leaf
fresh weight ratio, flower fresh weight, length and diameter of the
rose shoot, while the number of days until flowering was not
affected. With the 17/26C treatment, rose shoots were 3-4 cm
shorter, and with the 23/14C treatment flowering occurred about 2
days earlier than with the other temperature treatments. The
results were the same for Rosa cultivars 'Frisco' and 'Kiss'. No
significant interactions between CO2 and temperature were found.
Plant dry weight and fresh weight of flowers in Kalanchoe were
generally enhanced by CO2 enrichment. The effects of CO2 on dry
weight, plant height and flower stem length were greater with the
23/14C treatment compared with the effects of the other
temperature treatments. A constant temperature (20/20C) and the
23/14C treatments gave the shortest and tallest plants,
respectively.

Rosa/rose/Kalanchoe blossfeldiana

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, FLOWERING,
GROWTH, HORTICULTURAL CROPS, TEMPERATURE

503  
Mortensen, L.M., and M. Sandvik. 1987. Effects of CO2 Enrichment at
Varying Photon Flux Density on the Growth of Picea abies (L.)
Karst. Seedlings. Scandinavian Journal of Forest Research 2:335-342.

Seedlings of Norway spruce (Picea abies (L.)) were grown at 335 and
1000 uL CO2/L for 118 days in growth rooms at different irradiance
levels. Photon flux density ranging from 8.6 to 34.6 mol/m2/day
(PAR) was given either as constant light or as alternating levels
in intervals of two or six hours. CO2 enrichment increased the
plant dry weight from 36% to 105% by increasing photon flux density
from 8.6 to 25.9 mol/m2/day. At constant light the dry weight
apparently reached its maximum at a photon flux density of 25.9
mol/m2/day. At the lower radiation levels alternating in CO2
enriched air gave slightly higher dry weights compared to constant
light levels. At the highest radiations the effect on dry weight
was the opposite. High CO2 concentration and 300 umol/m2/s constant
light (25.9 mol/m2/day) gave the best growth and quality of plants.
Top, root, stem and foliage weight were proportionally affected.
Shoot length was enhanced by CO2 enrichment. Shoot weight per cm
was substantially increased both by CO2 enrichment and increasing
photon flux density.

Picea abies/Norway spruce

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
LIGHT, TREES

504  
Mortensen, L.M., and R. Ulsaker. 1985. Effect of CO2 Concentration
and Light Levels on Growth, Flowering and Photosynthesis of Begonia
x hiemalis Fotsch. Scientia Horticulturae 27:133-141.

Increasing the CO2 concentration from 330 to 900 uL/L significantly
increased the dry weight, number of leaves and flowers and reduced
the time until flowering at a range of light levels (45, 130, 270
and 390 umol/m2/s). The mean relative growth rate was enhanced 16%
by CO2 enrichment. The plants flowered 7 days earlier in CO2-enriched air at the lowest light level, but not earlier at the
highest level. Generally the effect of increasing the CO2
concentration from 900 to 1500 uL/L was negligible. Increasing the
irradiance from 45 to 270 umol/m2/s significantly increased plant
growth and number of flowers, and reduced the time until flowering.
Net photosynthetic rate measured by net CO2 uptake of the plants
was increased by increasing the CO2 concentration from 330 to 1500-2000 uL/L at 45, 120 and 195 umol/m2/s photon flux density. The
effect of CO2 enrichment was similar at different air temperatures
(16, 20, 24 and 28C). Oxygen inhibition of photosynthesis
increased with temperature, but was substantially reduced by
elevated CO2 concentration.

Begonia hiemalis

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, FLOWERING, GROWTH
ANALYSIS, LIGHT, OXYGEN, PHOTOSYNTHESIS, TEMPERATURE

505  
Mott, K.A. 1988. Do Stomata Respond to CO2 Concentrations Other
than Intercellular? Plant Physiology 86:0200-0203.

Most studies on stomatal responses to CO2 assume that guard cells
respond only to intercellular CO2 concentration and are insensitive
to the CO2 concentrations in the pore and outside the leaf. If
stomata are sensitive to the CO2 concentration at the surface of
the leaf or in the stomatal pore, the stomatal response to
intercellular CO2 concentration will be incorrect for a 'normally'
operating leaf (where ambient CO2 concentration is a constant). In
this study asymmetric CO2 concentrations for the two surfaces of
amphistomatous leaves were used to vary intercellular and leaf
surface CO2 concentrations independently in Xanthium strumarium L.
and Helianthus annuus L. The response of stomata to intercellular
CO2 concentration when the concentration at the leaf surface was
held constant was found to be the same as the response when the
surface concentration was varied. In addition, stomata did not
respond to changes in leaf surface CO2 concentration when the
intercellular concentration for that surface was held constant. It
is concluded that stomata respond to intercellular CO2
concentration and are insensitive to the CO2 concentration at the
surface of the leaf and in the stomatal pore.

Xanthium strumarium/Helianthus annuus

KEYWORDS: CI:CA, CONDUCTANCE, STOMATA

506  
Mott, K.A. 1990. Sensing of Atmospheric CO2 by Plants. Plant, Cell
and Environment 13:731-737.

Despite recent interest in the effects of high CO2 on plant growth
and physiology, very little is known about the mechanisms by which
plants sense changes in the concentration of this gas. Because
atmospheric CO2 concentration is relatively constant and because
the conductance of the cuticle to CO2 is low, sensory mechanisms
are likely to exist only for intercellular CO2 concentration.
Therefore, responses of plants to changes in atmospheric CO2 will
depend on the effect of these changes on intercellular CO2
concentration. Although a variety of plant responses to atmospheric
CO2 concentration have been reported, most of these can be
attributed to the effects of intercellular CO2 on photosynthesis or
stomatal conductance. Short-term and long-term effects of CO2 on
photosynthesis and stomatal conductance are discussed as sensory
mechanisms for responses of plants to atmospheric CO2. Available
data suggest that plants do not fully realize the potential
increases in productivity associated with increased atmospheric
CO2. This may be because of genetic and environmental limitations
to productivity or because plant responses to CO2 have evolved to
cope with variations in intercellular CO2 caused by factors other
than changes in atmospheric CO2.

KEYWORDS: MORPHOLOGY, PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION,
REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASE, STOMATA

507  
Mousseau, M. 1993. Effects of Elevated CO2 on Growth,
Photosynthesis and Respiration of Sweet Chestnut (Castanea sativa
Mill.). Vegetatio 104/105:413-419.

Two year old sweet chestnut seedlings (Castanea sativa Mill.) were
grown in pots at ambient (350 umol/mol) and double (700 umol/mol)
atmospheric CO2 concentration in constantly ventilated greenhouses
during entire growing seasons. CO2 enrichment caused either no
significant change or a decrease in shoot growth response,
depending on yearly weather conditions. Similarly, leaf area was
either reduced or unchanged under elevated CO2. However, when grown
under controlled conditions in a growth chamber, leaf area was
enlarged with elevated CO2. The CO2 exchanges of whole plants were
measured during the growing season. In elevated CO2, net
photosynthetic rate was maximum in May and then decreased, reaching
the level of the control at the end of the season. End of night
dark respiration of enriched plants was significantly lower than
that of control plants; this difference decreased with time and
became negligible in the fall. The original CO2 level acted
instantaneously on the respiration rate: a double concentration in
CO2 decreased the respiration of control plants and a reduced
concentration enhanced the respiration of enriched plants. The
carbon balance of a chestnut seedling may then be modified in
elevated CO2 by increased carbon inputs and decreased carbon
outputs.

sweet chestnut/Castanea sativa

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
GREENHOUSE, GROWTH, RESPIRATION, TREES

508  
Mousseau, M., A. El Kohen, and B. Saugier. 1992. The Shoot Carbon
Balance of Young Chestnut Trees (Castanea sativa Mill.) in Double
CO2. IN: Responses of Forest Ecosystems to Environmental Changes
(A. Teller, P. Mathy, and J.N.R. Jeffers, eds.), Elsevier Applied
Science, London, pp. 699-700.

Castanea sativa/sweet chestnut

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, OUTDOOR GROWTH
CHAMBERS, RESPIRATION, TREES

509  
Mousseau, M., and H.Z. Enoch. 1989. Carbon Dioxide Enrichment
Reduces Shoot Growth in Sweet Chestnut Seedlings (Castanea sativa
Mill.). Plant, Cell and Environment 12:927-934.

Two-year-old potted sweet chestnut seedlings were grown at 350 ppm
CO2 and 700 ppm, day and night in constantly ventilated tunnels
during two full growing seasons, near Paris, France (48 N, 2 E).
Enrichment with CO2 caused an unusual shoot growth response. After
the end of July, stem elongation ceased in 62% of the CO2 enriched
plants as compared with 37% in the control. The leaves of CO2-enriched seedlings showed early senescence, indicated by premature
yellowing and a decrease in chlorophyll content. This was
associated with nutrient dilution brought about by the rapid growth
of these trees. The increase in total dry weight of the CO2-enriched seedlings was essentially the result of increase in the
root dry weight (69%). Shoot weight decreased by 22% relative to
the control. Total leaf area per enriched plant was 25% smaller
than the control. This unusual pattern of growth and carbon
allocation of the CO2 treated Chestnut trees emphasizes the concept
of a response specificity within trees to an increase of
atmospheric CO2.

Castanea sativa/sweet chestnut

KEYWORDS: ALLOCATION, NITROGEN, NUTRITION, OUTDOOR GROWTH CHAMBERS,
SENESCENCE, TREES

510  
Mousseau, M., and H.Z. Enoch. 1989. Effect of Doubling Atmospheric
CO2 Concentration on Growth, Dry Matter Distribution and CO2
Exchange of 2-Yr Old Sweet Chestnut Trees (Castanea sativa Mill.).
Annales des Sciences Forestieres 46 suppl:506-508.

Castanea sativa/sweet chestnut

KEYWORDS: CANOPY PHOTOSYNTHESIS, GROWTH, LEAF AREA DEVELOPMENT,
OUTDOOR GROWTH CHAMBERS, RESPIRATION, TREES

511  
Mousseau, M., and B. Saugier. 1992. The Direct Effect of Increased
CO2 on Gas Exchange and Growth of Forest Tree Species. Journal of
Experimental Botany 43:1121-1130.

CO2 enrichment of the atmosphere is now well documented and its
effect on the growth of world forests is being questioned by the
scientific community. The direct effects of increased CO2 on tree
species are reviewed: the different experimental approaches are
described, as well as the principal results already obtained.
Short-term experiments have shown an increased photosynthetic rate,
as predicted by leaf models. In longer experiments this increase is
reduced after a few weeks or months by mechanisms that remain to be
found. Elevated CO2 seems to decrease the dark respiration rate,
but the results are still controversial. Biomass partitioning in
elevated CO2 is clearly related to the mineral supply of the trees:
An increase in root investment in elevated CO2 is related to a poor
mineral status. The mineral content of trees grown in elevated CO2
is generally lowered compared to controls. No general rule has yet
been found for the effect of increased CO2 on leaf area
development. The paper emphasizes large areas of ignorance: the
reasons for the different responses of different species, which may
be related to their developmental strategies, are largely ignored.
Much experimental effort is needed to parameterize all the
physiological processes which are susceptible to change with an
increase in atmospheric CO2, leading to a change in forest tree
growth.

KEYWORDS: ALLOCATION, EXPOSURE METHODS, FOREST, GROWTH STAGES, LEAF
PHOTOSYNTHESIS, LITTER DECOMPOSITION, LITTER QUALITY, NUTRITION,
PHOTOSYNTHETIC ACCLIMATION, RESPIRATION, REVIEW, SCALING, TREES

512  
Muchow, R.C., and T.R. Sinclair. 1991. Water Deficit Effects on
Maize Yields Modeled under Current and 'Greenhouse' Climates.
Agronomy Journal 83:1052-1059.

The availability of water imposes one of the major limits on
rainfed maize (Zea mays L.) productivity. This analysis was
undertaken in an attempt to quantify the effects of limited water
on maize growth and yield by extending a simple, mechanistic model
in which temperature regulates crop biomass accumulation. A soil
water budget was incorporated into the model by accounting for
inputs from rainfall and irrigation, and water use by soil
evaporation and crop transpiration. The response functions of leaf
area development and crop gas exchange to the soil water budget
were developed from experimental studies. The model was used to
interpret a range of field experiments using observed daily values
of temperature, solar radiation, and rainfall or irrigation, where
water deficits of varying durations developed at different stages
of growth. The relative simplicity of the model and its robustness
in simulating maize yields under a range of water-availability
conditions allows the model to be readily used for studies of crop
performance under alternate conditions. One such study, presented
here, was a yield assessment for rainfed maize under possible
'greenhouse' climates where temperature and atmospheric CO2
concentration were increased. An increase in temperature combined
with decreased rainfall lowered grain yield, although the increase
in crop water use efficiency associated with elevated CO2
concentration, ameliorated the response to the greenhouse climate.
Grain yields for the greenhouse climates as compared to current
conditions increased, or decreased only slightly, except when the
greenhouse climate was assumed to result in severely decreased
rainfall.

Zea mays/corn

KEYWORDS: CANOPY PHOTOSYNTHESIS, CROP MODEL, LEAF AREA DEVELOPMENT,
LIGHT, MODELING, SIMULATION, TEMPERATURE, TRANSPIRATION, WUE, YIELD

513  
Musgrave, M.E. 1986. Studies on the Physiological Significance of
Cyanide-Resistant Respiration. Doctoral Dissertation, Duke
University, Dissertation Abstracts Vol.47:09-B, p.3626 (169 pp.).

Studies of the relationship between cyanide-resistant (alternative)
respiration and plant responses to relatively low (20-40 uM)
concentrations of cytokinins showed a disengagement of the
alternative pathway to occur prior to evidence of a cytokinin
response in six different bioassays. Treatment of bioassay material
with specific inhibitors of the alternative pathway produced
results expected from cytokinins. These results suggest that
disengagement of the alternative pathway is an early step in some
plant responses to cytokinins. Two pea cultivars differing in the
presence of absence of the alternative pathway were used to
investigate the above relationship further. The cultivar lacking
the alternative pathway failed to respond to exogenous application
of cytokinins. Hybridization of the cultivars showed the
alternative pathway to be a maternally inherited character and, in
reciprocal F-1's, only the cross having the alternative pathway was
responsive to cytokinins in the ethylene bioassay. A comparison of
the growth of pea hybrids differing in the presence of absence of
the alternative pathway was undertaken. Plants were grown in
Phytotron greenhouses at 350 or 650 ppm carbon dioxide to test the
hypothesis that the alternative pathway operates under conditions
of excess carbon assimilates. The results showed the hybrid lacking
the pathway to outperform the reciprocal cross in terms of total
dry matter, seed weight and height. The hybrid lacking the
alternative pathway responded markedly to carbon dioxide enrichment
with increases in a number of growth parameters while the
reciprocal cross showed little response to elevated carbon dioxide
levels. The results suggest that the alternative pathway does
consume luxury carbohydrates and may be an important component of
whole plant carbon budgets. Respiration by seven male-sterile lines
of four unrelated species was compared with that of fertile lines.
Alternative respiration was generally not expressed in tissues from
male-sterile plants. Male-sterile lines have been reported to have
higher vigor than corresponding fertile lines, and it is suggested
that the absence of the energetically wasteful alternative pathway
may account for these observed differences in vigor.

pea/Pisum sativum

KEYWORDS: CYANIDE-RESISTANT RESPIRATION, GREENHOUSE, GROWTH

514  
Musgrave, M.E., and B.R. Strain. 1988. Response of Two Wheat
Cultivars to CO2 Enrichment under Subambient Oxygen Conditions.
Plant Physiology 87:346-350.

Two cultivars of wheat (Triticum aestivum L. cvs Sonoita and Yecora
Rojo) were grown to maturity in a growth chamber within four sub-chambers under two CO2 levels (350 or 1000 microliters per liter)
at either ambient (21%) or low O2 (5%). Growth analysis was used to
characterize changes in plant carbon budgets imposed by the gas
regimes. Large increases in leaf areas were seen in the low O2
treatments, due primarily to a stimulation of tillering. Roots
developed normally at 5% O2. Seed development was inhibited by the
subambient O2 treatment, but this effect was overcome by CO2
enrichment at 1000 microliters per liter. Dry matter accumulation
and seed number responded differently to the gas treatments. The
greatest dry matter production occurred in the low O2, high CO2
treatment, while the greatest seed production occurred in the
ambient O2, high CO2 treatment. Growth and assimilation were
stimulated more by either CO2 enrichment or low O2 in cv Yecora
Rojo than in Sonoita. These experiments are the first to explore
the effect of whole plant low O2 treatments on growth and
reproduction. The finding that CO2 enrichment overcomes low O2-induced sterility may help elucidate the nature of this effect.

wheat/Triticum aestivum

KEYWORDS: CARBON BUDGET, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, OXYGEN

515  
Musgrave, M.E., B.R. Strain, and J.N. Siedow. 1986. Response of Two
Pea Hybrids to CO2 Enrichment: A Test of the Energy Overflow
Hypothesis for Alternative Respiration. Proceedings of the National
Academy of Science USA 83:8157-8161.

Two pea (Pisum sativum L.) hybrids differing in the presence or
absence of the cyanide-resistant (alternative) pathway of
respiration were constructed by reciprocally crossing cv. Alaska
and cv. Progress No. 9. The F1 hybrids were grown in greenhouses
maintained at either 350 or 650 ppm CO2, and the growth, flowering,
and dry matter accumulation were compared. The objective was to
assess the significance of the alternative respiratory pathway to
whole-plant carbon budgets and further to test the hypothesis that
the alternative pathway is important in oxidizing excess
carbohydrates such as might accumulate under conditions of CO2
enrichment. More carbohydrates were available in the F1 hybrid
lacking the pathway, as evidenced by greater plant height, leaf
area, specific leaf weight, and total dry matter compared with the
reciprocal hybrid, especially at 650 ppm CO2. Specific leaf weight
increased markedly under CO2 enrichment in the hybrid lacking the
pathway, while it was the same at 350 and 650 ppm in the reciprocal
cross. The hybrid lacking the alternative pathway also outperformed
the reciprocal cross in terms of total dry matter and seed
production. Increased branching with CO2 enrichment was observed in
the hybrid lacking the pathway, while branching in the reciprocal
cross was only slightly stimulated. These results suggest that
alternative respiration consumes luxury carbohydrate and that
respiration via this pathway may be considered energetically
wasteful in terms of whole-plant carbon budgets.

pea/Pisum sativum

KEYWORDS: CARBON BUDGET, CYANIDE-RESISTANT RESPIRATION, GREENHOUSE,
GROWTH

516  
Musselman, R.C., P.M. McCool, R.J. Oshima, and R.R. Teso. 1986.
Field Chambers for Assessing Crop Loss from Air Pollutants. Journal
of Environmental Quality 15:152-157.

A new field fumigation facility has been developed for determining
effects of air pollutants on cops. The permanent facility consists
of closed-top, octagonal chambers 2.1 m tall by 2.5 m across. Each
chamber is supplied with air via underground ducting from two
centralized blowers, one charcoal-filtered and the other
nonfiltered. Individual chambers can be adjusted to 100% filtered
air for fumigation with specific levels of pollutants, or a
pollutant gradient can be generated by combining filtered and
ambient air. Air exchange rates through the chambers are also
adjustable. Each chamber is constructed of several flat aluminum-frame panels covered with Teflon film which has remained clear and
durable after three years of continuous service. Panels are easily
removed for repair if necessary. Teflon film walls minimize
environmental differences between chamber and ambient air. Chamber
temperatures closely track ambient, but are higher than ambient at
midday. Temperatures remain uniform at different locations within
each chamber. Light intensity within chambers averages 11% less
than ambient. Pollutant levels set within each chamber remain
relatively stable in both time and space. Native soil under each
chamber has been replaced with a standard greenhouse soil mix which
is irrigated with a drip system. The fumigation facility is
comparable in construction costs to open-top fumigation chamber
systems, and is especially useful for experiments requiring precise
control of pollutant levels.

KEYWORDS: EXPOSURE METHODS

517  
Nagy, J., K.F. Lewin, G.R. Hendrey, F.W. Lipfert, and M.L. Daum.
1992. FACE Facility Engineering Performance in 1989. Critical
Reviews in Plant Sciences 11:165-185.

Following prototype development of the first BNL FACE system on
Long Island in 1986, the first full-scale (22-m diameter) FACE
array was built at Yazoo City, MS, in 1987. Three additional arrays
were built (with some modification of the configuration of all four
arrays) in 1988 in Yazoo City. In 1989 the four arrays were moved
to Maricopa, AZ. The FACE system has proven to be very reliable
with 3 to 7% of available experimental time lost to system failures
in 1989 in the various arrays. Analysis of modes of failure and
component failures are presented. Wind speed, direction and
stability are the most important variables governing CO2
distribution within the FACE arrays. For this reason detailed
analyses of system control deviations as a function of these
variables are presented. A statistical model relating CO2 use to
wind speed and solar altitude (a surrogate for stability) is
derived that may be helpful in evaluating CO2 use for FACE
experiments planned for other locations. System reliability and
control improved with changes in engineering features between 1987
and 1989. Over the entire 1989 growing season, omitting times when
the FACE systems were not functioning properly, average CO2
concentrations measured at the center of the arrays were within 1
umol/mol of the 550 umol/mol target concentration. Averaging over
all four arrays and all periods of operation, the 1-s observations
measured at the center of the FACE arrays remained within +/- 20%
of 550 umol/mol for 88% of the time. The corresponding 1-min
average was within +/- 10% for 88% of the time and within +/- 20%
for 98% of the time. Studies of spatial control within one of the
arrays demonstrated the general acceptability of control of CO2
concentrations in a central plot of 12-m diameter. Experiments
using tracers and multi-port monitoring of the spatial distribution
of CO2 showed that this area constituted a 'sweet spot' within
which CO2 concentrations were +/- 20% of the target CO2
concentration at least 80% of the time. A 63-port selectable
sequencing sampler was set up as a three-dimensional sampling
system. Over 16,000 observations of 1-s grab samples were taken
with this multiport sampler. Average values at each sampling node
showed that spatial variability of CO2 concentrations throughout
the volume of the 'sweet spot' in 1989 varied by less that +/- 5%.
Of these 1-s grab samples 0.44% exceeded twice the target
concentration of 550 umol/mol but 110 umol at the top of the
canopy. Grab-samples taken in 'bucket tests' averaging over 5-min
found a wind-dependent gradient across the 'sweet spot' that was as
high as 160 umol. However, those ranges are still within the design
criteria.

KEYWORDS: EXPOSURE METHODS, FACE

518  
Nakayama, F.S., and B.A. Kimball. 1988. Soil Carbon Dioxide
Distribution and Flux within the Open-top Chamber. Agronomy Journal
80:394-398.

Open-top chamber use for exposing plants to various levels of CO2
and pollutant gases is increasing in field studies. In making a C
balance of cotton [Gossypium hirsutum (L.) 'Deltapine-61'] for such
a system, soil CO2 fluxes were observed to be significantly greater
outside than inside the chamber. To find the cause, CO2
concentration was measured in the soil profile from 50 to 60-cm
depths of an Avondale clay loam [fine-loamy, mixed (calcareous),
hyperthermic Typic Trifluvent]. The soil CO2 contents at the
various depths sampled outside the chamber were higher than those
inside the chamber. The differences in concentration were
observable within 2 wk after the blower used to pass ambient or
CO2-enriched air through the chamber was turned on. The largest
differences were present approximately 16 wk after the system had
been in operation. Approximately 30 d was required for the soil CO2
levels inside and outside the chamber to become similar after the
blower was turned off. Soil water content was not a factor causing
this difference because it was nearly equal at both sites. Pressure
differentials inside the growth chamber resulting from the blower
operation could lead to a decrease in soil CO2 concentration and
fluxes measured using the closed chamber technique.

KEYWORDS: EXPOSURE METHODS, OPEN-TOP CHAMBERS, SOIL CO2
CONCENTRATION

519  
Nederhoff, E.M. 1990. Technical Aspects, Management and Control of
CO2 Enrichment in Greenhouses. Acta Horticulturae 268:127-138.

KEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2,
GREENHOUSE

520  
Nederhoff, E.M. 1992. Effects of CO2 on Greenhouse Grown Eggplant
(Solanum melongena L.) I. Leaf Conductance. Journal of
Horticultural Science 67:795-803.

Leaf conductance of eggplant (Solanum melongena L., cv. Cosmos) was
measured comparatively in two glasshouse compartments, with
continuously low or high CO2 (on average 415 or 685 umol/mol,
respectively). Measurements were carried out on eight days between
February and June 1991 in an early planted crop. A regression
equation was fitted to the data to account for the effects of PAR,
air humidity and CO2 on leaf conductance. Calculations with this
equation demonstrated that leaf conductance was reduced by 10.2%
per 100 umol/mol increase in CO2, which is a three to four times
stronger response than in other fruit vegetable crops. When, on
some occasional days, CO2 was kept equal in the two compartments,
leaf conductance was not different, indicating that stomatal
behaviour had not adapted to long lasting CO2 conditions. The rate
of crop transpiration, as estimated with the Penman-Monteith
combination equation, was reduced by elevated CO2 by only a few
percent on average and by about 15% in a period of some weeks in
spring.

Solanum melongena/eggplant

KEYWORDS: CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS,
TRANSPIRATION

521  
Nederhoff, E.M., and K. Buitelaar. 1992. Effects of CO2 on
Glasshouse Grown Eggplant (Solanum melongena L.) II. Leaf Chlorosis
and Fruit Production. Journal of Horticultural Science 67:805-812.

The effect of CO2 on leaf boron content, Leaf Tip Chlorosis (LTC)
and fruit production of eggplant (Solanum melongena L., cv. Cosmos)
was investigated in the spring of 1991. Two levels of CO2 (413 and
663 umol/mol) were maintained in duplicate, in four glasshouse
compartments (16m x 16m). LTC was significantly more severe at high
than at low CO2. Leaf boron content was lower in leaves with LTC
than in other leaves and was lower in leaves from high CO2 than in
those from low CO2. These results, in combination with observed
reduction in leaf conductance (part I), support the hypothesis that
LTC is caused by reduced translocation to young, fast growing
leaves, because of reduced transpiration. More specific research on
boron is necessary to confirm this hypothesis. Fruit production was
significantly higher (24%) at high CO2 than low CO2, despite more
severe LTC.

Solanum melongena/eggplant

KEYWORDS: BORON, GREENHOUSE, HORTICULTURAL CROPS, NUTRITION,
TRANSPIRATION

522  
Nederhoff, E.M., A.N.M. de Koning, and A.A. Rijsdijk. 1992. Leaf
Deformation and Fruit Production of Glasshouse Grown Tomato
(Lycopersicon esculentum Mill.) as Affected by CO2, Plant Density
and Pruning. Journal of Horticultural Science 67:411-420.

During summer, glasshouse grown tomato plants (Lycopersicon
esculentum Mill.) often demonstrate leaf deformation, reduced leaf
area (short leaves) and low Specific Leaf Area (SLA), sometimes
accompanied by higher dry matter content of leaves and stems and
higher leaf starch content. This so-called 'Short Leaves Syndrome'
(SLS), which decreases the production capacity, was investigated
with emphasis on the effects of CO2 concentration. As a working
hypothesis it was postulated that SLS is indirectly caused by an
oversupply of assimilates relative to the sink capacity. An
experiment was conducted between 10 May and 31 July 1990 in 12
glasshouse compartments. The sink/source ratio was varied by
maintaining two levels of CO2, multifactorially combined with two
plant densities and three pruning treatments. CO2 enrichment and
wider planting enhanced SLS and decreased leaf area and SLA of
upper leaves. Leaf pruning and fruit pruning, however, did not give
clear effects on vegetative characteristics, although the impact on
the sink/source ratio was of the same order of magnitude. As a
mechanism for these effects, we suggest that SLS is caused by
calcium deficiency in the apex, a condition more severe when much
phloem sap (with low calcium content) is available, i.e. when the
sink/source ratio is lower. Stronger effects of CO2 and plant
density than of pruning on the incidence of SLS, may be due to
local effects of sink/source relationships or to involvement of
other processes, like transpiration. In crops with little SLS-symptoms, CO2 enrichment increased the weight of fruits grown
during the treatment period by 31%, whereas in crops with severe
SLS, CO2 enrichment aggravated SLS and had no significant effect on
fruit production. CO2 enrichment in summer is beneficial if SLS is
prevented, which can be achieved by maintaining a higher plant
density or, in an early crop, an extra shoot on the plants in
spring and summer.

tomato/Lycopersicon esculentum

KEYWORDS: CALCIUM, CARBOHYDRATES, GREENHOUSE, HORTICULTURAL CROPS,
LEAF INJURY, PRUNING, SPECIFIC LEAF WEIGHT, TEMPERATURE, YIELD

523  
Nederhoff, E.M., and A.A. Rijsdijk. 1990. CO2 kan verdamping teveel
beinvloeden. Groenten en Fruit 45:28-29.

In Dutch.

524  
Nederhoff, E.M., A.A. Rijsdijk, and R. de Graaf. 1992. Leaf
Conductance and Rate of Crop Transpiration of Glasshouse Grown
Sweet Pepper (Capsicum annuum L.) as Affected by Carbon Dioxide.
Scientia Horticulturae 52:283-301.

The effects of carbon dioxide concentration (CO2) in the range of
300-1100 umol/mol on leaf conductance (g) and rate of crop
transpiration (E) of sweet pepper (Capsicum annuum L.) were
investigated in spring 1990. In two greenhouse compartments (154
m2) that were simultaneously exposed to different CO2 levels, leaf
conductance of the upper leaves was measured with three weighing
lysimeters per greenhouse compartment. Multiple regression
equations, describing the effects of photosynthetic active
radiation (PAR), vapour pressure deficit (VPD)-leaf-air, CO2 and
optionally leaf temperature on g, were fitted to the measured data.
The fitted regression curves demonstrated that 100 umol/mol
increase in CO2 reduced g by about 3%, at any level of CO2, VPD and
PAR, if VPD and PAR would remain constant. Measured rates of crop
transpiration were highly correlated to radiation and were in
reasonable accordance with the Penman-Monteith combination
equation. With the equation it was estimated that a 10% decrease in
g would reduce E by 1.5 - 3% at high levels of g (high radiation)
and by 4 - 7% at low g (dark weather), at least if VPD would remain
constant. In a greenhouse-crop system, however, owing to thermal
and hydrologic feedbacks, an increase in CO2 leads to a
considerable increase in VPD-leaf-air. This enforces the effect of
CO2 on g and counteracts the effect of CO2 on E, because the
driving force for transpiration is enhanced. Thus, in general the
apparent response of g to changes in CO2 is far greater than the
mentioned percentage, whereas the apparent response of E is
relatively small.

Capsicum annuum/sweet pepper

KEYWORDS: CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS,
TRANSPIRATION, VPD

525  
Nederhoff, E.M., and J.A.M. van Uffelen. 1988. Effects of
Continuous and Intermittent Carbon Dioxide Enrichment on Fruit Set
and Yield of Sweet Pepper (Capsicum annuum L.). Netherlands Journal
of Agricultural Science 36:209-217.

The effects of carbon dioxide (CO2) enrichment on vegetative
growth, fruit set and yield of an autumn crop of sweet pepper
(Capsicum annuum L., cv. Bolero) were studied. In 12 greenhouse
compartments of 9.6 m x 6 m each, 6 CO2 treatments were tested: 3
continuous CO2 levels, setpoints 200, 340 and 500 ppm (uL/L), 2
intermittent dosings (8 minutes per 40 and per 104 minutes,
respectively) and a control (without dosing or filtering). It was
not possible to maintain the set points of the continuous CO2
levels throughout the experiment, therefore the measured CO2
concentrations were used to explain the effects. The results show
a positive effect of elevated CO2 concentrations on fruit set and
yield. The number of fruits harvested per m2 was 60% higher at the
500 ppm treatment than at the 200 ppm treatment, whereas the
average fruit weight was not significantly affected. The dry matter
content of the leaves increased, the SLA and LAR were smaller at
higher CO2 concentrations. The vegetative growth tended to decrease
at higher CO2 levels, which was ascribed to competition between
vegetative and generative organs. The results with respect to the
setting and yield were less favourable at intermittent CO2
enrichment than at continuous CO2 levels, if plotted versus the
measured, average CO2 concentration.

Capsicum annuum/sweet pepper

KEYWORDS: GREENHOUSE, GROWTH ANALYSIS, INTERMITTENT ENRICHMENT,
YIELD

526  
Nie, D., H. He, M.B. Kirkham, and E.T. Kanemasu. 1992.
Photosynthesis of a C3 Grass and a C4 Grass under Elevated CO2.
Photosynthetica 26:189-198.

The net photosynthetic rate (Pn), intercellular CO2 concentration
(Ci), transpiration rate (E), stomatal resistance (rs), and water
potential (Psi-w) of a C3 grass (Kentucky bluegrass, Poa pratensis
L.) and a C4 grass (big bluestem, Andropogon gerardii Vitman)
growing in the spring in a tallgrass prairie under two levels of
CO2 (ambient and twice ambient) were compared. Elevated CO2 (HC)
increased Pn of Kentucky bluegrass (C3) by 47.0% but did not affect
Pn of big bluestem (C4). HC increased Ci of both grasses by about
the same amount (about 270 cm3/m3), but reduced E (and parallelly
increased rs) of big bluestem more than those of Kentucky
bluegrass. HC increased (Psi-w) of both grasses by about 30%.
Kentucky bluegrass had a lower (Psi-w) than big bluestem, but HC
increased Psi-w of Kentucky bluegrass to values more similar to
those of big bluestem under ambient CO2 (LC). Hence a high Psi-w
resulting from HC, was necessary for high Pn.

Kentucky bluegrass/Poa pratensis/big bluestem/Andropogon gerardii

KEYWORDS: C3, C4, GRASSES, LEAF PHOTOSYNTHESIS, OUTDOOR GROWTH
CHAMBERS, TALLGRASS PRAIRIE, WATER STRESS

527  
Nie, D., H. He, G. Mo, M.B. Kirkham, and E.T. Kanemasu. 1992.
Canopy Photosynthesis and Evapotranspiration of Rangeland Plants
under Doubled Carbon Dioxide in Closed-top Chambers. Agricultural
and Forest Meteorology 61:205-217.

It is important to know how the increasing atmospheric
concentration of carbon dioxide (CO2) will affect growth of
agricultural plants. The objective of this study was to determine
the effect of elevated CO2 on canopy photosynthetic rate of prairie
(rangeland) plants growing under natural field conditions. The
dominant plants were warm-season grasses with the C4 type of
photosynthesis. Sixteen closed-top, cylindrical, plastic chambers
(1.5 m in diameter; 1.8 m tall) were placed on the prairie to
maintain two levels of CO2 (ambient and twice ambient) over a full
growing season in 1990. The soil (silty clay loam) was kept at a
high water (field capacity) or a low water level (no water added).
Carbon dioxide concentration, air temperature, net radiation,
canopy photosynthetic rate, and canopy evapotranspiration rate were
measured in the 16 chambers on 49 sunny days during the season. The
target value for high-CO2 chambers was 720 cm3 CO2/m3; the measured
mean concentrations varied from 710.8 to 720.1 cm3 CO2/m3. For
chambers with ambient CO2, the chamber-to-chamber variation was
minor, with mean values ranging from 350.8 to 356.0 cm3 CO2/m3.
Daytime air temperatures at 100 cm aboveground in the chambered
plots averaged 2.7C warmer than outside. Early in the season, net
radiation was usually similar among chambers with the different CO2
and water treatments, but late in the season, differences occurred
among chambers, possibly because of the amount of tall grasses that
shaded the radiometers. Under the high-water treatment, canopy
photosynthesis of plants grown with doubled and ambient CO2
averaged 41.8 umol/m2/s and 44.5 umol/m2/s, respectively. These
results are consistent with previous findings, which showed that
the photosynthetic rate of C4 plants on rangeland was not augmented
when the CO2 concentration was increased. Under the low-water
treatment, photosynthesis of plants grown with doubled CO2 was
slightly more (36.9 umol/m2/s) than that of plants grown with
ambient CO2 (31.7 umol/m2/s). This observation is in agreement with
other results, which have shown that high CO2 alleviates water-stress effects on plants. Elevated CO2 reduced canopy
evapotranspiration rate by 18 and 8%, under the high- and low-water
levels, respectively. The results suggested that, as the CO2
concentration in the atmosphere increases, water lost from
rangelands will be reduced.

big bluestem/Andropogon gerardii/little bluestem/Andropogon
scoparius/Indiangrass/Sorghastrum nutans

KEYWORDS: C4, CANOPY PHOTOSYNTHESIS, EVAPOTRANSPIRATION, EXPOSURE
METHODS, LIGHT, OUTDOOR GROWTH CHAMBERS, RANGELAND, TALLGRASS
PRAIRIE, TEMPERATURE, WATER STRESS

528  
Nie, D., M.B. Kirkham, L.K. Ballou, D.J. Lawlor, and E.T. Kanemasu.
1992. Changes in Prairie Vegetation under Elevated Carbon Dioxide
Levels and Two Soil Moisture Regimes. Journal of Vegetation Science
3:673-678.

It is important to know how increasing levels of atmospheric CO2
will affect native vegetation. The objective of this study was to
determine the effect of elevated CO2 concentrations on species
composition in a tallgrass prairie kept at a high water level (730
mm of water in a 2000 mm soil profile) and a low water level (660
mm of water in 2000 mm). 16 cylindrical plastic chambers were
placed on the prairie to maintain two levels of CO2 (ambient or
twice ambient) during two growing seasons in 1989 and 1990.
Frequency of species was determined on 25 July 1989 and on 5 and 10
October 1990. At the beginning of the study, Poa pratensis
(Kentucky bluegrass), the dominant C3 species, had the highest
frequency of 43.3%, but decreased with time. However, at the end of
the experiment and under the high soil-water level, there were more
P. pratensis plants in the elevated CO2 treatment (frequency:
13.5%) than in the ambient CO2 treatment (1.0 %). Under the low
soil water regime, the reverse occurred (frequencies: 3.6% and
11.0% for high and low CO2, respectively). The frequency of major
C4 plants, Andropogon gerardii (big bluestem), A. scoparius (little
bluestem) and Sorghastrum nutans (Indian grass) was not affected by
CO2. However, water did affect their frequency. Under low water,
the frequency of A. gerardii decreased between 1989 and 1990. Under
both soil moisture levels, the frequencies of S. nutans and A.
scoparius increased. At the end of the study, Indian grass grown
with high water had the highest frequency of all species on the
prairie (frequency at the end of the study in October, 1990, of
44.4% and 47.4% for the high and low CO2 levels, respectively).
Unlike Indian grass, little bluestem grew better under low water
conditions than under high water conditions. These results suggest
that, if the climate becomes drier, A. scoparius will flourish more
than S. nutans or A. gerardii and P. pratensis may die out.
Elevated CO2 might not increase survival of C3 plants under dry
conditions, if temperatures are too high for them.

Poa pratensis/Kentucky bluegrass/Andropogon gerardii/big
bluestem/Andropogon scoparius/little bluestem/Sorghastrum
nutans/Indiangrass

KEYWORDS: C3, C4, GRASSES, OUTDOOR GROWTH CHAMBERS, SPECIES
COMPETITION, TALLGRASS PRAIRIE, WATER STRESS

529  
Nijs, I., and I. Impens. 1993. Effects of Long-term Elevated
Atmospheric Carbon Dioxide on Lolium perenne and Trifolium repens,
Using a Simple Photosynthesis Model. Vegetatio 104/105:421-431.

Changes in gross canopy photosynthetic rate (PGc), produced by
long-term exposure to an elevated atmospheric CO2 level (626 +/- 50
umol/mol), were modelled for Lolium perenne L. cv. Vigor and
Trifolium repens L. cv. Blanca, using a simple photosynthesis
model, based on biochemical and physiological information (leaf
gross CO2 uptake in saturating light, Pmax, and leaf quantum
efficiency, alpha) and structural vegetation parameters (leaf area
index, LAI, canopy extinction coefficient, k, leaf transmission,
M). Correction of PGc for leaf respiration allowed comparison with
previously measured canopy net CO2 exchange rates, with the average
divergence from model prediction amounting to about 6%. Sensitivity
analysis showed that for a three-week old canopy, the PGc increased
in high CO2 could be attributed largely to changes in Pmax and
alpha, while differences in canopy architecture were no longer
important for the PGc-stimulation (which they were in the early
growth stages). As a consequence of this increasing LAI with canopy
age, the gain of daytime CO2 uptake is progressively eroded by the
increasing burden of canopy respiration in high-CO2 grown Lolium
perenne. Modelling canopy photosynthesis in different regrowth
stages after cutting (one week, two weeks,. . .), revealed that the
difference in a 24-h CO2 balance between the ambient and the high
CO2 treatment is reduced with regrowth time and completely
disappears after 6 weeks.

Lolium perenne/perennial ryegrass/Trifolium repens/white clover

KEYWORDS: LEAF AREA DEVELOPMENT, MODELING, OUTDOOR GROWTH CHAMBERS,
PHOTOSYNTHESIS MODEL, RESPIRATION

530  
Nijs, I., I. Impens, and T. Behaeghe. 1988. Effects of Rising
Atmospheric Carbon Dioxide Concentration on Gas Exchange and Growth
of Perennial Ryegrass. Photosynthetica 22:44-50.

Long-term effects of rising atmospheric CO2 concentrations on gas
exchange, growth and productivity were investigated on Lolium
perenne L. cv. Vigor. Pure stands of this species in vernalized
condition were cultivated in small acrylic greenhouses in an
artificial atmosphere of mean 367 or 620 cm3/m3 CO2 (C350 or C600),
respectively. Canopies grown at C600 showed an average higher dry
matter of almost 43% than those of C350. Functional growth analysis
indicated that an important fraction of the yield increase under
C600 originated from CO2 fixed in the first few days of the
regrowth period after cutting the stand. Gas exchange measurements
in spring showed a higher maximum canopy photosynthetic rate of 77%
and a higher transpiration rate of around 20% at C600 than C350 if
expressed on a ground area basis. Development of a larger canopy
leaf area was the primary cause for both increases. Water-use
efficiency calculations on the summer data indicated a slight
decrease under C600.

Lolium perenne/perennial ryegrass

KEYWORDS: CANOPY PHOTOSYNTHESIS, GROWTH ANALYSIS, OUTDOOR GROWTH
CHAMBERS, PHOTOSYNTHESIS MODEL, TRANSPIRATION, WUE

531  
Nijs, I., I. Impens, and T. Behaeghe. 1988. Effects of Elevated
Atmospheric Carbon Dioxide on Gas Exchange and Growth of White
Clover. Photosynthesis Research 15:163-176.

Effects of rising atmospheric CO2 concentrations on gas exchange,
growth and productivity were investigated on an important grassland
species, Trifolium repens L. cv. Blanca. Pure stands of this
species were cultivated over an entire growing season in small
acrylic greenhouses with an artificial atmosphere of +/- 367 or +/-
620 ppm CO2, respectively. Effects on growth and development were
examined in a functional growth analysis, while consequences for
gas exchange were determined by photosynthesis and transpiration
measurements on canopy level. The stands were regularly clipped for
production assessment. Canopies grown at high CO2 levels showed an
average increase in productivity of almost 75%. Growth analysis
indicated development of a larger foliage area as the major cause,
particularly in the first days of regrowth after cutting. The
growth advantage that began in this stage was maintained or
bettered during the following weeks. The difference between gas
exchange measurements expressed per unit leaf area and per unit
ground area suggested that changes in net photosynthesis and
respiration did not contribute to the increase in total yield.
Transpiration declined under high CO2 if expressed on a leaf area
basis but total canopy transpiration was at least as large as in
ambient CO2 due to the larger leaf area. Water-use efficiency
calculations on the summer data indicated a 35% improvement with a
doubling of CO2 concentration.

Trifolium repens/white clover

KEYWORDS: CANOPY PHOTOSYNTHESIS, GROWTH ANALYSIS, OUTDOOR GROWTH
CHAMBERS, TRANSPIRATION, WUE

532  
Nijs, I., I. Impens, and T. Behaeghe. 1989. Effects of Long-term
Elevated Atmospheric CO2 Concentration on Lolium perenne and
Trifolium repens Canopies in the Course of a Terminal Drought
Stress Period. Canadian Journal of Botany 67:2720-2725.

A terminal drought stress regime was imposed on vegetatively fully
developed Lolium perenne L. cv. Vigor and Trifolium repens L. cv.
Blanca canopies in semicontrolled growth chambers that provided a
high (626 +/- 50 uL/L) and an ambient (358 +/- 35 uL/L) CO2 growth
environment. The chambers served as measurement units in an open
system for continuous CO2 and water vapour exchange assessment.
When stress was building up, high CO2 increased the ratio of real
to potential canopy evapotranspiration in both species, thus
reducing the higher potential rates that are generally observed in
high CO2 under unstressed conditions towards the level of the
ambient CO2 stands, without immediately affecting the net higher
CO2 exchange rates that characterize the high CO2 treatment. Lolium
perenne is more sensitive to drought stress in its initial response
and divides the available amount of water more proportionally over
the stress period than Trifolium repens. Water-use efficiency is
roughly doubled and is affected later by drought stress in high CO2
for both species. It is concluded that long-term high CO2 treatment
favours the survival of the species examined when exposed to
severe, rapidly developing drought stress.

Lolium perenne/perennial ryegrass/Trifolium repens/white clover

KEYWORDS: CANOPY PHOTOSYNTHESIS, EVAPOTRANSPIRATION, OUTDOOR GROWTH
CHAMBERS, WUE

533  
Nijs, I., I. Impens, and T. Behaeghe. 1989. Effects of Different
CO2 Environments on the Photosynthesis-Yield Relationship and the
Carbon and Water Balance of a White Clover (Trifolium repens L. cv.
Blanca) Sward. Journal of Experimental Botany 40:353-359.

Effects of atmospheric CO2 enrichment to a level above 600 ppm on
leaf and canopy gas exchange characteristics were investigated in
Trifolium repens, using an open system for gas exchange
measurement. The cuvette of the system served as growth chambers,
allowing continuous measurement in a semi-controlled environment of
+/- 350 and +/- 600 ppm, respectively. Carbon balance data were
compared with crop yield and effects on the canopy level were
compared with measured leaf responses of photosynthesis and
stomatal behavior. Photosynthetic stimulation by high CO2 was
stronger at the canopy level (103% on average) than for leaves (90%
in full light), as a consequence of accelerated foliage area
development. The latter increased absolute water consumption by
16%, despite strong stomatal closure. The overall result was a 63%
improvement in canopy water use efficiency (WUE), while leaf WUE
increased almost 3-fold in saturating light. The stomatal response
was such that, while the internal CO2 concentration in the leaf,
Ci, increased with rising atmospherical CO2 concentration, Ca,
Ci/Ca was somewhat decreased. Total canopy resistance, Rc, was
generally lower at high CO2 levels, despite higher leaf resistance.
Higher canopy CO2 loss at night and faster light extinction in a
larger-sized high CO2 canopy were major drawbacks which prevented
a further increase in dry matter production (the harvest index was
increased by a factor 1.83).

Trifolium repens/white clover

KEYWORDS: CANOPY PHOTOSYNTHESIS, CI:CA, CONDUCTANCE, LEAF AREA
DEVELOPMENT, LEAF PHOTOSYNTHESIS, OUTDOOR GROWTH CHAMBERS, WUE,
YIELD

534  
Nijs, I., I. Impens, and T. Behaeghe. 1989. Leaf and Canopy
Responses of Lolium perenne to Long-term Elevated Atmospheric
Carbon-dioxide Concentration. Planta 177:312-320.

The relationship between leaf photosynthetic capacity (Pn,max), net
canopy CO2- and H20-exchange rate (NCER and Et, respectively) and
canopy dry-matter production was examined in Lolium perenne L. cv.
Vigor in ambient (363 +/-30 uL/L) and elevated (631 +/-31 uL/L) CO2
concentrations. An open system for continuous and simultaneous
regulation of atmospheric CO2 concentration and NCER and Et
measurement was designed and used over an entire growth cycle to
calculate a carbon and a water balance. While NCERmax of full-grown
canopies was 49% higher at elevated CO2 level, stimulation of
Pn,max was only 46% (in spite of a 50% rise in one-sided stomatal
resistance for water-vapour diffusion), clearly indicating the
effect of a higher leaf-area index under high CO2 (approx. 10% in
one growing period examined). A larger amount of CO2-deficient
leaves resulted in higher canopy dark-respiration rates and higher
canopy light compensation points. The structural component of the
high-CO2 effect was therefore a disadvantage at low irradiance, but
a far greater benefit at high irradiance. Higher canopy dark-respiration rates under elevated CO2 level and low irradiance
during the growing period are the primary causes for the increase
in dry-matter production (19%) being much lower than expected
merely based on the NCERmax difference. While total water use was
the same under high and low CO2 levels, water-use efficiency
increased 25% on the canopy level and 87% on a leaf basis. In the
course of canopy development, allocation towards the root system
became greater, while stimulation of shoot dry-matter accumulation
was inversely affected. Over an entire growing season the
root/shoot production ratio was 22% higher under high CO2
concentration.

Lolium perenne/perennial ryegrass

KEYWORDS: ALLOCATION, CANOPY PHOTOSYNTHESIS, EVAPOTRANSPIRATION,
GROWTH, LEAF AREA DEVELOPMENT, OUTDOOR GROWTH CHAMBERS, ROOT:SHOOT
RATIO, WUE

535  
Nijs, I., I. Impens, and P. Van Hecke. 1992. Diurnal Changes in the
Response of Canopy Photosynthetic Rate to Elevated CO2 in a Coupled
Temperature-Light Environment. Photosynthesis Research 32:121-130.

The relative increase with elevated CO2 of canopy CO2 uptake rate
(A), derived from continuous measurements during the day, was
examined in full-cover vegetative Lolium perenne canopies after 17
days of regrowth. The stands were grown at ambient 358 +/- 50
umol/mol) and increased (626 +/- 50 umol/mol) CO2 concentration in
sunlit growth chambers. Over the entire range of temperature and
light conditions (which were strongly coupled and increased
simultaneously), A was on average twice as large in high compared
to ambient CO2. This response (called M = A in high CO2/A in
ambient CO2) could not be explained by changes in canopy
conductance for CO2 diffusion (GC). In spite of interaction and
strong coupling between temperature and light intensity, there was
evidence that temperature rather than light determined M. Further,
high CO2 treatment was found to alleviate the afternoon depression
in A observed in ambient CO2. A temperature optimum shift or/and a
larger carbohydrate sink capacity through altered root/shoot ratio
are proposed in explanation.

Lolium perenne/perennial ryegrass

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, LIGHT, OUTDOOR GROWTH
CHAMBERS, SOURCE-SINK BALANCE, TEMPERATURE

536  
Nobel, P.S. 1991. Environmental Productivity Indices and
Productivity for Opuntia ficus-indica under Current and Elevated
Atmospheric CO2 Levels. Plant, Cell and Environment 14:637-646.

The productivity of the prickly-pear cactus Opuntia ficus-indica,
which is cultivated worldwide for its fruits and stem segments, was
predicted based on the responses of its net CO2 uptake to soil
water status, air temperature and photosynthetic photon flux
density (PPFD). Each of these environmental factors was represented
by an index with maximum value of unity when that factor was not
limiting net CO2 uptake over a 24-h period. The water index, the
temperature index, and the PPFD index were determined for 87 sites
in the contiguous United States using data from 189 weather
stations and for 148 sites worldwide using data from 1464 weather
stations. The product of these three indices, the environmental
productivity index (EPI), was used to predict the productivity of
O. ficus-indica under current climatic conditions and under those
accompanying a possible increase in the atmospheric CO2 level to
650 umol/mol. Sites with temperatures always above -10C and hence
suitable for prickly-pear cultivation numbered 37 in the United
States and 110 worldwide; such sites increased by 43 and 5%,
respectively, for the global warming accompanying the elevated CO2.
Productivity of O. ficus-indica was at least 15 tonnes dry
weight/hectare/year, comparable to that of many agronomic crops,
for 20 sites with temperatures always above -10C in the contiguous
United States and for 12 such sites worldwide under current
climatic conditions; such sites increased by 85 and 117%,
respectively, under the elevated CO2 condition, mainly because of
direct effects of the atmospheric CO2 level on net CO2 uptake. In
summary, simulations based on EPI indicate that O. ficus-indica may
presently be advantageously cultivated over a substantial fraction
of the earth's surface, such regions increasing markedly with a
future doubling in atmospheric CO2 levels.

prickly pear cactus/Opuntia ficus-indica

KEYWORDS: CAM, ENVIRONMENTAL PRODUCTIVITY INDEX, LIGHT, MODELING,
REVIEW, SIMULATION, TEMPERATURE, WATER STATUS

537  
Nobel, P.S., and V.G. de Cortazar. 1991. Growth and Predicted
Productivity of Opuntia ficus-indica for Current and Elevated
Carbon Dioxide. Agronomy Journal 83:224-230.

Opuntia ficus-indica (L.) Mill., a prickly pear cactus cultivated
worldwide for its fruits and stem segments, can have an annual dry
weight productivity exceeding that of many crops. Using a recently
introduced environmental productivity index (EPI), the influences
of water status, temperature, and photosynthetically active
radiation (PAR) on its productivity can be predicted. This
investigation calculated the water index, the temperature index,
and the PAR index, whose product equals EPI, for 169 sites
distributed approximately uniformly across the contiguous USA for
present climatic conditions as well as for those associated with an
elevated CO2 concentration of 650 uL/L. The effect of elevated CO2
on growth of O. ficus-indica was directly measured, and low
temperature limitations on productivity were considered. The dry
weight gain of O. ficus-indica during 6 mo in an environmental
growth chamber was 23% greater at 650 compared with 350 uL/L CO2
and increased as the duration of the wet period increased, in
agreement with predictions of the water index (the fraction of
maximal net CO2 uptake during a 24-h period for the prevailing
plant water status). For closely spaced plants that lead to a high
productivity per unit ground area, EPI averaged about 0.10, except
in desert regions where the water index lowered EPI, in the far
North or South and at high elevations where the temperature index
lowered EPI, and in the Northeast and Northwest where the PAR index
lowered EPI. The predicted annual dry weight productivity for O.
ficus-indica was 12.8 Mg/ha/yr under current conditions, and 16.3
Mg/ha/yr under those associated with 650 uL/L CO2. Both
productivities are relatively high compared with other agronomic
plants. The percentage of sites where temperatures fall below -15C
at least once during the 10 years simulated, which would be lethal
to most prickly pear cacti, was reduced from 49 to 18% by the
general warming expected to accompany an approximate doubling of
the atmospheric CO2 concentration.

Opuntia ficus-indica/prickly pear cactus

KEYWORDS: ENVIRONMENTAL PRODUCTIVITY INDEX, LIGHT, MODELING,
SIMULATION, TEMPERATURE, WATER STATUS

538  
Nobel, P.S., and T.L. Hartsock. 1986. Short-term and Long-term
Responses of Crassulacean Acid Metabolism Plants to Elevated CO2.
Plant Physiology 82:604-606.

For the leaf succulent Agave deserti and the stem succulent
Ferocactus acanthodes, increasing the ambient CO2 level from 350
microliters per liter to 650 microliters per liter immediately
increased daytime net CO2 uptake about 30% while leaving nighttime
net CO2 uptake of these Crassulacean acid metabolism (CAM) plants
approximately unchanged. A similar enhancement of about 30% was
found in dry weight gain over 1 year when the plants were grown at
650 microliters CO2 per liter compared with 350 microliters per
liter. Based on these results plus those at 500 microliters per
liter, net CO2 uptake over 24-hour periods and dry weight
productivity of these two CAM succulents is predicted to increase
an average of about 1% for each 10 microliters per liter rise in
ambient CO2 level up to 650 microliters per liter.

Agave deserti/Ferocactus acanthodes

KEYWORDS: ALLOCATION, CAM, GREENHOUSE, GROWTH, PHOTOSYNTHESIS

539  
Nonhebel, S. 1990. The Impact of Changes in Weather and CO2
Concentration on Spring Wheat Yields in Western Europe. IN: The
Greenhouse Effect and Primary Productivity in European Agro-ecosystems; 5-10 April 1990; Wageningen, The Netherlands (J.
Goudriaan, H. van Keulen, and H.H. van Laar, eds.), Pudoc,
Wageningen, pp. 48-50.

wheat/Triticum aestivum

KEYWORDS: AGRICULTURE, CROP MODEL, MODELING, SIMULATION,
TEMPERATURE, YIELD

540  
Norby, R.J. 1987. Nodulation and Nitrogenase Activity in Nitrogen-fixing Woody Plants Stimulated by CO2 Enrichment of the Atmosphere.
Physiologia Plantarum 71:77-82.

The responses of three species of nitrogen-fixing trees to CO2
enrichment of the atmosphere were investigated under nutrient-poor
conditions. Seedlings of the legume, Robinia pseudoacacia L. and
the actinorhizal species, Alnus glutinosa (L.) Gairtn. and
Elaeagnus angustifolia L. were grown in an infertile forest soil in
controlled environment chambers with atmospheric CO2 concentrations
of 340 uL/L (ambient) or 700 uL/L. In R. pseudoacacia and A.
glutinosa, total nitrogenase (N2 reduction) activity per plant,
assayed by the acetylene reduction method, was significantly higher
in elevated CO2, because the plants were larger and had more nodule
mass than did plants in ambient CO2. The specific nitrogenase
activity of the nodules, however, was not consistently or
significantly affected by CO2 enrichment. Substantial increases in
plant growth occurred with CO2 enrichment despite probable nitrogen
and phosphorus deficiencies. These results support the premises
that nutrient limitations will not preclude growth responses of
woody plants to elevated CO2 and that stimulation of symbiotic
activity by CO2 enrichment of the atmosphere could increase
nutrient availability in infertile habitats.

Robinia pseudoacacia/Alnus glutinosa/Elaeagnus angustifolia

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
NITROGEN FIXATION, NITROGENASE ACTIVITY, NODULATION, NUTRITION,
PHOSPHORUS, TREES

541  
Norby, R.J. 1989. Direct Responses of Forest Trees to Rising
Atmospheric Carbon Dioxide. IN: Proceedings of the Second US-USSR
Symposium, Air Pollution Effects on Vegetation including Forest
Ecosystems, 13-25 September 1988, Corvallis, Oregon, Raleigh, North
Carolina, Gatlinburg, Tennessee, and Broomall, Pennsylvania (R.D.
Noble, J.L. Martin, and K.F. Jensen, eds.), USDA Forest Service,
Northeastern Forest Experiment Station, pp. 243-248.

KEYWORDS: FOREST, TREES

542  
Norby, R.J., C.A. Gunderson, S.D. Wullschleger, E.G. O'Neill, and
M.K. McCracken. 1992. Productivity and Compensatory Responses of
Yellow-poplar Trees in Elevated CO2. Nature 357:322-324.

Increased forest growth in response to globally rising CO2
concentrations could provide an additional sink for the excess
carbon added to the atmosphere from fossil fuels. The response of
trees to increased CO2, however, can be expected to be modified by
the interactions of other environmental resources and stresses,
higher-order ecological interactions and internal feedbacks
inherent in the growth of large, perennial organisms. To test
whether short-term stimulation of tree growth by elevated CO2 can
be sustained without inputs from other environmental resources, we
grew yellow-poplar (Liriodendron tulipifera L.) saplings for most
of three growing seasons with continuous exposure to ambient or
elevated concentrations of atmospheric CO2. Despite a sustained
increase in leaf-level photosynthesis and lower rates of foliar
respiration in CO2-enriched trees, whole-plant carbon storage did
not increase. The absence of a significant growth response is
explained by changes in carbon allocation patterns, specifically a
relative decrease in leaf production and an increase in fine root
production. Although these compensatory responses reduced the
potential increase in carbon storage in increased CO2
concentrations, they also favour the efficient use of resources
over the longer term.

Liriodendron tulipifera/yellow poplar

KEYWORDS: ALLOCATION, GROWTH EFFICIENCY, LEAF PHOTOSYNTHESIS,
NITROGEN, OPEN-TOP CHAMBERS, RESPIRATION, TREES

543  
Norby, R.J., and E.G. O'Neill. 1989. Growth Dynamics and Water Use
of Seedlings of Quercus alba L. in CO2-enriched Atmospheres. New
Phytologist 111:491-500.

White oak (Quercus alba L.) seedlings were grown from a half-sib
collection of acorns in pots containing a nutrient-poor forest soil
and maintained in controlled-environment chambers having mean
atmospheric CO2 concentrations of 389, 496, and 793 cm3/m3.
Additions of nitrogen and phosphorus to the soil increased plant
growth, indicating that the unfertilized plants were nutrient
deficient. Despite the nutrient deficiency, the plants grown in
elevated concentrations of CO2 generally were larger than those in
ambient CO2, but dry weight data from harvests at 5, 12, 24, and 36
weeks provided insufficient evidence of an effect of CO2 because of
the high variability associated with the recurrently-flushing habit
of these seedlings. Mathematical growth analysis based on periodic
non-destructive measurements allowed comparisons of the continuous
growth patterns of the plants and avoided the problems of
ontogenetic variation. CO2 enrichment was thus shown to increase
plant growth rate primarily through increased unit leaf rate rather
than increased leaf area production. Unit leaf rate during the
second half of the experiment was 22 and 27% higher in the medium
and high concentrations of CO2 compared with that in low CO2.
Instantaneous measurements of foliar gas exchange also showed that
CO2 assimilation increased with CO2 enrichment. The most pronounced
effect of CO2 enrichment was increased water-use efficiency, which
was shown both through whole-plant gravimetric analysis and
instantaneous gas exchange measurements. Whole-plant water-use
efficiency for the duration of the experiment was increased by 52
and 82% by the medium and high concentrations of CO2. Limitations
of resources, including water and nutrients, do not preclude plant
growth responses to CO2 enrichment of the atmosphere.

Quercus alba/white oak

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS,
NITROGEN, NUTRITION, PHOSPHORUS, TREES, WUE

544  
Norby, R.J., and E.G. O'Neill. 1991. Leaf Area Compensation and
Nutrient Interactions in CO2-enriched Seedlings of Yellow-poplar
(Liriodendron tulipifera L.). New Phytologist 117:515-528.

The responses of yellow-poplar (Liriodendron tulipifera L.)
seedlings to elevated levels of atmospheric CO2 were investigated
to identify attributes governing growth and physiological responses
to CO2. Based on the pattern of leaf initiation and nutrient
requirements of the species, it was predicted that (1) CO2
enrichment would enhance growth of yellow-poplar seedlings both
through accelerated leaf area production and through higher rates
of carbon assimilation per unit leaf area; and (2) growth
enhancement of yellow-poplar by CO2 enrichment would be reduced by
nutrient limitations. The hypotheses were tested in an experiment
in which yellow-poplar plants were grown from seed for 24 weeks in
controlled environment chambers. The experimental design comprised
three atmospheric CO2 concentrations (371, 493, and 787 cm3/m3),
two levels of mineral nutrients (unfertilized or weekly additions
of complete nutrient solution), and three harvests (6, 12, and 24
weeks). Plant growth rate, water use, foliar gas exchange,
component dry weights, and nutrient contents were measured. Both
hypotheses were rejected. Whole-plant dry weight increased
similarly with CO2 enrichment in plants provided with additional
mineral nutrients and in unfertilized plants, although the
fertilized plants grew 10-fold larger. The increase in dry weight
resulting from elevated CO2 occurred only in root systems. Although
leaves were produced continuously during the experiment, leaf area
was slightly reduced in elevated CO2, and the whole-plant growth
response was wholly attributable to an increase in carbon
assimilation per unit leaf area. Although the compensation between
photosynthesis and leaf area reduced the potential growth response
to CO2, the reduction in leaf area ratio was associated with a
significant increase in water-use efficiency. This unexpected
result demonstrated the importance of feedbacks and interactions
between resources in shaping the response of a plant to CO2.

Liriodendron tulipifera/tulip poplar

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, LEAF AREA DEVELOPMENT, PHOTOSYNTHESIS, TREES, WUE

545  
Norby, R.J., E.G. O'Neill, W.G. Hood, and R.J. Luxmoore. 1987.
Carbon Allocation, Root Exudation and Mycorrhizal Colonization of
Pinus echinata Seedlings Grown under CO2 Enrichment. Tree
Physiology 3:203-210.

Increased exudation of carbon compounds from roots may provide a
mechanism for enhancement of nutrient availability to plants
growing in a CO2-enriched atmosphere. Therefore, the effect of
atmospheric CO2 concentration on carbon allocation and root
exudation was investigated in Pinus echinata Mill. (shortleaf pine)
seedlings. After 34 and 41 weeks, seedlings growing in 695 uL/L CO2
allocated proportionately more 14C-labeled photosynthate to fine
roots than did seedlings growing in ambient air. This was
associated with greater fine root mass and mycorrhizal density in
CO2-enriched plants after 34 weeks. Exudation of soluble, 14C-labeled compounds from roots also was greater in these plants at 34
weeks, but the effect of CO2 concentration on exudation did not
persist at 41 weeks.

Pinus echinata/shortleaf pine

KEYWORDS: 14C, ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS,
MYCORRHIZAE, NUTRITION, ROOT EXUDATION, ROOTS, TREES

546  
Norby, R.J., E.G. O'Neill, and R.J. Luxmoore. 1986. Effects of
Atmospheric CO2 Enrichment on the Growth and Mineral Nutrition of
Quercus alba Seedlings in Nutrient-poor Soil. Plant Physiology
82:83-89.

One-year-old dormant white oak (Quercus alba L.) seedlings were
planted in a nutrient-deficient forest soil and grown for 40 weeks
in growth chambers at ambient (362 microliters per liter) or
elevated (690 microliters per liter) levels of CO2. Although all of
the seedlings became severely N deficient, CO2 enrichment enhanced
growth by 85%, with the greatest enhancement in root systems. The
growth enhancement did not increase the total water use per plant,
so water-use efficiency was significantly greater in elevated CO2.
Total uptake of N, S, and B was not affected by CO2, therefore,
tissue concentrations of these nutrients were significantly lower
in elevated CO2. An increase in nutrient-use efficiency with
respect to N was apparent in that a greater proportion of the
limited N pool in the CO2-enriched plants was in fine roots and
leaves. The uptake of other nutrients increased with CO2
concentration, and P and K uptake increased in proportion to
growth. Increased uptake of P by plants in elevated CO2 may have
been a result of greater proliferation of fine roots and associated
mycorrhizae and rhizosphere bacteria stimulating P mineralization.
The results demonstrate that a growth response to CO2 enrichment is
possible in nutrient-limited systems, and that the mechanisms of
response may include either increased nutrient supply or decreased
physiological demand.

Quercus alba/white oak

KEYWORDS: ALLOCATION, ALUMINUM, BORON, CALCIUM, CONTROLLED
ENVIRONMENT CHAMBERS, COPPER, IRON, MAGNESIUM, MANGANESE,
MYCORRHIZAE, NITROGEN, NUTRIENT USE EFFICIENCY, NUTRITION,
PHOSPHORUS, POTASSIUM, SOIL MICROORGANISMS, STRONTIUM, SULFUR,
TREES, WUE, ZINC

547  
Norby, R.J., J. Pastor, and J.M. Melillo. 1986. Carbon-nitrogen
Interactions in CO2-enriched White Oak: Physiological and Long-term
Perspectives. Tree Physiology 2:233-241.

The responses of forest trees to atmospheric CO2 enrichment will
depend in part on carbon-nutrient linkages. Insights into the
possible long-term ecological consequences of CO2 enrichment can be
gained from studying physiological responses in short-term
experiments. One-year-old white oak (Quercus alba L.) seedlings
were grown in unfertilized forest soil for 40 weeks in controlled
environment chambers with ambient (362 uL/L) or elevated (690 uL/L)
CO2. As previously reported, seedling dry weight was 85% greater in
the elevated CO2 environment, despite severe nitrogen deficiency in
all seedlings. The increase in growth occurred without a
concomitant increase in nitrogen uptake, indicating an increase in
nitrogen-use efficiency in elevated CO2. The weight of new buds was
greater in elevated CO2, suggesting that shoot growth in the next
year would have been enhanced relative to that of seedlings in
ambient CO2. However, there was less translocatable nitrogen in
perennial woody tissue in elevated CO2; thus, further increases in
nitrogen-use efficiency may not be possible. The leaves that
abscised from seedlings in elevated CO2 contained higher amounts of
soluble sugars and tannin and a lower amount of lignin compared
with amounts in abscised leaves in ambient CO2. Based on lignin:N
and lignin:P ratios, the rates of litter decomposition might not be
greatly affected by CO2 enrichment, but the total amount of
nitrogen returned to soil would be lower in elevated CO2.

Quercus alba/white oak

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
LITTER QUALITY, NITROGEN, NUTRITION, PHOSPHORUS, TREES

548  
Norby, R.J., and L.L. Sigal. 1989. Nitrogen Fixation in the Lichen
Lobaria pulmonaria in Elevated Atmospheric Carbon Dioxide.
Oecologia 79:566-568.

Thalli of Lobaria pulmonaria (L.) Hoffm., a nitrogen-fixing
epiphyte common in mesic temperate forests, were collected in a
Douglas-fir (Pseudotsuga menziesii Franco) forest near Corvallis,
Oregon, and maintained for 20 to 40 days in controlled-environment
chambers with atmospheric CO2 concentrations of 374 and 700 uL/L.
Nitrogenase activity, which was assayed by the acetylene reduction
method, was approximately doubled in the lichen maintained in
elevated CO2. Increases in nitrogen fixation by lichens may be an
important part of the integrated ecosystem response to rising CO2.

Lobaria pulmonaria/lichen

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN FIXATION,
NITROGENASE ACTIVITY

549  
Oberbauer, S.F., W.C. Oechel, and G.H. Riechers. 1986. Soil
Respiration of Alaskan Tundra at Elevated Atmospheric Carbon
Dioxide Concentrations. Plant and Soil 96:145-148.

CO2 efflux from tussock tundra in Alaska that had been exposed to
elevated CO2 for 2.5 growing seasons was measured to assess the
effect of long- and short-term CO2 enrichment on soil respiration.
Long-term treatments were: 348, 514, and 683 uL/L CO2 and 680 uL/L
CO2 + 4C above ambient. Measurements were made at 5 CO2
concentrations between 87 and 680 uL/L CO2. Neither long- or short-term CO2 enrichment significantly affected soil CO2 efflux. Tundra
developed at elevated temperature and 680 uL/L CO2 had slightly
higher, but not statistically different, mean respiration rates
compared to untreated tundra and to tundra under CO2 control alone.

KEYWORDS: SOIL RESPIRATION, TEMPERATURE, TRACKING CHAMBERS, TUNDRA

550  
Oberbauer, S.F., N. Sionit, S.J. Hastings, and W.C. Oechel. 1986.
Effects of CO2 Enrichment and Nutrition on Growth, Photosynthesis,
and Nutrient Concentration of Alaskan Tundra Plant Species.
Canadian Journal of Botany 64:2993-2998.

Three Alaskan tundra species, Carex bigelowii Torr., Betula nana
L., and Ledum palustre L., were grown in controlled-environment
chambers at two nutrition levels with two concentrations of
atmospheric CO2 to assess the interactive effects of these factors
on growth, photosynthesis, and tissue nutrient content. Carbon
dioxide concentrations were maintained at 350 and 675 uL/L under
photosynthetic photon flux densities of 450 umol/m2/s and
temperatures of 20:15C (light:dark). Nutrient treatments were
obtained by watering daily with 1/60- or 1/8-strength Hoagland's
solution. Leaf, root, and total biomass were strongly enhanced by
nutrient enrichment regardless of the CO2 concentration. In
contrast, enriched atmospheric CO2 did not significantly affect
plant biomass and there was no interaction between nutrition and
CO2 concentration during growth. Leaf photosynthesis was increased
by better nutrition in two species but was unchanged by CO2
enrichment during growth in all three species. The effects of
nutrient addition and CO2 enrichment on tissue nutrient
concentrations were complex and differed among the three species.
The data suggest that CO2 enrichment with or without nutrient
limitations has little effect on the biomass production of these
three tundra species.

Carex bigelowii/Betula nana/Ledum palustre

KEYWORDS: ALLOCATION, BORON, CALCIUM, CONTROLLED ENVIRONMENT
CHAMBERS, COPPER, GROWTH, IRON, LEAF PHOTOSYNTHESIS, MAGNESIUM,
MANGANESE, NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM, TUNDRA, ZINC

551  
Oechel, W.C., S. Hastings, D. Hilbert, W. Lawrence, T. Prudhomme,
G. Riechers, and D. Tissue. 1984. The Response of Arctic Ecosystems
to Elevated Carbon Dioxide Regimes, 019 in Green Report Series,
Response of Vegetation to Carbon Dioxide. U.S. Dept. of Energy,
Carbon Dioxide Research Division, Washington, D.C.

Carex bigelowii/Eriophorum vaginatum/Ledum palustre/Vaccinium
vitis-idaea/Vaccinium uliginosum/Betula nana/Salix pulchra

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON SEQUESTERING, COMMUNITY
LEVEL CO2 RESPONSES, EXPOSURE METHODS, MODELING, RESPIRATION,
SPECIES COMPETITION, TRACKING CHAMBERS, TUNDRA

552  
Oechel, W.C., G. Riechers, W.T. Lawrence, T.I. Prudhomme, N.
Grulke, and S.J. Hastings. 1992. 'CO2LT' an Automated, Null-balance
System for Studying the Effects of Elevated CO2 and Global Climate
Change on Unmanaged Ecosystems. Functional Ecology 6:86-100.

An automated, CO2-controlled, long-term greenhouse system ('CO2LT')
has been developed to provide replicated in situ ecosystem-level
manipulation of atmospheric CO2 concentration and temperature for
intact plots of tussock tundra, and to measure the instantaneous
ecosystem-level CO2 exchange rates within each of the plots under
the treatments imposed. This is a computer-controlled, closed,
null-balance greenhouse system consisting of 12 chambers with
individual control of CO2 concentration and temperature. Carbon
dioxide can be maintained in each chamber at concentrations from
well below ambient (150-200 uL/L) to more than 900 uL/L. Air
temperature can be fixed, set to track ambient, or can track
ambient temperature with a specified offset allowing studies of the
interaction of CO2 and temperature. Despite the complications
involved in tracking a naturally fluctuating environment, the CO2LT
system performs very well. Temperatures in individual chambers
averaged within 1C of ambient or target temperatures over a 24-h
period and carbon dioxide concentration control rivals that of
laboratory-based, control-environment systems. Photon flux density
within the chambers is within 93% of ambient values. Comparison to
unenclosed tundra indicates minimal chamber effects on depth of
thaw, air, leaf or soil temperatures, or net ecosystem CO2 flux.
Chamber effects are generally small, and the experimental design
allows separation and interpretation of treatment effects despite
any unavoidable chamber effects. Both diurnal and seasonal patterns
of net ecosystem CO2 flux can be accurately tracked with this
system. Field measurements indicate net ecosystem CO2 loss under
current environmental conditions, a possible response to recent
climate change. Field measurements also indicate initial
enhancement of net ecosystem CO2 uptake with elevated atmospheric
CO2. Photosynthetic adjustment to elevated CO2 lowers ecosystem
response to that of ambient chambers by mid-season. Also indicated
is the possibility of delayed senescence of photosynthetic capacity
at elevated CO2.

KEYWORDS: CANOPY PHOTOSYNTHESIS, EXPOSURE METHODS, TRACKING
CHAMBERS, TUNDRA

553  
Oechel, W.C., G.H. Riechers, J. Beyers, S. Cowles, N. Grulke, S.
Hastings, S. Oberbauer, T. Prudhomme, and N. Sionit. 1986. Response
of a Tundra Ecosystem to Elevated Atmospheric Carbon Dioxide, 037
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington,
D.C.

Vaccinium vitis-idaea/Eriophorum vaginatum/Ledum palustre/Carex
bigelowii/Betula nana

KEYWORDS: ALLOCATION, EXPOSURE METHODS, LEAF PHOTOSYNTHESIS,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, SOIL RESPIRATION, TRACKING
CHAMBERS, TUNDRA

554  
Oechel, W.C., and B.R. Strain. 1985. Native Species Responses to
Increased Atmospheric Carbon Dioxide Concentration. IN: Direct
Effects of Increasing Carbon Dioxide on Vegetation, DOE/ER-0238
(B.R. Strain and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide
Research Division, Washington, D.c., pp. 117-154.

KEYWORDS: ALLOCATION, ECOSYSTEM LEVEL CO2 RESPONSES, GROWTH, LEAF
PHOTOSYNTHESIS, MODELING, PHENOLOGY, PHYSIOLOGICAL CO2 RESPONSES,
RESPIRATION, REVIEW, ROOT EXUDATION, WUE

555  
Olesen, J.E. 1990. Evaluating the Effect of Climatic Change on
Productivity of Agricultural Crops in Denmark. IN: The Greenhouse
Effect and Primary Productivity in European Agro-ecosystems; 5-10
April 1990; Wageningen, The Netherlands (J. Goudriaan, H. van
Keulen, and H.H. van Laar, eds.), Pudoc, Wageningen, pp. 53-56.

KEYWORDS: AGRICULTURE, CROP MODEL, LIGHT, MODELING, SIMULATION,
TEMPERATURE, WATER STRESS

556  
O'Neill, E.G., R.J. Luxmoore, and R.J. Norby. 1987. Elevated
Atmospheric CO2 Effects on Seedling Growth, Nutrient Uptake, and
Rhizosphere Bacterial Populations of Liriodendron tulipifera L.
Plant and Soil 104:3-11.

Yellow-poplar (Liriodendron tulipifera L.) seedlings were planted
in unfertilized forest soil in boxes with a removable side panel
and grown in atmospheres containing either ambient (367 uL/L) or
elevated (692 uL/L) CO2. Numbers of total bacteria, nitrifiers, and
phosphate-dissolving bacteria in the rhizosphere and in
nonrhizosphere soil were measured every 6 weeks for 24 weeks.
Seedling growth and nutrient content were measured at a final
whole-plant harvest. Root, leaf, and total dry weights were
significantly greater, and specific leaf area was significantly
less, in 692 uL/L than in ambient CO2. Uptake per gram plant dry
weight of N, S, and B was lower at elevated CO2 whereas uptake of
P, K, Cu, Al, and Fe was proportional to growth in both CO2
treatments. Total uptake and uptake per g plant dry weight of Ca,
Mg, Sr, Ba, Zn, and Mn were not affected by CO2 treatment.
Bacterial populations differed due to CO2 only at the final
harvest, where there were significantly fewer nitrite-oxidizers and
phosphate-dissolving bacteria in the rhizosphere of seedlings grown
at 692 uL/L CO2.

yellow poplar/Liriodendron tulipifera

KEYWORDS: ALUMINUM, BARIUM, BORON, CALCIUM, CONTROLLED ENVIRONMENT
CHAMBERS, COPPER, GROWTH, IRON, MAGNESIUM, MANGANESE, NITROGEN,
NUTRITION, PHOSPHORUS, POTASSIUM, RHIZOSPHERE, SOIL MICROORGANISMS,
STRONTIUM, SULFUR, TREES, ZINC

557  
O'Neill, E.G., R.J. Luxmoore, and R.J. Norby. 1987. Increases in
Mycorrhizal Colonization and Seedling Growth in Pinus echinata and
Quercus alba in an Enriched CO2 Atmosphere. Canadian Journal of
Forest Research 17:878-883.

Forest tree biomass is hypothesized to increase in a CO2-enriched
atmosphere if mechanisms exist to ensure acquisition of limiting
nutrients in forest soils. Investment of additional photosynthate
produced at elevated CO2 into mycorrhizal proliferation and root
growth may provide one such mechanism. To test this hypothesis,
mycorrhizal density and seedling biomass were measured in shortleaf
pine (Pinus echinata Mill.) and white oak (Quercus alba L.) grown
in unfertilized forest soil in controlled-environment chambers at
360 uL/L and 700 uL/L CO2. Mycorrhizal density was greater at
elevated CO2 in both species after 6 weeks of exposure; in white
oak, the increased density persisted for 24 weeks. Root dry weight
was increased 76% in P. echinata and 91% in Q. alba at 700 uL/L
CO2; total seedling dry weight was increased by 66 and 56%,
respectively. It is hypothesized that increased photosynthesis at
elevated CO2 offsets the carbon requirement for mycorrhizal
establishment on shortleaf pine. Greater mycorrhizal density and
enhanced 1st year root growth in both species may facilitate future
nutrient acquisition, supporting further increases in an enriched
CO2 atmosphere.

Quercus alba/white oak/Pinus echinata/shortleaf pine

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, MYCORRHIZAE,
NUTRITION, SOIL MICROORGANISMS, TREES

558  
Osbrink, W.L.A., J.T. Trumble, and R.E. Wagner. 1987. Host
Suitability of Phaseolus lunata for Trichoplusia ni (Lepidoptera:
Noctuidae) in Controlled Carbon Dioxide Atmospheres. Environmental
Entomology 16:639-644.

Elevated atmospheric carbon dioxide (CO2) levels of 1,000 parts per
million (ppm) significantly increased consumption of foliage by
Trichoplusia ni (Hubner) and significantly enhanced growth of
Phaseolus lunata L. when compared with ambient levels of 340 ppm.
Mean pupal weight was less under treatments with elevated
atmospheric CO2 under a high fertilization regime, but larval
survival and percent nitrogen content of pupae were not affected by
level of CO2 treatments at high, medium or low fertilizer rates.
Regardless of CO2 concentration, larval survival and pupal weight
were reduced in absence of fertilizer. Nitrogen and protein
consumption increased with fertilization rate. Because percent leaf
area of plants consumed by T. ni larvae was not affected by CO2
concentration, this study suggests that increased plant growth
resulting from elevated atmospheric CO2 may benefit the plant
proportionately more than the insect.

Phaseolus lunata/lima bean

KEYWORDS: CABBAGE LOOPER, GROWTH, HERBIVORY, INSECTS, NITROGEN,
TRICHOPLUSIA NI

559  
Overdieck, D. 1986. Long-term Effects of an Increased CO2
Concentration on Terrestrial Plants in Model Ecosystems. Morphology
and Reproduction of Trifolium repens L. and Lolium perenne L.
International Journal of Biometeorology 30:323-332.

Mixtures (ratio 1:1, 45 seeds/dm2) of perennial ryegrass (Lolium
perenne) and white clover (Trifolium repens) were enclosed in
environmentally controlled acrylic mini-glasshouses and supplied
with additional CO2 from September 1981 until September 1982 (547-600 ppm, control: about 340 ppm CO2). At growth optimum the single
leaf area of white clover was 30% greater and the specific leaf
weight 19% higher with additional CO2; with the perennial ryegrass
it was 18% resp. 29%. The length growth of the white clover
petioles was enhanced by the additional CO2: in the beginning 67%
longer leafstalks, at growth optimum no effect and at the end of
the experiment 100%. At growth optimum the specific petiole weight
was approximately 52% higher. When the growing was terminated the
blades of perennial ryegrass were 19% longer at high CO2. The
average volume of the flowerheads was about 53% greater and the
adult ears 13% longer. The number of flowers per flower head and
the number of earlets per ear did not increase significantly. On
the average the white clover seeds were 28% heavier and the
caryopses were 4% lighter.

Trifolium repens/white clover/Lolium perenne/perennial ryegrass

KEYWORDS: GRASSES, GROWTH, MORPHOLOGY, PASTURE, REPRODUCTION,
SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

560  
Overdieck, D. 1987. Untersuchungen uber die voraussichtlichen
Langzeiteffekte einer CO2-bedingten Klimaveranderung auf die
einheimische Vegetation. Universitat Osnabruck, Fachbereich
Biologie/Chemie, Arbeitsgruppe Okologie, Osnabruck.

Long-term experiments were conducted on herbaceous species at
constant microclimatic conditions and at natural conditions on
simplified stands of Middle-European grassland-vegetation units
using atmospheric CO2 concentrations from 270 to 650 uL/L CO2. At
elevated CO2 supply stems grow longer and more voluminously, leaf
areas increase, and in most cases more material is translocated to
storage organs. A minor CO2 impoverishment (270 uL/L CO2) leads to
overproportionate losses in production. Increasing CO2
concentrations have more effect at lower than at higher CO2 levels.
The CO2 enrichment effect is enhanced by increasing light
intensities. Increasing temperatures support the positive CO2
effect up to 35C beyond that their effect is negative. Grassland
ecosystems can only be an effective sink for additionally emitted
CO2 during their juvenile phases and after mowing. This CO2 effect
on the systems decreases in the second year considerably. CO2
enrichment influences the performance of grassland species in
competition (changes in the spectrum of species). At the beginning
of growth the absolute nutrient uptake increases with CO2
enrichment which can lead to nutrient deficiencies on poorer soils.
Two mathematical methods were developed for modelling the CO2
effect on grassland-ecosystems in dependance of many ecological
factors including all microclimatic factors of the experiments (1st
approach: 4 factors, 2nd: 7 factors). One of the methods is based
on pseudocubical splines. In German.

Vigna unguiculata/cowpea/Abelmoschus esculentus/okra/Raphanus
sativus/radish/Lolium perenne/perennial ryegrass/Trifolium
repens/white clover/Festuca pratensis/meadow fescue/Trifolium
pratense/red clover

KEYWORDS: ANATOMY, CALCIUM, ECOSYSTEM LEVEL CO2 RESPONSES,
ECOSYSTEM MODEL, GRASSES, LIGHT, MODELING, NITROGEN, NUTRITION,
PHOSPHORUS, POTASSIUM, PRE-INDUSTRIAL CO2 CONCENTRATION, SPECIES
COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, TEMPERATURE

561  
Overdieck, D. 1989. The effects of Preindustrial and Predicted
Future Atmospheric CO2 Concentration on Lyonia mariana L.D. Don.
Functional Ecology 3:569-576.

CO2 net assimilation and transpiration rates were measured on the
entire above-ground parts of 7-8-month-old seedlings of Lyonia
mariana L.D. Don (Ericaceae) grown for 2-3 months at 270
(preindustrial concentration), 350 and 650 uL CO2/L at constant
climatic conditions in growth chambers. Slight CO2-enrichment from
270 to 350 uL CO2/L elevated the level of the light response curve
by about 25% at light saturation and enrichment from 350 to 650 uL
CO2/L elevated this level by about 27%. The light compensation
points decreased with increasing CO2 (270: about 108; 350: about
94; 650 uL CO2/L: about 83 umol photons/m2/s. At each CO2 treatment
the response to the increase of internal CO2 could be described by
polynomials (maxima at 600-800 uL CO2/L). The curves differed in
CO2 compensation points (270: about 55; 350: about 58; 650 uL
CO2/L: about 70 uL CO2/L (Ci). The initial CO2 yield per uL CO2/L
concentration increase amounted to about 10.5 (270), about 9.5
(350) and 7.1 ug CO2/dm2/h (650 uL CO2/L). The mean transpiration
rate during the investigation of light and CO2-response was 16%
lower at 350 than at 270 and 15.5% lower at 650 than at 350 uL
CO2/L.

Lyonia mariana

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LIGHT, MODELING,
PHOTOSYNTHESIS, PRE-INDUSTRIAL CO2 CONCENTRATION, TRANSPIRATION

562  
Overdieck, D. 1990. Direct Effects of Elevated CO2 Concentration
Levels on Grass and Clover in 'Model-ecosystems'. IN: Expected
Effects of Climatic Change on Marine Coastal Ecosystems (J.J.
Beukema, W.J. Wolff, and J.J.W.M. Brouns, eds.), Kluwer Academic
Publishers, Dordrecht, The Netherlands, pp. 41-47.

In long-term experiments (up to 2.5 vegetation periods)
grass/clover-mixtures (1:1) were exposed to 4 CO2 concentration
levels (340, 450, 600, and 800 mm3/dm3) in acrylic-miniglasshouses
which were climatized according to the microclimate outside. At 600
mm3/dm3, plant growth and production were enhanced by 20-40%
compared to cultures at 340 mm3/dm3. Only the seed weight of the
clover species increased by max. 28% with elevated CO2
concentration levels. Without clippings, the clover species tended
to be more enhanced by additional CO2. With clippings, the grass
was more successful in competition. The C/N-, C/P-, C/Ca- and C/K-relationships were higher at elevated CO2 concentration level. The
CO2 net fixation of the whole canopy increased by 40% when the CO2
concentration was raised from 340 to 600 mm3/dm3. This enhancement
decreased until the end of the third vegetation period to about
10%. The ecological consequences of these findings are discussed.

Trifolium repens/white clover/Lolium perenne/perennial
ryegrass/Trifolium pratense/red clover/Festuca pratensis/meadow
grass

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON:NITROGEN RATIO, ECOSYSTEM
LEVEL CO2 RESPONSES, GRASSES, GROWTH, NITROGEN, NUTRITION, PASTURE,
REPRODUCTION, SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT
CHAMBERS

563  
Overdieck, D. 1990. Effects of Elevated CO2-concentration Levels on
Nutrient Contents of Herbaceous and Woody Plants. IN: The
Greenhouse Effect and Primary Productivity in European Agro-ecosystems; 5-10 April 1990; Wageningen, The Netherlands (J.
Goudriaan, H. van Keulen, and H.H. van Laar, eds.), Pudoc,
Wageningen, pp. 31-37.

Trifolium pratense/red clover/Festuca pratensis/meadow fescue/Acer
pseudoplatanus/mountain maple/sycamore maple/Fagus sylvatica/beech

KEYWORDS: CALCIUM, GRASSES, IRON, MAGNESIUM, MANGANESE, NITROGEN,
NUTRITION, PHOSPHORUS, POTASSIUM, SUNLIT CONTROLLED ENVIRONMENT
CHAMBERS, TREES, ZINC

564  
Overdieck, D. 1993. Elevated CO2 and the Mineral Content of
Herbaceous and Woody Plants. Vegetatio 104/105:403-411.

The CO2 enrichment effects (300-650 umol/mol) on mineral
concentration (N, P, K, Ca, Mg, Mn, Fe, Zn), absolute total mineral
contents per individual and of whole stands of four herbaceous
(Trifolium repens L., Trifolium pratense L., Lolium perenne L.,
Festuca pratensis HUDS.) and two woody species (Acer pseudoplatanus
L., Fagus sylvatica L.) were investigated. In general, the mineral
concentration of the plant tissues decreased (all six species:
N>Ca>K>Mg) with the exception of P. Mn and Fe were only determined
for the tree species. Both decreased in concentration (Mn>Fe). Zn
was only analysed for Trifolium pratense and Festuca pratensis and
decreased significantly in the grass. Despite of decreases in
concentrations of as much as 20% in some cases there were increases
in absolute amounts per individual and, therefore, in the whole
vegetation up to 25% because of the enhanced dry matter
accumulation at elevated CO2 supply.

Trifolium repens/white clover/Trifolium pratense/red clover/Lolium
perenne/perennial ryegrass/Festuca pratensis/meadow fescue/Acer
pseudoplatanus/sycamore maple/Fagus sylvatica/beech

KEYWORDS: CALCIUM, GRASSES, MAGNESIUM, MANGANESE, NITROGEN,
NUTRITION, PHOSPHORUS, POTASSIUM, SUNLIT CONTROLLED ENVIRONMENT
CHAMBERS, TREES, ZINC

565  
Overdieck, D., and D. Bossemeyer. 1985. Langzeit-Effekte eines
erhohten CO2-Angebotes auf den CO2-Gaswechsel eines Modell-Okosystems. Angewandte Botanik 59:179-198.

A model ecosystem composed of 30 cm deep homogenized garden soil
and a mixture of clover and grass (Trifolium repens L. and Lolium
perenne L., 1:1, 45 seeds/dm2) was supplied with about 600 ppm CO2
in the air in an acrylic glasshouse from the beginning of
germination for a total period of one year (03. Sept.-31. Aug.).
With slight deviations (+/- 0.5C) the air temperature in the
glasshouse was adjusted to the air outside. The values of relative
air humidity corresponded approximately with the outside values.
Besides, the photon flux density (photosynthetically active
radiation) inside the glasshouse and the CO2 gas exchange rates of
the system were continuously registered together with the climatic
parameters (measuring interval: 48 s). A parallel control
experiment was run in the same way; there the CO2 concentration was
held at about 330 ppm. The better CO2 supply caused higher CO2 net
fixation rates during the whole experiment with the exception of
days with low photon flux densities (mostly <100 umol/m2/s). This
positive CO2 effect grew with increasing photon flux density and
increasing air temperature. An influence of the relative air
humidity on the CO2 effect could not be identified. In most cases
the relationship between photon flux density and CO2 gas exchange
rates within different temperature classes and different stages of
development could easily be approximated by saturation curves. With
growing age the 600 ppm CO2 system reached increasingly higher
compensation points compared to the 330 ppm CO2 system and the
level of irradiation saturation was relatively more elevated than
at 330 ppm CO2. In the total balance at about 600 ppm CO2
approximately 1.7 kg/m2/a more CO2 were net fixed than at about 330
ppm (50% more). At the peak of growth the difference of the total
phytomass between the systems was 0.6 g/m2 (dry matter increase of
43%). In German.

Trifolium repens/white clover/Lolium perenne/perennial ryegrass

KEYWORDS: CANOPY PHOTOSYNTHESIS, GRASSES, GROWTH, HUMIDITY, LIGHT,
PASTURE, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, TEMPERATURE

566  
Overdieck, D., and M. Forstreuter. 1991. Carbon Dioxide Effects on
Vegetation. IN: Modern Ecology: Basic and Applied Aspects (G. Esser
and D. Overdieck, eds.), Elsevier, New York, pp. 623-657.

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, ECOSYSTEM LEVEL CO2
RESPONSES, GROWTH, MODELING, REPRODUCTION, REVIEW, SUNLIT
CONTROLLED ENVIRONMENT CHAMBERS, WATER STATUS, WUE

567  
Overdieck, D., and H. Lieth. 1986. Long-term Effects of an
Increased Atmospheric CO2 Concentration Level on Terrestrial Plants
in Model-ecosystems. Universitat Osnabruck, Fachbereich
Biologie/Chemie, Arbeitsgruppe Okologie, Osnabruck.

The following results are most important for European landscape
management, agriculture, and forestry (30 plants were tested): 1.
A number of plants increase their productivity with increasing
atmospheric CO2 concentrations only during the juvenile phase of
development. 2. Different plants growing together in semi-natural
or managed plant communities vary in their response to increasing
CO2 concentrations. 3. Increasing atmospheric CO2 will cause
changes in competition of plants. 4. The additional growth at
elevated CO2 is not nutrient-limited on medium fertile soils. 5.
The absolute nutrient uptake increases at CO2-enrichment. Grassland
communities are a sink for additional CO2 only in the first
vegetation period after sowing. 6. The CO2-effect on growth and
productivity is enhanced by increasing light intensity. 7.
Increasing temperatures support the positive CO2 effect up to 35C.
8. The vegetation period starts earlier for several plants under
higher CO2 concentrations. The results of the experiments were used
to construct models for better data analysis and to improve our
regional and global models. From the results we can conclude that
no immediate major threats to plant growth may be expected from
slightly elevated CO2 concentrations. Most probable are changes in
species composition in several ecosystems due to different
responses of growth and seed production, there may be a higher
susceptibility to late frosts in certain species, and there may be
higher nutrient-uptake rates. These aspects require further studies
because they are important for the management of grasslands,
orchards, and fields. In German.

Lolium perenne/perennial ryegrass/Trifolium repens/white
clover/Fagus sylvatica/Picea abies/Pinus sylvestris/Lyonia
mariana/Lyonia lucida/Acer pseudoplatanus/Quercus robur/Beta
vulgaris/sugar beet/beet/Chenopodium album/white chenopod/Plantago
major/broadleaf plantain/Urtica dioica/stinging nettle/Rumex
obtusifolia/bluntleaved sorrel/Taraxacum
officinale/dandelion/Polygonum aviculare/bird's knotweed/Capsella
bursa-pastoris/shepherd's purse/Festuca rubra/red fescue/Festuca
pratensis/meadow fescue/Trifolium pratense/red clover/Secale
cereale/rye/Triticum aestivum/wheat/Hordeum vulgare/barley

KEYWORDS: CALCIUM, CANOPY PHOTOSYNTHESIS, GREENHOUSE, GROWTH
ANALYSIS, GROWTH STAGES, LIGHT, NET PRIMARY PRODUCTIVITY, NITROGEN,
NUTRITION, PASTURE, PHOSPHORUS, POTASSIUM, PRE-INDUSTRIAL CO2
CONCENTRATION, REPRODUCTION, SPECIES COMPETITION, SUNLIT CONTROLLED
ENVIRONMENT CHAMBERS, TEMPERATURE

568  
Overdieck, D., C. Reid, and B.R. Strain. 1988. The Effects of
Preindustrial and Future CO2 Concentrations on Growth, Dry Matter
Production and the C/N Relationship in Plants at Low Nutrient
Supply: Vigna unguiculata (Cowpea), Abelmoschus esculentus (Okra)
and Raphanus sativus (Radish). Angewandte Botanik 62:119-134.

The effects of preindustrial atmospheric CO2 concentration (270
uL/L), of current ambient CO2 concentration (350 uL/L) and the CO2
concentration predicted for the next century (650 uL/L) on growth,
dry matter production and the carbon/nitrogen relationship in dry
matter was studied with herbaceous annual plants grown from seed
for 32-34 days in environmentally controlled chambers. The plants
were cowpea (Vigna unguiculata L.), okra (Abelmoschus esculentus
(L.) Moench) and radish (Raphanus sativus L.). Total soil nutrients
were lowered to 1/8 of a normal Hoagland's solution. Stem length,
petiole length, and leaf area were not significantly affected by
the different CO2 levels. Stem diameter increased with increasing
CO2 in all three species. Lowering the CO2 concentration from
ambient to 270 uL/L decreased the mean total dry matter
accumulation by+/-8% and increasing the CO2 concentration to 650
uL/L enhanced it by +/- 40%. The CO2 response was the least in okra
where only the dry weight of the roots differed noticeably between
the CO2 treatments. With the 'root crop' radish, the hypocotyl
provided a sink for assimilates. Specific leaf areas (SLA) of the
three species increased under low CO2 and decreased under CO2
enrichment. Net Assimilation rates (NAR) increased with increasing
CO2 supply (270 < 340 < 650 uL/L). The highest nitrogen contents on
total dry weight basis were found at 270 uL/L, medium contents at
350 uL/L, and lowest at 650 uL/L. The differences were the greatest
in leaves. The roots of the legume cowpea contained the greatest N-amounts with 650 uL CO2/L at the end of the experiment. C/N ratios
increased with increasing atmospheric CO2 concentrations (except
for cowpea roots). Total absolute carbon accumulated per plant
increased 20-63% from 270 to 650 uL/L CO2 by the end of the study.

cowpea/Vigna unguiculata/okra/Abelmoschus
esculentus/radish/Raphanus sativus

KEYWORDS: ALLOCATION, CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH ANALYSIS, NITROGEN, PRE-INDUSTRIAL CO2
CONCENTRATION

569  
Overdieck, D., and E. Reining. 1986. Effect of Atmospheric CO2
Enrichment on Perennial Ryegrass (Lolium perenne L.) and White
Clover (Trifolium repens L.) Competing in Managed Model-ecosystems.
II. Nutrient Uptake. Acta Oecologica/Oecologia Plantarum 7:367-378.

A model ecosystem composed of 0.14 m3 homogenized garden soil and
a mixture of Trifolium repens L. and Lolium perenne L. (1:1, 45
seeds/dm2) was supplied with about 620 ppm CO2 in an acrylic
glasshouse (0.26 m3) for 90 days, started 10 days after germination
(9 July-5 October, 1983). A control experiment was run at about 300
ppm CO2. Aerial phytomass was removed by mowing four times in both
systems. Air temperatures and relative humidities in the glasshouse
corresponded approximately with those from the outside, the wind
velocity was at 0.5 m/s. The soil was medium fertile and was
loosing more Ca (total and Na-formate extractable), P (total and
Na-formate extractable), and K (Na-formate extractable) at about
620 ppm CO2 until the end of the experiment. This was not the case
of Kjeldahl-N. Due to the lower N contents of the plant tissues the
C/N relationships were higher at the elevated CO2 concentration.
These differences were greater with the grass than with the clover.
P was not significantly influenced, but at about 620 ppm CO2 lower
K percentages were found in the petioles and leaves of clover and
lower Ca percentages in the grass (total). Expressed on the ground
area unit (m2) 49.6% C, 10.9% N, 39.1% P, 32.8% K and 36.4% more Ca
was totally exported from the system with the elevated CO2
concentration via the mowed above ground plant parts.

Trifolium repens/white clover/Lolium perenne/perennial ryegrass

KEYWORDS: CALCIUM, CARBON:NITROGEN RATIO, GRASSES, NITROGEN,
NUTRITION, PASTURE, PHOSPHORUS, POTASSIUM, SUNLIT CONTROLLED
ENVIRONMENT CHAMBERS

570  
Overdieck, D., and F. Reining. 1986. Effect of Atmospheric CO2
Enrichment on Perennial Ryegrass (Lolium perenne L.) and White
Clover (Trifolium repens L.) Competing in Managed Model-ecosystems.
I. Phytomass Production. Acta Oecologica/Oecologia Plantarum 7:357-366.

A model ecosystem composed of 0.14 m3 homogenized garden soil and
a mixture of Trifolium repens L. and Lolium perenne L. (1:1, 45
seeds/dm2) was supplied with about 620 ppm CO2 in an acrylic
glasshouse (0.26 m3) for 90 days, started 10 days after germination
(9 July-5 October, 1983). A control experiment was run at about 300
ppm CO2. Aerial phytomass was removed by mowing four times in both
systems. Air temperatures in the glasshouses were adjusted to that
of the air outside (+/- 0.5C) and the wind velocity to 0.5 m/s.
The relative air humidities corresponded approximately with those
from the outside (+15%). Leaf area and above and below ground
phytomass accumulation of both species, net primary production and
net primary productivity were enhanced by the CO2 enrichment.
Before mowing Trifolium repens was more enhanced but after mowing
Lolium perenne became the most enhanced species.

Trifolium repens/white clover/Lolium perenne/perennial ryegrass

KEYWORDS: GRASSES, NET PRIMARY PRODUCTIVITY, PASTURE, ROOTS,
SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

571  
Owensby, C.E., P.I. Coyne, and L.M. Auen. 1989. Rangeland-Plant
Responses to Elevated CO2. Part II: Large-Chamber Systems, 059 in
Green Report Series, Response of Vegetation to Carbon Dioxide. U.S.
Dept. of Energy, Atmospheric and Climate Research Division,
Washington, D.C.

Andropogon gerardii/big bluestem/Indiangrass/Sorghastrum
nutans/Kentucky bluegrass/Poa pratensis/sideoats grama/Bouteloua
curtipendula/tall dropseed/Sporobolus asper/western
ragweed/Ambrosia psilostachya/Louisiana sagewort/Artemisia
ludoviciana/manyflower scurfpea/Psoralea tenuiflora

KEYWORDS: EXPOSURE METHODS, GRASSES, GRAZING, GROWTH, LEAF AREA
DEVELOPMENT, OPEN-TOP CHAMBERS, RUMINANTS, TALLGRASS PRAIRIE

572  
Owensby, C.E., P.I. Coyne, L.M. Auen, and N. Sionit. 1990.
Rangeland-Plant Response to Elevated CO2: Large-Chamber System;
Washington, D.C, 054 in Green Report Series, Response of Vegetation
to Carbon Dioxide. U.S. Dept. of Energy, Atmospheric and Climate
Research Division, Washington, D.C.

Andropogon gerardii/big bluestem/Sorghastrum nutans/Indiangrass/Poa
pratensis/Kentucky bluegrass/Bouteloua curtipendula/sideoats
grama/Sporobolus asper/tall dropseed/Ambrosia psilostachya/western
ragweed/Artemisia ludoviciana/Louisiana sagewort/Psoralea
tenuiflora/manyflower scurfpea

KEYWORDS: ACID DETERGENT FIBER, EXPOSURE METHODS, FORAGE QUALITY,
GRASSES, LITTER QUALITY, NITROGEN, OPEN-TOP CHAMBERS, ROOTS,
RUMINANTS, TALLGRASS PRAIRIE

573  
Pallas, J.E. 1986. CO2 Measurement and Control. IN: Status and CO2
Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide
Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton,
Florida, pp. 77-98.

The needs for CO2 measurement and control are many. We know (see
other chapters of these two volumes) that plants are very
responsive to the atmospheric CO2 concentration in which they are
growing. In some instances greater economic return can even be
obtained by elevating ambient CO2 concentration. In controlled
environmental experimentation the researcher should always measure
CO2 concentration for it may be his greatest variable. If it is
highly variable then it obviously needs control. Generally infrared
gas analyzers are the workhorses behind such CO2 measurement and
control. This chapter is primarily intended to not only provide
information but inspiration to those attempting control and
measurement.

KEYWORDS: CO2 MEASUREMENT AND CONTROL

574  
Palmqvist, K., Z.M. Ramazanov, P. Gardestrom, and G. Samuelsson.
1990. Mechanisms of Adaptation of Microalgae to Conditions of
Carbon Dioxide Limitation of Photosynthesis. Possible Role of
Carbonic Anhydrase. Fiziologiya Rastenii 37:912-920.

KEYWORDS: ALGAE, AQUATIC PLANTS, CELL CULTURE, ENZYMES, GROWTH
ANALYSIS, PHOTOSYNTHESIS

575  
Parker, M.L. 1985. Recent Abnormal Increase in Tree-ring Widths: A
Possible Effect of Elevated Atmospheric Carbon Dioxide. IN:
Proceedings of the International Symposium on Ecological Aspects of
Tree Ring Analysis (G.C. Jacoby and J.W. Hornbeck, eds.), NTIS,
Springfield, Virginia, pp. 511-521.

Atmospheric CO2 has increased from a preindustrial level of from
250 to 290 parts per million to a current level of about 345 ppm.
It is expected to double at some time in the 21st century.
Increased levels of CO2 have been shown to increase tree growth
under controlled conditions. Some forest trees may respond to
increased CO2 with increases in ring width, but this effect may be
obscured by other environmental influences at some sites. Ring
width values of Douglas-fir trees from a moist British Columbia
site show a marked increase during the past few decades.
Environmental influences other than increased CO2 have not been
found that would explain this. Pronounced growth increase during
the last few decades is not present for Douglas-fir from the dry
British Columbia interior. Raw ring width values were examined for
individual radii of trees from 17 sites in Canada and the northwest
United States. For the period after 1920, 7 sites show greater
ring-width growth than would be expected if age were the only
factor influencing growth. There is enough evidence to conclude
that increased atmospheric CO2, as well as other environmental
factors, can affect forest growth. We should now determine the
extent of that effect.

KEYWORDS: FOREST, TREE-RING ANALYSIS, TREES

576  
Parker, M.L., F.G. Taylor, T.W. Doyle, B.E. Foster, C. Cooper, and
D.C. West. 1985. Radiation Densitometry in Tree-Ring Analysis: A
Review and Procedure Manual, 020 in Green Report Series, Response
of Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon
Dioxide Research Division, Washington, D.C., and Environmental
Sciences Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee.

KEYWORDS: DENDROCHRONOLOGY, REVIEW, TREE-RING ANALYSIS, WOOD
PROPERTIES, X-RAY DENSITOMETRY

577  
Parry, M.A.J., E. Delgado, J. Vadell, A.J. Keys, D.W. Lawlor, and
H. Medrano. 1993. Water Stress and the Diurnal Activity of
Ribulose-1,5 Bisphosphate Carboxylase in Field Grown Nicotiana
tabacum Genotypes Selected for Survival at Low CO2 Concentrations.
Plant Physiology and Biochemistry 31:113-120.

Despite large differences in total dry matter at final harvest, no
significant differences (p </= 0.05) were detected in the activity
of ribulose-1,5 bisphosphate carboxylase/oxygenase (Rubisco; EC
4.1.1.39) or in its regulation by carbamylation between tobacco
genotypes selected for survival at low CO2 and their source
cultivar. Irrigated and water stressed plants of these genotypes
differed in the diurnal pattern of Rubisco activity in their
leaves. In irrigated plants Rubisco was not fully active even in
the presence of saturating irradiance in the middle of the day. The
maximum total activity reached during the day was higher in water
stressed plants than in irrigated ones. Through the day
decarbamylation of lysine 201 increased progressively in water
stressed plants but remained less significant in the regulation of
Rubisco activity than tight binding inhibitors.

tobacco/Nicotiana tabacum

KEYWORDS: CARBAMYLATION, CULTIVAR RESPONSES, RIBULOSE BISPHOSPHATE
CARBOXYLASE, WATER STRESS

578  
Patterson, D.T. 1986. Responses of Soybean (Glycine max) and Three
C4 Grass Weeds to CO2 Enrichment during Drought. Weed Science
34:203-210.

In controlled-environment chambers at 29/33 C day/night and 1000
uE/m2/s photosynthetic photon flux density (PPFD), increasing the
CO2 concentration from 340 to 675 ppm (v/v) did not affect leaf
area or total dry weight of well-watered plants of barnyardgrass
[Echinochloa crus-galli (L.) Beauv. #3 ECHCG], goosegrass [Eleusine
indica (L.) Gaertn. #ELEIN], or southern crabgrass [Digitaria
ciliaris (Retz.) Koel. # DIGSP] after 30 days. However, the whole
plant transpiration rate per unit leaf area decreased, and the
water use efficiency increased, in response to CO2 enrichment. In
a subsequent experiment, with water availability limited by an
imposed drought, CO2 enrichment reduced the effects of water stress
and significantly increased leaf area and total dry weight of the
three C4 grasses and soybean [Glycine max (L.) Merr. 'Ransom'].
Growth enhancement in response to CO2 enrichment was greater in
soybean than in the C4 grasses. By improving their water economy,
CO2 enrichment can increase the growth of both C3 and C4 plants
under water stress. However, growth stimulation can be expected to
be greater in C3 plants.

soybean/Glycine max/barnyardgrass/Echinochloa crus-galli/goosegrass/Eleusine indica/crabgrass/Digitaria ciliaris

KEYWORDS: ALLOCATION, C3, C4, GROWTH ANALYSIS, SPECIES COMPETITION,
TRANSPIRATION, WATER STATUS, WATER STRESS, WEEDS

579  
Patterson, D.T., and E.P. Flint. 1990. Implications of Increasing
Carbon Dioxide and Climate Change for Plant Communities and
Competition in Natural and Managed Ecosystems. IN: Impact of Carbon
Dioxide, Trace Gases and Climate Change on Global Agriculture,
Special Publication No. 53 (B.A. Kimball, N.J. Rosenberg, and L.H.
Allen Jr., eds.), American Society of Agronomy, Madison, Wisconsin,
pp. 83-110.

Future increases in the CO2 concentration of the Earth's atmosphere
will directly affect the physiological processes and growth of
plants. Indirect climatic effects, including global warming and
changes in precipitation patterns and the frequency of weather
extremes, may have greater impact than direct effects of CO2 on
physiological processes. Carbon dioxide enrichment up to twice
ambient levels or more generally increases plant growth, although
the magnitude of growth stimulation varies greatly with species,
photosynthetic pathway, growth stage, and water and nutrient
status. In both natural and managed ecosystems, differential growth
responses to both CO2 concentration and climatic change will affect
future competitive ability and fitness of plants. The relative
importance of various weed species in agroecosystems may change,
but selection of adapted crop varieties and management methods may
minimize negative impacts. In natural ecosystems, species
extinctions probably will increase, because migration and
adaptation through natural selection may be too slow to accommodate
the rapid climatic changes involved. Weedy species with broad
ecological amplitudes are likely to prosper at the expense of
endemic species or those already in marginal habitats.

KEYWORDS: AGRICULTURE, ECOSYSTEM LEVEL CO2 RESPONSES, REVIEW,
SPECIES COMPETITION, WEEDS

580  
Patterson, D.T., M.T. Highsmith, and E.P. Flint. 1988. Effects of
Temperature and CO2 Concentration on the Growth of Cotton
(Gossypium hirsutum), Spurred Anoda (Anoda cristata), and
Velvetleaf (Abutilon theophrasti). Weed Science 36:751-757.

Cotton, spurred anoda, and velvetleaf were grown in controlled-environment chambers at day/night temperatures of 32/23 or 26/17 C
and CO2 concentrations of 350 or 700 ppm. After 5 weeks, CO2
enrichment to 700 ppm increased dry matter accumulation by 38, 26,
and 29% in cotton, spurred anoda, and velvetleaf, respectively, at
26/17 C and by 61, 41, and 29% at 32/23 C. Increases in leaf weight
accounted for over 80% of the increase in total plant weight in
cotton and spurred anoda in both temperature regimes. Leaf area was
not increased by CO2 enrichment. The observed increases in dry
matter production with CO2 enrichment were caused by increased net
assimilation rate. In a second experiment, plants were grown at 350
ppm CO2 and 29/23 C day/night for 17 days before exposure to 700
ppm CO2 at 26/17 C for 1 week. Short-term exposure to high CO2
significantly increased net assimilation rate, dry matter
production, total dry weight, leaf dry weight, and specific leaf
weight in comparison with plants maintained at 350 ppm CO2 at 26/17
C. Increases in leaf weight in response to short-term CO2
enrichment accounted for 100, 87, and 68% of the observed increase
in total plant dry weight of cotton, spurred anoda, and velvetleaf,
respectively. Comparisons among the species showed that CO2
enrichment decreased the weed/crop ratio for total dry weight,
possibly indicating a potential competitive advantage for cotton
under elevated CO2, even at suboptimum temperatures.

velvetleaf/Abutilon theophrasti/cotton/Gossypium hirsutum/spurred
anoda/Anoda cristata

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, SPECIES COMPETITION, TEMPERATURE, WEEDS

581  
Pavel, E.W., and T.M. DeJong. 1993. Seasonal CO2 Exchange Patterns
of Developing Peach (Prunus persica) Fruits in Response to
Temperature, Light and CO2 Concentration. Physiologia Plantarum
88:322-330.

CO2 exchange rates per unit dry weight, measured in the field on
attached fruits of the late-maturing Cal Red peach cultivar, at
1200 umol photons/m2/s and in dark, and photosynthetic rates,
calculated by the difference between the rates of CO2 evolution in
light and dark, declined over the growing season. Calculated
photosynthetic rates per fruit increased over the season with
increasing fruit dry matter, but declined in maturing fruits
apparently coinciding with the loss of chlorophyll. Slight net
fruit photosynthetic rates ranging from 0.087 +/- 0.06 to 0.003 +/-
0.05 nmol CO2/g dry weight/s were measured in midseason under
optimal temperature (15 and 20C) and light (1200 umol
photons/m2/s) conditions. Calculated fruit photosynthetic rates per
unit dry weight increased with increasing temperatures and photon
flux densities during fruit development. Dark respiration rates per
unit dry weight doubled within a temperature interval of 10C; the
mean seasonal Q10 value was 2.03 between 20 and 30C. The highest
photosynthetic rates were measured at 35C throughout the growing
season. Since dark respiration rates increased at high temperatures
to a greater extent than CO2 exchange rates in light, fruit
photosynthesis was apparently stimulated by high internal CO2
concentrations via CO2 refixation. At 15C, fruit photosynthetic
rates tended to be saturated at about 600 umol photons/m2/s. Young
peach fruits responded to increasing ambient CO2 concentrations
with decreasing net CO2 exchange rates in light, but more mature
fruits did not respond to increases in ambient CO2. Fruit CO2
exchange rates in the dark remained fairly constant, apparently
uninfluenced by ambient CO2 concentrations during the entire
growing season. Calculated fruit photosynthetic rates clearly
revealed the difference in CO2 response of young and mature peach
fruits. Photosynthetic rates of younger peach fruits apparently
approached saturation at 370 uL CO2/L. In CO2-free air, fruit
photosynthesis was dependent on CO2 refixation since CO2 uptake by
the fruits from the external atmosphere was not possible. The
difference in photosynthetic rates between fruits in CO2-free air
and 370 uL CO2/L indicated that young peach fruits were apparently
able to take up CO2 from the external atmosphere. CO2 uptake by
peach fruits contributed between 28 and 16% to the fruit
photosynthetic rate early in the season, whereas photosynthesis in
maturing fruits was supplied entirely by CO2 fixation.

peach/Prunus persica

KEYWORDS: FRUIT CO2 EXCHANGE, LIGHT, RESPIRATION, TEMPERATURE

582  
Peet, M.M. 1986. Acclimation to High CO2 in Monoecious Cucumbers.
I. Vegetative and Reproductive Growth. Plant Physiology 80:59-62.

CO2 concentrations of 1000 compared to 350 microliters per liter in
controlled environment chambers did not increase total fruit weight
or number in a monoecious cucumber (Cucumis sativus L. cv Chipper)
nor did it increase biomass, leaf area, or relative growth rates
beyond the first 16 days after seeding. Average fruit weight was
slightly but not significantly greater in the 1000 microliters per
liter CO2 treatment because fruit numbers were changed more than
total weight. Plants grown at 1000 and 350 microliters per liter
CO2 were similar in distribution of dry matter and leaf area
between mainstem, axillary, and subaxillary branches. Early flower
production was greater in 1000 microliters per liter plants.
Subsequent flower numbers were either lower in enriched plants or
similar in the two treatments, except for the harvest at fruiting
when enriched plants produced many more male flowers than the 350
microliters per liter treatments.

Cucumis sativus/cucumber

KEYWORDS: ACCLIMATION, CONTROLLED ENVIRONMENT CHAMBERS, FLOWERING,
GROWTH, REPRODUCTION, YIELD

583  
Peet, M.M., S.C. Huber, and D.T. Patterson. 1986. Acclimation to
High CO2 in Monoecious Cucumbers. II. Carbon Exchange Rates, Enzyme
Activities, and Starch and Nutrient Concentrations. Plant
Physiology 80:63-67.

Carbon exchange capacity of cucumber (Cucumis sativus L.)
germinated and grown in controlled environment chambers at 1000
microliters per liter CO2 decreased from the vegetative growth
stage to the fruiting stage, during which time capacity of plants
grown at 350 microliters per liter increased. Carbon exchange rates
(CERs) measured under growth conditions during the fruiting period
were, in fact, lower in plants grown at 1000 microliters per liter
CO2 than those grown at 350. Progressive decreases in CERs in 1000
microliters per liter plants were associated with decreasing
stomatal conductances and activities of ribulose bisphosphate
carboxylase and carbonic anhydrase. Leaf starch concentrations were
higher in 1000 microliters per liter CO2 grown-plants than in 350
microliters per liter grown plants but calcium and nitrogen
concentrations were lower, the greatest difference occurring at
flowering. Sucrose synthase and sucrose-P-synthase activities were
similar in 1000 microliters per liter compared to 350 microliters
per liter plants during vegetative growth and flowering but higher
in 350 microliters per liter plants at fruiting. The decreased
carbon exchange rates observed in this cultivar at 1000 microliters
per liter CO2 could explain the lack of any yield increase (MM Peet
1986 Plant Physiol 80:59-62) when compared with plants grown at 350
microliters per liter.

Cucumis sativus/cucumber

KEYWORDS: ACCLIMATION, CARBOHYDRATES, CARBONIC ANHYDRASE,
CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES, LEAF
PHOTOSYNTHESIS, RIBULOSE BISPHOSPHATE CARBOXYLASE, SUCROSEPHOSPHATE
SYNTHASE

584  
Peet, M.M., and D.H. Willits. 1987. Greenhouse CO2 Enrichment
Alternatives: Effects of Increasing Concentration or Duration of
Enrichment on Cucumber Yields. Journal of the American Society of
Horticultural Science 112:236-241.

Extended duration (delayed venting) and greater intensity were
investigated as alternatives for CO2 enrichment of fall and spring
greenhouse cucumber (Cucumis sativus L.) crops in North Carolina.
The use of rockstorages allowed greenhouses to be enriched an
average of 83% longer than was possible in conventionally
ventilated greenhouses. Differences in daily enrichment times
between rockstorage and conventionally ventilated houses were
greatest during periods of high temperatures and high solar
radiation levels in the early fall and late spring. In the
rockstorage houses, enrichment increased fruit weights from 31-57%.
Plants enriched to 600 uL/L yield as well or better than those
enriched to 1000 or 1200 uL/L CO2. In the conventional houses,
enrichment to 1000, 3000, and 5000 uL/L raised yields 18.5-34.5% in
Fall 1983, Spring 1984, and Fall 1984. Cucumbers enriched to 1000
uL/L produced slightly less than the control plants in Spring 1983,
however. In the conventionally vented houses, spring crops yielded
best at the highest CO2 enrichment level, whereas for the fall
crops the reverse was true.

Cucumis sativus/cucumber

KEYWORDS: CO2 ENRICHMENT DURATION, CO2 MEASUREMENT AND CONTROL,
COMMERCIAL USE OF CO2, GREENHOUSE, YIELD

585  
Peet, M.M., D.H. Willits, K.E. Tripp, W.K. Kroen, D.M. Pharr, M.A.
Depa, and P.V. Nelson. 1991. CO2 Enrichment Responses of
Chrysanthemum, Cucumber and Tomato: Photosynthesis, Growth,
Nutrient Concentrations and Yield. IN: Proceedings of the Indo-US
Workshop, Global Climatic Changes on Photosynthesis and Plant
Productivity; 8-12 January 1991; New Delhi, India, Oxford and IBH
Publishing Co. Pvt. Ltd., New Delhi, pp. 193-212.

Yield increases from CO2 enrichment varied from 54% in cucumber
fruit weight, to 37% in chrysanthemum dry weight and 20% in tomato
fruit weight. To determine the basis for response differences,
photosynthesis was modeled in chrysanthemum and photosynthesis,
growth and leaf concentrations of starch, nutrients and carbon were
measured in tomato. CO2-enriched chrysanthemum leaves were more
efficient than ambient-CO2 grown leaves at irradiances below 400
umol (photons)/m2/s because of greater photosynthetic efficiencies.
At higher irradiances, ambient CO2-grown leaves were more efficient
because of greater CO2 conductance, but dry weights and in situ
photosynthetic rates were still higher in enriched plants. Cucumber
yield data appeared to fit this model, but CO2-enriched tomatoes
were much less responsive to CO2 increases. In tomatoes, response
to CO2 enrichment did not increase with increasing irradiance and
short daily periods of enrichment did not increase yield,
suggesting that the CO2 conductances declined significantly. Lower
leaves of CO2-enriched tomato plants were inrolled, chlorotic and
purpled. We thought this was because of carbohydrate accumulation,
possibly associated with feedback inhibition of photosynthesis. We
concluded, however, after a 3-year study, that deformation severity
was not directly related to foliar starch concentrations. We found
more starch in CO2-enriched leaves, but the pattern of accumulation
did not appear to account for changes in deformation through
development and with source-sink treatments. Severity of leaf
deformity was also not correlated with low leaf photosynthetic
rates. In situ photosynthetic rates were only slightly higher in
enriched plants and did not differ with genotype. Severity of
deformation was correlated with high fruit yields and high C/N
ratios, but low root weights and low foliar concentrations of K and
N. We suggest that in tomatoes CO2-enrichment increases sink
strength more than source strength in tomatoes. During fruit
development, carbohydrates may be partitioned to fruit at the
expense of roots, leading to higher yields, but late-season
nutrient stress.

chrysanthemum/Chrysanthemum morifolium/cucumber/Cucumis
sativus/tomato/Lycopersicon esculentum

KEYWORDS: CARBOHYDRATES, CO2 ENRICHMENT DURATION, CONTROLLED
ENVIRONMENT CHAMBERS, GREENHOUSE, GROWTH, HORTICULTURAL CROPS, LEAF
PHOTOSYNTHESIS, LIGHT, NUTRITION, PHOTOSYNTHETIC ACCLIMATION,
SOURCE-SINK BALANCE, YIELD

586  
Peet, M.M., D.H. Willits, K.E. Tripp, D.M. Pharr, M.A. Depa, J.S.
Kuehny, and P.V. Nelson. 1990. Case Studies of CO2 Enrichment
Responses: Chrysanthemum, Cucumbers and Tomatoes. IN: Proceedings,
Global Climate Change Symposium, 9 April 1990; McKimmon Center,
North Carolina State University, North Carolina Agricultural
Research Service, Raleigh, pp. 52-61.

In experiments conducted in our greenhouses from 1981-1988, yield,
photosynthetic and carbohydrate responses to CO2 enrichment were
compared in chrysanthemum, cucumbers and tomatoes. Cucumbers were
the most responsive, showing a 54% increase in yield with daylong
enrichment. Tomatoes were the least responsive, showing only a 20%
yield response when enriched for most of the day. Tomatoes also
exhibited foliar deformation, purpling and chlorosis at high CO2
concentrations. We had hypothesized that this deformation was
caused by high starch levels in leaves of enriched plants. We found
more leaf deformation in CO2-enriched tomatoes and higher starch,
but based on developmental patterns and differential responses to
source/sink manipulations, starch did not appear to cause leaf
deformation. In tomatoes, in situ lower leaf canopy photosynthetic
rates were not much different in enriched and ambient plants. In
chrysanthemum, dry weight increases with enrichment averaged 37%
across 5 experiments, ranging from 24% to 52%. Photosynthesis
models showed that CO2-enriched chrysanthemum leaves were more
efficient at irradiances below 400 umol/m2/s, but above this
irradiance, ambient-grown leaves were more efficient because of
greater CO2 conductance. Thus, measured at the same CO2
concentration, ambient leaves had higher photosyunthetic rates than
enriched leaves. In situ photosynthetic rates were still higher in
enriched plants, however, accounting for the higher dry weights
observed.

tomato/Lycopersicon esculentum/cucumber/Cucumis
sativus/chrysanthemum/Chrysanthemum morifolium

KEYWORDS: CARBOHYDRATES, CO2 ENRICHMENT DURATION, GREENHOUSE,
GROWTH ANALYSIS, HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS, LIGHT,
PHOTOSYNTHETIC ACCLIMATION, SOURCE-SINK BALANCE, YIELD

587  
Penuelas, J., and J. Azcon-Bieto. 1992. Changes in Leaf Delta 13C
of Herbarium Plant Species during the Last 3 Centuries of CO2
Increase. Plant, Cell and Environment 15:485-489.

Delta 13C were determined for herbarium specimens of 12 C3 plants
(trees, shrubs and herbs) collected during the last 240 years in
Catalonia, an area with a Mediterranean climate. Values were 19.91
(S.E. = 0.32, n = 21) for 1750--1760, 19.86 (S.E. = 0.21, n = 49)
for 1850-1890 and 19.95 (S.E. = 0.29, n = 25) for 1925-1950, and
decreased significantly to 18.87 (S.E. = 0.31, n = 29) for 1982-1988. More irregular temporal changes were found in delta 13 C of
two C4 species, but they also suggest a decrease in discrimination
in recent decades. These results suggest that either carbon
assimilation rates have increased or stomatal conductance has
decreased, and therefore, that there has been an increase in water
use efficiency over the last few decades.

Pinus uncinata/Pinus pinea/Alnus glutinosa/Betula pendula/Juniperus
communis/Ceratonia siliqua/Buxus sempervirens/Pistacia
lentiscus/Helleborus foetidus/Rhododendron ferrugineum/Amaranthus
caudatus/Papaver alpinum/Cynodon dactylon/Gentiana alpina

KEYWORDS: 13C, CI:CA, HERBARIUM SPECIMENS, ISOTOPE DISCRIMINATION,
PRE-INDUSTRIAL CO2 CONCENTRATION

588  
Penuelas, J., and R. Matamala. 1990. Changes in N and S Leaf
Content, Stomatal Density and Specific Leaf Area of 14 Plant
Species during the Last Three Centuries of CO2 Increase. Journal of
Experimental Botany 41:1119-1124.

Parallel to the increase in atmospheric CO2 from 278 umol/mol in AD
1750 to the current ambient level of 348 umol/mol there have been
overall decreases in leaf nitrogen content and stomatal density
from 144% and 121%, respectively, in AD 1750 to 100% today of
herbarium specimens of 14 trees, shrubs, and herbs collected over
the last 240 years in Catalonia, a Mediterranean climate area.
These decreases were steeper during the initial slower increases in
CO2 atmospheric levels as compared with the relatively faster CO2
increases in recent years. The declines in leaf N content and
stomatal density have also been reported in experimental studies on
leaves of plants grown under enriched CO2 environments. Meanwhile,
the stomatal index and overall carbon and sulphur leaf contents
have not changed significantly. Leaf S content was higher in the
1940s samples coinciding with the burning of increased quantities
of sulphur-rich coal. Consequently, the epidermal cell density has
decreased parallel to the stomatal density and the C/N ratio of
leaves has increased, implying possible important consequences on
herbivores, decomposers and ecosystems. An overall decrease in the
specific leaf area (SLA) from 184% in the 18th century to 100%
today has also been found, as would be expected under CO2
enrichment, but which might also be an artifact of prolonged
storage.

Pinus pinea/Alnus glutinosa/Betula pendula/small birch/Juniperus
communis/Ceratonia siliqua/Buxus sempervirens/Pistacia
lentiscus/Helleborus foetidus/Rhododendron ferrugineum/Amaranthus
caudatus/Papaver alpinum/Cynodon dactylon/Gentiana alpina

KEYWORDS: 13C, CARBON:NITROGEN RATIO, HERBARIUM SPECIMENS, ISOTOPE
DISCRIMINATION, PRE-INDUSTRIAL CO2 CONCENTRATION, STOMATAL DENSITY,
STOMATAL INDEX, SULFUR

589  
Pettersson, R., and A.J.S. McDonald. 1992. Effects of Elevated
Carbon Dioxide Concentration on Photosynthesis and Growth of Small
Birch Plants (Betula pendula Roth.) at Optimal Nutrition. Plant,
Cell and Environment 15:911-919.

Small birch plants (Betula pendula Roth.) were grown from seed for
periods of up to 70 d in a climate chamber at optimum nutrition and
at present (350 umol/mol) or elevated (700 umol/mol) concentrations
of atmospheric CO2. Nutrients were sprayed over the roots in
Ingestad-type units. Relative growth rate and net assimilation rate
were slightly higher at elevated CO2, whereas leaf area ratio was
slightly lower. Smaller leaf area ratio was associated with lower
values of specific leaf area. Leaves grown at elevated CO2 had
higher starch concentrations (dry weight basis) than leaves grown
at present levels of CO2. Biomass allocation showed no change with
CO2, and no large effects on stem height, number of side shoots and
number of leaves were found. However, the specific root length of
fine roots was higher at elevated CO2. No large difference in the
response of carbon assimilation to intercellular CO2 concentration
(A/Ci curves) were found between CO2 treatments. When measured at
the growth environments, the rates of photosynthesis were higher in
plants grown at elevated CO2 than in plants grown at present CO2.
Water use efficiency of single leaves was higher in the elevated
treatment. This was mainly attributable to higher carbon
assimilation rate at elevated CO2. The difference in water use
efficiency diminished with leaf age. The small treatment difference
in relative growth rate was maintained throughout the experiment,
which meant that the difference in plant size became progressively
greater. Thus, where plant nutrition is sufficient to maintain
maximum growth, small birch plants may potentially increase in size
more rapidly at elevated CO2.

small birch/Betula pendula

KEYWORDS: ALLOCATION, CARBOHYDRATES, CONTROLLED ENVIRONMENT
CHAMBERS, GROWTH, GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS,
PHOTOSYNTHETIC ACCLIMATION, ROOTS, TREES, WUE

590  
Pinter, P.J., R.J. Anderson, B.A. Kimball, and J.R. Mauney. 1990.
In situ Measurements of Canopy Reflectance for Evaluating Cotton
Responses to Free Air Carbon Dioxide Enrichment. IN: Proceedings,
Beltwide Cotton Production Research Conferences; 9-14 January 1990;
La Vegas, Nevada (J.M. Brown and D.A. Richter, eds.), National
Cotton Council of America, Memphis, Tennessee, pp. 717-719.

Remotely-sensed observations of visible and near-infrared canopy
reflectance were used to monitor the response of cotton to elevated
CO2 concentrations during the 1989 FACE Experiment. Data were
collected several times each week using a portable, handheld
radiometer along permanent transects in four enriched arrays (550
ppm CO2 and paired controls (ambient CO2). A spectral vegetation
index (VI) was computed as the ratio of NIR and Red reflectances.
The VI was sensitive to the amount and condition of green plant
material viewed by the radiometer. Differences in growth, leaf area
and biomass between enriched and control cotton plants were evident
in the temporal VI values. The non-destructive spectral
measurements were useful for quantifying plant response to
experimental treatment variables between biweekly, destructive
samples of plant material. These techniques can be used in a near-realtime fashion to supervise conduct of the experiment.

cotton/Gossypium hirsutum

KEYWORDS: BEMISIA TABACI, FACE, RADIATION, REFLECTANCE, REMOTE
SENSING

591  
Pinter, P.J., Jr., R.J. Anderson, and B.A. Kimball. 1992.
Evaluating Cotton Response to Free-Air Carbon Dioxide Enrichment
with Canopy Reflectance Observations. Critical Reviews in Plant
Sciences 11:241-249.

cotton/Gossypium hirsutum

KEYWORDS: AGRICULTURE, FACE, NORMALIZED DIFFERENCE VEGETATION
INDEX, RADIATION, REFLECTANCE, REMOTE SENSING

592  
Polle, A., T. Pfirrmann, S. Chakrabarti, and H. Rennenberg. 1993.
The Effects of Enhanced Ozone and Enhanced Carbon Dioxide
Concentrations on Biomass, Pigments and Antioxidative Enzymes in
Spruce Seedlings. Plant, Cell and Environment 16:311-316.

During one growing period, 5-year-old spruce trees (Picea abies L.
Karst.) were exposed in environmental chambers to elevated
concentrations of carbon dioxide (750 cm3/m3) and ozone (0.08
cm3/m3) as single variables or in combination. Control
concentrations of the gases were 350 cm3/m3 CO2 and 0.02 cm3/m3
ozone. To investigate whether an elevated CO2 concentration can
prevent adverse ozone effects by reducing oxidative stress, the
activities of the protective enzymes superoxide dismutase, catalase
and peroxidase were determined. Furthermore, shoot biomass, pigment
and protein contents of two needle age classes were investigated.
Ozone caused pigment reduction and visible injury in the previous
year's needles and growth reduction in the current year's shoots.
In the presence of elevated concentrations of ozone and CO2, growth
reduction in the current year's shoots was prevented, but emergence
of visible damage in the previous year's needles was only delayed
and pigment reduction was still found. Elevated concentrations of
ozone or CO2 as single variables caused a significant reduction in
the activities of superoxide dismutase and catalase in the current
year's needles. Minimum activities of superoxide dismutase and
catalase and decreased peroxidase activities were found in both
needle age classes from spruce trees grown at enhanced
concentrations of both CO2 and ozone. These results suggest a
reduced tolerance to oxidative stress in spruce trees under
conditions of elevated concentrations of both CO2 and ozone.

Picea abies/Norway spruce

KEYWORDS: AIR POLLUTION, CATALASE, CONTROLLED ENVIRONMENT CHAMBERS,
ENZYMES, OZONE, PEROXIDASE, PIGMENTS, PROTEINS, SUPEROXIDE
DISMUTASE, TREES

593  
Polley, H.W., H.B. Johnson, and H.S. Mayeux. 1992. Carbon Dioxide
and Water Fluxes of C3 Annuals and C3 and C4 Perennials at
Subambient CO2 Concentrations. Functional Ecology 6:693-703.

1. The C3 annuals,Avena sativa and Brassica kaber, and C3 and C4
perennials, Prosopis glandulosa and Schizachyrium scoparium,
respectively, were grown in a 38-m long chamber along a continuous
gradient of daytime CO2 concentrations ([CO2]) from near the
current 350 umol/mol to 150 (annuals) or 200 umol/mol (perennials). 
Diurnal CO2 and water fluxes were calculated for plant stands in
five consecutive, 7.6-m lengths of the chamber arranged linearly
along the [CO2] gradient. 2. The ratio of night respiration (Rn) to
daytime net assimilation (Pd) was greatest in A. sativa/B. kaber
exposed to mean [CO2] below 200 umol/mol, while Rn/Pd differed
little among five stands of P. glandulosa/S. scoparium that were
grown at mean [CO2] from 219 to 331 umol/mol. 3. Evapotranspiration
was reduced and water-use efficiency (WUE) was increased in A.
sativa/B. kaber stands by higher [CO2]. 4. Pd and WUE of P.
glandulosa/S. scoparium were not related to [CO2] across either of
two growing seasons.  Both Pd and WUE, however, were greater at
higher [CO2] in three of four stands when [CO2] was varied in
consecutive days. 5. We conclude that past increases in atmospheric
[CO2] have promoted higher WUE and increased carbon uptake in C3-dominated ecosystems.

Avena sativa/oat/Brassica kaber/field mustard/Prosopis
glandulosa/mesquite/Schizachyrium scoparium/little bluestem

KEYWORDS: C3, C4, EVAPOTRANSPIRATION, GRADIENT EXPOSURE TUNNEL,
PRE-INDUSTRIAL CO2 CONCENTRATION, RESPIRATION, WUE

594  
Polley, H.W., H.B. Johnson, H.S. Mayeux, and S.R. Malone. 1993.
Physiology and Growth of Wheat Across a Subambient Carbon Dioxide
Gradient. Annals of Botany 71:347-356.

Two cultivars of wheat (Triticum aestivum L.), 'Yaqui 54' and 'Seri
M82', were grown along a gradient of daytime carbon dioxide
concentrations ([CO2]) from near 350-200 umol CO2/mol air in a 38
m long controlled environment chamber. Carbon dioxide fluxes and
evapotranspiration were measured for stands (plants and soil) in
five consecutive 7.6-m lengths of the chamber to determine
potential effects of the glacial/interglacial increase in
atmospheric [CO2] on C3 plants. Growth rates and leaf areas of
individual plants and net assimilation per unit leaf area and daily
(24-h) net CO2 accumulation of wheat stands rose with increasing
[CO2]. Daytime net assimilation (PD, mmol CO2/m2 soil surface area)
and water use efficiency of wheat stands increased and the daily
total of photosynthetic photon flux density required by stands for
positive CO2 accumulation (light compensation point) declined at
higher [CO2]. Nighttime respiration (RN, mmol CO2/m2 soil surface)
of wheat, measured at 369-397 umol/mol CO2, apparently was not
altered by growth at different daytime [CO2], but RN/PD of stands
declined linearly as daytime [CO2] and PD increased. The responses
of wheat to [CO2] if representative of other C3 species, suggest
that the 75-100% increase in [CO2] since glaciation and the 30%
increase since 1800 reduced the minimum light and water
requirements for growth and increased the productivity of C3
plants.

wheat/Triticum aestivum

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, GRADIENT EXPOSURE
TUNNEL, GRASSES, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, LIGHT
UTILIZATION EFFICIENCY, PRE-INDUSTRIAL CO2 CONCENTRATION,
RESPIRATION, TEMPERATURE, WUE

595  
Poorter, H. 1989. Interspecific Variation in Relative Growth Rate:
On Ecological Causes and Physiological Consequences. IN: Causes and
Consequences of Variation in Growth Rate and Productivity of Higher
Plants (H. Lambers, M.L. Cambridge, H. Konings, and T.L. Pons,
eds.), SPB Academic Publishing, The Hague, pp. 45-68.

KEYWORDS: GROWTH ANALYSIS

596  
Poorter, H. 1993. Interspecific Variation in the Growth Response of
Plants to an Elevated Ambient CO2 Concentration. Vegetatio
104/105:77-97.

The effect of a doubling in the atmospheric CO2 concentration on
the growth of vegetative whole plants was investigated. In a
compilation of literature sources, the growth stimulation of 156
plant species was found to be on average 37%. This enhancement is
small compared to what could be expected on the basis of CO2-response curves of photosynthesis. The causes for this stimulation
being so modest were investigated, partly on the basis of an
experiment with 10 wild plant species. Both the source-sink
relationship and size constraints on growth can cause the growth-stimulating effect to be transient. Data on the 156 plant species
were used to explore interspecific variation in the response of
plants to high CO2. The growth stimulation was larger for C3
species than for C4 plants. However the difference in growth
stimulation is not as large as expected as C4 plants also
significantly increased in weight (41% for C3 vs. 22% for C4). The
few investigated CAM species were stimulated less in growth (15%)
than the average C4 species. Within the group of C3 species,
herbaceous crop plants responded more strongly than herbaceous wild
species (58% vs. 35%) and potentially fast-growing wild species
increased more in weight than slow-growing species (54% vs. 23%).
C3 species capable of symbiosis with N2-fixing organisms had higher
growth stimulations compared to other C3 species. A common
denominator in these 3 groups of more responsive C3 plants might be
their large sink strength. Finally, there was some tendency for
herbaceous dicots to show a larger response than monocots. Thus, on
the basis of this literature compilation, it is concluded that also
within the group of C3 species differences exist in the growth
response to high CO2.

Carex diandra/Deschampsia flexuosa/Festuca ovina/Alnus
glutinosa/Lolium perenne/perennial ryegrass/Trifolium repens/white
clover/Plantago major/broadleaf plantain/Silene dioica/Taraxacum
officinale/dandelion/Urtica dioica/stinging nettle

KEYWORDS: C3, C4, CAM, GROWTH ANALYSIS, REVIEW, SOURCE-SINK BALANCE

597  
Poorter, H., R.M. Gifford, P.E. Kriedemann, and S.C. Wong. 1992. A
Quantitative Analysis of Dark Respiration and Carbon Content as
Factors in the Growth Response of Plants to Elevated CO2.
Australian Journal of Botany 40:501-513.

An analysis of elevated CO2 effects (2-4 times ambient) on dark
respiration rate and carbon content was undertaken for a wide range
of plant species, using both published reports and new data. On
average, leaf respiration per unit leaf area was slightly higher
for plants grown at high CO2 (16%), whereas a small decrease was
found when respiration was expressed on a leaf weight basis (14%).
For the few data on root respiration, no significant change due to
high CO2 could be detected. Carbon content of leaves and stem
showed a small increase (1.2 and 1.7% respectively), whereas C-content of roots was not significantly affected. In both data sets
direction of responses was variable. A sensitivity analysis of
carbon budgets under elevated CO2 identified changes in respiration
rate, and to a lesser extent carbon content, as important factors
affecting the growth response to elevated CO2 in quite a number of
cases. Any comprehensive analysis of growth responses to increased
CO2 should therefore include measurements of these two variables.

KEYWORDS: CARBON BUDGET, RESPIRATION, REVIEW

598  
Poorter, H., S. Pot, and H. Lambers. 1988. The Effect of an
Elevated Atmospheric CO2 Concentration on Growth, Photosynthesis
and Respiration of Plantago major. Physiologia Plantarum 73:553-559.

The effect of an elevated atmospheric CO2 concentration on growth,
photosynthesis and respiration of Plantago major L. ssp. major L.
was investigated. Plants were grown in a nutrient solution in
growth chambers at 350 and 700 uL/L CO2 during 7 weeks. The total
dry weight of the CO2-enriched plants at the end of this period was
50% higher than that of control plants. However, the relative
growth rate (RGR) was stimulated only during the first half of the
growing period. The transient nature of the stimulation of the RGR
was not likely to be due to end-product inhibition of
photosynthesis. It is suggested that in P. major, a rosette plant,
self-shading causes a decline in photosynthesis and results in an
increase in the shoot:root ratio and a decrease in RGR. CO2-enriched plants grow faster and consequently suffer more from self-shading. Corrected for this ontogenetic drift, high CO2
concentrations stimulated the RGR of P. major throughout the entire
experiment.

Plantago major/broadleaf plantain

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH ANALYSIS, PHOTOSYNTHETIC FEEDBACK INHIBITION, RESPIRATION,
ROOT:SHOOT RATIO

599  
Porter, J.R. 1990. Modeling the Effects of Climate Change on Cereal
Production. IN: The Greenhouse Effect and Primary Productivity in
European Agro-ecosystems; 5-10 April 1990; Wageningen, The
Netherlands (J. Goudriaan, H. van Keulen, and H.H. van Laar, eds.),
Pudoc, Wageningen, pp. 57-59.

KEYWORDS: AGRICULTURE, CROP MODEL, MODELING, REVIEW, TEMPERATURE

600  
Porter, M.A., and B. Grodzinski. 1985. CO2 Enrichment of Protected
Crops. Horticultural Reviews 7:345-398.

KEYWORDS: CO2 ENRICHMENT STUDIES, CO2 MEASUREMENT AND CONTROL, CO2
SOURCES, COMMERCIAL USE OF CO2, EXPOSURE METHODS, HORTICULTURAL
CROPS, REVIEW

601  
Potvin, C. 1985. Amelioration of Chilling Effects by CO2
Enrichment. Physiologie Vegetale 23:345-352.

To analyse the effect of CO2 enrichment on the chilling-sensitivity
of C4 plants from contrasting habitats, plants of Echinochloa crus-galli from Quebec, North Carolina and Mississippi and of Eleusine
indica from Mississippi were grown for 4 weeks under three
thermoperiods (28/22, 24/18 and 21/15C and two atmospheric CO2
concentrations (350 and 675 uL/L). They were then submitted to 1
night chilling at 7C. Photosynthetic carbon uptake, stomatal
conductances, and internal CO2 concentration were measured using an
infra-red gas analyser in an open system before and after chilling
and during the recovery. Chilling induces a decrease in
photosynthesis and conductance and, at 350 uL/L, in internal CO2.
The decrease in photosynthesis is less important for high CO2 grown
plants at 28/22C. Chilling generates chlorotic bands on leaf
blades but less chlorosis is observed in enriched CO2.

Echinochloa crus-galli/barnyardgrass/Eleusine indica/goosegrass

KEYWORDS: C4, CHILLING, CONDUCTANCE, ECOTYPES, GRASSES, GREENHOUSE,
LEAF PHOTOSYNTHESIS, TEMPERATURE

602  
Potvin, C., J.-P. Simon, and B.R. Strain. 1986. Effect of Low
Temperature on the Photosynthetic Metabolism of the C4 Grass
Echinochloa crus-galli. Oecologia 69:499-506.

CO2 curves of photosynthesis and activities of the four C4 enzymes
and Ribulose bisphosphate carboxylase (RUBPc) were compared in two
populations of the C4 grass Echinochloa crus-galli from contrasting
thermal environments (Quebec and Mississippi). Analyses were
conducted both before and after 14 h of chilling at 7C under high
light conditions. This comparison provides the opportunity to
assess which steps of the C4 pathway are more susceptible to become
limiting at low temperatures. Both populations maintained, after
chilling, a pattern of CO2 fixation typical of C4 plants with
photosynthesis saturating at low external CO2 concentrations.
However, the chilling treatment led to reductions in carbon uptake
and in the activities of the C4 enzymes. RUBPc activity was not
significantly affected by chilling. Reductions in photosynthesis
were significantly larger for plants of the Mississippi population.
The enzyme data suggest that two steps of the C4 pathway, NADP+ -malate dehydrogenase and pyruvate Pi dikinase, are likely to be
associated with the reduction of CO2 uptake in C4 plants under cool
conditions. When the experiment was replicated under enriched
atmospheric CO2 (675 uL/L CO2), similar differences were observed
between the two populations. CO2 enrichment resulted in an increase
of activity of phospho-enol-pyruvate carboxylase and NADP+ -malate
dehydrogenase while activities of phospho-enol-pyruvate carboxylase
and NADP+ -malic enzyme were less reduced following chilling. Such
an interaction was not observed for gas exchange parameters but net
photosynthesis was lower when plants were grown under enriched CO2.

Echinochloa crus-galli/barnyardgrass

KEYWORDS: C4, CHILLING, ECOTYPES, ENZYMES, GRASSES, GREENHOUSE,
LEAF PHOTOSYNTHESIS, NADP+ -MALATE DEHYDROGENASE,
PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE BISPHOSPHATE CARBOXYLASE,
TEMPERATURE

603  
Potvin, C.J. 1985. Responses of Two Carbon(4) Grasses to Carbon
Dioxide Enrichment and Low Temperature: Implications for
Biogeographical Distribution of Carbon (4) Plants (Mississippi,
North Carolina, Quebec). Doctoral Dissertation, Duke University,
Dissertation Abstracts Vol. 46:11-B, p. 3690 (171 pp.).

This study was carried out to examine the responses of C4 plants to
low temperature and to CO2 enrichment. Such information should help
to understand the distributional limits of C4 plants in cool
environments and to predict how a global increase in atmospheric
CO2 concentration would affect C4 distribution. Two C4 grasses were
analyzed, Echinochloa crus-galli and Eleusine indica. Echinochloa
crus-galli was represented by 3 populations originating from
contrasting thermal environments (Quebec, North Carolina,
Mississippi) while a single population of Eleusine indica, from
Mississippi, was included in the study. The results indicate clear
physiological differences among northern and southern plants.
Plants from Quebec have higher photosynthetic rates and more
efficient translocation of 11C regardless of the temperature at
which they are grown. Plants from the north have a better potential
to adjust to chilling with or without light. The growth pattern of
plants from Quebec is characterized by a shorter life cycle; the
northern plants flower consistently before the other populations.
Plants from all three populations were grown in field plots in
North Carolina and in Quebec. While plants from Quebec do not
survive through the summer in North Carolina, those from
Mississippi fail to reproduce in Quebec. Thus, it appears that the
various populations are ecotypically differentiated. The effects of
CO2 enrichment on the physiology and growth of the two C4 grasses
under study were minor. Plants respond to high CO2 concentration by
a slight increase in photosynthesis, in export pool size and in net
assimilation rates during the first 20 days of growth. There was a
consistent temperature by CO2 interaction in both chilling
experiments. CO2 enrichment partially ameliorates the deleterious
effects of chilling.

Echinochloa crus-galli/barnyardgrass/Eleusine indica/goosegrass

KEYWORDS: 11C, C4, CHILLING, ECOTYPES, ENZYMES, GRASSES,
GREENHOUSE, LEAF PHOTOSYNTHESIS

604  
Prior, S.A., H.H. Rogers, N. Sionit, and R.P. Patterson. 1991.
Effects of Elevated Atmospheric CO2 on Water Relations of Soya
Bean. Agriculture, Ecosystems and Environment 35:13-25.

Soya bean (Glycine max (L.) Merr. 'Bragg') plants were grown in
large containers in open-top field chambers under five atmospheric
CO2 concentrations (349-946 uL/L) and two water regimes. Rate of
soil water depletion for the high CO2 treatments started to
decrease under well-watered conditions during anthesis and by early
pod formation under water-stressed conditions. During reproductive
growth, normal and stressed plants at 349 uL/L (ambient level)
received irrigation water 29 and 12 times, respectively, compared
with 21 and 9 times, respectively, at 946 uL/L CO2. At both
anthesis and pod fill, plants grown under CO2 enrichment exhibited
greater leaf area. Nevertheless, water use per plant either
remained constant (stressed plants at anthesis) or else declined
(well-watered plants at pod fill; both moisture levels during pod
fill) in response to CO2 enrichment. At pod fill, leaves of CO2-enriched plants generally displayed a higher stomatal resistance,
except near the end of the sampling period when a sudden increase
in resistance was observed under low CO2 owing to low soil water
availability. Midday xylem potential for well-watered plants was
greater than values for stressed plants and was unaffected by CO2
treatment. Under low moisture conditions, elevated CO2 had no
effect on xylem potential at anthesis; however, during pod fill
potential increased significantly with increasing CO2
concentration, as elevated CO2 decreased water use rates, lowering
soil water stress. Alleviations of water stress during critical
reproductive phases was strongly suggested.

Glycine max/soybean

KEYWORDS: CONDUCTANCE, GROWTH STAGES, OPEN-TOP CHAMBERS, WATER
STATUS, WATER STRESS

605  
Radin, J.W., W. Hartung, B.A. Kimball, and J.R. Mauney. 1988.
Correlation of Stomatal Conductance with Photosynthetic Capacity of
Cotton Only in a CO2-enriched Atmosphere: Mediation by Abscisic
Acid? Plant Physiology 88:1058-1062.

Some evidence indicates that photosynthetic rate (A) and stomatal
conductance (g) of leaves are correlated across diverse
environments. The correlation between A and g has led to the
postulation of a 'messenger' from the mesophyll that directs
stomatal behavior. Because A is a function of intercellular CO2
concentration (Ci), which is in turn a function of g, such a
correlation may be partially mediated by Ci if g is to some degree
an independent variable. Among individual sunlit leaves in a cotton
(Gossypium hirsutum L.) canopy in the field, A was significantly
correlated with g (r2 = 0.41, n = 63). The relative photosynthetic
capacity of each leaf was calculated as a measure of mesophyll
properties independent of Ci. This approach revealed that, in the
absence of Ci effects, mesophyll photosynthetic capacity was
unrelated to g (r2 = 0.06). When plants were grown in an atmosphere
enriched to about 650 microliters per liter of CO2, however,
photosynthetic capacity remained strongly correlated with g even
though the procedure discounted any effect of variable Ci. This
'residual' correlation implies the existence of a messenger in CO2-enriched plants. Enriched CO2 also greatly increased stomatal
response to abscisic acid (ABA) injected into intact leaves. The
data provide no evidence for a messenger to coordinate g with A at
ambient levels of CO2. In a CO2-enriched atmosphere, though, ABA
may function as such a messenger because the sensitivity of the
system to ABA is enhanced.

cotton/Gossypium hirsutum

KEYWORDS: ABA, CI:CA, CONDUCTANCE, LEAF PHOTOSYNTHESIS, OPEN-TOP
CHAMBERS, STOMATA

606  
Radin, J.W., B.A. Kimball, D.L. Hendrix, and J.R. Mauney. 1987.
Photosynthesis of Cotton Plants Exposed to Elevated Levels of
Carbon Dioxide in the Field. Photosynthesis Research 12:191-203.

The cotton (Gossypium hirsutum L.) plant responds to a doubling of
atmospheric CO2 with almost doubled yield. Gas exchange of leaves
was monitored to discover the photosynthetic basis of this large
response. Plants were grown in the field in open-top chambers with
ambient (nominally 350 uL/L) or enriched (nominally either 500 or
650 uL/L) concentrations of atmospheric CO2. During most of the
season, in fully-irrigated plants the relationship between
assimilation (A) and intercellular CO2 concentration (Ci) was
almost linear over an extremely wide range of Ci. CO2 enrichment
did not alter this relationship or diminish photosynthetic capcity
(despite accumulation of starch to very high levels) until very
late in the season, when temperature was somewhat lower than at
midseason. Stomatal conductance at midseason was very high and
insensitive to CO2, leading to estimates of Ci above 85% of
atmospheric CO2 concentration in both ambient and enriched
chambers. Water stress caused A to show a saturation response with
respect to Ci, and it increased stomatal closure in response to CO2
enrichment. In fully-irrigated plants CO2 enrichment to 650 uL/L
increased A more than 70%, but in water-stressed plants enrichment
increased A only about 52%. The non-saturating response of A to Ci,
the failure of CO2 enrichment to decrease photosynthetic capcity
for most of the season, and the ability of the leaves to maintain
very high Ci, form in part the basis for the very large response to
CO2 enrichment.

cotton/Gossypium hirsutum

KEYWORDS: CI:CA, CONDUCTANCE, LEAF PHOTOSYNTHESIS, OPEN-TOP
CHAMBERS, STOMATA, WATER STRESS

607  
Radoglou, K.M., P. Aphalo, and P.G. Jarvis. 1992. Response of
Photosynthesis, Stomatal Conductance and Water Use Efficiency to
Elevated CO2 and Nutrient Supply in Acclimated Seedlings of
Phaseolus vulgaris L. Annals of Botany 70:257-264.

Plants of Phaseolus vulgaris L. were grown from seed in open-top
growth chambers at present day (350 umol/mol) and double the
present day (700 umol/mol) atmospheric CO2 concentration with
either low (L, without additional nutrient solution) or relatively
high (H, with additional nutrient solution) nutrient supply.
Measurements of assimilation rate, stomatal conductance and water
use efficiency were started 17 d after sowing on each fully
expanded, primary leaf of three plants per treatment. Measurements
were made in external CO2 concentrations (Ca) of 200, 350, 450, 550
and 700 umol/mol and related to both Ca and to Ci, the mean
intercellular space CO2 concentration. Fully adjusted, steady state
measurements were made after approximately 2 h equilibration at
each CO2 concentration. The rate of CO2 assimilation by leaves
increased and stomatal conductance decreased similarly over the
range of Ca or Ci in all four CO2 and nutrient supply treatments
but both assimilation rate and stomatal conductance were higher in
the high nutrient supply treatment than in the low nutrient
treatment. The relation between assimilation rate or stomatal
conductance and Ci was not significantly different amongst plants
grown in present-day or elevated CO2 concentration in either
nutrient supply treatment, i.e., there was no evidence of down
regulation of photosynthesis or stomatal response. Increase in CO2
concentration from 350 to 700 umol/mol doubled water use efficiency
of individual leaves in the high nutrient supply treatment and
tripled water use efficiency in the low nutrient supply treatment.
The results support the hypothesis that acclimation phenomena
result from unbalanced growth that occurs after the seed reserves
are exhausted, when the supply of resources becomes growth
limiting.

Phaseolus vulgaris/bean

KEYWORDS: CONDUCTANCE, GREENHOUSE, LEAF PHOTOSYNTHESIS, OPEN-TOP
CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, STOMATA, WUE

608  
Radoglou, K.M., and P.G. Jarvis. 1990. Effects of CO2 Enrichment on
Four Poplar Clones. II. Leaf Surface Properties. Annals of Botany
65:627-632.

The poplar clones Columbia River, Beaupre, Robusta and Raspalje
have been investigated in the present (350 umol/mol) and double
(700 umol/mol) atmospheric CO2 concentration. Cuttings were planted
in pots and were grown in open-top chambers inside a glasshouse.
Stomatal density, stomatal index, length of stomatal pore and
epidermal cell density were not affected by CO2 enrichment in any
of the clones. Lack of differences in stomatal density or index
indicate that there were no direct effects of CO2 enrichment on the
initiation of the number of stomata during ontogenesis or on
epidermal cell expansion at a later stage. Stomatal conductance
decreased because of the effect of CO2 on stomatal opening. The
average reduction in both adaxial and abaxial surface has been
estimated at 41%. Beaupre showed the largest response of stomatal
conductance and Columbia River the smallest.

Populus deltoides/Populus trichocarpa/Populus euroamericana

KEYWORDS: CLONAL RESPONSES, CONDUCTANCE, GREENHOUSE, OPEN-TOP
CHAMBERS, STOMATAL DENSITY, STOMATAL INDEX

609  
Radoglou, K.M., and P.G. Jarvis. 1990. Effects of CO2 Enrichment on
Four Poplar Clones. I. Growth and Leaf Anatomy. Annals of Botany
65:617-626.

The poplar clones Columbia River, Beaupre, Robusta and Raspalje
have been investigated under the present (350 umol/mol) and double
the present (700 umol/mol) atmospheric CO2 concentration. Cuttings
were planted in pots and were grown in open-top chambers inside a
glasshouse for 92 d. The number of leaves, total length of stem,
total leaf area, overall growth rate, total leaf, stem and root d.
wt responded positively to increased CO2, but the leaf size and
biomass allocation showed no change with CO2 enrichment. Beaupre
and Robusta showed a larger growth response than either Columbia
River or Raspalje. The effects of CO2 enrichment were restricted to
the early phase of growth at the beginning of the growth season.
Leaf cell numbers in all the clones were not affected by CO2
enrichment. Leaf thickness was affected; this was mainly the result
of larger mesophyll cells and more extensive intercellular spaces.

Populus trichocarpa/Populus euroamericana/Populus deltoides

KEYWORDS: ALLOCATION, ANATOMY, CLONAL RESPONSES, GREENHOUSE, GROWTH

610  
Radoglou, K.M., and P.G. Jarvis. 1992. The Effects of CO2
Enrichment and Nutrient Supply on Growth Morphology and Anatomy of
Phaseolus vulgaris L. Seedlings. Annals of Botany 70:245-256.

Plants of Phaseolus vulgaris were grown from seed in open-top
growth chambers at the present (P, 350 umol/mol) atmospheric CO2
concentration and at an elevated (E, 700 umol/mol) CO2
concentration, and at low (L, without additional nutrient solution)
and high (H, with additional nutrient solution) nutrient supply for
28 d. The effects of CO2 and nutrient availability were examined on
growth, morphological and biochemical characteristics. Leaf area
and dry mass were significantly increased by CO2 enrichment and by
high nutrient supply. Stomatal density, stomatal index and
epidermal cell density were not affected by elevated CO2
concentration or by nutrient supply. Leaf thickness responded
positively to CO2 increasing particularly in mesophyll area as a
result of cell enlargement. Intercellular air spaces in the
mesophyll decreased slightly in plants grown in elevated CO2. Leaf
chlorophyll content per unit leaf area or dry mass was
significantly lower in elevated CO2 grown plants and increased
significantly with increasing nutrient availability. The content of
reducing carbohydrates of leaves, stem, and roots was not affected
by CO2 but was significantly increased by nutrient addition in all
plant parts. Starch content in leaves and stem was significantly
increased by elevated CO2 concentration and by high nutrient
supply.

Phaseolus vulgaris/bean

KEYWORDS: ALLOCATION, ANATOMY, CARBOHYDRATES, GREENHOUSE, GROWTH,
NUTRITION, OPEN-TOP CHAMBERS, PIGMENTS, STOMATAL DENSITY, STOMATAL
INDEX

611  
Radoglou, K.M., and P.G. Jarvis. 1993. Effects of Atmospheric CO2
Enrichment on Early Growth of Vicia faba, a Plant with Large
Cotyledons. Plant, Cell and Environment 16:93-98.

Seedlings of Vicia faba L. were grown in open-top growth chambers
at present (P = 350 umol/mol) and at elevated (E = 700 umol/mol)
atmospheric CO2 concentration. The effects of CO2 enrichment on the
first phase of growth after germination were examined over 45 days.
There were no positive effects of CO2 enrichment on growth of the
seedlings during this early phase. No differences were observed in
leaf area or in total dry weight. No differences were found in
morphology or anatomy of the leaves. The numbers of stomatal and
epidermal cells, thickness of leaf of epidermis and of mesophyll
cell-layers were unaffected by CO2 enrichment. Also no differences
were observed in leaf concentrations of chlorophyll, reducing
carbohydrates or starch. These results contrast markedly with
results from similar experiments on poplar hybrids and Phaseolus
vulgaris obtained in the same growth facility. It seems that the
initial growth is under internal control such that the atmospheric
CO2 concentration has no effects. The lack of response in this case
may be attributed to the presence and longevity of the large
cotyledons which provided available substrate for growth.

Vicia faba/broad bean

KEYWORDS: ANATOMY, CARBOHYDRATES, GROWTH, OPEN-TOP CHAMBERS,
STOMATAL DENSITY, STOMATAL INDEX

612  
Rallo, L., and C. del Rio. 1990. Effect of a CO2-enriched
Environment on the Rooting Ability and Carbohydrate Level of Olive
Cuttings. Advances in Horticultural Science 4:129-130.

olive/Olea europaea

KEYWORDS: CARBOHYDRATES, HORTICULTURAL CROPS, ROOTING

613  
Raschke, K. 1986. The Influence of the CO2 Content of the Ambient
Air on Stomatal Conductance and the CO2 Concentration in Leaves.
IN: Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A.
Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC
Press, Inc., Boca Raton, Florida, pp. 88-102.

KEYWORDS: ABA, C3, C4, CAM, CHILLING, CI:CA, CONDUCTANCE,
ENVIRONMENTAL INTERACTIONS, NUTRITION, REVIEW, STOMATA

614  
Rastetter, E.B., M.G. Ryan, G.R. Shaver, J.M. Melillo, K.J.
Nadelhoffer, J.E. Hobbie, and J.D. Aber. 1991. A General
Biogeochemical Model Describing the Responses of the C and N Cycles
in Terrestrial Ecosystems to Changes in CO2, Climate, and N
Deposition. Tree Physiology 9:101-126.

A model that simulates carbon (C) and nitrogen (N) cycles in
terrestrial ecosystems is developed.  The model is based on the
principle that the responses of terrestrial ecosystems to changes
in CO2, climate, and N deposition will encompass enzymatic
responses, shifts in tissue stoichiometry, changes in biomass
allocation among plant tissues, altered rates of soil organic
matter turnover and N mineralization, and ultimately a
redistribution of C and N between vegetation and soils.  The model
is a highly aggregated, process-based, biogeochemical model
designed to examine changes in the fluxes and allocation of C and
N among foliage, fine roots, stems, and soils in response to
changes in atmospheric CO2 concentration, temperature, soil water,
irradiance, and inorganic nitrogen inputs.  We use the model to
explore how changes in CO2 concentration, temperature, and N inputs
affect carbon storage in two ecosystems:  arctic tundra and
temperate hardwood forest.  The qualitative responses of the two
ecosystems were similar.  Quantitative differences are attributed
to the initial distribution of C and N between vegetation and
soils, to the amounts of woody tissue in the two ecosystems, and to
their relative degree of N limitation.  We conclude with a critical
analysis of the model's strengths and weaknesses, and discuss
possible future direction.

KEYWORDS: CLIMATE, ECOSYSTEM LEVEL CO2 RESPONSES, ECOSYSTEM MODEL,
MODELING, TEMPERATE FOREST, TUNDRA

615  
Raven, J.A. 1991. Physiology of Inorganic C Acquisition and
Implications for Resource Use Efficiency by Marine Phytoplankton:
Relation to Increased CO2 and Temperature. Plant, Cell and
Environment 14:779-794.

Photosynthesis by many marine phytoplankton algae is saturated by
the inorganic C concentration in air-equilibrated sea water. These
organisms appear to use an active inorganic C transport process
(CO2-concentrating mechanism) which increases the CO2 concentration
around rubisco and saturates this enzyme with CO2 and suppresses
its oxygenase activity. A minority of marine phytoplankton algae
have photosynthetic characteristics more suggestive of diffusive
CO2 entry; the inorganic C concentration present in sea water does
not saturate photosynthesis by these organisms. Theoretical
considerations, tested when possible against observation, suggest
that the organisms with a CO2-concentrating mechanism could have a
lower cost of photons, nitrogen, iron, manganese and molybdenum to
achieve a given rate of carbon accumulation by the cells than is
the case for the organisms with diffusive CO2 entry. Zinc and
selenium costs may show the reverse effect. The increased sea-surface inorganic C, and CO2 concentrations which will result from
anthropogenic increases in atmospheric CO2 content are predicted to
increase the rate of photosynthesis, and of growth when other
resources are abundant, and to reduce, or reverse, the higher
resource (photons, nitrogen, iron, manganese and molybdenum) cost
of a given rate of CO2 assimilation in organisms with CO2 diffusion
relative to those which have CO2 concentrating mechanisms and do
not repress them at higher inorganic C concentrations. These
effects may well alter species composition, and overall resource
cost of growth, of phytoplankton; any influence that these effects
may have on CO2 removal from the atmosphere are severely
constrained by other trophic levels and, especially, oceanic
circulation patterns. Changed sea-surface temperatures are unlikely
to qualitatively alter these conclusions.

KEYWORDS: ALGAE, AQUATIC PLANTS, GROWTH EFFICIENCY, IRON,
MANGANESE, MOLYBDENUM, NITROGEN, PHYTOPLANKTON, REVIEW, SELENIUM,
TEMPERATURE, ZINC

616  
Rawson, H.M. 1992. Plant Response to Temperature under Conditions
of Elevated CO2. Australian Journal of Botany 40:473-490.

A literature survey of the interactive effects of CO2 enrichment
and temperature on plant development and growth, indicated that the
responses cannot be interpreted within a simple framework. For
example, although plant development is generally accelerated by
increased temperature, CO2 enrichment can accelerate it even
further in some instances, or CO2 enrichment may have neutral or
even retarding effects in other cases. Where the temperature and
CO2 effects are additive, it is argued that CO2 is operating in the
same way as radiation to reduce a carbon limitation. If this were
true, CO2 enrichment would be most likely to accelerate development
in tropical regions during the low-radiation monsoon season.
Similarly, while it would be expected that CO2-enrichment would
have increasingly enhancing effects with increasing temperature on
phytomass growth, this is not invariably the case. In extreme
examples which followed the expected trend, plants grown in twice-normal CO2-enriched atmospheres performed progressively better than
those grown at current levels of CO2 by 8.7% for every 1C rise in
temperature. However, the difference between the two CO2 treatments
more commonly increased by only around 2% for every 1C rise in
temperature. Of examples examined, both sunflower and nodulated
cowpea showed the reverse response to temperature, while non-nodulated cowpea, supplied with luxuriant levels of nutrition,
showed no interaction with temperature but a strong interaction
between CO2 and radiation. Other aspects of the environment such as
nutrition and radiation strongly modify the responses to
temperature. It is also clear that plant factors such as stage of
development can alter the response to CO2. Long-term studies with
several species are required which will take into account many
environmental variables within a realistic envelope. One
methodology for doing this is presented. There was no evidence
among species that responses to CO2 arise through any consistent
change in morphology such as via increased branching or increased
leaf number. Plant plasticity is such that responses can be
expressed in a variety of ways determined by other environmental
variables.

KEYWORDS: ENVIRONMENTAL INTERACTIONS, REVIEW, TEMPERATURE

617  
Reardon, J.C., J.R. Lambert, and B. Acock. 1990. The Influence of
Carbon Dioxide Enrichment on the Seasonal Patterns of Nitrogen
Fixation in Soybeans, 016 in Green Report Series, Response of
Vegetation to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide
Research Division, and U.S. Dept. of Agriculture, Agric. Res.
Serv., Washington, D.C.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, NITROGEN FIXATION, SPAR UNITS

618  
Reddy, V.R., B. Acock, and M.C. Acock. 1989. Seasonal Carbon and
Nitrogen Accumulation in Relation to Net Carbon Dioxide Exchange in
a Carbon Dioxide-Enriched Soybean Canopy. Agronomy Journal 81:78-83.

Crop modelers routinely equate net CO2 exchange (CE) in crop
canopies with biomass to simulate crop growth and productivity.
This study was initiated to validate this relationship
experimentally by monitoring CE during a whole-season CO2-enrichment study on soybean [Glycine max (L.) Merr. cv. Forrest].
Dry weights of soybean grown in sunlit plant growth chambers in CO2
concentrations ([CO2]) of 330, 450, 600, or 800 uL/L were sampled
at 25 d after emergence (DAE) and after physiological maturity.
Photosynthetic rates (P) and respiration rates were calculated from
CE rates measured at 0.25-h intervals, day and night, throughout an
entire season. The accuracy of CE measurement was tested by
plotting gross P against [CO2] at 28, 54, and 80 DAE (days when
light flux density was at least 1300 umol photons/m2/s). Gross P
had the expected hyperbolic dependence on [CO2] with all estimated
coefficients of determination > 0.93. The net CO2 required for
producing various plant parts was calculated from measurements of
dry weight and N content and from assumptions about carbohydrate,
oil, mineral, and lignin content. The amount of C required to fix
1.0 g of N symbiotically has been reported to be anywhere from 2.5
to 19.4 g. In this study the relationship between CO2 fixation and
biomass was closest when calculations were based on the theoretical
value of 2.0 g of C for each gram of N reduced for all [CO2]
treatments except 800 uL/L, where a value of 4.0 g of C per gram of
N fitted the data better.

soybean/Glycine max

KEYWORDS: ALLOCATION, CANOPY PHOTOSYNTHESIS, CARBON BUDGET, CROP
MODEL, DRY MATTER CONTENT, GROWTH MODEL, NITROGEN, NITROGEN
FIXATION, SPAR UNITS

619  
Reekie, E.G., and F.A. Bazzaz. 1989. Competition and Patterns of
Resource Use among Seedlings of Five Tropical Trees Grown at
Ambient and Elevated CO2. Oecologia 79:212-222.

Seedlings of five tropical trees, Cecropia obtusifolia, Myriocarpa
longipes, Piper auritum, Senna multijuga and Trichospermum
mexicanum, were grown both as individuals, and in competition with
each other at ambient (350) and two levels of elevated CO2 (525 and
700 uL/L) for a period of 111 days. Growth, allocation, canopy
architecture, mid-day leaf water potential and soil moisture
content were assessed three times over this period for individually
grown plants, and at the end of the experiment for competitively
grown plants. In addition, leaf photosynthesis and conductance were
assessed for the individually grown plants midway through the
experiment, and light profile curves were determined for the
competitive arrays at three stages of development. Elevated CO2 did
not affect photosynthesis or overall growth of the individually-grown plants but did affect canopy architecture; mean canopy height
increased with CO2 in Piper and Trichospermum and decreased in
Senna. Stomatal conductance decreased slightly as CO2 increased
from 350 to 525 uL/L but this had no significant effect upon whole
plant water use or leaf water potential. Soil moisture content for
the individuals increased marginally as CO2 increased, but this did
not occur in the competitive arrays. There was a marked effect of
CO2 upon species composition of the competitive arrays; Senna
decreased in importance as CO2 increased while Cecropia,
Trichospermum and Piper increased in importance. Stepwise
regression analysis using competitive performance as the dependent
variable, and the various morphological and physiological
parameters measured on the individually grown plants as independent
variables, suggested that canopy height was the single most
important variable determining competitive ability. Also
significant were photosynthetic rate (particularly at low light
levels) and allocation to roots early in the experiment. Light
profiles in the canopy revealed that less than 15% of incident
light penetrated to the level of mean canopy height. Results
suggest that competition for light was the major factor determining
community composition and that CO2 affected competitive outcome
through its effect upon canopy architecture.

Cecropia obtusifolia/Myriocarpa longipes/Piper auritum/Senna
multijuga/Trichospermum mexicanum

KEYWORDS: ALLOCATION, ARCHITECTURE, CONDUCTANCE, LEAF
PHOTOSYNTHESIS, LIGHT, MORPHOLOGY, SPECIES COMPETITION, SUNLIT
CONTROLLED ENVIRONMENT CHAMBERS, TREES, TROPICAL PLANTS, WATER
STATUS

620  
Reekie, E.G., and F.A. Bazzaz. 1991. Phenology and Growth in Four
Annual Species Grown in Ambient and Elevated CO2. Canadian Journal
of Botany 69:2475-2481.

The objectives of this study were (i) to test the hypothesis that
changes in phenology with CO2 are a function of the effect of CO2
upon growth and (ii) to determine if CO2-induced changes in
phenology can influence competitive outcome. We examined the effect
of 350, 525, and 700 uL/L CO2 on Guara brachycarpa, Gailardia
pulchella, Oenothera laciniata, and Lupinus texensis. Plants were
grown as individuals in 150-, 500-, or 1000-ml pots and in
competition in 1000-ml pots. Growth and development were monitored
at twice-weekly intervals by recording the number of leaves and
noting the presence or absence of stem elongation, branching,
flower buds, and open flowers. Elevated CO2 affected both growth
and phenology, but the direction and magnitude of effects varied
with species and soil volume. Elevated CO2 did not appear to affect
development through its effect on growth. Those treatments in which
there were significant effects of CO2 on growth were generally
different from those treatments in which CO2 affected phenology.
Rather than affecting phenology by changing plant size, CO2
appeared to affect phenology by modifying the size at which plants
switched from one stage to the next. The level of CO2 changed
competitive outcome; the importance of Lupinus increased whereas
that of Oenothera decreased with increased CO2. These changes were
more closely related to the effect of CO2 on growth than its effect
on phenology.

Guara brachycarpa/Gailardia pulchella/Oenothera laciniata/Lupinus
texensis

KEYWORDS: FLOWERING, GROWTH STAGES, LEAF AREA DEVELOPMENT,
PHENOLOGY, PHOTOPERIOD, REPRODUCTION, SPECIES COMPETITION, SUNLIT
CONTROLLED ENVIRONMENT CHAMBERS

621  
Reining, E. 1991. Langzeiteffekte von erhohtem CO2-Angebot auf den
Mineralstoffhaushalt von Acer pseudoplatanus und Fagus sylvatica.
Doctoral Dissertation, Universitat Osnabruck, Fachbereich
Biologie/Chemie, Osnabruck, Germany.

In German.

Acer pseudoplatanus/Fagus sylvatica

KEYWORDS: CALCIUM, CARBOHYDRATES, GROWTH ANALYSIS, IRON, ISOTOPE
DISCRIMINATION, MAGNESIUM, MANGANESE, NITROGEN, NUTRITION,
PHOSPHORUS, PIGMENTS, POTASSIUM, TREES

622  
Reining, F. 1990. Langzeiteffekte von erhohtem CO2-Angebot auf das
Wachstum von Acer pseudoplatanus und Fagus sylvatica. Doctoral
Dissertation, Universitat Osnabruck, Fachbereich Biologie/Chemie,
Osnabruck, Germany.

In German

Acer pseudoplatanus/Fagus sylvatica

KEYWORDS: CARBOHYDRATES, GROWTH ANALYSIS, ISOTOPE DISCRIMINATION,
PIGMENTS, TREES

623  
Retzlaff, W.A. 1987. Effect of Carbon-dioxide Enrichment on
Container-grown Pinus taeda L. Seedlings and Their Field Survival
Potential. Doctoral Dissertation, Clemson University, Dissertation
Abstracts Vol. 48:06-B, p.563 (113 pp.).

The effects of increased atmospheric CO2 levels on growth of
container-grown loblolly pine (Pinus taeda L.) seedlings were
examined. Seedlings were grown in CO2 concentrations of 363, 430,
780, and 1263 ppm in near airtight chambers. A 4 x 4 Latin Square
experimental design was employed with four 90-day replications
among four treatment-chambers. At 10-day intervals during each
replication, nine seedlings from each treatment were harvested to
measure growth. Foliar and rooting medium nutrient analyses,
diffusive resistance and photosynthetic rates of foliar types,
tissue starch content, seedling root growth potential, and stomate
physiology were also examined. Following each replication,
pretreated seedlings were outplanted to determine field survival
and growth. Seedling morphology was significantly different
(alpha=0.05) with increasing CO2 concentration. Carbon dioxide
enrichment increased total seedling height, root collar diameter,
number and projected surface area of primary needles, and root,
stem, primary needle, shoot and total dry weights of the seedlings.
Growth analysis at 90-days shows that optimum CO2 concentration for
growth occurs at 1000 ppm. Balanced root and shoot growth suggests
there was some mechanism for response to CO2 enrichment other than
changes in biomass partitioning. Carbon dioxide transfer resistance
measurements showed that both diffusive resistance and internal
(intercellular) CO2 concentration were unaffected by the CO2 level
in the atmosphere. However, net photosynthesis increased tenfold in
the 1009 ppm atmospheric CO2 concentration when compared to the 350
ppm CO2 concentration. Because photosynthetic rates of primary and
secondary needle tissue were greater in high atmospheric CO2
concentrations and less in the low atmospheric CO2 concentrations,
and diffusive resistance and internal CO2 concentration were
unaffected by atmospheric CO2 concentration, it was concluded that
biochemical resistance was the rate limiting process in the flux
relationship for primary and secondary needle tissue at ambient CO2
levels. No differences in field survival were found. Also, first-year height and diameter growth was not significantly affected by
CO2 pretreatment. Initially larger seedlings from the higher CO2
pretreatments lost their significant size advantage following 1
year in the field.

Pinus taeda/loblolly pine

KEYWORDS: ALLOCATION, CI:CA, CONDUCTANCE, GROWTH ANALYSIS, LEAF
PHOTOSYNTHESIS, SURVIVORSHIP, TREES

624  
Reuveni, J., and J. Gale. 1985. The Effect of High Levels of Carbon
Dioxide on Dark Respiration and Growth of Plants. Plant, Cell and
Environment 8:623-628.

Raising ambient levels of CO2 during the night, between 350 and 950
cm3/m3, reduced the dark respiration rate of Medicago sativum
seedlings. The percentage effect was greater for maintenance
respiration then for dark respiration as a whole, and when the
plants were in a low photosynthate status. Twenty-four h carbon
balance studies confirmed a reduction in night time respiration and
an increase of net carbon gain when night time [CO2] was high.
Growth experiments showed a small but significant increase of dry
weight in Medicago sativum seedlings exposed to high [CO2] (about
1200 cm3/m3) at night. This effect was greater for plants grown
with Rhizobium nodules than for plants grown with nitrate in the
absence of Rhizobium. A similar, but smaller and statistically non-significant effect of high night time [CO2] on growth was found for
Xanthium strumarium seedlings. The significance of these findings
is discussed in relation to the rising CO2 content of the
atmosphere.

Medicago sativa/alfalfa/Xanthium strumarium

KEYWORDS: CARBON BUDGET, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
RESPIRATION, RHIZOBIUM

625  
Reynolds, J.F., and B. Acock. 1985. Modeling Approaches for
Evaluating Vegetation Responses to Carbon Dioxide Concentration.
IN: Direct Effects of Increasing Carbon Dioxide on Vegetation,
DOE/ER-0238 (B.R. Strain and J.D. Cure, eds.), Dept. of Energy,
Carbon Dioxide Research Division, Washington, D.c., pp. 33-51.

KEYWORDS: CARBON BUDGET, GROWTH MODEL, MODELING, PHOTOSYNTHESIS
MODEL, REVIEW

626  
Reynolds, J.F., and B. Acock. 1985. Predicting the Response of
Plants to Increasing Carbon Dioxide: A Critique of Plant Growth
Models. Ecological Modeling 29:107-129.

It is widely recognized that increasing global carbon dioxide
concentration in the atmosphere may alter the growth of plants.
This has led to speculation about the long-term impact of rising
CO2 on agricultural productivity and on natural ecosystems, e.g.,
shifts in native species distributions and sequestering of carbon
in forests. In this paper we critique some existing plant growth
models with regard to their potential for predicting and evaluating
possible scenarios of vegetation response to elevated CO2 levels.
To facilitate this, we present various criteria for model
evaluation, specify a minimum set of plant processes that should be
considered for inclusion in a generic model capable of predicting
plant response to CO2, survey numerous published plant growth
models with respect to these criteria, and propose a scheme for
identifying the various options available for modeling the response
of vegetation to CO2.

KEYWORDS: GROWTH MODEL, MODELING, REVIEW

627  
Reynolds, J.F., D. Bachelet, P. Leadley, and D. Moorhead. 1986.
Assessing the Effects of Elevated Carbon Dioxide on Plants: Towards
the Development of a Generic Plant Growth Model, 028 in Green
Report Series, Response of Vegetation to Carbon Dioxide. U.S. Dept.
of Energy, Carbon Dioxide Research Division, Washington, D.C.

KEYWORDS: GENERIC MODEL, GROWTH MODEL, MODELING

628  
Reynolds, J.F., J. Chen, P.C. Harley, D.W. Hilbert, R.L. Dougherty,
and J.D. Tenhunen. 1992. Modeling the Effects of Elevated CO2 on
Plants: Extrapolating Leaf Response to a Canopy. Agricultural and
Forest Meteorology 61:69-94.

The response of canopies to short-duration exposure to elevated CO2
was examined by using a detailed submodel of single-leaf gas
exchange combined with a model of canopy structure and light
penetration. The leaf model included a mechanistic gas exchange
model and leaf energy balance equations, and the canopy model
included a detailed description of spatial variability in
environmental conditions within the canopy. The structure of the
canopy model was designed to facilitate implementation of different
leaf aggregation schemes. To compare six aggregation methods of
increasing simplicity, daily carbon gain, and water use were
simulated for Quercus coccifera under current ambient and future
doubled CO2. Analyses of simulated canopy responses confirmed the
importance of including (1) leaf energy balance and (2)
distinguishing between sunlit and shaded leaves. A multi-layer
canopy model with Gaussian integration for sunlit leaves and a
single leaf class for shaded leaves in each layer gave excellent
results. A multi-layer model with one shaded and one sunlit leaf
class gave a reasonable approximation, and the single-layer model
with one sunlit and one shaded leaf class resulted in errors of up
to 15%. Vertical gradients in leaf nitrogen content and leaf and
stem area index had greater effects on canopy assimilation and
transpiration than did gradients of stem or leaf inclination or
leaf width. However, predictions of the relative response of CO2
assimilation and transpiration to doubled CO2 are rather robust and
were not greatly affected by simplifications of the canopy model.

Quercus coccifera

KEYWORDS: CANOPY PHOTOSYNTHESIS, LEAF PHOTOSYNTHESIS, MODELING,
SCALING, SIMULATION, TRANSPIRATION MODEL

629  
Reynolds, J.F., R.L. Dougherty, J.D. Tenhunen, and P.C. Harley.
1988. A Model for the Simulation of Plant Response to Elevated CO2,
042 in Green Report Series, Response of Vegetation to Carbon
Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research Division,
Washington, D.C.

KEYWORDS: GENERIC MODEL, MODELING, PHOTOSYNTHESIS MODEL

630  
Reynolds, J.F., J.W. Skiles, and D.L. Moorhead. 1987. SERECO: A
Model for the Simulation of Ecosystem Response to Elevated CO2, 041
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington,
D.C.

KEYWORDS: ECOSYSTEM LEVEL CO2 RESPONSES, ECOSYSTEM MODEL, GENERIC
MODEL, MODELING, SCALING

631  
Riechers, G.H., and B.R. Strain. 1988. Growth of Blue Grama
(Bouteloua gracilis) in Response to Atmospheric CO2 Enrichment.
Canadian Journal of Botany 66:1570-1573.

Blue grama (Bouteloua gracilis (HBK.) Griffiths), an important C4
species in the Great Plains grasslands of the north central United
States, was grown under three concentrations of CO2: 350, 675, and
1000 uL/L. Growth of the blue grama was significantly enhanced by
enrichment to 675 but not to 1000 uL/L. At the end of the
experiment, 7 weeks after planting, plants grown at 675 uL/L had
35% more total biomass and nearly 90% greater leaf area than
controls grown at 350 uL/L. This growth enhancement is large for a
C4 species, but is modest compared with the response typical of C3
species. It is concluded that blue grama may experience increasing
competition from its C3 associates if atmospheric CO2 continues to
increase in the future.

Bouteloua gracilis

KEYWORDS: C4, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES, GROWTH
ANALYSIS

632  
Robinson, S.P., W.J.R. Grant, and B.R. Loveys. 1988. Stomatal
Limitation of Photosynthesis in Abscisic Acid-treated and in Water-stressed Leaves Measured at Elevated CO2. Australian Journal of
Plant Physiology 15:495-503.

Feeding 10(-5)M (+/-)-abscisic acid (ABA) via the petioles of
detached leaves of apricot (Prunus armeniaca) or sunflower
(Helianthus annuus) decreased stomatal conductance and assimilation
rate but not the calculated intercellular CO2 concentration (Ci)
suggesting non-stomatal as well as stomatal inhibition of
photosynthesis. Evidence for non-stomatal inhibition was not
observed in spinach (Spincia oleracea). There was no significant
decrease in rates of electron transport nor ribulose bisphosphate
carboxylase (Rubisco) activity in intact chloroplasts isolated from
ABA-treated sunflower leaves. Oxygen evolution by leaf discs with
3% CO2 in the gas phase was inhibited in ABA-treated sunflower and
apricot leaves but not in spinach; the inhibition was only half as
great as the inhibition of assimilation rate at ambient CO2. The
quantum yield of oxygen evolution decreased in ABA-treated
sunflower leaves in proportion to the decrease in the light-saturated rate. There was no significant difference in room
temperature chlorophyll fluorescence of ABA-treated leaves compared
to controls. Stomatal conductance of sunflower leaves decreased by
more than 90% when the CO2 concentration was increased from 340 ppm
to 1000 ppm but at much higher CO2 concentrations the stomata
appeared to reopen. Stomatal conductance at 2-3% CO2 (20,000-30,000
ppm) was 50% that at ambient CO2. This reopening of stomata at high
CO2 was inhibited in previously water-stressed or ABA-treated
plants. In unstressed leaves, the maximum rate of oxygen evolution
occurred at 0.5-2% CO2 but in ABA-treated leaves 10-15% CO2 was
required for maximum rates. It is suggested that stomatal closure
may limit photosynthesis in ABA-treated or previously water-stressed leaves even at the relatively high CO2 concentrations
normally used in the leaf disc oxygen electrode. The inhibition of
photosynthesis by ABA is largely overcome at saturating CO2. The
apparent non-stomatal inhibition suggested by gas exchange
measurements and the decreased quantum yield could be explained by
patchy stomatal closure in response to ABA.

Prunus armeniaca/apricot/Helianthus annuus/sunflower/Spinacia
oleracea/spinach

KEYWORDS: ABA, CI:CA, CONDUCTANCE, FLUORESCENCE, LEAF
PHOTOSYNTHESIS, QUANTUM REQUIREMENT, RIBULOSE BISPHOSPHATE
CARBOXYLASE, STOMATA, WATER STRESS

633  
Rochefort, L., and F.A. Bazzaz. 1992. Growth Response to Elevated
CO2 in Seedlings of Four Co-occurring Birch Species. Canadian
Journal of Forest Research 22:1583-1587.

Seedlings of four birch species were examined to evaluate the
presence and extent of phylogenetic constraints on the response of
species to global CO2 change. The species differ in their habitat
preferences and their successional status. Seedlings were grown for
3 months at near ambient (380 uL/L) and double (690 uL/L) CO2
concentrations in glasshouses. We found the following: (i) yellow
birch (Betula alleghaniensis Britton) was the only species whose
survival differed among CO2 treatments. Survival was slightly
increased by elevated CO2. (ii) All growth parameters considered in
all four species were significantly stimulated by enriched CO2
conditions, but the magnitude of response was different among
species. The most shade-intolerant, fast-growing species (grey
birch; Betula populifolia Marsh.) took greater advantage of the
elevated CO2 resource than the more shade-tolerant, later
successional species (e.g., yellow birch). (iii) Patterns of
allocation, shoot architecture, and leaf nitrogen content were
affected differently by CO2 concentrations for the different
species. (iv) The presence and identity of a neighbor did not
influence the magnitude or pattern of response to CO2 in birches of
a given community. Our results suggest that congeneric species
might be more similar in their response to global CO2 in comparison
to unrelated species of the same ecosystem that had been studied by
others, despite the fact that these closely related birch species
differ in their habitat preferences and successional status.

Betula lenta/black birch/Betula papyrifera/white birch/Betula
alleghaniensis/yellow birch/Betula populifolia/grey birch

KEYWORDS: ALLOCATION, FAMILY RESPONSES, GREENHOUSE, GROWTH,
NITROGEN, SPECIES COMPETITION, SURVIVORSHIP, TREES

634  
Rochefort, L., and F.I. Woodward. 1992. Effects of Climate Change
and a Doubling of CO2 on Vegetation Diversity. Journal of
Experimental Botany 43:1169-1180.

A model is presented for predicting the response of global family
diversity to global environmental change. The model assumes that
three primary mechanisms determine diversity: the capacity to
survive the absolute minimum temperature of a site, the ability to
complete the life cycle in a given length and warmth of the growing
season, and the capacity to expand leaves in a defined regime of
precipitation and vegetation transpiration. The direct effects of
CO2 on vegetation transpiration are also included. About one-third
of the floristic regions of the world exhibit increased diversity
with a 3C increase in temperature, a 10% increase in
precipitation, and a doubling of the CO2 concentration. The
addition of CO2 offsets the increased rates of transpiration,
caused by global warming through its capacity to reduce
transpiration. As a consequence, the diversity of dry regions
displayed the greatest increase in diversity due to increased CO2.

KEYWORDS: CLIMATE CHANGE, GCM'S, MODELING, PLANT DIVERSITY,
TRANSPIRATION

635  
Rogers, H.H., R.D. Beck, G.E. Bingham, J.D. Cure, J.M. Davis, W.W.
Heck, J.O. Rawlings, A.J. Riordan, N. Sionit, J.M. Smith, and J.F.
Thomas. 1981. Field Studies of Plant Responses to Elevated Carbon
Dioxide Levels, 005 in Green Report Series, Response of Vegetation
to Carbon Dioxide. U.S. Dept. of Energy, Carbon Dioxide Research
Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.,
Washington, D.C.

soybean/Glycine max

KEYWORDS: ANATOMY, CARBOHYDRATES, EXPOSURE METHODS, GROWTH, OPEN-TOP CHAMBERS, WATER STRESS, YIELD

636  
Rogers, H.H., G.E. Bingham, C. Brownie, J.D. Cure, B.G. Drake, W.W.
Heck, S.C. Huber, and D.W. Israel. 1982. Field Studies of Plant
Responses to Elevated Carbon Dioxide Levels, 009 in Green Report
Series, Response of Vegetation to Carbon Dioxide. U.S. Dept. of
Energy, Carbon Dioxide Research Division, and U.S. Dept. of
Agriculture, Agric. Res. Serv, Washington, D.C.

soybean/Glycine max

KEYWORDS: ANATOMY, CARBOHYDRATES, CONDUCTANCE, EXPOSURE METHODS,
GROWTH, LEAF PHOTOSYNTHESIS, MODELING, NITROGEN FIXATION, OPEN-TOP
CHAMBERS, RHIZOBIUM, YIELD

637  
Rogers, H.H., G.E. Bingham, J.D. Cure, W.W. Heck, A.S. Heagle, D.W.
Israel, J.M. Smith, K.A. Surano, and J.F. Thomas. 1980. Field
Studies of Plant Responses to Elevated Carbon Dioxide Levels, 001
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S.
Dept. of Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max/loblolly pine/Pinus taeda/sweetgum/Liquidambar
styraciflua/corn/Zea mays

KEYWORDS: ANATOMY, CONDUCTANCE, EXPOSURE METHODS, GROWTH, LEAF
PHOTOSYNTHESIS, NITROGEN, NITROGEN FIXATION, OPEN-TOP CHAMBERS,
WUE, YIELD

638  
Rogers, H.H., C. Brownie, J.D. Cure, W.W. Heck, S.C. Huber, D.W.
Israel, F.L. Mowry, J.F. Reynolds, and J.F. Thomas. 1983. Field
Studies of Plant Responses to Elevated Carbon Dioxide Levels, 012
in Green Report Series, Response of Vegetation to Carbon Dioxide.
U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S.
Dept. of Agriculture, Agric. Res. Serv., Washington, D.C.

soybean/Glycine max/sweet potato/Ipomoea batatas

KEYWORDS: ANATOMY, CULTIVAR RESPONSES, EXPOSURE METHODS, LEAF AREA
DEVELOPMENT, NITROGEN, OPEN-TOP CHAMBERS, SEED PRODUCTION, WATER
STRESS, YIELD

639  
Rogers, H.H., J.D. Cure, and J.M. Smith. 1986. Soybean Growth and
Yield Response to Elevated Carbon Dioxide. Agriculture, Ecosystems
and Environment 16:113-128.

Soybeans (Glycine max L. Merr. 'Bragg') were grown in seeded rows
in open-top field chambers and exposed continuously to a range of
elevated CO2 concentrations throughout the 1982 and 1983 growing
seasons. During 1983, a water stress treatment was also imposed.
Comparison of vegetative growth with a similarly conducted pot
experiment showed an increased ratio of leaf area to total top dry
weight in the seeded row plants, but generally similar qualitative
effects of elevated CO2. Careful recording of mainstem leaf
emergence rates and reproduction stages showed no consistent effect
of CO2 under well watered conditions, but in 1983 there was a
distinct modification by high CO2 of the water stress-induced
hastening of the time to physiological maturity. In 1982, and for
the well watered plants in 1983, standing biomass at maturity was
increased significantly by elevated CO2, but harvest index
decreased and yield was (statistically) unaffected by the
treatment. The yield responses calculated for a doubling of the
current CO2 concentration for these well watered treatments were
1.07 and 0.93, respectively. In the water stress treatment in 1983,
however, harvest index did not decrease in the presence of elevated
CO2, and a highly significant yield response occurred (1.41 at 700
uL/L).

Glycine max/soybean

KEYWORDS: GROWTH ANALYSIS, GROWTH STAGES, HARVEST INDEX, OPEN-TOP
CHAMBERS, WATER STRESS, YIELD

640  
Rogers, H.H., and R.C. Dahlman. 1992. Crop Responses to CO2
Enrichment. Vegetatio 104/105:117-131.

Carbon dioxide is rising in the global atmosphere, and this
increase can be expected to continue into the foreseeable future.
This compound is an essential input to plant life. Crop function is
affected across all scales from biochemical to agro-ecosystems. An
array of methods (leaf cuvettes, field chambers, free-air release
systems) are available for experimental studies of CO2 effects.
Carbon dioxide enrichment of the air in which crops grow usually
stimulates their growth and yield. Plant structure and physiology
are markedly altered. Interactions between CO2 and environmental
factors that influence plants are known to occur. Implications for
crop growth and yield are enormous. Strategies designed to assure
future global food security must include a consideration of crop
responses to elevated atmospheric CO2. Future research should
include these targets: search for new insights, development of new
techniques, construction of better simulation models, investigation
of belowground processes, study of interactions, and the
elimination of major discrepancies in the scientific knowledge
base.

KEYWORDS: AGRICULTURE, ENVIRONMENTAL INTERACTIONS, REVIEW, SCALING

641  
Rogers, H.H., C.M. Peterson, J.N. McCrimmon, and J.D. Cure. 1992.
Response of Plant Roots to Elevated Atmospheric Carbon Dioxide.
Plant, Cell and Environment 15:749-752.

Plant root response to atmospheric CO2 enrichment can be great.
Results from this controlled environment investigation demonstrate
substantial effects on root system architecture, micromorphology
and physiology. The most pronounced effects were an increase in
root length (110%) and root dry weight (143%). Root diameter, stele
diameter, cortex width, root/shoot and root weight ratios all
increased; root numbers did not increase. The long-term
implications for belowground processes could be enormous.

soybean/Glycine max

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, MORPHOLOGY, NITROGEN,
ROOT:SHOOT RATIO, ROOTS

642  
Rogers, H.H., S.A. Prior, and E.G. O'Neill. 1992. Cotton Root and
Rhizosphere Responses to Free-Air CO2 Enrichment. Critical Reviews
in Plant Sciences 11:251-263.

The increase in atmospheric CO2 concentration is known to enhance
the growth and yield of many crops. However, there is a paucity of
data on belowground responses to CO2 enrichment. New information is
needed in the related areas of: root systems, rhizosphere
populations and dynamics, and the edaphic factors with which they
interact. Free-air CO2 enrichment (FACE) studies initiated at Yazoo
City, MS (1988), and Maricopa, AZ (1989) provided the first
opportunity to examine belowground processes of an agro-ecosystem
at elevated levels of CO2 under realistic environmental conditions.
Cotton (Gossypium hirsutum L.) was grown under ambient CO2
conditions (360 ppm) and CO2 enriched conditions (550 ppm). Carbon
dioxide exposure times were just over 6 weeks, ending August 31, in
1988 and 14 weeks, ending September 22, in 1989. In 1988, the
number of lateral roots was 20% higher for the elevated CO2
treatment. Strong increasing trends were observed for taproot
length, top diameter, dry weight, and volume. Root length and dry
weight densities were either significant or showed a tendency to
increase at depth increments between 0-45 cm and 15-30 cm soil
depth, respectively, due to CO2 enrichment. Whole profile root
length density appeared to be higher at the 550 ppm level; root dry
weight density went up by 33%. Consistent indications of increased
bacterial populations and microbial activity were observed.
Although mycorrhizal infection was not enhanced, the greater root
length densities suggested greater total plant mycorrhization. In
1989, CO2 enrichment increased taproot volume and dry weight by 73
and 83%, respectively. Lateral root length, dry weight, and total
number were up 100, 157, and 35%. At the 550 ppm treatment level
root length density was increased by 21-32% in the upper layers of
the soil profile (0-45 cm), with an average increase of 18% for the
whole profile. Root dry weight density showed a 100% increase due
to added CO2. Elevated CO2 increased dry weight densities by 71-147% at the top three depths (0-45 cm) and clear patterns of
increase were observed from 45-75 cm. Field data presented here
indicate that elevated CO2 stimulates cotton root proliferation.
These new data provide a valuable first time insight into
belowground responses of an agro-ecosystem exposed to elevated
atmospheric CO2.

cotton/Gossypium hirsutum

KEYWORDS: ALLOCATION, FACE, GROWTH, RHIZOSPHERE, ROOTS, SOIL
MICROORGANISMS

643  
Rose, D.W., A.R. Ek, and K.L. Belli. 1987. A Conceptual Framework
for Assessing Impacts of Carbon Dioxide Change on Forest
Industries. IN: The Greenhouse Effect, Climate Change, and U.S.
Forests (W.E. Shands and J.S. Hoffman, eds.), The Conservation
Foundation, Washington, D.C., pp. 259-279.

An analytical framework was developed for assessing possible
impacts on forest industries of global warming caused by rising
atmospheric carbon dioxide (CO2) levels. Impacts on the aspen-based
forest industry of the Great Lakes states and the loblolly pine-based forest industry of the southeastern United States were
analyzed with available, limited information. In the unchanged-CO2
scenario, long-term supply shortages are predicted for the Great
Lakes aspen-based and the southeastern United States Loblolly pine-based industries. These shortages can be reduced through
technological changes and substitution with underutilized hardwood
species. Because an increase of the aspen and loblolly pine range
is expected under the doubled-CO2 scenario, industrial decisions to
deal with pending supply shortages will be influenced more by less
speculative factors than future climate. Changes in species ranges
will, however, have important implications for state forestry
programs.

KEYWORDS: CLIMATE CHANGE, FOREST, MODELING, SPECIES RANGE

644  
Rosenberg, N.J., B.A. Kimball, P. Martin, and C.F. Cooper. 1990.
From Climate and CO2 Enrichment to Evapotranspiration. IN: Climate
Change and U.S. Water Resources (P.E. Waggoner, ed.), John Wiley &
Sons, New York, pp. 151-175.

KEYWORDS: CLIMATE CHANGE, ENVIRONMENTAL INTERACTIONS,
EVAPOTRANSPIRATION, FOREST, GCM'S, GRASSES, MODELING, REVIEW,
SIMULATION, STOMATA, TALLGRASS PRAIRIE, WUE

645  
Rouhier, H., G. Billes, P. Bottner, M. Mousseau, and M.M. Couteaux.
1992. The Effect of Increased Atmospheric CO2 Concentration on the
Growth and Nitrogen Allocation of a Woody Plant (Castanea sativa
Mill.). IN: Responses of Forest Ecosystems to Environmental Changes
(A. Teller, P. Mathy, and J.N.R. Jeffers, eds.), Elsevier Applied
Science, London, pp. 701-702.

The N uptake by the plants was not significantly modified by CO2
enrichment and the N distribution, expressed as N in the organs %
whole plant, was only slowly modified by the CO2 treatment. The
storage organs tended to act as source of N and the leaves and fine
roots as sink. The fundamental question is to know to what extent
the change of the quality of the plant material will modify the
decomposition rates, the residence time of carbon in the soil, and
the nitrogen availability.

Castanea sativa/sweet chestnut

KEYWORDS: ALLOCATION, GROWTH, NITROGEN, OUTDOOR GROWTH CHAMBERS,
TREES

646  
Rowland-Bamford, A.J., L.H. Allen Jr., J.T. Baker, and K.J. Boote.
1990. Carbon Dioxide Effects on Carbohydrate Status and
Partitioning in Rice. Journal of Experimental Botany 41:1601-1608.

The atmospheric carbon dioxide (CO2) concentration has been rising
and is predicted to reach double the present concentration sometime
during the next century. The objective of this investigation was to
determine the long-term effects of different CO2 concentrations on
carbohydrate status and partitioning in rice (Oryza sativa L. cv
IR-30). Rice plants were grown season-long in outdoor, naturally
sunlit, environmentally controlled growth chambers with CO2
concentrations of 160, 250, 330, 500, 660, and 900 umol CO2/mol
air. In leaf blades, the priority between the partitioning of
carbon into storage carbohydrates or into export changed with
developmental stage and CO2 concentration. During vegetative
growth, leaf sucrose and starch concentrations increased with CO2
concentration but tended to level off above 500 umol/mol CO2.
Similarly, photosynthesis also increased with CO2 concentrations up
to 500 umol/mol and then reached a plateau at higher
concentrations. The ratio of starch to sucrose concentration was
positively correlated with the CO2 concentration. At maturity,
increasing CO2 concentration resulted in an increase in total non-structural carbohydrate (TNC) concentration in leaf blades, leaf
sheaths and culms. Carbohydrates that were stored in vegetative
plant parts before heading made a smaller contribution to grain dry
weight at CO2 concentrations below 330 umol/mol than for treatments
at concentrations above ambient. Increasing CO2 concentration had
no effect on the carbohydrate concentration in the grain at
maturity.

rice/Oryza sativa

KEYWORDS: CARBOHYDRATES, GROWTH STAGES, PARTITIONING,
PHOTOSYNTHESIS, PRE-INDUSTRIAL CO2 CONCENTRATION, SPAR UNITS

647  
Rowland-Bamford, A.J., J.T. Baker, L.H. Allen Jr., and G. Bowes.
1991. Acclimation of Rice to Changing Atmospheric Carbon Dioxide
Concentration. Plant, Cell and Environment 14:577-583.

The effects were studied of season-long (75 and 88 d) exposure of
rice (Oryza sativa L. cv. IR-30) to a range of atmospheric CO2
concentrations in outdoor, computer-controlled, environment
chambers under natural solar radiation. The CO2 concentrations were
maintained at 160, 250, 330, 500, 660 and 900 umol/mol air.
Photosynthesis increased with increasing growth CO2 concentrations
up to 500 umol/mol, but levelled off at higher CO2 values. Specific
leaf area also increased significantly with increasing CO2.
Although leaf dry weight and leaf area index increased, the overall
response was not statistically significant. Leaf nitrogen content
dropped slightly with elevated CO2, but the response was not
statistically significant. The specific activity of ribulose
bisphosphate carboxylase/oxygenase (rubisco) declined significantly
over the CO2 concentration range 160 to 900 umol/mol. When
expressed on a leaf area basis, rubisco activity decreased by 66%.
This was accompanied by a 32% decrease in the amount of rubisco
protein as a fraction of the total soluble leaf protein, and by 60%
on a leaf area basis. For leaves in the dark, the total rubisco
activity (CO2/Mg(++)-activated) was reduced by more than 60%. This
indicates that rice accumulated an inhibitor in the dark, probably
2-carboxyarabinitol 1-phosphate (CA-1-P). However, the inhibitor
did not seem to be involved in the acclimation response. The degree
of carbamylation of the rubisco enzyme was unchanged by the CO2
growth regime, except at 900 umol/mol where it was reduced by 24%.
The acclimation of rice to different atmospheric CO2 conditions
involved the modulation of both the activity and amount of rubisco
protein in the leaf.

rice/Oryza sativa

KEYWORDS: CA-1-P, CARBAMYLATION, NITROGEN, PHOTOSYNTHETIC
ACCLIMATION, PRE-INDUSTRIAL CO2 CONCENTRATION, PROTEINS, RIBULOSE
BISPHOSPHATE CARBOXYLASE, SPAR UNITS

648  
Rowland-Bamford, A.J., C. Nordenbrock, J.T. Baker, G. Bowes, and
L.H. Allen Jr. 1990. Changes in Stomatal Density in Rice Grown
under Various CO2 Regimes with Natural Solar Irradiance.
Environmental and Experimental Botany 30:175-180.

Rice (Oryza sativa L. cv. IR-30), grown from seed under natural
solar irradiance, was exposed to CO2 concentrations ranging from
160 to 900 uL CO2/L air from 9 days after planting until
senescence. Stomatal density was determined from leaf impressions
at two growth stages: on leaf number 7 (31 days after planting),
and on flag leaves (104 days after planting). Increasing CO2
concentrations resulted in a rise in stomatal density of leaves at
both growth stages. The effect was greatest on the flag leaves,
which exhibited a 54% increase in abaxial stomatal density (from
550 to 810 stomata/mm2) at 500 as compared with 160 uL CO2/L.
Stomatal density increased with increasing CO2 up to 330 uL CO2/L;
enrichment above this level resulted in no further significant
increase in stomatal density. For both leaf ages, the abaxial
stomatal density was more influenced by increases in CO2 than the
adaxial surface. The increase in stomatal density was largely the
result of a rise in the number of stomata per row, although on the
abaxial surface more rows across the leaf also contributed to the
response. Flag leaf area was not significantly different among the
CO2 treatments, so the number of stomata per leaf followed similar
trends to the stomatal density. This indicated the number of
stomata per leaf followed similar trends to the stomatal density.
This indicated the CO2 effect was on stomatal, rather than leaf
area, development. The response of stomatal density to rising CO2
seems to be a species-dependent phenomenon, that varies with leaf
surface and CO2 range utilized.

rice/Oryza sativa

KEYWORDS: PRE-INDUSTRIAL CO2 CONCENTRATION, SPAR UNITS, STOMATAL
DENSITY

649  
Rozema, J. 1993. Plant Responses to Atmospheric Carbon Dioxide
Enrichment: Interactions with Some Soil and Atmospheric Conditions.
Vegetatio 104/105:173-190.

In general, C3 plant species are more responsive to atmospheric
carbon dioxide (CO2) enrichment than C4 plants. Increased relative
growth rate at elevated CO2 primarily relates to increased Net
Assimilation Rate (NAR), and enhancement of net photosynthesis and
reduced photorespiration. Transpiration and stomatal conductance
decrease with elevated CO2, water use efficiency and shoot water
potential increase, particularly in plants grown at high soil
salinity. Leaf area per plant and leaf area per leaf may increase
in an early growth stage with increased CO2, after a period of time
Leaf Area Ratio (LAR) and Specific Leaf Area (SLA) generally
decrease. Starch may accumulate with time in leaves grown at
elevated CO2. Plants grown under salt stress with increased (dark)
respiration as a sink for photosynthates, may not show such
acclimation to increased atmospheric CO2 levels. Plant growth may
be stimulated by atmospheric carbon dioxide enrichment and reduced
by enhanced UV-B radiation but the limited data available on the
effect of combined elevated CO2 and ultraviolet B (280-320 nm) (UV-B) radiation allow no general conclusion. CO2-induced increase of
growth rate can be markedly modified at elevated UV-B radiation.
Plant responses to elevated atmospheric CO2 and other environmental
factors such as soil salinity and UV-B tend to be species-specific,
because plant species differ in sensitivity to salinity and UV-B
radiation, as well as to other environmental stress factors
(drought, nutrient deficiency). Therefore, the effects of joint
elevated atmospheric CO2 and increased soil salinity or elevated
CO2 and enhanced UV-B to plants are physiologically complex.

Zea mays/corn/Triticum aestivum/wheat

KEYWORDS: CARBOHYDRATES, ENVIRONMENTAL INTERACTIONS, GROWTH
ANALYSIS, LIGHT, SALT STRESS, TEMPERATURE, UV-B RADIATION

650  
Rozema, J., F. Dorel, R. Janissen, G. Lenssen, R. Broekman, W. Arp,
and B.G. Drake. 1991. Effect of Elevated Atmospheric CO2 on Growth,
Photosynthesis and Water Relations of Salt Marsh Grass Species.
Aquatic Botany 39:45-55.

The C3 grass species Scirpus maritimus L. and Puccinellia maritima
(Huds.) Parl., and the C4 grass species Spartina anglica C.E.
Hubbard and Spartina patens (Ait.) Muhl. were grown at ambient (340
p.p.m. CO2) and elevated (580 p.p.m. CO2) atmospheric CO2
concentration, at low (10 mM NaCl) and high salinity (250 mM NaCl)
under aerated and anaerobic conditions in the culture solution. The
relative growth rate of both the C3 grass species was enhanced with
atmospheric CO2 enrichment, no such increase was found in the C4
grass species. High salinity reduced growth of the C3 species
tested, but this relative growth reduction was not prevented by
elevated CO2 concentration. The growth increase at elevated CO2 of
Scirpus maritimus and Puccinellia maritima is greater under aerated
than under anaerobic solution conditions. Water-use efficiency of
all species was increased by elevated CO2. In the case of Scirpus
(C3), this increase was caused by increased net photosynthesis, for
Spartina patens (C4) photosynthesis was not increased, but
transpiration was reduced. The water potential of the shoot was
less negative under conditions of CO2 enrichment, in particular at
increased salinity (250 mM NaCl).

Scirpus maritimus/Puccinellia maritima/Spartina anglica/Spartina
patens

KEYWORDS: C3, C4, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES, GROWTH
ANALYSIS, HALOPHYTES, LEAF PHOTOSYNTHESIS, OXYGEN, SALT MARSH, SALT
STRESS, TRANSPIRATION, WATER STATUS, WUE

651  
Rozema, J., G.M. Lenssen, W.J. Arp, and J.W.M. van de Staaij. 1991.
Global Change, the Impact of the Greenhouse Effect (Atmospheric CO2
Enrichment) and the Increased UV-B Radiation on Terrestrial Plants.
IN: Ecological Responses to Environmental Stresses (J. Rozema and
J.A.C. Verkleij, eds.), Kluwer Academic Publishers, The
Netherlands, pp. 220-231.

Atmospheric enrichment of CO2 will favour growth of C3 plant
species and as a result the competitive balance between C3 and C4
plant species may markedly change. The greenhouse effect consists,
however, of both an increase of atmospheric CO2 and global warming,
with an expected increase of the global temperature of 1.5-4.5C
with a doubling of the atmospheric concentration of carbon dioxide.
Such a rise of temperature will prove advantageous to C4 plants. It
is also indicated that below a mean air temperature of 18.5C no
positive growth response to CO2 enrichment will occur. Increased
UV-B radiation will negatively affect the growth of many plant
species, monocots possibly being less sensitive than dicot plants.
Both the causes of physiological damage by increased UV-B and
adaptations to increased UV-B are incompletely understood. There is
special need for assessment of UV-B effects on plants in long term
field studies. The combined effect of CO2 enrichment, global
warming, UV-B increase, and soil and air pollution (ozone, SO2,
acid rain, etc.) on terrestric and aquatic ecosystems is unknown.
The combined effects of climatic change factors and the soil and
air pollution factors need to be studied in the near future.

KEYWORDS: AIR POLLUTION, C3, C4, CLIMATE CHANGE, REVIEW, SALT
MARSH, SPECIES COMPETITION, TEMPERATURE, UV-B RADIATION

652  
Rozema, J., G.M. Lenssen, R.A. Broekman, and W.P. Arp. 1990.
Effects of Atmospheric Carbon Dioxide Enrichment on Salt-marsh
Plants. IN: Expected Effects of Climatic Change on Marine Coastal
Ecosystems (J.J. Beukema, W.J. Wolff, and J.J.W.M. Brouns, eds.),
Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 49-54.

Aster tripolium and Spergularia maritima were cultivated at 340 ppm
CO2 (Ambient) and 580 ppm CO2 (Elevated); salinity of the culture
medium was varied at 10 mM NaCl and 250 mM NaCl. Culture solutions
were flushed either with oxygen or nitrogen gas. In both species
the mean relative growth rate was increased at elevated CO2, but in
the present paper there was no significant interaction with the
salinity treatment. Flushing of the nutrient solution with nitrogen
reduced the mean relative growth rate of both species under all
conditions tested. Increased salinity reduced the mean relative
growth rate of both species under all conditions tested. The rate
of photosynthesis was increased with enriched CO2 in Spergularia
maritima and to a lesser extent in Aster tripolium. Transpiration
rates of both species decreased with CO2 enrichment. The total
water potential of the shoot was less negative at elevated CO2. As
a result of an increased photosynthetical rate and decreased
stomatal conductance the water use efficiency was significantly
increased in Spergularia maritima and less pronounced so in Aster
tripolium.

Aster tripolium/Spergularia maritima

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, HALOPHYTES, LEAF PHOTOSYNTHESIS, OXYGEN, SALT STRESS,
TEMPERATURE, TRANSPIRATION, WATER STATUS, WUE

653  
Rozema, J., G.M. Lenssen, and J.W.M. van de Staaij. 1990. The
Combined Effect of Increased Atmospheric CO2 and UV-B Radiation on
Some Agricultural and Salt Marsh Species. IN: The Greenhouse Effect
and Primary Productivity in European Agro-ecosystems; 5-10 April
1990; Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and
H.H. van Laar, eds.), Pudoc, Wageningen, pp. 68-71.

Aster tripolium/Lycopersicon esculentum/tomato/pea/Pisum sativum

KEYWORDS: GREENHOUSE, HORTICULTURAL CROPS, SALT MARSH, UV-B
RADIATION

654  
Rufty, T.W., Jr., D.M. Jackson, R.F. Severson, J.J. Lam Jr., and
M.E. Snook. 1989. Alterations in Growth and Chemical Constituents
of Tobacco in Response to CO2 Enrichment. Journal of Agricultural
and Food Chemistry 37:552-555.

tobacco/Nicotiana tabacum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, SECONDARY METABOLITES

655  
Ryan, M.G. 1991. Effects of Climate Change on Plant Respiration.
Ecological Applications 1:157-167.

KEYWORDS: CLIMATE CHANGE, RESPIRATION

656  
Ryle, G.J.A., and C.E. Powell. 1992. The Influence of Elevated CO2
and Temperature on Biomass Production of Continuously Defoliated
White Clover. Plant, Cell and Environment 15:593-599.

Clonal plants of white clover (Trifolium repens L.), grown singly
in pots of Perlite and solely dependent for nitrogen on root nodule
N2 fixation, were maintained in controlled environments which
provided four environments: 18/13C day/night temperature at 340
and 680 umol/mol CO2 and 20.5/15.5C day/night temperature at 340
and 680 umol/mol CO2. The daylength was 12 h and the photon flux
density 500 +/- 25 umol/m2/s (PFD). All plants were defoliated for
about 80 d, nominally every alternate day, to leave the youngest
expanded leaf intact on 50% of stolons, plus expanding leaves
(simulated grazing). Elevated CO2 increased the yield of biomass
removed at defoliation by a constant 45% during the second 40 d of
the experiment and by a varying amount in the first half of the
experiment. Elevated temperature had little effect on biomass
yield. Nitrogen, as a proportion of the harvested biomass, was only
fractionally affected by elevated CO2 or temperature. In contrast,
N2 fixation increased in concert with the promoting effect of
elevated CO2 on biomass production. The increased yield of biomass
harvested in 680 umol/mol CO2 was primarily due to the early
development and continued maintenance of more stolons. However, the
stolons of plants grown in elevated CO2 also developed leaves which
were heavier and slightly larger in area than their counterparts in
ambient CO2. The conclusion is that, when white clover plants are
maintained at constant mass by simulated grazing, they continue to
respond to elevated CO2 in terms of a sustained increase in biomass
production.

Trifolium repens/white clover

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GRAZING,
LEAF AREA DEVELOPMENT, NITROGEN, NITROGEN FIXATION, NODULATION,
TEMPERATURE

657  
Ryle, G.J.A., C.E. Powell, and V. Tewson. 1992. Effect of Elevated
CO2 on Photosynthesis, Respiration and Growth of Perennial
Ryegrass. Journal of Experimental Botany 43:811-818.

Single, seed-grown plants of ryegrass (Lolium perenne L. cv. Melle)
were grown for 49 d from the early seedling stage in growth
cabinets at a day/night temperature of 20/15C, with a 12 h
photoperiod, and a CO2 concentration of either 340 or 680 uL/L CO2.
Following complete acclimation to the environmental regimes, leaf
and whole plant CO2 effluxes and influxes were measured using
infra-red gas analysis techniques. Elevated CO2 increased rates of
photosynthesis of young, fully expanded leaves by 35-46% and of
whole plants by more than 50%. For both leaves and whole plants
acclimation to 680 uL/L CO2 reduced rates of photosynthesis in both
CO2 regimes, compared with plants acclimated to 340 uL/L. There was
no significant effect of CO2 regime on respiration rates of either
leaves or whole plants, although leaves developed in elevated CO2
exhibited generally lower rates than those developed in 340 uL/L
CO2. Initially the seedling plants in elevated CO2 grew faster than
their counterparts in 340 uL/L CO2, but this effect quickly petered
out and final plant weights differed by only c. 10%. Since the
total area of expanded and unexpanded laminae was unaffected by CO2
regime, specific leaf area was persistently 13-40% lower in
elevated CO2 while, similarly, root/shoot ratio was also reduced
throughout the experiment. Elevated CO2 reduced tissue nitrogen
contents of expanded leaves, but had no effect on the nitrogen
contents of unexpanded leaves, sheaths or roots. The lack of a
pronounced effect of elevated CO2 on plant growth was primarily due
to the fact that CO2 concentration did not influence tiller
(branch) numbers. In the absence of an effect on tiller numbers,
any possible weight increment was restricted to the c. 2-5 leaves
of each tiller. The reason for the lack of an effect on tillering
is not known.

perennial ryegrass/Lolium perenne

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, CONTROLLED
ENVIRONMENT CHAMBERS, GRASSES, GROWTH ANALYSIS, LEAF AREA
DEVELOPMENT, LEAF PHOTOSYNTHESIS, NITROGEN, RESPIRATION, ROOT:SHOOT
RATIO, WUE

658  
Sage, R.F. 1990. A Model Describing the Regulation of Ribulose-1,5-Bisphosphate Carboxylase, Electron Transport, and Triose Phosphate
Use in Response to Light Intensity and CO2 in C3 Plants. Plant
Physiology 94:1728-1734.

A model of the regulation of the activity of ribulose-1,5-bisphosphate carboxylase, electron transport, and the rate of
orthophosphate regeneration by starch and sucrose synthesis in
response to changes in light intensity and partial pressures of CO2
and O2 is presented. The key assumption behind the model is that
nonlimiting processes of photosynthesis are regulated to balance
the capacity of limiting processes. Thus, at CO2 partial pressures
below ambient, when a limitation on photosynthesis by the capacity
of rubisco is postulated, the activities of electron transport and
phosphate regeneration are down-regulated in order that the rate of
RuBP regeneration matches the rate of RuBP consumption by rubisco.
Similarly, at subsaturating light intensity or elevated CO2, when
electron transport of Pi regeneration may limit photosynthesis, the
activity of rubisco is downregulated to balance the limitation in
the rate of RuBP regeneration. Comparisons with published data
demonstrate a general consistency between modelled predictions and
measured results.

KEYWORDS: C3, MODELING, PHOTOSYNTHESIS MODEL, RIBULOSE BISPHOSPHATE
CARBOXYLASE

659  
Sage, R.F., and T.D. Sharkey. 1987. The Effect of Temperature on
the Occurrence of O2 and CO2 Insensitive Photosynthesis in Field
Grown Plants. Plant Physiology 84:658-664.

The sensitivity of photosynthesis to O2 and CO2 was measured in
leaves from field grown plants of six species (Phaseolus vulgaris,
Capsicum annuum, Lycopersicon esculentum, Scrophularia desertorum,
Cardaria draba, and Populus fremontii) from 5C to 35C using gas-exchange techniques. In all species but Phaseolus, photosynthesis
was insensitive to O2 in normal air below a species dependent
temperature. CO2 insensitivity occurred under the same conditions
that resulted in O2 insensitivity. A complete loss of O2
sensitivity occurred up to 22C in Lycopersicon but only up to 6C
in Scrophularia. In Lycopersicon and Populus, O2 and CO2
insensitivity occurred under conditions regularly encountered
during the cooler portions of the day. Because O2 insensitivity is
an indicator of feedback limited photosynthesis, these results
indicate that feedback limitations can play a role in determining
the diurnal carbon gain in the field. At higher partial pressures
of CO2 the temperature at which O2 insensitivity occurred was
higher, indicating that feedback limitations in the field will
become more important as the CO2 concentration in the atmosphere
increases.

Phaseolus vulgaris/bean/Capsicum annuum/bell pepper/Lycopersicon
esculentum/tomato/Scrophularia desertorum/Cardaria draba/hoary
cress/Populus fremontii/cottonwood

KEYWORDS: C3, CO2 INSENSITIVITY, OXYGEN INSENSITIVITY,
PHOTOSYNTHETIC FEEDBACK INHIBITION, TEMPERATURE

660  
Sage, R.F., T.D. Sharkey, and R.W. Pearcy. 1990. The Effect of Leaf
Nitrogen and Temperature on the CO2 Response of Photosynthesis in
the C3 Dicot Chenopodium album L. Australian Journal of Plant
Physiology 17:135-148.

The CO2 response of photosynthesis was studied in the C3 annual,
Chenopodium album L. Both the initial slope of the photosynthetic
CO2 response and the CO2 saturated rate of photosynthesis were
linearly dependent on organic leaf nitrogen content. As leaf
nitrogen increased or leaf temperature declined, the CO2 saturation
point of photosynthesis declined. Increasing leaf temperature from
15 to 34C stimulated the CO2-saturated rate of photosynthesis but
had little effect on the initial slope of the photosynthetic CO2
response. According to the photosynthesis model of Sharkey (1985
Bot. Rev. 51: 53-105), these results indicate that as leaf nitrogen
increased the capacity for RuP2 carboxylase and RuP2 regeneration
increased to a greater extent than the capacity of starch and
sucrose synthesis to regenerate orthophosphate. As a result, in
high nitrogen leaves, photosynthesis appeared to be limited by the
capacity to regenerate phosphate at lower CO2 partial pressures
than in low nitrogen leaves. In high nitrogen leaves, increasing
temperature appeared to enhance the phosphate regeneration capacity
to a greater extent than the capacity of RuP2 carboxylase.
Consequently, while under cool conditions (<20C), CO2 assimilation
in normal atmospheric air appeared to be limited by the phosphate
regeneration capacity, under warm conditions (34C), RuP2
carboxylase capacity appears to limit CO2 assimilation.

Chenopodium album/lambsquarters

KEYWORDS: C3, NITROGEN, PHOTOSYNTHESIS, PHOTOSYNTHESIS MODEL,
RIBULOSE BISPHOSPHATE CARBOXYLASE, TEMPERATURE

661  
Sage, R.F., T.D. Sharkey, and J.R. Seemann. 1988. The In-vivo
Response of the Ribulose-1,5-bisphosphate Carboxylase Activation
State and the Pool Sizes of Photosynthetic Metabolites to Elevated
CO2. Planta 174:407-416.

The short-term, in-vivo response to elevated CO2 of ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39) activity, and the
pool sizes of ribulose 1,5-bisphosphate, 3-phosphoglyceric acid,
triose phosphates, fructose 1,6-bisphosphate, glucose 6-phosphate
and fructose 6-phosphate in bean were studied, Increasing CO2 from
an ambient partial pressure of 360-1600 ubar induced a substantial
deactivation of RuBPCase at both saturating and subsaturating
photon flux densities. Activation of RuBPCase declined for 30 min
following the CO2 increase. However, the rate of photosynthesis re-equilibrated within 6 min of the switch to high CO2, indicating
that RuBP-Case activity did not limit photosynthesis at high CO.
Following a return to low CO2, RuBPCase activation increased to
control levels within 10 min. The photosynthetic rate fell
immediately after the return to low CO2, and then increased in
parallel with the increase in RuBPCase activation to the initial
rate observed prior to the CO2 increase. This indicated that
RuBPCase activity limited photosynthesis while RuBPCase activation
increased. Metabolite pools were temporarily affected during the
first 10 min after either a CO2 increase or decrease. However, they
returned to their original level as the change in the activation
state of RuBPCase neared completion. This result indicates that one
role for changes in the activation state of RuBPCase is to regulate
the pool sizes of photosynthetic intermediates.

Phaseolus vulgaris/bean

KEYWORDS: C3, METABOLITES, PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE BISPHOSPHATE
CARBOXYLASE

662  
Sage, R.F., T.D. Sharkey, and J.R. Seemann. 1989. Acclimation of
Photosynthesis to Elevated CO2 in Five C3 Species. Plant Physiology
89:590-596.

The effect of long-term (weeks to months) CO2 enhancement on (a)
the gas-exchange characteristics, (b) the content and activation
state of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c)
leaf nitrogen, chlorophyll, and dry weight per area were studied in
five C3 species (Chenopodium album, Phaseolus vulgaris, Solanum
tuberosum, Solanum melongena, and Brassica oleracea) grown at CO2
partial pressures of 300 or 900 to 1000 microbars. Long-term
exposure to elevated CO2 affected the CO2 response of
photosynthesis in one of three ways: (a) the initial slope of the
CO2 response was unaffected, but the photosynthetic rate at high
CO2 increased (S. tuberosum); (b) the initial slope decreased but
the CO2-saturated rate of photosynthesis was little affected (C.
album, P. vulgaris); (c) both the initial slope and the CO2-saturated rate of photosynthesis decreased (B. oleracea, S.
melongena). In all five species, growth at high CO2 increased the
extent to which photosynthesis was stimulated following a decrease
in the partial pressure of O2 or an increase in measurement CO2
above 600 microbars. This stimulation indicates that a limitation
on photosynthesis by the capacity to regenerate orthophosphate was
reduced or absent after acclimation to high CO2. Leaf nitrogen per
area either increased (S. tuberosum, S. melongena) or was little
changed by CO2 enhancement. The content of rubisco was lower in
only two of the five species, yet its activation state was 19% to
48% lower in all five species following long-term exposure to high
CO2. These results indicate that during growth in CO2-enriched air,
leaf rubisco content remains in excess of that required to support
the observed photosynthetic rates.

Chenopodium album/lambsquarters/Phaseolus vulgaris/bean/Solanum
tuberosum/potato/Solanum melongena/eggplant/Brassica
oleracea/cabbage

KEYWORDS: C3, CO2 INSENSITIVITY, NITROGEN, OXYGEN INSENSITIVITY,
PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE BISPHOSPHATE
CARBOXYLASE

663  
Sage, R.F., T.D. Sharkey, and J.R. Seemann. 1990. Regulation of
Ribulose-1,5-bisphosphate Carboxylase Activity in Response to Light
Intensity and CO2 in the C3 Annuals Chenopodium album L. and
Phaseolus vulgaris L. Plant Physiology 94:1735-1742.

The light and CO2 response of (a) photosynthesis, (b) the
activation state and total catalytic efficiency (Kcat) of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) the pool sizes of
ribulose 1,5-bisphosphate (RuBP), ATP, and ADP were studied in the
C3 annuals Chenopodium album and Phaseolus vulgaris at 25C. The
initial slope of the photosynthetic CO2 response curve was
dependent on light intensity at reduced light levels only (less
than 450 micromoles per square meter per second in C. album and
below 200 micromoles per square meter per second in P. vulgaris).
Modeled simulations indicated that the initial slope of the CO2
response of photosynthesis exhibited light dependency when the rate
of RuBP regeneration limited photosynthesis, but not when rubisco
capacity limited photosynthesis. Measured observations closely
matched modeled simulations. The activation state of rubisco was
measured at three light intensities in C. album (1750, 550, and 150
micromoles per square meter per second) and at intercellular CO2
partial pressures (Ci) between the CO2 compensation point and 500
microbars. Above a Ci of 120 microbars, the activation state of
rubisco was light dependent. At light intensities of 550 and 1750
micromoles per square meter per second, it was also dependent on
Ci, decreasing as the Ci was elevated above 120 microbars at 550
micromoles per square meter per second and above 300 microbars at
1750 micromoles per square meter per second. The pool size of RuBP
was independent of Ci only under conditions when the activation
state of rubisco was dependent on Ci. Otherwise, RuBP pool sizes
increased as Ci was reduced. ATP pools in C. album tended to
increase as Ci was reduced. In P. vulgaris, decreasing Ci at a
subsaturating light intensity of 190 micromoles per square meter
per second increased the activation state of rubisco but had little
effect on the Kcat. These results support modelled simulations of
the rubisco response to light and CO2, where rubisco is assumed to
be down-regulated when photosynthesis is limited by the rate of
RuBP regeneration.

Chenopodium album/lambsquarters/Phaseolus vulgaris/bean

KEYWORDS: C3, LIGHT, METABOLITES, MODELING, PHOTOSYNTHESIS,
RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE BISPHOSPHATE CARBOXYLASE,
SIMULATION

664  
Sasek, T.W. 1985. Implications of Atmospheric Carbon Dioxide
Enrichment for the Physiological Ecology and Distribution of Two
Introduced Woody Vines, Pueraria lobata Ohwi (Kudzu) and Lonicera
japonica Thunb. (Japanese Honeysuckle). Doctoral Dissertation, Duke
University, Dissertation Abstracts Vol. 47:02-B, p.479 (218 pp.).

The vine growth habit increases competitive potential for light
capture. More biomass is allocated to height and leaf area because
support structures are minimized. This study considered the effects
of the continuing increase in atmospheric carbon dioxide
concentration on the growth and morphology of vines. Vines were
hypothesized to allocate CO2-induced increases in production to
height and leaf area more efficiently than erect growth forms.
Kudzu (Pueraria lobata Ohwi) and Japanese honeysuckle (Lonicera
japonica Thunb.) are perennial woody vines, introduced into the
United States from Japan. Both have become naturalized in the
eastern US and are pernicious weeds in the Southeast capable of
suppressing the native flora. Kudzu and honeysuckle were grown in
controlled environment chambers in the Duke University phytotron at
350, 675 and 1000 uL/L CO2, simulating double and triple current
ambient CO2 concentration. Long-term growth at elevated CO2
concentrations resulted in less enhancement of photosynthesis than
predicted by short-term exposure. The reduction of photosynthetic
capacity was not due to stomatal limitations. Rather, starch
accumulation in the leaves at high CO2 probably reduces
photosynthesis by biochemical feedback inhibition. Dry weight and
leaf area were increased by CO2 enrichment especially in the young
seedlings. Kudzu stems were 40% and 60% longer at double and triple
CO2, respectively, than at current ambient CO2. Branching was
enhanced by 50% with CO2 enrichment. Honeysuckle stem height was
unaffected but branching was enhanced three-fold by CO2 enrichment.
Height increase with CO2 enrichment was much greater than stem
diameter increase, which is in contrast to erect growth forms.
Vines maintain their favorable allocation patterns while still
incorporating CO2-induced increases in productivity. Kudzu seedling
establishment, currently rare, may be enhanced by CO2 enrichment
due to improved growth at low irradiance and by increased water use
efficiency. The geographic range of both species may be increased
due to direct effects of CO2 enrichment and indirect climatic
effects due to the Greenhouse Effect. Westward spread may occur due
to enhanced water use efficiency. Northward spread may occur due to
improved growth at low temperatures with CO2 enrichment and due to
global warming that may increase minimum winter temperatures,
reducing die-back of overwintering stems.

Lonicera japonica/Japanese honeysuckle/Pueraria lobata/kudzu

KEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS, MORPHOLOGY, SPECIES RANGE,
VINES, WUE

665  
Sasek, T.W., and B.R. Strain. 1988. Effects of Carbon Dioxide
Enrichment on the Growth and Morphology of Kudzu (Pueraria lobata).
Weed Science 36:28-36.

Kudzu (Pueraria lobata Ohwi #4 PUELO) was grown from seeds in
controlled-environment chambers at 350, 675, or 1000 uL/L CO2.
Biomass and leaf area production, morphological characteristics,
and growth analysis components were determined at 14, 24, 45, and
60 days after emergence. At 60 days, plants grown at 1000 uL/L CO2
had 51% more biomass, 58% longer stems, and 50% more branches than
plants grown at 350 uL/L CO2. Plants grown at 675 uL/L CO2 were
intermediate. Growth analysis components indicated that CO2
enrichment increased growth by compounding effects due to increased
net assimilation rates and increased leaf area duration. Relative
growth rates were not significantly affected. The large CO2-induced
increase in stem height versus stem diameter is in marked contrast
to previously reported responses of woody erect growth forms.
Possible ecological implications for competitive abilities are
discussed.

kudzu/Pueraria lobata

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, VINES

666  
Sasek, T.W., and B.R. Strain. 1989. Effects of Carbon Dioxide
Enrichment on the Expansion and Size of Kudzu (Pueraria lobata)
Leaves. Weed Science 37:23-28.

Seedlings of kudzu were grown at 350, 675, or 1000 uL/L CO2 in
controlled-environment chambers. At elevated CO2 concentrations,
maximum leaf expansion rates were approximately 40% greater, leaves
were fully expanded several days sooner, fully expanded leaves were
larger at each leaf position, and leaf production rates were
increased 12%. Peak starch accumulation was much greater in plants
grown at elevated CO2 concentrations. Total xylem water potentials
were higher (less negative) at full hydration, and osmotic
potentials were decreased (more negative) by CO2 enrichment. At
1000 uL/L CO2, leaf turgor pressure was twice that at 350 uL/L CO2.
Results suggest that leaf expansion rates and leaf expansivity may
have been increased due to higher turgor pressure at the higher CO2
concentrations. The potential for successful seedling establishment
may be enhanced as the atmospheric CO2 concentration continues to
rise, increasing kudzu invasiveness.

Pueraria lobata/kudzu

KEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, LEAF AREA
DEVELOPMENT, VINES, WATER STATUS

667  
Sasek, T.W., and B.R. Strain. 1990. Implications of Atmospheric CO2
Enrichment and Climatic Change for the Geographical Distribution of
Two Introduced Vines in the U.S.A. Climatic Change 16:31-51.

The continuing increase in the atmospheric carbon dioxide
concentration resulting from fossil fuel combustion and
deforestation may change the ecological impact and geographical
distribution of kudzu (Pueraria lobata Ohwi) and Japanese
honeysuckle (Lonicera japonica Thunb.) in the U.S.A. Both vines
were introduced about a century ago from Japan and have become
naturalized weeds. Westward range expansion is currently limited by
drought during seedling establishment, while northward range
expansion is limited by low temperature sensitivity of
overwintering stems. Direct effects of CO2 enrichment on growth
were assessed by growing the plants in controlled environment
chambers at 350, 675, or 1000 uL/L CO2. In both species, CO2
enrichment increased instantaneous water use efficiency by
increasing photosynthetic rates and reducing transpiration rates.
During a drought stress, CO2 enrichment delayed significant decline
in total water potential of kudzu by several days. When grown in a
cool temperature regime of 18/12C day/night, the CO2 enrichment
significantly increased leaf area and total biomass of both species
and plants were taller and had more branches. These results
suggested that atmospheric CO2 enrichment may allow westward and
northward spread of both species in the U.S.A. Indirect effects of
CO2 induced climate change (Greenhouse Effect) on the vines'
distribution were assessed. Predictions based on current models of
climatic response were used to project changes in winter
temperatures at doubled CO2 concentrations. Increases in average
and minimum winter temperatures by 3C could allow northward spread
of both species by several hundred kilometers. Projected decreases
in summer precipitation may minimize westward spread, despite
improved water use efficiency and increased drought tolerance.

kudzu/Pueraria lobata/Japanese honeysuckle/Lonicera japonica

KEYWORDS: CLIMATE CHANGE, CONTROLLED ENVIRONMENT CHAMBERS, GCM'S,
GROWTH, LEAF AREA DEVELOPMENT, LEAF PHOTOSYNTHESIS, SPECIES RANGE,
TEMPERATURE, TRANSPIRATION, VINES, WATER STRESS, WUE

668  
Sasek, T.W., and B.R. Strain. 1991. Effects of CO2 Enrichment on
the Growth and Morphology of a Native and an Introduced Honeysuckle
Vine. American Journal of Botany 78:69-75.

Japanese honeysuckle (Lonicera japonica Thunb.), introduced to the
United States, and the native coral honeysuckle (Lonicera
sempervirens L.) were compared to determine how intrinsic
differences in their growth characteristics would affect their
response to atmospheric carbon dioxide enrichment. Plants of both
species grown from cuttings were harvested after 54 days of growth
in controlled environment growth chambers at 350, 675, or 1,000
uL/L CO2. The biomass of Japanese honeysuckle was increased 135% at
675 uL/L CO2 and 76% at 1,000 uL/L CO2 after 54 days.
Morphologically, the main effect of CO2 enrichment was to triple
the number of branches and to increase total branch length six
times. Enhanced and accelerated branching also increased total leaf
area 50% at elevated CO2 concentrations. In coral honeysuckle,
total biomass was only 50% greater in the elevated CO2 treatments.
Branching was quadrupled but had not proceeded long enough to
affect total leaf area. Main stem height was increased 36% at 1,000
uL/L CO2. The much less significant height response of other woody
erect growth forms suggests that vines may increase in importance
during competition if atmospheric CO2 concentrations increase as
predicted. The impact of Japanese honeysuckle in the United States
may become more serious.

Lonicera japonica/Japanese honeysuckle/coral honeysuckle/Lonicera
sempervirens

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
MORPHOLOGY, VINES

669  
Saxe, H. 1986. Effects of NO, NO2 and CO2 on Net Photosynthesis,
Dark Respiration and Transpiration of Pot Plants. New Phytologist
103:185-197.

Eight cultivars of the pot plants (Ficus elastica 'Robusta', Ficus
benjamina, Hedera helix 'Anne Marie', Hedera canariensis
'Montgomery', Hibiscus rosa-sinensis 'Red', Hibiscus rosa-sinensis
'Moesiana', Dieffenbachia maculata 'Compacta' and Nephrolepis
exaltata 'Bostoniensis') most commonly grown in Danish commercial
greenhouses were subjected to 4 d exposures to 1 ml/L of CO2, 1
ml/L CO2 + 1 uL/L NO, 1 uL/L NO alone and 1 uL/L NO2 alone. Effects
on net photosynthesis and dark respiration of aerial parts and
effects on whole plant transpiration were observed before, during
and after exposures. The measurements were mathematically
transformed to double relative values, to indicate the effects of
the different gaseous treatments. Carbon dioxide enrichment
enhanced net photosynthesis by 40.9% and subsequent dark
respiration by 23.5%, while transpiration was reduced. NO reduced
photosynthesis (approximately 20%) and transpiration (the latter at
high CO2 only), but did not affect respiration. NO2 rarely had
significant effects. All effects of the gaseous treatments on
photosynthesis and transpiration were reversible and had
independent mechanisms, while effects on respiration were non-reversible. On the average, 1 uL/L NO was four times more
inhibitory to photosynthesis than 1 uL/L NO2. Short-term effects (4
d) on photosynthesis of exposure to CO2 + NO correlated
significantly (P<0.03) with the long-term effects (four to five
months) on dry weight found using the same cultivars in similar
treatments.

Ficus elastica/Ficus benjamina/Hedera helix/Hedera
canariensis/Hibiscus rosa-sinensis/Dieffenbachia
maculata/Nephrolepis exaltata

KEYWORDS: AIR POLLUTION, CANOPY PHOTOSYNTHESIS, CONTROLLED
ENVIRONMENT CHAMBERS, HORTICULTURAL CROPS, RESPIRATION,
TRANSPIRATION

670  
Saxe, H., and O.V. Christensen. 1985. Effects of Carbon Dioxide
with and without Nitric Oxide Pollution on Growth, Morphogenesis
and Production Time of Pot Plants. Environmental Pollution 38:159-169.

Eight of the cultivars of pot plants grown most commonly in Danish
commercial glasshouses were subjected to long-term CO2 enrichment
with or without nitric oxide pollution. Effects on the morphology
and productivity of the plants were determined. The advantage
obtained from the use of CO2 was generally reduced by the addition
of nitric oxide, although visual damage, such as scorched leaves,
was only found in one species.

Ficus elastica/Ficus benjamina/Hedera helix/Hedera
canariensis/Hibiscus rosa-sinensis/Dieffenbachia
maculata/Nephrolepis exaltata

KEYWORDS: AIR POLLUTION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
HORTICULTURAL CROPS, MORPHOLOGY, NITROGEN

671  
Schapendonk, A.H.C.M., S.C. van de Geijn, and E. Dayan. 1990.
Effect of CO2 Concentration and Temperature on Photosynthesis and
Assimilate Partitioning of a Closed Canopy. IN: The Greenhouse
Effect and Primary Productivity in European Agro-ecosystems; 5-10
April 1990; Wageningen, The Netherlands (J. Goudriaan, H. van
Keulen, and H.H. van Laar, eds.), Pudoc, Wageningen, pp. 38-41.

tomato/Lycopersicon esculentum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GREENHOUSE,
HORTICULTURAL CROPS, PARTITIONING, PHOTOSYNTHESIS MODEL,
RESPIRATION, SENESCENCE, SIMULATION, TEMPERATURE

672  
Schlesinger, W.H. 1993. Response of the Terrestrial Biosphere to
Global Climate Change and Human Perturbation. Vegetatio 104-105:295-305.

Despite 20 years of intensive effort to understand the global
carbon cycle, the budget for carbon dioxide in the atmosphere is
unbalanced. To explain why atmospheric CO2 is not increasing as
rapidly as it should be, various workers have suggested that land
vegetation acts as a sink for carbon dioxide. Here, I examine
various possibilities and find that the evidence for a sink of
sufficient magnitude on land is poor. Moreover, it is unlikely that
the land vegetation will act as a sink in the postulated warmer
global climates of the future. In response to rapid human
population growth, destruction of natural ecosystems in the tropics
remains a large net source of CO2 for the atmosphere, which is only
partially compensated by the potential for carbon storage in
temperate and boreal regions. Direct and inadvertent human effects
on land vegetation might increase the magnitude of regional CO2
storage on land, but they are unlikely to play a significant role
in moderating the potential rate of greenhouse warming in the
future.

KEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CARBON BUDGET, CARBON
SEQUESTERING, CLIMATE CHANGE, DEFORESTATION

673  
Schonfeld, M., R.C. Johnson, and D.M. Ferris. 1989. Development of
Winter Wheat under Increased Atmospheric CO2 and Water Limitation
at Tillering. Crop Science 29:1083-1086.

Atmospheric CO2 concentrations are increasing world-wide and are
expected to double within the next century. This study was
conducted to determine the combined effects of CO2 enrichment and
dehydration stress on development of 'TAM W-101' winter wheat
(Triticum aestivum L.) at the tillering stage. Seedlings (one per
pot) were grown in growth chambers maintained at 350 (ambient) or
700 (enriched) uL/L CO2, and subjected to three levels of soil
moisture (well watered, medium stress, and severe stress).
Plastochron (the developmental time for one leaf) decreased 2 to 3%
at all water levels under CO2 enrichment. Averaged over CO2
treatments, water limitation increased plastochron from 90 thermal
units under well-watered conditions to 126 under medium stress and
151 under severe stress. Similarly, water limitation reduced tiller
number from 26 to 14 and 12 under medium and severe stress,
respectively. The ratio of leaf dry wt. to leaf area (specific leaf
wt.) and water use efficiency were significantly higher in plants
grown under CO2 enrichment. Although CO2 enrichment had positive
effects on growth and development of winter wheat at tillering,
these were insufficient to counterbalance the debilitating effects
of water limitation.

Triticum aestivum/wheat

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF AREA DEVELOPMENT,
WATER STRESS, WUE

674  
Schonfeld, M.A. 1987. Drought Sensitivity in Winter Wheat
Populations under Field Conditions and Elevated Atmospheric Carbon-Dioxide. Doctoral Dissertation, Oklahoma State University,
Dissertation Abstracts 48:10-B, p.2829 (86 pp.).

In the first part of this study, the effect of drought stress on
tillering pattern, water potential and relative water content (RWC)
of winter wheat plants differing in drought resistance was
investigated in the field. The purpose was to find suitable traits
for use in a breeding program as selection criteria for improved
drought resistance. In the second part of the study, the effects of
elevated atmospheric CO2 and drought stress on development and
photosynthesis of winter wheat seedlings were studied. Plants were
grown in growth chambers at ambient or enriched CO2 and were either
kept well watered or subjected to two levels of drought stress.
Photosynthesis was measured when the plants were 40 days old, and
dry matter production was determined. Tillering pattern was similar
among genetic populations derived from TAM W-101 and Sturdy. Water
potential and RWC declined with increasing drought stress; but RWC
was the only trait investigated that differed significantly between
the populations. The differences in RWC appeared to be controlled
predominantly by genes with additive effects. Thus, RWC shows
promise as a selection criterion for drought resistance in winter
wheat. CO2 enrichment caused increases in dry weight and other
growth parameters, but the negative effect of drought stress was
much larger than the positive CO2 effect. The carbon assimilation
rate increased approximately 20% at double ambient CO2
concentration, but CO2 enrichment did not precondition the plants
for higher photosynthesis; plants from both CO2 environments
exhibited a similar CO2 response. The plants grown under enriched
CO2 conditions had significantly less chlorophyll per unit leaf
area at each water level, indicating that they were more efficient
in using chlorophyll for photosynthesis at elevated CO2.

Triticum aestivum/wheat

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES,
GROWTH, PHOTOSYNTHETIC ACCLIMATION, PIGMENTS, WATER STATUS, WATER
STRESS

675  
Schwartz, N., and B.R. Strain. 1990. Carbon -- a Plant Nutrient,
Deficiency and Sufficiency. Journal of Plant Nutrition 13:1073-1078.

Toxicity symptoms of carbon dioxide (CO2) have been observed at
10,000 ppm concentration after six days in seven species. Maize is
an indicator plant for C-toxicity, developing zebra-like stripes.
Full recovery from C-toxicity occurred only in wheat and maize
plants. No deficiency symptoms of carbon have been determined. Root
exposure during six days to 10,000 ppm CO2 or near zero CO2 had no
visible effect, and plants develop normally.

wheat/Triticum aestivum/maize/Zea mays/soybean/Glycine
max/tomato/Lycopersicon esculentum/lettuce/Lactuca
sativa/radish/Raphanus sativus/bean/Phaseolus vulgaris

KEYWORDS: CARBON DEFICIENCY, CARBON TOXICITY, CONTROLLED
ENVIRONMENT CHAMBERS, NUTRITION

676  
Setter, T.L., I. Waters, I. Wallace, P. Bhekasut, and H. Greenway.
1989. Submergence of Rice. I. Growth and Photosynthetic Response to
CO2 Enrichment of Floodwater. Australian Journal of Plant
Physiology 16:251-263.

Growth and photosynthetic response of lowland rice following
complete submergence is related to the concentration of CO2
dissolved in floodwater. Submergence of plants in stagnant solution
at low CO2 concentration or solution gassed with air at 0.03 kPa
CO2 (equilibrium of 0.01 mol/m3 dissolved CO2) decreased
carbohydrates, and little or no growth occurred. Plants submerged
in solutions gassed with 3-20 kPa CO2 in air (equilibrium of 0.9-6
mol/m3 CO2) showed at most small decreases in carbohydrates, and
growth was up to 100% of the non-submerged plants. At pH 7.5, there
was little net photosynthetic O2 evolution by detached submerged
leaves even at high HCO3(-) concentrations, which suggests that
these rice leaves could utilise only CO2 and not HCO3(-). At pH
6.5, O2 evolution in solutions in equilibrium with 7.4 Pa CO2 was
3-4 fold higher than in solutions in equilibrium with 0.6 kPa CO2.
Photorespiration was indicated by a decrease in the rate of net O2
evolution with increasing external O2. In stagnant solutions this
reduction of O2 evolution was pronounced; at a CO2 concentration of
0.25 mol/m3 net O2 evolution ceased when the O2 concentration in
the water had reached only 0.125 mol/m3. The requirement of
photosynthesis for a combination of high CO2 concentrations and low
external O2 was presumably due to slow diffusion of these gases in
the unstirred layer of solution around the leaves.

rice/Oryza sativa

KEYWORDS: CARBOHYDRATES, GROWTH, PHOTOSYNTHESIS, RESPIRATION,
SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

677  
Shaer, Y.A. 1985. Effect of Carbon Dioxide Enrichment on Diffusive
Resistance for Gas Exchange, Water Use, and Water Use Efficiency of
Greenhouse Tomatoes. Doctoral Dissertation, Texas A&M University,
Dissertation Abstracts 47:01-B, p.6 (118 pp.).

Three adjacent ventilated mini-greenhouses (MGH) made of clear
polyethylene film, transmitting natural solar radiation, were
enclosed in a conventional inflated polyethylene greenhouse. In
each MGH, an equal number of tomato plants were grown in the Spring
and the Fall of 1984, and kept at optimum levels of moisture and
nutrients. From 10 to 98 days after emergence, CO2 levels in the
mini-greenhouses were maintained at about 340, 700, and 1000 ppmv
during the daytime. As CO2 levels in the MGH air increased from 340
to 1000 ppmv, the crop surface resistance, measured with a
porometer, increased from about 30 to 100 s/m. CO2 enrichment also
increased the ratio between the internal and the external CO2
levels of the leaves from 0.70 to 0.85. From the Fall 1984 data, a
linear equation was derived to relate surface resistance to the
internal CO2 level with an R-square value of 0.8. At an air
exchange rate of 30 m3/m2/h in the MGH, the aerodynamic resistance,
measured using a heated brass plate, or as computed by the residual
method, averaged 225 s/m. This parameter dominated gas exchange by
the plants at all CO2 levels. Therefore, the water use as measured
by weighing mini-lysimeters (pots) on clear days, decreased only
slightly, 15-20%, as result of the CO2 enrichment. This occurred in
spite of an increase in leaf temperature of about 1.5C. The leaf
area and stomatal density were not markedly affected by CO2
enrichment. Both the instantaneous and the seasonal water use
efficiency increased markedly, by about 70%, by growing the plants
at a CO2 level of 1000 ppmv rather than 340 ppmv. In part, this was
due to the reduction of water use, but mainly to the increase in
assimilation rate, in total dry matter, and in the mass of fresh
fruit harvested, being 70%, 31%, and 50%, respectively.

Lycopersicon esculentum/tomato

KEYWORDS: CI:CA, CONDUCTANCE, GREENHOUSE, GROWTH, HORTICULTURAL
CROPS, STOMATAL DENSITY, WUE

678  
Shaer, Y.A., and C.H.M. van Bavel. 1991. Relationships between
Stomatal Resistance and CO2 Level around and inside Leaves of
Greenhouse Tomatoes. HortScience 26:72.

Lycopersicon esculentum/tomato

KEYWORDS: CI:CA, CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS,
STOMATA

679  
Shaish, A., N. Roth-Bejerano, and C. Itai. 1989. The Response of
Stomata to CO2 Relates to Its Effect on Respiration and ATP Levels.
Physiologia Plantarum 76:107-111.

External ATP enhanced stomatal opening of Commelina communis L.
differently from EDTA. ATP was more effective in opening stomata
than EDTA, when both were applied in amounts yielding equivalent
free Ca++ concentration. The stimulation by ATP depended upon its
de-phosphorylation and was not due to the Pi released. Hence an
energetical contribution of external ATP appears possible. Increase
in CO2 concentration increased the stimulation of stomatal opening
by ATP and diminished the internal ATP level, ATP/(ADP + AMP) ratio
and respiration.

Commelina communis

KEYWORDS: ADENYLATES, CONDUCTANCE, RESPIRATION, STOMATA

680  
Sharkey, T.D., F. Loreto, and C.F. Delwiche. 1991. High Carbon
Dioxide and Sun/Shade Effects on Isoprene Emission from Oak and
Aspen Tree Leaves. Plant, Cell and Environment 14:333-338.

Isoprene (2-methyl 1,3-butadiene) is emitted from many plants,
especially trees. We tested the effect of growth at high CO2
partial pressure and sun versus shade conditions on the capacity of
Quercus rubra L. (red oak) and Populus tremuloides Michx. (quaking
aspen) leaves to make isoprene. Oak leaves grown at high CO2
partial pressure (65 Pa) had twice the rate of isoprene emission as
leaves grown at 40 Pa CO2. However, aspen leaves behaved
oppositely, with high CO2-grown leaves having just 60-70% the rate
of isoprene emission as leaves grown in 40 Pa CO2. Similar
responses were observed from 25 to 35C leaf temperature during
assay. The stimulation of isoprene emission by growth at high CO2
and the stimulation in high temperature resulted in isoprene
emission consuming over 15% of the carbon fixed during
photosynthesis in high-CO2 grown oak leaves assayed at 35C. Leaves
from the south (sunny) sides of trees growing in natural conditions
had rates of isoprene emission double those of leaves growing in
shaded locations on the same trees. This effect was similar in both
aspen and oak. The leaves used for these experiments had
significantly different chlorophyll a/b ratios indicating they were
functionally sun (from the sunny locations) or shade leaves (from
the protected locations). Because the metabolic pathway of isoprene
synthesis is unknown, we are unable to speculate about how or why
these effects occur. However, these effects are more consistent
with metabolic control of isoprene release rather than a metabolic
leak of isoprene from metabolism. The results are also important
for large scale modelling of isoprene emission and for predicting
the effect of future increases in atmospheric CO2 level on isoprene
emission from vegetation.

red oak/Quercus rubra/quaking aspen/Populus tremuloides

KEYWORDS: AIR POLLUTION, ISOPRENE, LEAF PHOTOSYNTHESIS, PIGMENTS,
TREES

681  
Sharkey, T.D., and P.J. Vanderveer. 1989. Stromal Phosphate
Concentration Is Low during Feedback Limited Photosynthesis. Plant
Physiology 91:679-684.

It has been hypothesized that photosynthesis can be feedback
limited when the phosphate concentration cannot be both low enough
to allow starch and sucrose synthesis at the required rate and high
enough for ATP synthesis at the required rate. We have measured the
concentration of phosphate in the stroma and cytosol of leaves held
under feedback conditions. We used nonaqueous fractionation
techniques with freeze-clamped leaves of Phaseolus vulgaris plants
grown on reduced phosphate nutrition. Feedback was induced by
holding leaves in low O2 or high CO2 partial pressure. We found 7
millimolar phosphate in the stroma of leaves in normal oxygen but
just 2.7 millimolar phosphate in leaves held in low oxygen. Because
1 to 2 millimolar phosphate in the stroma may be metabolically
inactive, we estimate that in low oxygen, the metabolically active
pool of phosphate is between negligible and 1.7 millimolar. We
conclude that halfway between these extremes, 0.856 millimolar is
a good estimate of the phosphate concentration in the stroma of
feedback-limited leaves and that the true concentration could be
even lower. The stromal phosphate concentration was also low when
leaves were held in high CO2, which also induces feedback-limited
photosynthesis, indicating that the effect is related to feedback
limitation, not to low oxygen per se. We conclude that the
concentration of phosphate in the stroma is usually in excess and
that it is sequestered to regulate photosynthesis, especially
starch synthesis. The capacity for this regulation is limited by
the coupling factor requirement for phosphate.

Phaseolus vulgaris

KEYWORDS: ENZYMES, LEAF PHOTOSYNTHESIS, METABOLITES, NUTRITION,
PHOSPHORUS, PHOTOSYNTHETIC FEEDBACK INHIBITION

682  
Shina, G., and I. Seginer. 1989. Optimal Management of Tomato
Growth in Greenhouses. Acta Horticulturae 248:307-313.

tomato/Lycopersicon esculentum

KEYWORDS: GREENHOUSE, HORTICULTURAL CROPS, YIELD

683  
Shishido, Y., N. Seyama, S. Imada, and Y. Hori. 1989. Carbon Budget
in Tomato Plants as Affected by Night Temperature Evaluated by
Steady State Feeding with 14-CO2. Annals of Botany 63:357-367.

tomato/Lycopersicon esculentum

KEYWORDS: 14C, CARBON BUDGET, TEMPERATURE

684  
Shugart, H.H., M.Y. Antonovsky, P.G. Jarvis, and A.P. Sandford.
1986. CO2, Climatic Change and Forest Ecosystems. IN: The
Greenhouse Effect, Climatic Change, and Ecosystems, Vol. 29 (B.
Bolin, B.R. Doos, J. Jager, and R.A. Warrick, eds.), Scientific
Committee on Problems of the Environment, John Wiley and Sons,
Chichester, England, pp. 475-521.

The forests of the Earth constitute a complex system with many
possible responses, both to the direct effects of an increase in
atmospheric CO2 concentration and to the possible changes in
climate. These responses may originate from phenomena that operate
on very different time and space scales. In general, formidable
difficulties are encountered in 'scaling-up' the short-term
physiological and biochemical responses of leaves and individual
plants to estimate the intermediate and long-term responses of
forests. The difficulties arise from the large uncertainties
involved in the methods of extrapolation and from the complex
interactions that occur at larger scales. The two uncertainties are
presently large enough to preclude meaningful discussions of the
interactions between CO2 concentrations and climate except in the
most general way. With respect to the direct effects of CO2, these
problems of scaling-up are compounded by the lack of experimental
evidence for relevant forest species, particularly for plants that
have been allowed to acclimate to enhanced CO2 concentrations over
one or more growing cycles. Although higher concentrations of CO2
have been shown to increase CO2 assimilation and, consequently,
growth rates of individual trees in controlled conditions over the
short term, it is highly uncertain whether such effects would be
sustained and would lead to increased productivity in actual forest
environments over the long term. In uncontrolled environments, the
direct CO2 effects are complicated by micrometeorological
differences in the degree of coupling between forests and
atmosphere (within as well as between forest systems), and by
species competition and interactions. If, indeed, elevated CO2
concentrations do result in long-term growth enhancement, increases
in productivity would be more likely to occur in commercial forests
than in mature forests in which the capacities for increased carbon
storage are more limited. Direct experimentation at this scale,
however, is largely impracticable. In order, therefore, to assess
the responses of forest systems to both higher CO2 concentrations
and changes in climate, experimental studies must be augmented by
empirical observation and simulation modelling. With respect to the
effects of climatic change, empirical climate-vegetation models and
forest simulation models have been used to assess the responses of
forests at scales ranging from a single point in a forest to an
entire continental system. In general, from the results of a
limited number of such studies, together with our understanding of
the basic underlying processes, we conclude that: Climatic changes
of the order of magnitude predicted by climate models for a
doubling of atmospheric CO2 are potentially sufficient to produce
substantial intermediate and long-term changes in the composition,
size and location of the forests of the world. At continental and
regional scales, simulation models indicate considerable spatial
heterogeneity in the response of forests. The natural forests of
the high latitudes in general and the boreal forests in particular,
appear sensitive to predicted temperature changes. Warmer
conditions could possibly lead to large reductions in the areal
extent of boreal forests and a poleward shift in their boundaries.
It is at these latitudes that climate models predict the largest
warming to occur as a result of increased concentrations of
greenhouse gases, with smaller temperature changes in the lower
latitudes. The forests of the tropical and sub-tropical zones would
probably be more sensitive to changes in precipitation than
temperature. Because of the high uncertainty regarding future
changes in precipitation in the tropics, and because of the present
lack of models that can be used to simulate the effects of tropical
ecosystems to changes in climate variables, our knowledge of the
responses of tropical forests to future climatic changes is meagre.

KEYWORDS: CLIMATE CHANGE, FOREST, GCM'S, MODELING, PHOTOSYNTHESIS,
REVIEW, SCALING, TREES

685  
Silvola, J. 1990. Combined Effects of Varying Water Content and CO2
Concentration on Photosynthesis in Spagnum fuscum. Holarctic
Ecology 13:224-228.

The photosynthesis of Spagnum fuscum (Schimp.) Klinggr. at
different water contents and CO2 concentrations was measured in the
laboratory. The optimal water content for photosynthesis near the
current atmospheric CO2 concentration is 600-800% (percentage of
dry weight). The decrease in photosynthesis is very steep towards
lower water contents and less steep towards higher water contents.
The optimal water content range moves higher and becomes wider with
increasing CO2 concentration. At 3000 ppm there is no longer any
decrease in photosynthesis with increasing water content. The water
content of S. fuscum has a considerable effect on the response of
photosynthesis to CO2 concentration. In a moss saturated with
water, photosynthesis increases gradually until 8000 ppm CO2, but
this saturation concentration becomes lower with decreasing water
content, being c. 1500 ppm at a water content of 700-800%. An
increase in CO2 concentration over 300 ppm will raise
photosynthesis very little in dry moss with a water content of only
300-400%.

Spagnum fuscum/moss

KEYWORDS: PHOTOSYNTHESIS, WATER STATUS

686  
Simon, J.-P., C. Potvin, and B.R. Strain. 1989. Effects of
Temperature and CO2 Enrichment on Kinetic Properties of NADP+ -Malate Dehydrogenase in Two Ecotypes of Barnyard Grass (Echinochloa
crus-galli (L.) Beauv.) from Contrasting Climates. Oecologia
81:138-144.

The apparent energy of activation (Ea), Michaelis-Menten constant
(Km for oxaloacetate), Vmax/Km ratios and specific activities of
NADP+ -malate dehydrogenase (NADP+ -MDH; EC 1.1.1.82) were analyzed
in plants of Barnyard grass from Quebec (QUE) and Mississippi
(MISS) acclimated to two thermoperiods (28/22C, 21/15C, and grown
under two CO2 concentrations, 350 uL/L and 675 uL/L. Ea values of
NADP+ -MDH extracted from QUE plants were significantly lower than
those of MISS plants. Km values and Vmax/Km ratios of the enzyme
from both ecotypes were similar over the range of 10-30C but
reduced Vmax/Km ratios were found for the enzyme of QUE plants at
30 and 40C assays. MISS plants had higher enzyme activities when
measured on a chlorophyll basis but this trend was reversed when
activities were expressed per fresh weight leaf or per leaf surface
area. Activities were significantly higher in plants of both
populations acclimated to 22/28C. CO2 enrichment did not modify
appreciably the catalytic properties of NADP+ -MDH and did not have
a compensatory effect upon catalysis or enzyme activity under cool
acclimatory conditions. NADP+ -MDH activities were always in excess
of the amount required to support observed rates of CO2
assimilation and these two parameters were significantly
correlated. The enhanced photosynthetic performance of QUE plants
under cold temperature conditions, as compared to that of MISS
plants, cannot be attributed to kinetic differences of NADP+ -malate dehydrogenase among these ecotypes.

barnyardgrass/Echinochloa crus-galli

KEYWORDS: C4, CONTROLLED ENVIRONMENT CHAMBERS, ECOTYPES, GRASSES,
NADP+ -MALATE DEHYDROGENASE, TEMPERATURE

687  
Sinclair, T.R. 1992. Mineral Nutrition and Plant Growth Response to
Climate Change. Journal of Experimental Botany 43:1141-1146.

The limiting factor concept has often been used to describe plant
growth responses to altered availability of resources. However,
even preliminary experiments, where atmospheric CO2 concentrations
and solution mineral concentrations were varied, demonstrated that
a more complex concept was required to interpret the potential
effects of climate change and mineral availability on plant growth.
It is proposed that these resources for plant growth may be better
viewed as simultaneously limiting. Further, in considering the
limitation in plant growth to mineral nutrition it is important to
consider both the solution concentration and the total amount of
the individual minerals available to the plant. Sustaining a
positive response to increased CO2 concentration, for example,
requires an increase in plant uptake of the total amount of
minerals. Consequently, it is very difficult to predict the plant
growth response to climate change because of the large uncertainty
about mineral availability. On the one hand, increased CO2
concentrations should stimulate nitrogen fixation by both free-living organisms and symbiotic systems, and improve soil properties
for mineral availability as a result of increased organic matter
deposition in the soil. On the other hand, increased temperature
and altered rainfall patterns may result in increased losses of
soil minerals. Even the direction in the net change in available
soil minerals is unclear. Realistic evaluations of the effects of
climate change on plant growth will be challenged to contend with
the large uncertainty and complexities in understanding mineral
availability and plant mineral nutrition.

KEYWORDS: CLIMATE CHANGE, LITTER DECOMPOSITION, MINERALIZATION,
NITROGEN, NITROGEN FIXATION, NUTRITION, PHOSPHORUS, REVIEW

688  
Sionit, N., and P.J. Kramer. 1986. Woody Plant Reactions to CO2
Enrichment. IN: Physiology, Yield, and Economics, Vol. II (H.Z.
Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of
Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 69-85.

Woody plants constitute an important sink for CO2 and are
ecologically important species in forest communities. It is
therefore important to characterize their responses to increasing
atmospheric CO2 concentration. To reach this major objective with
some certainty will require a comprehensive research effort in both
laboratory and field. Based on the few data available, doubling the
present level of CO2 in the atmosphere would affect physiology,
morphology, and biomass production of woody plants, and is likely
to have differential effects on the establishment and growth of
tree seedlings. However, the responses of plants to increasing CO2
concentration depend on the extent of the growth limitation imposed
by other environmental factors such as available supplies of water
and nutrients, light and temperature. Most of our information comes
from short-term experiments conducted under controlled conditions.
Large-scale research projects are needed to more specifically
determine the combined effects of CO2 enrichment and other
environmental factors.

KEYWORDS: AIR POLLUTION, CONDUCTANCE, FOREST, PHOTOSYNTHESIS,
REPRODUCTION, RESPIRATION, REVIEW, ROOTING, SOIL MICROORGANISMS,
TRANSPIRATION, TREES, WATER STRESS, WUE

689  
Sionit, N., B.R. Strain, and E.P. Flint. 1987. Interaction of
Temperature and CO2 Enrichment on Soybean: Photosynthesis and Seed
Yield. Canadian Journal of Plant Science 67:629-636.

Seed yield and photosynthetic responses of soybean (Glycine max L.
Merr. 'Ransom') were studied in growth chambers at day/night
temperatures of 18/12, 22/16, and 26/20C and atmospheric CO2
concentrations of 350, 675 and 1000 uL/L. No seeds were produced at
18/12C within any of the CO2 concentrations. Numbers of pods and
seeds increased with increasing temperature and CO2 levels. Carbon
dioxide enrichment increased seed yield of soybean grown at
moderately cool temperatures. This increase was associated with an
increase in net photosynthetic rate. Leaf photosynthesis in
response to CO2 enrichment increased more at 22/16C than at
26/20C. Increases in temperature and CO2 levels enhanced total
growth of plants but hastened senescence of leaves. The extended
photosynthetic capacity at cool temperatures did not result in
allocating more dry matter to developing pods. CO2 enrichment at
26/20C resulted in greater seed yield increases than CO2
enrichment at lower temperatures.

soybean/Glycine max

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH
ANALYSIS, LEAF PHOTOSYNTHESIS, SEED PRODUCTION, TEMPERATURE, YIELD

690  
Sionit, N., B.R. Strain, and E.P. Flint. 1987. Interaction of
Temperature and CO2 Enrichment on Soybean: Growth and Dry Matter
Partitioning. Canadian Journal of Plant Science 67:59-67.

Projected increases in atmospheric CO2 concentration will affect
growth and productivity of many plant species under various
environmental conditions. Since these increases in CO2 may also
increase mean annual temperatures, it is important to determine how
the soybean (Glycine max (L.) Merr.) will respond to changes in
temperature regimes associated with atmospheric CO2 enrichment.
Morphology and growth responses of the Ransom cultivar, which is
adapted to a southern U.S.A. climate, to day/night temperature
regimes of 18/12, 22/16, and 26/20C and atmospheric CO2
concentrations of 350, 675 and 1000 uL/L were studied in controlled
environment chambers. Plant responses were determined at 20, 40, 67
and 115 (late senescence to maturity) days after planting. Plant
height and number of branches increased slightly with CO2
enrichment and more significantly with increasing temperature. Root
to shoot ratio remained unchanged at different CO2 concentrations
but decreased as temperature increased. Leaf weight ratio and
specific leaf weight decreased with increasing temperature. Low
temperature reduced dry weight of all plant parts, but the
reduction was ameliorated by increasing atmospheric CO2
concentration. The results show that increasing the atmospheric CO2
level causes soybean to grow more vigorously at low temperatures.
Although controlled environment experiments have their drawbacks in
regard to natural field conditions, the present data indicate that
soybean will have enhanced growth even at moderately cool
temperatures in the future global CO2 concentration.

soybean/Glycine max

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH,
ROOT:SHOOT RATIO, TEMPERATURE

691  
Sionit, N., B.R. Strain, H. Hellmers, G.H. Riechers, and C.H.
Jaeger. 1985. Long-term Atmospheric CO2 Enrichment Affects the
Growth and Development of Liquidambar styraciflua and Pinus taeda
Seedlings. Canadian Journal of Forest Research 15:468-471.

Growth and development of native species of trees in response to
long-term increases in atmospheric CO2 concentration were studied.
Seedlings of two competing perennials, Pinus taeda L. and
Liquidambar styraciflua L., were obtained from germinated seeds and
grown through one complete growing season at 350, 500, and 650 uL/L
CO2. The plants were grown in CO2 controlled greenhouses under
natural photoperiods and light regimes, with temperature controlled
to simulate mean local climate. Stem length and basal stem diameter
increased with increasing CO2 in both species. Liquidambar
styraciflua maintained size dominance in all concentrations. The
dry weights of stems, roots, and leaves increased in both species.
In P. taeda, however, the seedlings reached maximum size at 500
uL/L while L. styraciflua continued to increase up to 650 uL/L.
Liquidambar styraciflua produced significantly more branches and
leaves at the higher CO2 concentrations than at 350 uL/L.
Differences in plant shape and responses in growth rate of these
two naturally competing tree species suggest that continuing
atmospheric CO2 enrichment could affect future interactions between
the species and might produce changes in community composition.

sweetgum/Liquidambar styraciflua/Pinus taeda/loblolly pine

KEYWORDS: GREENHOUSE, GROWTH, TREES

692  
Slack, G. 1986. CO2 Enrichment of Tomato Crops. IN: Physiology,
Yield, and Economics, Vol. II (H.Z. Enoch and B.A. Kimball, eds.),
Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc.,
Boca Raton, Florida, pp. 151-163.

The benefits of enriching tomato crops with CO2 were first
demonstrated experimentally in the 1920s but the technique was not
used commercially until some 40 years later when cheap sources of
CO2 became available to the protected crops industry. The practice
is now well established and is used by most of the major tomato
producers. Increases in yield are highest when enrichment can be
maintained for long periods during daylight hours without the need
for ventilation. A threefold increase in CO2 concentration
increases leaf net photosynthesis by about 50% in both low and high
light conditions. In the vegetative phase, enrichment enhances
plant growth by increasing net assimilation rate and leaf area.
Relative growth rate is increased initially but eventually falls to
that of nonenriched plants. There is no significant effect on the
rate of leaf production. Dry weight may be increased by 40 to 50%
and leaf area by 20 to 25%. The effects in low light are
particularly important since large numbers of plants are propagated
commercially in late autumn and winter. Increasing CO2 level in
these conditions has a similar effect on dry matter production, as
does increasing light. Growth responses to enrichment are directly
attributable to enhanced photosynthetic activity so there is no
effect on seed germination nor from enrichment during the night
period. In the reproductive phase, enrichment induces earlier
flowering, but the effect is small and is restricted to flowers of
the first truss (3 to 9 days). Enrichment also improves flower
setting and fruit development of the early trusses in poor light
conditions, and a relationship between truss abortion and CO2
concentration has been shown. Increases in both the number and the
weight of fruits on individual trusses are seen with enriched
plants so that early and total fruit yields are greater and
profitability higher. Published results vary considerably in the
size of the effect but generally quote total yield increases of
around 30%. Fruit yield and profitability are maximzed when the CO2
concentration is maintained at about 1000 uL/L. Data on the effects
of elevated CO2 levels on fruit quality is scarce and conflicting.
Large differences in cultivar response were reported in the 1960s
but later reports suggest little or no effect. The response of
tomato plant growth and fruit yield to elevated CO2 levels is a
function of CO2 concentration and time. Whole-day enrichment would
therefore be expected to maximize growth and yield, though there is
a possibility that shorter daily periods may be more cost-effective. Results from experiments designed to test this
possibility show that some reduction in the duration of daily
enrichment during the pre-planting period would be acceptable,
although this course of action would not lead to large monetary
savings. In the post-planting period, any reduction would be
detrimental since the loss of revenue from the crop would far
outweigh any savings made from reduced gas usage. The enrichment
technique is generally restricted to the winter and early spring
periods of the year when ventilation for temperature control is
minimal. As ambient temperatures rise and ventilation periods
increase, enrichment becomes uneconomic and is stopped. Without
enrichment, CO2 levels in the glasshouse decline during the daytime
and may be substantially below ambient for long periods in bright
light. Recently two techniques have been developed to alleviate
this problem. In the first, ventilation is avoided by cooling the
CO2-enriched air in evaporative cooling towers and returning it to
the glasshouse. This method, compared with a conventionally
ventilated (fan and pad) crop grown without enrichment, increased
fruit yield by 17 and 48% when CO2 level was controlled at 650 and
1000 uL/L, respectively. The second method assumes that it is
uneconomic to practice threefold CO2 enrichment throughout the
summer months but that it is worthwhile enriching with CO2 to
maintain a level of 350 to 400 uL/L. This technique avoids the
detrimental effects of CO2 depletion and has the potential for
increasing yield.

tomato/Lycopersicon esculentum

KEYWORDS: CO2 ENRICHMENT DURATION, COMMERCIAL USE OF CO2,
GREENHOUSE, HORTICULTURAL CROPS, LIGHT, PHOTOSYNTHESIS,
REPRODUCTION, YIELD

693  
Slack, G., J.S. Fenlon, and D.W. Hand. 1988. The Effects of Summer
CO2 Enrichment and Ventilation Temperatures on the Yield, Quality
and Value of Glasshouse Tomatoes. Journal of Horticultural Science
63:119-129.

The responses of January-sown tomatoes to a range of CO2
concentrations (ambient, 375, 450 and 525 vpm) in summer were
investigated in two experiments. The first was designed to examine
the effects of summer CO2 on the fruit yield of four cultivars
planted in two rooting substrates (soil or peat-bags). The aim of
the second was to increase the cost-effectiveness of the treatment
by delaying greenhouse ventilation in order that reductions in the
inputs of CO2 might be achieved at levels of enrichment above
ambient. Summer CO2 enrichment was applied for eighteen weeks
starting at the end of April. Fruiting response was linearly
related to summer CO2 concentration. The yield response slopes for
plants grown in different rooting substrates, ventilation
temperatures and seasons were not significantly different. The
overall response increment showed that in the range 320 to 526 vpm
(the mean measured values), marketable fruit yield increased by
2.65 +/- 0.201 kg/m2 for each 100 vpm increase in mean CO2 level.
Delaying glasshouse ventilation reduced the amount of CO2 supplied
to the greenhouses by 23 to 35% but total marketable yield fell by
11% and the weight of fruits graded CLass 1 was reduced on average
by 20% in the higher temperature regimen making the treatment
commercially unacceptable.

tomato/Lycopersicon esculentum

KEYWORDS: COMMERCIAL USE OF CO2, CULTIVAR RESPONSES, GREENHOUSE,
HORTICULTURAL CROPS, TEMPERATURE, YIELD

694  
Slack, G., and D.W. Hand. 1985. The Effect of Winter and Summer CO2
Enrichment on the Growth and Fruit Yield of Glasshouse Cucumber.
Journal of Horticultural Science 60:507-516.

The responses of January-sown cucumbers to a range of CO2
concentrations in winter and in summer were examined together with
a non-enriched treatment. In winter the CO2 concentration in the
glasshouses was ambient, 400 or 1000 vpm, and in the summer, 350,
380, 400 or 450 vpm. Winter CO2 enrichment to 1000 vpm produced
large increases in growth by early March. Mean CO2 concentration in
the ambient treatment during this period was 370 vpm and there were
no differences between the effect of this and the 400 vpm
treatment. Fruit yield by mid-April was doubled when CO2 level was
maintained at 400 vpm and trebled when the level was raised to 1000
vpm. Gross monetary value was similarly increased. CO2 enrichment
also increased mean fruit weight, by 10% at 400 vpm and 23% at 1000
vpm. During April the mean CO2 concentration in the non-enriched
treatments averaged 262 vpm with some daily means falling below 200
vpm. With summertime CO2 enrichment fruit yields and gross monetary
values improved with increasing CO2. Maintaining levels of 350,
380, 400 or 450 vpm CO2 increased total fruit yields by 5, 11, 15
and 22%. Fruit yield was linearly related to mean CO2
concentration. Between 318 and 455 vpm CO2, fruit yield increased
by 54 g/m2 for each vpm increase in mean summertime CO2
concentration. The enrichment treatments were cost-effective.

cucumber/Cucumis sativus

KEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, YIELD

695  
Slack, G., and D.W. Hand. 1986. The Effects of Propagation
Temperature, CO2 Concentration and Early Post-harvest Night
Temperature on the Fruit Yield of January-sown Cucumbers. Journal
of Horticultural Science 61:303-306.

Growth and fruiting responses of four January-sown cucumber
cultivars to two propagation temperatures (day 21C, night 19C and
day 24C, night 17C), three levels of CO2 enrichment (400, 1000
and 1600 vpm) and three stages of post-planting night temperature
reduction (1, 3 and 6 weeks after first harvest) were examined in
a glasshouse experiment. Early (4-week) fruit yield and monetary
returns were significantly increased when the higher day
temperature treatment was combined with the 1600 vpm CO2. The early
advantage was soon lost and after 20 weeks harvesting there were no
differences between the propagation temperature treatments. After
two weeks of CO2 treatment total dry weight of aerial parts, leaf
area and stem length were increased by 88, 73, and 69%,
respectively, when the CO2 level was raised from 400 to 1000 vpm.
A further rise from 1000 to 1600 vpm produced no further increases
indicating that 1000 vpm is probably near the optimum concentration
for growth at the temperatures applied. In the early (4-week)
harvest period, fruit yield and gross monetary returns increased by
c. 30% when CO2 was raised from 400 to 1000 vpm but there was
little or no difference between plants grown in 1000 or 1600 vpm.
The early yield advantage from enrichment at 1000 vpm CO2 was
maintained throughout the season (20 weeks of harvesting). The most
economic level of CO2 enrichment for January-sown cucumbers was c.
1000 vpm. Lowering night temperature at the start of harvesting
reduced fruit yield and monetary value compared with lowering the
temperature 3 or 6 weeks after fruit picking commenced. The
estimated savings in fuel from this treatment were too small to
offset the loss of revenue from the crop. The most economic time to
reduce night temperature in the January-sown crop was 3 weeks after
the start of harvesting.

cucumber/Cucumis sativus

KEYWORDS: COMMERCIAL USE OF CO2, CULTIVAR RESPONSES, GREENHOUSE,
TEMPERATURE, YIELD

696  
Smith, S.D., B.R. Strain, and T.D. Sharkey. 1987. Effects of CO2
Enrichment on Four Great Basin Grasses. Functional Ecology 1:139-143.

Plants of four Great Basin grass species were grown from seed in
two greenhouses at low (340 uL/L) and high (680 uL/L) CO2
concentration. In all four species, high CO2 promoted mean
increases in the number of basal stems, leaf area, specific leaf
weight and above-ground dry weight. High CO2 resulted in an
increase in CO2 assimilation in two C3 grasses but not in a C4
grass, while all three species showed decreases in stomatal
conductance. Mean increases of 60% in above-ground dry weight and
80% in water-use-efficiency are consistent with previously reported
high CO2 effects on grasses. No consistent differential effects of
high CO2 were observed when comparing annual vs perennial species.
Global CO2 enrichment may alter the competitive balance of Great
Basin plant communities, possibly enhancing the dominance of Bromus
tectorum L. on degraded rangelands.

Bromus tectorum/Agropyron smithii/Eragrostis orcuttiana/Oryzopsis
hymenoides

KEYWORDS: ALLOCATION, C3, C4, GRASSES, GREENHOUSE, GROWTH, LEAF
PHOTOSYNTHESIS, RANGELAND, ROOT:SHOOT RATIO, WUE

697  
Socias, F.X., H. Medrano, and T.D. Sharkey. 1993. Feedback
Limitation of Photosynthesis of Phaseolus vulgaris L. Grown in
Elevated CO2. Plant, Cell and Environment 16:81-86.

The capacity for photosynthesis is often affected when plants are
grown in air with elevated CO2 partial pressure. We grew Phaseolus
vulgaris L. in 35 and 65 Pa CO2 and measured photosynthetic
parameters. When assayed at the growth CO2 level, photosynthesis
was equal in the two CO2 treatments. The maximum rate of ribulose-1,5-bisphosphate (RuBP) consumption was lower in plants grown at 65
Pa, but the CO2 partial pressure at which the maximum occurred was
higher in the high-CO2-grown plants, indicating acclimation to high
CO2. The acclimation of RuBP consumption to CO2 involved a
reduction of the activity of RuBP carboxylase which resulted from
reduced carbamylation, not a loss of protein. The rate of RuBP
consumption declined with CO2 when the CO2 partial pressure was
above 50 Pa in plants grown under both CO2 levels. This was caused
by feedback inhibition as judged by a lack of response to removing
O2 from the air stream. The rate of photosynthesis at high CO2 was
lower in the high-CO2-grown plants and this was correlated with
reduced activity of sucrose-phosphate synthase. This is only the
second report of O2-insensitive photosynthesis under growth
conditions for plants grown in high CO2.

Phaseolus vulgaris/bean

KEYWORDS: CARBAMYLATION, CONTROLLED ENVIRONMENT CHAMBERS, LEAF
PHOTOSYNTHESIS, OXYGEN INSENSITIVITY, PHOTOSYNTHETIC ACCLIMATION,
PROTEINS, RIBULOSE 1,5-BISPHOSPHATE, RIBULOSE BISPHOSPHATE
CARBOXYLASE, SUCROSEPHOSPHATE SYNTHASE

698  
Spencer, W., and G. Bowes. 1986. Photosynthesis and Growth of Water
Hyacinth under CO2 Enrichment. Plant Physiology 82:528-533.

Water hyacinth (Eichhornia crassipes [Mart.] Solms) plants were
grown in environmental chambers at ambient and enriched CO2 levels
(330 and 600 microliters CO2 per liter). Daughter plants (ramets)
produced in the enriched CO2 gained 39% greater dry weight than
those at ambient CO2, but the original mother plants did not. The
CO2 enrichment increased the number of leaves per ramet and leaf
area index, but did not significantly increase leaf size or the
number of ramets formed. Flower production was increased 147%. The
elevated CO2 increased the net photosynthetic rate of the mother
plants by 40%, but this was not maintained as the plants acclimated
to the higher CO2 level. After 14 days at the elevated CO2, leaf
resistance increased and transpiration decreased, especially from
the adaxial leaf surface. After 4 weeks in elevated as compared to
ambient CO2, ribulose bisphosphate carboxylase activity was 40%
less, soluble protein content 49% less, and chlorophyll content 26%
less; whereas starch content was 40% greater. Although at a given
CO2 level the enriched CO2 plants had only half the net
photosynthetic rate of their counterparts grown at ambient CO2,
they showed similar internal CO2 concentrations. This suggested
that the decreased supply of CO2 to the mesophyll, as a result of
the increased stomatal resistance, was counterbalanced by a
decreased utilization of CO2. Photorespiration and dark respiration
were lower, such that the CO2 compensation point was not altered.
The photosynthetic light and CO2 saturation points were not greatly
changed, nor was the O2 inhibition of photosynthesis (measured at
330 microliters CO2 per liter). It appears that with CO2 enrichment
the temporary increase in net photosynthesis produced larger
ramets. After acclimation, the greater total ramet leaf area more
than compensated for the lower net photosynthetic rate on a unit
leaf area basis, and resulted in a sustained improvement in dry
weight gain.

water hyacinth/Eichhornia crassipes

KEYWORDS: AQUATIC PLANTS, CARBOHYDRATES, CI:CA, CONTROLLED
ENVIRONMENT CHAMBERS, GROWTH, LEAF AREA PRODUCTION, LEAF
PHOTOSYNTHESIS, LIGHT, OXYGEN, PHOTOSYNTHETIC ACCLIMATION,
PIGMENTS, PROTEINS, REPRODUCTION, RESPIRATION, RIBULOSE
BISPHOSPHATE CARBOXYLASE

699  
Sritharan, R., and F. Lenz. 1990. The Effect of CO2 Concentration
and Water Supply on Photosynthesis, Dry Matter Production and
Nitrate Concentrations of Kohlrabi (Brassica oleracea var.
gongylodes L.). Acta Horticulturae 268:43-54.

Kohlrabi plants were grown under controlled environmental
conditions at two levels of CO2 concentration (300 uL/L and 900
uL/L). They were supplied with modified Hoagland solution and
subjected to three levels of water supply (100, 50 and 25%) for
three weeks. At high CO2 concentration plants produced more leaf
area, dry matter and had higher photosynthetic rates than those
grown at low CO2. This effect was more pronounced at low water
supply though the absolute rates of growth, dry matter,
photosynthesis, transpiration and stomatal conductance were
reduced. The nitrate concentration in all plant organs were
significantly reduced at high CO2. Low water supply resulted in
increased NO3 concentrations especially in lamina and tuber. These
results indicate that CO2 enrichment and adequate water supply can
reduce nitrate concentration considerably in Kohlrabi plants.
Possible control mechanisms and effects of CO2 on dry matter
production and nitrogen metabolism at water stress are discussed.

Brassica oleracea/kohlrabi

KEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
GROWTH, HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS, NITROGEN,
NUTRITION, TRANSPIRATION, WATER STRESS

700  
Stanev, V.P., and T.D. Tsonev. 1986. CO2 Enrichment in Some
Countries of Eastern Europe: Research and Practical Application.
IN: Status and CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball,
eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press,
Inc., Boca Raton, Florida, pp. 35-48.

KEYWORDS: CO2 ENRICHMENT STUDIES, CO2 MEASUREMENT AND CONTROL,
COMMERCIAL USE OF CO2, GREENHOUSE

701  
Stewart, J.D., and J. Hoddinott. 1993. Photosynthetic Acclimation
to Elevated Atmospheric Carbon Dioxide and UV Irradiation in Pinus
banksiana. Physiologia Plantarum 88:493-500.

Pinus banksiana seedlings were grown for 9 months in enclosures in
greenhouses at CO2 concentrations of 350 or 750 umol/mol with
either low (0.005 to 0.3 W/m2) or high (0.25 to 0.90 W/m2)
ultraviolet-B (UV-B) irradiances. Total seedling dry weight
decreased with high UV treatment but was unaffected by CO2
enrichment. High UV treatment also shifted biomass partitioning in
favor of leaf production. Both CO2 and UV treatments decreased the
dark respiration rate and light compensation point. High UV light
inhibited photosynthesis at 350 but not at 750 umol/mol CO2 due to
a UV induced increase in ribulose-1,5-bisphosphate
carboxylase/oxygenase efficiency and ribulose-1,5-bisphosphate
regeneration. Stomatal density was increased by high UV irradiance
but was unchanged by CO2 enrichment.

Pinus banksiana/jack pine

KEYWORDS: ALLOCATION, GREENHOUSE, LEAF PHOTOSYNTHESIS, LIGHT
UTILIZATION EFFICIENCY, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION,
RIBULOSE BISPHOSPHATE CARBOXYLASE, STOMATAL DENSITY, TREES, UV-B
RADIATION

702  
Stitt, M. 1991. Rising CO2 Levels and Their Potential Significance
for Carbon Flow in Photosynthetic Cells. Plant, Cell and
Environment 14:741-762.

In the first part of this review, I discuss how we can predict the
direct short-term effect of enhanced CO2 on photosynthetic rate in
C3 terrestrial plants. To do this, I consider: (1) to what extent
enhanced CO2 will stimulate or relieve demand on partial processes
like carboxylation, light harvesting and electron transport, the
Calvin cycle, and end-product synthesis; and (2) the extent to
which these various processes actually control the rate of
photosynthesis. I conclude that control is usually shared between
Rubisco (which responds sensitively to CO2) and other components
(which respond less sensitively), and that photosynthesis will be
stimulated by 25-75% when the CO2 concentration is doubled from 35
to 70 Pa. This is in good agreement with the published responses.
In the next part of the review, I discuss the evidence that most
plants undergo a gradual inhibition of photosynthesis during
acclimation to enhanced CO2. I argue that this is related to an
inadequate demand for carbohydrate in the remainder of the plant.
Differences in the long-term response to CO2 may be explained by
differences in the sink-source status of plants, depending upon the
species, the developmental stage, and the developmental conditions.
In the third part of the review, I consider the biochemical
mechanisms which are involved in 'sink' regulation of
photosynthesis. Accumulating carbohydrate could lead to a direct
inhibition of photosynthesis, involving mechanical damage by large
starch grains or Pi-limitation due to inhibition of sucrose
synthesis. I argue that Pi is important in the short-term
regulation of partitioning to sucrose and starch, but that its
contribution to 'sink' regulation has not yet been conclusively
demonstrated. Indirect or 'adaptive' regulation of photosynthesis
is probably more important, involving decreases in amounts of key
photosynthetic enzymes, including Rubisco. This decreases the rate
of photosynthesis, and potentially would allow resources (e.g.
amino acids) to be remobilized from the leaves and reinvested in
sink growth to readjust the sink-source balance. In the final part
of the review, I argue that similar changes of Rubisco and,
possibly, other proteins are probably also involved during
acclimation to high CO2.

KEYWORDS: CARBOHYDRATES, PARTITIONING, PHOTOSYNTHESIS,
PHOTOSYNTHETIC ACCLIMATION, REVIEW, RIBULOSE BISPHOSPHATE
CARBOXYLASE, SOURCE-SINK BALANCE

703  
Stitt, M., W.P. Quick, U. Schurr, E.-D. Schulze, S.R. Rodermel, and
L. Bogorad. 1991. Decreased Ribulose-1,5-bisphosphate Carboxylase-oxygenase in Transgenic Tobacco Transformed with 'Antisense' rbcS.
Planta 183:555-566.

Transgenic tobacco (Nicotiana tabacum L.) plants transformed with
'antisense' rbcS to produce a series of plants with a progressive
decrease in the amount of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco) have been used to investigate the
contribution of Rubisco to the control of photosynthesis at
different irradiance, CO2 concentrations and vapour-pressure
deficits. Assimilation rates, transpiration, the internal CO2
concentration and chlorophyll fluorescence were measured in each
plant. (i) The flux-control coefficient of Rubisco was estimated
from the slope of the plot of Rubisco content versus assimilation
rate. The flux-control coefficient had a value of 0.8 or more in
high irradiance, (1050 umol/m2/s), low vapour pressure deficit (4
mbar) and ambient CO2 (350 ubar). Control was marginal in enhanced
CO2 (450 ubar) or low light (310 umol/m2/s) and was also decreased
at high vapour-pressure deficit (17 mbar). No control was exerted
in 5% CO2. (ii) The flux-control coefficients of Rubisco were
compared with the fractional demand placed on the calculated
available Rubisco capacity. Only a marginal control on
photosynthetic flux is exerted by Rubisco until over 50% of the
available capacity is being used. Control increases as utilisation
rises to 80%, and approaches unity (i.e. strict limitation) when
more than 80% of the available capacity is being used. (iii) In low
light, plants with reduced Rubisco have very high energy-dependent
quenching of chlorophyll fluorescence (qE) and a decreased apparent
quantum yield. It is argued that Rubisco still exerts marginal
control in these conditions because decreased Rubisco leads to
increased thylakoid energisation and high-energy dependent
dissipation of light energy, and lower light-harvesting efficiency.
(iv) The flux-control coefficient of stomata for photosynthesis was
calculated from the flux-control coefficient of Rubisco and the
internal CO2 concentration, by applying the connectivity theorem.
Control by the stomata varies between zero and about 0.25. It is
increased by increased irradiance, decreased CO2 or decreased
vapour-pressure deficit. (v) Photosynthetic oscillations in
saturating irradiance and CO2 are suppressed in decreased-activity
transformants before the steady-state rate of photosynthesis is
affected. This provides direct evidence that these oscillations
reveal the presence of 'excess' Rubisco. (vi) Comparison of the
flux-control coefficients of Rubisco with mechanistic models of
photosynthesis provides direct support for the reliability of these
models in conditions where Rubisco has a flux-control coefficient
approach unity (i.e. 'limits' photosynthesis), but also indicates
that these models are less useful in conditions where control is
shared between Rubisco and other components of the photosynthetic
apparatus.

tobacco/Nicotiana tabacum

KEYWORDS: FLUORESCENCE, FLUX CONTROL COEFFICIENT, PHOTOSYNTHESIS,
PHOTOSYNTHESIS MODEL, RIBULOSE BISPHOSPHATE CARBOXYLASE, TRANSGENIC
PLANTS

704  
Strain, B.R. 1987. Direct Effects of Increasing Atmospheric CO2 on
Plants and Ecosystems. Tree 2:18-21.

The long term effects of allowing the concentration of CO2 in the
global atmosphere to double by the middle of the next century are
not yet predictable. However, it is inevitable that there will be
a change in climatic and ecological patterns. Increasing the
atmospheric CO2 concentration under experimental conditions has
been shown to alter the growth rate and reproductive potential of
plants, and must ultimately affect interactions at the community
level and beyond.

KEYWORDS: CLIMATE CHANGE, COMMUNITY LEVEL CO2 RESPONSES, ECOSYSTEM
LEVEL CO2 RESPONSES, PHYSIOLOGICAL CO2 RESPONSES, PLANT-PLANT
INTERACTIONS, REVIEW

705  
Strain, B.R. 1991. Possible Genetic Effects of Continually
Increasing Atmospheric CO2. IN: Ecological Genetics and Air
Pollution (G.E. Taylor Jr., L.F. Pitelka, and M.T. Clegg, eds.),
Springer-Verlag, Inc., New York, pp. 237-244.

This commentary extends the discussion on differential plant
sensitivity to air quality changes other than the toxic air
pollutants which induce the classic stress syndrome of declining
physiology and growth. Global atmospheric changes that
differentially increase plant growth and vigor among genotypes of
an ecosystem will induce ecological stresses associated with the
differential competitive potentials and survival of individuals. If
these changes proceed in a unidirectional manner for long periods
of time, the genetic structure of populations and communities will
likely change.

KEYWORDS: AGRICULTURE, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST,
PHYSIOLOGICAL CO2 RESPONSES, REVIEW, SELECTION PRESSURE,
SURVIVORSHIP

706  
Strain, B.R. 1992. Atmospheric Carbon Dioxide: A Plant Fertilizer?
The New Biologist 4:87-89.

Horticulturists have long known that increasing carbon dioxide
concentration in greenhouses would increase crop yield under
optimal conditions of other environmental factors; hence, some
people have proposed that the CO2 emission need not be curbed. In
unmanaged systems, however, plant productivity may not always
increase with increasing CO2. Rangeland and forest managers, for
instance, as well as third world farmers, may not observe
significant plant growth increases because nutrients incorporated
into plant and litter material may not be recycled at rates
sufficient to meet the demand resulting from carbon fertilization.
Another proposed benefit of increased CO2 concentration, decreased
water loss from plants due to lower leaf stomatal conductance, may
be offset by increases in leaf area. Carbon sequestration as a
result of tree planting will not be important in reducing CO2
concentrations in the long term. The rate of change predicted to
occur if fossil fuel consumption continues to grow unabated may not
be tolerable.

KEYWORDS: AGRICULTURE, C3, C4, CARBON SEQUESTERING, NUTRITION,
REVIEW, WUE, YIELD

707  
Strain, B.R., and R.B. Thomas. 1992. Field Measurements of CO2
Enhancement and Climate Change in Natural Vegetation. Water, Air,
and Soil Pollution 64:45-60.

It is generally assumed that healthy, natural ecosystems have the
potential to sequester carbon under favorable environmental
conditions. There is also evidence that CO2 acts as a plant
fertilizer. It is of interest to know if these assumptions are
valid and how natural systems might respond under future scenarios
of CO2 increase and possible climate changes. Few measurements of
the effects of CO2 increase and possible climate changes have been
made on 'natural' ecosystems under realistic field conditions. Most
measurements have been conducted in the synthetic environments of
totally controlled greenhouses and growth chambers. Several lines
of evidence indicate that controlled environment studies using
plants growing in pots induce experimental artifacts that reduce
confidence in the use of results for prediction of future global
responses. Open top chambers are being used in several
autecological field studies in an attempt to obtain more realistic
field environments. A few field microcosm studies have been
completed and a system for the free air release of CO2 has been
applied in cotton fields. Unfortunately, the requirement of large
amounts of CO2 and financial restrictions have precluded the
initiation of larger scale field studies in natural vegetation.
This paper lists and summarizes the best field studies available
but draws heavily on studies from artificial environments and
conditions in an attempt to summarize knowledge of global
environmental change on forests and other non-agricultural
ecosystems. Finally the paper concludes that there is a need for
the development and application of equipment for field measurements
in several representative natural ecosystems and makes specific
recommendation of the creation of a tropical research center.

KEYWORDS: ANNUAL GRASSLAND, CO2 ENRICHMENT STUDIES, ECOSYSTEM LEVEL
CO2 RESPONSES, PASTURE, RANGELAND, REVIEW, SALT MARSH, SHORT GRASS
PRAIRIE, TALLGRASS PRAIRIE, TEMPERATE FOREST, TROPICAL FOREST,
TUNDRA

708  
Strain, B.R., Group Leader. 1991. Available Technologies for Field
Experimentation with Elevated CO2 in Global Change Research. IN:
Ecosystem Experiments, Report of the Scientific Committee on
Problems of the Environment (International Council of Scientific
Unions), Vol. 45 (H.A. Mooney, E. Medina, D.W. Schindler, E.-D.
Schulze, and B.H. Walker, eds.), John Wiley and Sons, Ltd., New
York, pp. 245-261.

KEYWORDS: ECOCOSMS, ECOSYSTEM LEVEL CO2 RESPONSES, EXPOSURE
METHODS, FACE, OPEN-TOP CHAMBERS, REVIEW, SPAR UNITS, TRACKING
CHAMBERS

709  
Stuhlfauth, T., K. Klug, and H.P. Fock. 1987. The Production of
Secondary Metabolites by Digitalis lanata during CO2 Enrichment and
Water Stress. Phytochemistry 26:2735-2739.

The influence of atmospheric CO2 enrichment and water stress on the
production of biomass and cardioactive substances by the woolly
foxglove Digitalis lanata was investigated. Carbon dioxide
enrichment (1000 ppm) had a 'fertilizing' effect in that both
biomass and cardenolide content increased to about 160% of the
control. The yield of the pharmacologically relevant major product,
digoxin, significantly increased following enrichment, whereas two
other compounds decreased. Water stress, in the physiological
range, reduced fresh weight more than either cardenolide content or
dry weight. The amount of digitoxigenin was considerably reduced,
whereas the other cardenolides, including digoxin, were less
affected. CO2-enriched plants, which were also subjected to
drought, exhibited mixed responses. We conclude from these
investigations that not only primary, but also secondary metabolism
is influenced by variations of the environment. Possible ecological
consequences of changes in secondary metabolism due to atmospheric
CO2 enrichment and water stress are discussed.

Digitalis lanata/woolly foxglove

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, SECONDARY METABOLITES,
WATER STRESS

710  
Stulen, I., and J. Den Hertog. 1992. Root Growth and Functioning
under Atmospheric CO2 Enrichment. Vegetatio 104/105:99-115.

This paper examines the extent to which atmospheric CO2 enrichment
may influence growth of plant roots and function in terms of uptake
of water and nutrients, and carbon allocation towards symbionts. It
is concluded that changes in dry matter allocation greatly depend
on the experimental conditions during the experiment, the growth
phase of the plant, and its morphological characteristics. Under
non-limiting conditions of water and nutrients for growth, dry
matter partitioning to the root is not changed by CO2 enrichment.
The increase in root/shoot ratio, frequently observed under
limiting conditions of water and/or nutrients, enables the plant to
explore a greater soil volume, and hence acquire more water and
nutrients. However, more data on changes in dry matter allocation
within the root due to atmospheric CO2 are needed. It is concluded
that nitrogen fixation is favored by CO2 enrichment since nodule
mass is increased, concomitant with an increase in root length. The
papers available so far on the influence of CO2 enrichment on
mycorrhizal functioning suggest that carbon allocation to the roots
might be increased, but also here more experiments are needed.

KEYWORDS: ALLOCATION, MYCORRHIZAE, NITROGEN FIXATION, RESPIRATION,
REVIEW, ROOT:SHOOT RATIO, ROOTS

711  
Surano, K.A., P.F. Daley, J.L.J. Houpis, J.H. Shinn, J.A. Helms,
R.J. Palassou, and M.P. Costella. 1986. Growth and Physiological
Responses of Pinus ponderosa Dougl. ex P. Laws. to Long-term
Elevated CO2 Concentration. Tree Physiology 2:243-259.

Seven-year-old ponderosa pine (Pinus ponderosa Dougl. ex P. Laws.)
saplings and one- and two- year-old ponderosa pine seedlings of a
Sierra Nevada and a Rocky Mountain seed source, respectively, were
exposed to CO2-enriched atmospheres in an outdoor open-top chamber
facility for 2.5 years. Seedling growth (main stem diameter,
height, volume) increased with increasing CO2 concentration, though
the two populations exhibited different patterns of response. By
the beginning of the last growth season, however, the trees under
the highest CO2 concentrations showed signs of stress that included
accelerated needle abscision, chlorosis, and apparent alteration of
tolerance to heat. The stress response is at least partly
attributable to elevated foliar temperatures resulting from CO2-induced stomatal closure, which in turn lowered transpirational
cooling of needles.

Pinus ponderosa/ponderosa pine

KEYWORDS: CONDUCTANCE, GROWTH, OPEN-TOP CHAMBERS, POPULATION LEVEL
CO2 RESPONSES, TEMPERATURE, TRANSPIRATION, TREES

712  
Suzuki, K., and M.H. Spalding. 1989. Adaptation of Chlamydomonas
reinhardtii High CO2-requiring Mutants to Limiting CO2. Plant
Physiology 90:1195-1200.

Photosynthetic characteristics of four high-CO2-requiring mutants
of Chlamydomonas reinhardtii were compared to those of wild type
before and after a 14-hour exposure to limiting CO2 concentrations. 
The four mutants represent two loci involved in the CO2-concentrating system of this unicellular alga.  All mutants had a
lower photosynthetic affinity for inorganic carbon than did the
wild type when grown at an elevated CO2 concentration, indicating
that the genetic lesion in each is expressed even at elevated CO2
concentrations.  Wild type and all four mutants exhibited adaptive
responses to limiting CO2 characteristic of the induction of the
CO2-concentrating system, resulting in an increased affinity for
inorganic carbon only in wild type.  Although other components of
the CO2-concentrating system were induced in these mutants, the
defective component in each was sufficient to prevent any increase
in the affinity for inorganic carbon. It was concluded that the
genes corresponding to theca-1 and pmp-1 loci exhibit at least
partially constitutive expression and that all components of the
CO2-concentrating system may be required to significantly affect
the photosynthetic affinity for inorganic carbon.

Chlamydomonas reinhardtii

KEYWORDS: ACCLIMATION, ALGAE, AQUATIC PLANTS, CELL CULTURE, MUTANT,
PHOTOSYNTHESIS

713  
Szarek, S.R., P.A. Holthe, and I.P. Ting. 1987. Minor Physiological
Response to Elevated CO2 by CAM Plant Agave vilmoriniana. Plant
Physiology 83:938-940.

One-year-old plants of the CAM leaf succulent Agave vilmoriniana
Berger were grown outdoors at Riverside, California. Potted plants
were acclimated to CO2-enrichment (about 750 microliters per liter)
by growth for 2 weeks in an open-top polyethylene chamber. Control
plants were grown nearby where the ambient CO2 concentration was
about 370 microliters per liter. When the plants were well watered,
CO2-induced differences in stomatal conductances and CO2
assimilation rates over the entire 24-hour period were not large.
There was a large nocturnal acidification in both CO2 treatments
and insignificant differences in leaf chlorophyll content. Well
watered plants maintained water potentials of -0.3 to -0.4
megapascals. When other plants were allowed to dry to water
potentials of -1.2 to-1.7 megapascals, stomatal conductance and CO2
uptake rates were reduced in magnitude, with the biggest difference
in Phase IV photosynthesis. The minor nocturnal response to CO2
concentration by this species is interpreted to indicate saturated,
or nearly saturated, phosphoenolpyruvate carboxylase activity at
current atmospheric CO2 concentrations. CO2-enhanced diurnal
activity of ribulose bisphosphate carboxylase activity remains a
possibility.

Agave vilmoriniana

KEYWORDS: CAM, CONDUCTANCE, LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE BISPHOSPHATE CARBOXYLASE,
WATER STRESS

714  
Telewski, F.W., and B.R. Strain. 1987. Densitometric and Ring Width
Analysis of 3-year-old Pinus taeda L. and Liquidambar styraciflua
L. Grown under Three Levels of CO2 and Two Water Regimes. IN:
Proceedings of the International Symposium on Ecological Aspects of
Tree-ring Analysis, DOE Conf-8608144 (G.C. Jacoby Jr. and J.W.
Hornbeck, eds.), NTIS, U.S. Department of Commerce, Springfield,
Virginia.

Trees of Pinus taeda and Liquidambar styraciflua were grown from
seed and treated for three years at 350, 500 and 650 ppm CO2. Water
stress was applied to one half of the plants in years 2 and 3. The
twelve treatment groups were harvested and measurements were made
on total stem diameter, ring width and wood density. In all
treatment groups, increased CO2 increased stem diameter. Individual
ring widths also increased with increase in CO2, the trend being
clearer in Liquidambar styraciflua. There is no change in latewood
density of L. styraciflua with CO2 treatment. There was an apparent
increase in latewood density in water stressed saplings compared
with non-stressed saplings which is independent of CO2 treatment.
An apparent increase in latewood density was observed in P. taeda,
especially in the last growth ring. Because of the great increase
in individual ring widths in L. styraciflua the total ring biomass
(integral density) increases with CO2 treatment in well watered
trees but decreases with drought. A similar trend was observed in
the integral density in P. taeda. No significant changes were
observed in average density between any treatment group for either
species. It is suggested that, at least for 3 year old saplings,
ring width and integral density (a measure which includes ring
width) are more sensitive indicators of increased CO2 under both
drought and non-drought conditions than latewood maximum density or
average ring density.

Pinus taeda/loblolly pine/Liquidambar styraciflua/sweetgum

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, TREE-RING ANALYSIS,
TREES, X-RAY DENSITOMETRY

715  
Teramura, A.H., J.H. Sullivan, and L.H. Ziska. 1990. Interaction of
Elevated Ultraviolet-B Radiation and CO2 on Productivity and
Photosynthetic Characteristics in Wheat, Rice, and Soybean. Plant
Physiology 94:470-475.

Wheat (Triticum aestivum L. cv Bannock), rice (Oryza sativa L. cv
IR-36, and soybean (Glycine max [L.] Merr cv Essex) were grown in
a factorial greenhouse experiment to determine if CO2-induced
increases in photosynthesis, biomass, and yield are modified by
increases in ultraviolet (UV)-B radiation corresponding to
stratospheric ozone depletion. The experimental conditions
simulated were: (a) an increase in CO2 concentration from 350 to
650 microliters per liter; (b) an increase in UV-B radiation
corresponding to a 10% ozone depletion at the equator; and (c) a
and b in combination. Seed yield and total biomass increased
significantly with elevated CO2 in all three species when compared
to the control. However, with concurrent increases in UV-B and CO2,
no increase in either seed yield (wheat and rice) or total biomass
(rice) was observed with respect to the control. In contrast, CO2-induced increases in seed yield and total plant biomass were
maintained or increased in soybean within the elevated CO2, UV-B
environment. Whole leaf gas exchange indicated a significant
increase in photosynthesis, apparent quantum efficiency (AQE) and
water-use-efficiency (WUE) with elevated CO2 in all 3 species.
Including elevated UV-B radiation with high CO2 eliminated the
effect of high CO2 on photosynthesis and WUE in rice and the
increase in AQE associated with high CO2 in all species. Elevated
CO2 did not change the apparent carboxylation efficiency (ACE) in
the three species although the combination of elevated CO2 and UV-B
reduced ACE in wheat and rice. The results of this experiment
illustrate that increased UV-B radiation may modify CO2-induced
increases in biomass, seed yield and photosynthetic parameters and
suggest that available data may not adequately characterize the
potential effect of future, simultaneous changes in CO2
concentration and UV-B radiation.

wheat/Triticum aestivum/rice/Oryza sativa/soybean/Glycine max

KEYWORDS: CARBOXYLATION EFFICIENCY, ENVIRONMENTAL INTERACTIONS,
GREENHOUSE, GROWTH, LEAF PHOTOSYNTHESIS, QUANTUM REQUIREMENT, UV-B
RADIATION, WUE, YIELD

716  
Thomas, R.B. 1987. Responses of Two Summer Annuals to Interactions
of Atmospheric Carbon-dioxide and Soil Nitrogen. Doctoral
Dissertation, Clemson University, Dissertation Abstracts Vol.49:05-B, p.1508 (187 pp.).

An increase in atmospheric CO2 is likely to have profound effects
on ecosystems. Responses by plant species to elevated CO2 might
depend on factors such as the species' photosynthetic pathway.
Increased competitiveness of C3 species relative to C4 species can
be anticipated in response to CO2 enrichment due to enhanced
carboxylation rates, but when soil nitrogen is limiting, C3 plants
may be unable to increase carboxylation rates due to enzyme
deficiency. The competitive relationship between Chenopodium album
L. (C3) and Amaranthus hybridus L. (C4) was investigated in two
atmospheric CO2 levels (350 and 600 uL/L) and two soil nitrogen
levels (1 and 15 mM NH4NO3). Biomass and leaf surface area of
Amaranthus plants did not respond to CO2 enrichment. Only in high
nitrogen did Chenopodium plants respond to increased CO2 with
greater biomass and leaf surface area. Nitrogen use efficiency
(NUE) was higher in Amaranthus than in Chenopodium in all
treatments except for the high-nitrogen and high-CO2 treatment.
Under conditions of high nitrogen and low CO2, Chenopodium was a
poor competitor, but competition favored Chenopodium in high
nitrogen and high CO2. In low nitrogen and high CO2, competition
favored Chenopodium on a dry weight basis, but favored Amaranthus
on a seed weight basis, reflecting early senescence of Chenopodium.
In low nitrogen and high CO2, competition favored Amaranthus on a
dry weight basis, but favored Chenopodium on a seed weight basis.
Physiological aspects of the growth of Chenopodium and Amaranthus
were studied. Acclimation to elevated CO2 occurred at the enzyme
level in Chenopodium. Under conditions of high nitrogen and no
competition, individual Chenopodium plants responded to elevated
CO2 with greater biomass, leaf surface area, and maximum net
photosynthetic rates. In high nitrogen, leaf nitrogen, soluble
protein, and RuBP carboxylase activity of Chenopodium decreased and
NUE increased when grown in elevated CO2. In low nitrogen without
competition, Chenopodium showed no significant response to CO2
enrichment. Amaranthus grown in high CO2 and low nitrogen without
competition showed no significant changes in leaf nitrogen, soluble
protein, carboxylase activity, chlorophyll, or NUE in response to
CO2 enrichment. Future shifts in competitive relationships between
C3 and C4 plants will not only be influenced by increasing
atmospheric CO2, but will be modified by other environmental
factors including availability of nitrogen.

Chenopodium album/lambsquarters/Amaranthus hybridus/pigweed

KEYWORDS: GROWTH, LEAF PHOTOSYNTHESIS, NITROGEN, NUTRITION, OUTDOOR
GROWTH CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, PIGMENTS, PROTEINS,
RIBULOSE BISPHOSPHATE CARBOXYLASE, SPECIES COMPETITION

717  
Thomas, R.B., D.D. Richter, H. Ye, P.R. Heine, and B.R. Strain.
1991. Nitrogen Dynamics and Growth of Seedlings of an N-fixing Tree
(Gliricidia sepium (Jacq.) Walp.) Exposed to Elevated Atmospheric
Carbon Dioxide. Oecologia 88:415-421.

Seeds of Gliricidia sepium (Jacq.) Walp., a tree native to seasonal
tropical forests of Central America, were inoculated with N-fixing
Rhizobium bacteria and grown in growth chambers for 71 days to
investigate interactive effects of atmospheric CO2 and plant N
status on early seedling growth, nodulation, and N accretion.
Seedlings were grown with CO2 partial pressures of 350 and 650
ubars (current ambient and a predicted partial pressure of the mid-21st century) and with plus N or minus N nutrient solutions to
control soil N status. Of particular interest was seedling response
to CO2 when grown without available soil N, a condition in which
seedlings initially experienced severe N deficiency because
bacterial N-fixation was the sole source of N. Biomass of leaves,
stems, and roots increased significantly with CO2 enrichment (by
32%, 15% and 26%, respectively) provided seedlings were supplied
with N fertilizer. Leaf biomass of N-deficient seedlings was
increased 50% by CO2 enrichment but there was little indication
that photosynthate translocation from leaves to roots or that plant
N (fixed by Rhizobium) was altered by elevated CO2. In seedlings
supplied with soil N, elevated CO2 increased average nodule weight,
total nodule weight per plant, and the amount of leaf nitrogen
provided by N-fixation (as indicated by leaf delta 15N). While CO2
enrichment reduced the N concentration of some plant tissues, whole
plant N accretion increased. Results support the contention that
increasing atmospheric CO2 partial pressures will enhance
productivity and N-fixing activity of N-fixing tree seedlings, but
that the magnitude of early seedling response to CO2 will depend
greatly on plant and soil nutrient status.

Gliricidia sepium

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN FIXATION,
NODULATION, RHIZOBIUM, TREES, TROPICAL PLANTS

718  
Thomas, R.B., and B.R. Strain. 1991. Root Restriction as a Factor
in Photosynthetic Acclimation of Cotton Seedlings Grown in Elevated
Carbon Dioxide. Plant Physiology 96:627-634.

Interactive effects of root restriction and atmospheric CO2
enrichment on plant growth, photosynthetic capacity, and
carbohydrate partitioning were studied in cotton seedlings
(Gossypium hirsutum L.) grown for 28 days in three atmospheric CO2
partial pressures (270, 350, and 650 microbars) and two pot sizes
(0.38 and 1.75 liters). Some plants were transplanted from small
pots into large pots after 20 days. Reduction of root biomass
resulting from growth in small pots was accompanied by decreased
shoot biomass and leaf area. When root growth was less restricted,
plants exposed to higher CO2 partial pressures produced more shoot
and root biomass than plants exposed to lower levels of CO2. In
small pots, whole plant biomass and leaf area of plants grown in
270 and 350 microbars of CO2 were not significantly different.
Plants grown in small pots in 650 microbars of CO2 produced greater
total biomass than plants grown in 350 microbars, but the dry
weight gain was found to be primarily an accumulation of leaf
starch. Reduced photosynthetic capacity of plants grown at elevated
levels of CO2 was clearly associated with inadequate rooting
volume. Reductions in net photosynthesis were not associated with
decreased stomatal conductance. Reduced carboxylation efficiency in
response to CO2 enrichment occurred only when root growth was
restricted suggesting that ribulose-1,5-bisphosphate
carboxylase/oxygenase activity may be responsive to plant source-sink balance rather than to CO2 concentration as a single factor.
When root-restricted plants were transplanted into large pots,
carboxylation efficiency and ribulose-1,5-bisphosphate regeneration
capacity increased indicating that acclimation of photosynthesis
was reversible. Reductions in photosynthetic capacity as root
growth was progressively restricted suggest sink-limited feedback
inhibition as a possible mechanism for regulating net
photosynthesis of plants grown in elevated CO2.

cotton/Gossypium hirsutum

KEYWORDS: CARBOHYDRATES, CARBOXYLATION EFFICIENCY, CONTROLLED
ENVIRONMENT CHAMBERS, PARTITIONING, PHOTOSYNTHETIC ACCLIMATION,
PHOTOSYNTHETIC FEEDBACK INHIBITION, RIBULOSE BISPHOSPHATE
CARBOXYLASE, ROOT RESTRICTION, SOURCE-SINK BALANCE

719  
Thompson, G.B. 1990. The Influence of CO2 Enrichment on the Growth,
Nitrogen Concentration, and Mildew Infection of Cereals. Doctoral
Dissertation, University of Cambridge.

KEYWORDS: GRASSES, NITROGEN

720  
Thornley, J.H.M., D. Fowler, and G.R. Cannell. 1991. Terrestrial
Carbon Storage Resulting from CO2 and Nitrogen Fertilization in
Temperate Grasslands. Plant, Cell and Environment 14:1007-1011.

A temperate grassland model has been used to simulate carbon
sequestration under various environmental conditions. The results
suggest that the CO2 and nitrogen fertilization that has occurred
may contribute appreciably to the so-called missing carbon sink,
which it has been suggested must exist to balance the global carbon
budget.

KEYWORDS: CARBON BUDGET, CARBON SEQUESTERING, LITTER DECOMPOSITION,
MODELING, NITROGEN, SIMULATION, TEMPERATURE

721  
Tissue, D.T., and W.C. Oechel. 1987. Response of Eriophorum
vaginatum to Elevated CO2 and Temperature in the Alaskan Tussock
Tundra. Ecology 68:401-410.

Small greenhouses were used in the arctic to maintain Eriophorum
vaginatum-dominated tussock tundra for 10 wk at ambient CO2 (340
uL/L), elevated CO2 (510 or 680 uL/L), or elevated CO2 and 4C
above ambient temperature (680 uL/L, ambient + 4C). These
treatments represent present levels of atmospheric CO2 and
temperature, and those predicted for the next century. Within 3 wk,
plants maintained at elevated CO2 exhibited a physiological
adjustment of their photosynthetic rate so that plants grown at
ambient and elevated CO2 levels had similar photosynthetic rates at
their respective growth CO2 concentrations. The reduction in
photosynthetic capacity for plants grown at elevated CO2 levels did
not appear to be due to stomatal closure or end-product inhibition.
Other possible mechanisms were not explored. Transpiration rates
and water use efficiency did not differ among treatments in the
generally wet environment of tussock tundra. Relative leaf growth
rate and the seasonal pattern of growth were also unaltered,
suggesting that the growth of mature tillers is not, under normal
ambient conditions, limited by temperature or carbohydrate.
However, new tiller production was significantly increased at
elevated CO2, suggesting that the long-term effect of CO2
enhancement in this sedge may be the production of a greater number
of new tillers rather than an increase in the size or productivity
of existing tillers. Our results are consistent with the notion
that growth of Eriophorum vaginatum in the field is more limited by
nutrient supply than by photosynthesis. We further suggest that
photosynthetic rates reflect the sink activity. It is therefore
very difficult to assign cause and effect between growth rates and
photosynthetic rates.

Eriophorum vaginatum

KEYWORDS: LEAF AREA DEVELOPMENT, PHOTOSYNTHETIC ACCLIMATION,
SOURCE-SINK BALANCE, TEMPERATURE, TRACKING CHAMBERS, TUNDRA, WUE

722  
Titus, J.E., R.S. Feldman, and D. Grise. 1990. Submerged Macrophyte
Growth at Low pH. I. CO2 Enrichment Effects with Fertile Sediment.
Oecologia 84:307-313.

Vallisneria americana was grown for six weeks in a greenhouse on
relatively fertile sediment to test for factors other than nutrient
limitation which may slow growth of this submersed macrophyte at pH
5. On the basis of dry mass accumulated, (1) low pH significantly
depressed Vallisneria growth at constant free CO2 levels; (2) free
CO2 enrichment, however, greatly stimulated Vallisneria growth at
pH 5, by 2.8-fold and 10-fold at 3.2 times and 10 times air-equilibrated CO2 levels, respectively; and (3) growth was greater
by far at pH 5 than at higher pH with constant total dissolved
inorganic carbon (DIC). Free CO2 availability was thus an important
controller of growth at low pH by Vallisneria americana on fertile
sediment, and low pH was not directly deleterious. Field surveys of
acidic lakes in the Adirondack Mountains of New York state revealed
that DIC levels in low pH lakes were often well above equilibrium
values and could potentially support vigorous macrophyte growth.
Aluminum and/or iron toxicity did not appear to impair growth at
low pH, and aluminum concentrations in Vallisneria shoots
significantly decreased with increasing free CO2 concentrations at
pH 5.0, perhaps due to growth dilution. Rosette production (a
measure of asexual reproduction), maximum leaf length, and extent
of flowering within treatments were positively correlated with
plant biomass, rather than with pH or free CO2 levels per se.

Vallisneria americana

KEYWORDS: ALUMINUM, AQUATIC PLANTS, FLOWERING, IRON, NUTRITION, PH,
VEGETATIVE REPRODUCTION

723  
Tremblay, N., S. Yelle, and A. Gosselin. 1987. Effects of CO2
Enrichment, Nitrogen and Phosphorus Fertilization on Growth and
Yield of Celery Transplants. HortScience 22:875-876.

Celery transplants (Apium graveolens L. cv. Florida 683) were
fertilized with complete nutrient solutions at three N
concentrations and three concentrations of P in a factorial
combination, both with or without atmospheric CO2 enrichment. They
then were planted on a muck soil and harvested at the end of July.
Carbon dioxide enrichment increased the transplant leaf area as
well as shoot and root dry weight and decreased the leaf area ratio
(LAR), but had no significant effect on growth parameters at
harvest. Nitrogen affected leaf area, dry weight, leaf area ratio,
and dry mater content of transplant shoots together with root:shoot
dry weight ratio. Total, marketable, and side shoot weights at
harvest were significantly increased by the intermediate N
concentration (400 ppm N) provided during transplant raising.
Phosphorus had no effect on transplant growth but interacted with
N on the weight of marketable shoots harvested.

celery/Apium graveolens

KEYWORDS: GREENHOUSE, NITROGEN, NUTRITION, PHOSPHORUS, YIELD

724  
Tremblay, N., S. Yelle, and A. Gosselin. 1988. Effects of CO2
Enrichment, Nitrogen and Phosphorus Fertilization during the
Nursery Period on Mineral Composition of Celery. Journal of Plant
Nutrition 11:37-49.

This experiment aimed at determining the effects of
pretransplanting nutritional conditioning (PNC) on celery elemental
composition at planting and harvest time. Celery seedlings (Apium
graveolens L. cv. Florida 683) were fertilized with complete
nutrient solutions at 3 concentrations of urea nitrogen and 3
concentrations of phosphorus in factorial combination, both with or
without atmospheric CO2 enrichment. They were then planted in a
muck soil and harvested at the end of July. CO2 enrichment
decreased N, P, K, Mg and B concentrations in seedling shoot. It
reduced N and K and increased Mg, but had no effect on P, Ca and B
concentrations in roots. Nitrogen fertilization increased N
concentration in shoot and roots but decreased P, K and Ca
concentration in roots. The low urea-N level resulted in low shoot
P concentration. Phosphorus fertilization increased P concentration
in seedling shoot and roots but depressed K in shoot. Maximum Ca
and Mg concentrations in shoot were measured at low P
fertilization. At harvest, shoot N concentration was found to have
increased linearly with the P fertilization rate provided during
seedling preparation. Therefore, PNC can modify the nutritional
status of celery plants not only at planting time but also for the
entire growing season.

celery/Apium graveolens

KEYWORDS: ALLOCATION, BORON, CALCIUM, GREENHOUSE, MAGNESIUM,
NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM

725  
Tripp, K.E., W.K. Kroen, M.M. Peet, and D.H. Willits. 1992. Fewer
Whiteflies Found on CO2-enriched Greenhouse Tomatoes with High C:N
Ratios. HortScience 27:1079-1080.

Eight tomato (Lycopersicon esculentum) cultivars were grown for 16
weeks in greenhouses enriched for an average of 8.1 hours daily to
1000 uL CO2/L of air or in greenhouses maintained at ambient CO2.
Carbon dioxide enrichment significantly decreased the mean number
of greenhouse whiteflies [Trialeurodes vaporariorum (Westward),
Homoptera: Aleyrodidae] as measured by counts from commercial
yellow sticky traps. The number of whiteflies present was
negatively correlated with both seasonal foliar C:N ratio and
percent C but positively correlated with percent N in the foliage.
Thus, CO2 enrichment apparently alters plant composition in such a
way as to reduce significantly the population growth of greenhouse
whiteflies.

tomato/Lycopersicon esculentum

KEYWORDS: CARBON:NITROGEN RATIO, GREENHOUSE, HERBIVORY,
HORTICULTURAL CROPS, INSECTS, TRIALEURODES VAPORARIORUM, WHITEFLIES

726  
Tripp, K.E., M.M. Peet, D.M. Pharr, D.H. Willits, and P.V. Nelson.
1991. CO2-enhanced Yield and Foliar Deformation among Tomato
Genotypes in Elevated CO2 Environments. Plant Physiology 96:713-719.

Yield increases observed among eight genotypes of tomato
(Lycopersicon esculentum Mill.) grown at ambient CO2 (about 350) or
1000 microliters per liter CO2 were not due to carbon exchange rate
increases. Yield varied among genotypes while carbon exchange rate
did not. Yield increases were due to a change in partitioning from
root to fruit. Tomatoes grown with CO2 enrichment exhibited
nonepinastic foliar deformation similar to nutrient deficiency
symptoms. Foliar deformation varied among genotypes, increased
throughout the season, and became most severe at elevated CO2.
Foliar deformation was positively related to fruit yield. Foliage
from the lower canopy was sampled throughout the growing season and
analysed for starch, K, P, Ca, Mg, Fe, and Mn concentrations.
Foliar K and Mn concentrations were the only elements correlated
with deformation severity. Foliar K decreased while deformation
increased. In another study, foliage of half the plants of one
genotype received foliar applications of 7 millimolar KH2PO4.
Untreated foliage showed significantly greater deformation than
treated foliage. Reduced foliar K concentration may cause CO2-enhanced foliar deformation. Reduced K may occur following
decreased nutrient uptake resulting from reduced root mass due to
the change in partitioning from root to fruit.

tomato/Lycopersicon esculentum

KEYWORDS: ALLOCATION, CALCIUM, CARBOHYDRATES, FAMILY RESPONSES,
FOLIAR DEFORMATION, GREENHOUSE, IRON, LEAF PHOTOSYNTHESIS,
MAGNESIUM, MANGANESE, NUTRITION, PHOSPHORUS, POTASSIUM,
REPRODUCTION, YIELD

727  
Tripp, K.E., M.M. Peet, D.H. Willits, and D.M. Pharr. 1991. CO2-enhanced Foliar Deformation of Tomato: Relationship to Foliar
Starch Concentration. Journal of the American Society of
Horticultural Science 116:876-880.

Two cultivars of greenhouse tomato (Lycopersicon esculentum Mill.)
were grown with ambient or 1000 uL CO2/L during Jan.-June 1987 and
1988. In both years, CO2-enrichment increased foliar deformation
and foliar starch, but during the season, foliar starch levels
decreased while deformation increased. 'Laura' had more
deformation, while 'Michigan-Ohio' had higher foliar starch
concentration. During an entire season, there was no significant
relationship between foliar starch concentration and deformation
severity. Foliar C exchange rates in the lower canopy were not
affected by severity of deformation. Data from these experiments do
not support the hypothesis that excess foliar starch is responsible
for foliar deformation at elevated CO2.

tomato/Lycopersicon esculentum

KEYWORDS: CARBOHYDRATES, FOLIAR DEFORMATION, GREENHOUSE,
HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS

728  
Troeng, E., and L. Ackzell. 1990. Effects of Carbon Dioxide
Enrichment on Bud Formation and Growth of Coniferous Seedlings.
Acta Horticulturae 268:179-189.

First-year seedlings of Pinus sylvestris, Pinus contorta and Picea
abies were exposed to elevated (900 ppm or 1800 ppm) or ambient
atmospheric carbon dioxide levels before or during budset. Total
seedling biomass increased at high carbon dioxide concentrations,
root dry weight increasing more than shoot dry weight. Formation of
needle primordia in the bud was not influenced by carbon dioxide
enrichment. Pinus contorta showed a high percentage Lammas growth
when exposed to high carbon dioxide concentrations. For Picea
abies, nutrient supply, temperature regimes and winter hardening
were also studied in relation to carbon dioxide supply during bud
formation. The number of needle primordia formed was strongly
influenced by air temperature. Lack of nutrients during bud
formation had a slightly negative effect on frost hardiness.

Picea abies/Norway spruce/Pinus contorta/longleaf pine/Pinus
sylvestris/Scots pine

KEYWORDS: BUD FORMATION, GREENHOUSE, GROWTH, TEMPERATURE, TREES

729  
Tsuzuki, M., and S. Miyachi. 1991. CO2 Syndrome in Chlorella.
Canadian Journal of Botany 69:1003-1007.

Chlorella spp.

KEYWORDS: ALGAE, AQUATIC PLANTS, CELL CULTURE, ENZYMES,
PHOTOSYNTHESIS

730  
Tsuzuki, M., E. Ohnuma, N. Sato, T. Takatu, and A. Kawaguchi. 1990.
Effects of CO2 Concentration during Growth on Fatty Acid
Composition in Microalgae. Plant Physiology 93:851-856.

The degree of unsaturation of fatty acids was higher in Chlorella
vulgaris 11h cells grown with air (low-CO2 cells) than in the cells
grown with air enriched with 2% CO2 (high-CO2 cells). The change in
the ratio of linoleic acid to alpha-linolenic acid was particularly
significant. This change of the ratio was observed in four major
lipids (monogalactosyldiacylglycerol, digalactosyldiacylglycerol,
phosphatidylcholine, and phosphatidylethanolamine). The relative
contents of lipid classes were essentially the same both in high-CO2 and low-CO2 cells. After high-CO2 cells were transferred to low
CO2 condition, total amount of fatty acids remained constant but
the relative content of alpha-linolenic acid increased during a 6-hour lag phase in growth with concomitant decreases in linoleic and
oleic acids. When low-CO2 cells were transferred to high CO2
condition, total amount of fatty acids and relative content of
oleic acid increased significantly. The amount of alpha-linolenic
acid remained almost constant, while the amounts of palmitic,
oleic, and linoleic acids increased. Similar, but smaller, changes
in fatty acid compositions were observed in two species of green
algae Chlamydomonas reinhardtii and Dunaliella tertiolecta.
However, no difference was found in Euglena gracilis, Porphyridium
cruentum, Anabaena variabilis, and Anacystis nidulans.

Chlorella vulgaris/Dunaliella tertiolecta/Anacystis
nidulans/Chlamydomonas reinhardtii/Euglena gracilis/Porphyridium
cruentum

KEYWORDS: ALGAE, AQUATIC PLANTS, CELL CULTURE, FATTY ACIDS

731  
Tyree, M.T., and J.D. Alexander. 1993. Plant Water Relations and
the Effects of Elevated CO2: A Review and Suggestions for Future
Research. Vegetatio 104/105:47-62.

Increased ambient carbon dioxide (CO2) has been found to ameliorate
water stress in the majority of species studied. The results of
many studies indicate that lower evaporative flux density is
associated with high CO2-induced stomatal closure. As a result of
decreases in evaporative flux density and increases in net
photosynthesis, also found to occur in high CO2 environments,
plants have often been shown to maintain higher water use
efficiencies when grown at high CO2 than when grown in normal,
ambient air. Plants grown at high CO2 have also been found to
maintain higher total water potentials, to increase biomass
production, have larger root-to-shoot ratios, and to be generally
more drought resistant (through avoidance mechanisms) than those
grown at ambient CO2 levels. High CO2-induced changes in plant
structure (i.e., vessel or tracheid anatomy, leaf specific
conductivity) may be associated with changes in vulnerability to
xylem cavitation or in environmental conditions in which runaway
embolism is likely to occur. Further study is needed to resolve
these important issues. Methodology and other CO2 effects on plant
water relations are discussed.

KEYWORDS: REVIEW, ROOT:SHOOT RATIO, WATER STATUS, WATER STRESS, WUE

732  
Van Berkel, N. 1986. CO2 Enrichment in the Netherlands. IN: Status
and CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.), Carbon
Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca
Raton, Florida, pp. 17-33.

KEYWORDS: CO2 SOURCES, COMMERCIAL USE OF CO2, HORTICULTURAL CROPS,
PHYSIOLOGICAL CO2 RESPONSES, REVIEW

733  
van de Geijn, S.C., and J.A. van Veen. 1993. Implications of
Increased Carbon Dioxide Levels for Carbon Input and Turnover in
Soils. Vegetatio 104/105:283-292.

The complexity of the plant-soil system in its interactions with
the changing climate is discussed. It is shown that processes at
the level of organic matter inputs into the soil and the fluxes and
pools involved in the global cycle are not known in sufficient
detail to allow an estimation of the future quantitative shifts.
Even the direction in which the level of stored carbon in the soil
organic matter pool will develop is not clear. The importance of
the nitrogen cycle, which is intimately coupled to the carbon cycle
through the turnover of soil organic matter is underlined. In its
turn, the mineralisation of soil organic matter takes place at a
rate which is highly dependent on the nature of inputs and the
availability of mineral nutrients. Aspects of shifts in
temperature, changes in cultivation practices (reduced tillage) and
unintended spreading of inputs in chemical N-fertilizers are of
great importance at a regional and global scale. The complexity of
the interactions in the process of mineralisation do require
further studies to clarify the point whether a substantial and
durable additional storage of carbon in soil organic matter is
likely, or that shifts in temperature will cause an overriding
acceleration of the mineralisation, and trigger corresponding net
release of carbon.

KEYWORDS: CARBON IN SOILS, CARBON SEQUESTERING, CARBON:NITROGEN
RATIO, CLIMATE CHANGE, LITTER DECOMPOSITION, LITTER QUALITY,
MINERALIZATION, NITROGEN, REVIEW, RHIZOSPHERE, SOIL MICROORGANISMS

734  
van de Staaij, J.W.M., G.M. Lenssen, M. Stroetenga, and J. Rozema.
1993. The Combined Effects of Elevated CO2 Levels and UV-B
Radiation on Growth Characteristics of Elymus athericus (= E.
pycnanathus). Vegetatio 104/105:433-439.

Elymus athericus (Link) Kerguelen, a C3 grass, was grown in a
greenhouse experiment to determine the effect of enhanced
atmospheric CO2 and elevated UV-B radiation levels on plant growth.
Plants were subjected to the following treatments: a) ambient CO2-control UV-B, b) ambient CO2-elevated UV-B, c) double CO2-control
UV-B, d) double CO2-elevate UV-B. Elevated CO2 concentrations
stimulated plant growth, biomass production was 67% higher than at
ambient CO2. Elevated UV-B radiation had a negative effect on
growth, biomass production was depressed by 31%. Enhanced CO2
combined with elevated UV-B levels caused a biomass depression of
8% when compared with the control plants. UV-B induced growth
depression can be modified by a growth stimulus caused by high CO2
concentrations. Growth analysis has been performed and possible
physiological mechanisms behind changing growth parameters are
discussed.

Elymus athericus

KEYWORDS: GRASSES, GREENHOUSE, GROWTH ANALYSIS, UV-B RADIATION

735  
van Keulen, H. 1990. The Impact of the Greenhouse Effect on Factors
Limiting Primary Production. IN: The Greenhouse Effect and Primary
Productivity in European Agro-ecosystems; 5-10 April 1990;
Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H.
van Laar, eds.), Pudoc, Wageningen, pp. 62-63.

KEYWORDS: AGRICULTURE, RESPIRATION, REVIEW, TEMPERATURE, WUE

736  
van Kraalingen, D.W.G. 1990. Effects of CO2 Enrichment on Nutrient-deficient Plants. IN: The Greenhouse Effect and Primary
Productivity in European Agro-ecosystems; 5-10 April 1990;
Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H.
van Laar, eds.), Pudoc, Wageningen, pp. 42-45.

Triticum aestivum/wheat/barley/Hordeum vulgare

KEYWORDS: ALLOCATION, GREENHOUSE, NITROGEN, NUTRITION, YIELD

737  
Van Oosten, J.-J., D. Afif, and P. Dizengremel. 1992. Long-term
Effects of a CO2 Enriched Atmosphere on Enzymes of the Primary
Carbon Metabolism of Spruce Trees. Plant Physiology and
Biochemistry 30:541-547.

The long-term effects of an enriched CO2 atmosphere on the primary
carbon metabolism of 4-year-old spruce trees (Picea abies L. Karst)
were examined. Eight key enzymes were studied in 1-year-old needles
of trees submitted for two years in open-top chambers to three CO2
levels (350, 480 and 570 ppmV). The specific activity and quantity
of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO, EC
4.1.1.39), and the specific activities of photorespiratory enzymes,
glycolate oxidase (EC 1.1.3.15) and hydroxypyruvate reductase (HPR,
EC 1.1.1.29) showed a significant decrease in the CO2-enriched
atmospheres. By contrast, a net increase was found for the specific
activities of the mitochondrial enzymes, NAD-malic enzyme (NAD-ME,
EC 1.1.1.39) and especially fumarase (EC 4.2.1.2). The specific
activity of phosphofructophosphotransferase (PFP, EC 2.7.1.90), a
glycolytic enzyme, did not change while a slight decrease of the
activity of glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49),
a pentose phosphate pathway enzyme, was observed. The carboxylating
enzyme, phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) showed
a marked decrease in activity. These results clearly demonstrate
both increases in enzyme activities linked to the respiratory
process and decreases in activites of CO-fixing enzymes as a result
of long-term exposure to less than twice the ambient level of CO2.

Norway spruce/Picea abies

KEYWORDS: ENZYMES, OPEN-TOP CHAMBERS, PHOSPHOENOLPYRUVATE
CARBOXYLASE, RESPIRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, TREES

738  
Van Oosten, J.-J., E. Laitat, P. Dizengremel, and D. Gerant. 1992.
The Effects of CO2 Enrichment on the Biochemistry of Photosynthesis
and Photorespiration of Spruce Trees Cultivated in Open-top
Chambers. IN: Responses of Forest Ecosystems to Environmental
Changes (A. Teller, P. Mathy, and J.N.R. Jeffers, eds.), Elsevier
Applied Science, London, pp. 655-656.

Picea abies/Norway spruce

KEYWORDS: ENZYMES, OPEN-TOP CHAMBERS, PHOSPHOENOLPYRUVATE
CARBOXYLASE, PHOTOSYNTHESIS, RESPIRATION, RIBULOSE BISPHOSPHATE
CARBOXYLASE, TREES

739  
van Veen, J.A., E. Liljeroth, L.J.A. Lekkerkerk, and S.C. van de
Geijn. 1991. Carbon Fluxes in Plant-soil Systems at Elevated CO2
Levels. Ecological Applications 1:175-181.

The flow of carbon from photosynthesizing tissues of higher plants,
through the roots and into the soil is one of the key processes in
terrestrial ecosystems. An increased level of CO2 in the atmosphere
will likely result in an increased input of organic carbon into the
soil due to the expected increase in primary production. Whether
this will lead to accumulation of greater amounts of organic carbon
in soil depends on the flow of carbon through the plant into the
soil and its subsequent transformation in the soil by
microorganisms. In this paper the major controls of carbon
translocation via roots into the soil as well as the subsequent
microbial turnover of root-derived carbon are reviewed. We discuss
possible consequences of an increased CO2 level in the atmosphere
on these processes.

KEYWORDS: ALLOCATION, LITTER DECOMPOSITION, MODELING, MYCORRHIZAE,
NUTRITION, REVIEW, RHIZOSPHERE, ROOT EXUDATION, ROOTS, SOIL
MICROORGANISMS

740  
Vassey, T.L., W.P. Quick, T.D. Sharkey, and M. Stitt. 1991. Water
Stress, Carbon Dioxide, and Light Effects on Sucrose-phosphate
synthase Activity in Phaseolus vulgaris. Physiologia Plantarum
81:37-44.

The characteristics of sucrose-phosphate synthase (SPS; EC
2.4.1.14) activity in leaves of Phaseolus vulgaris L. cv. Linden
was studied in plants subjected to water stress and various CO2 and
light treatments. When water was withheld for 3 days causing mild
water stress (-0.9 MPa), the activity of SPS measured in crude
extracts was reduced ca 50%. The effect of water stress was most
evident when the enzyme was assayed with saturating amounts of its
substrates fructose-6-phosphate and UDP glucose. Placing a water-stressed plant in an atmosphere containing 1% CO2 reversed the
effect of water stress on SPS activity over 5 h even though the
water stress was not relieved. Holding unstressed leaves in low CO2
partial pressure reduced the extractable activity of SPS. After 1
h of low CO2 treatment the effect of low CO2 could be reversed by
20 min of 5% CO2. However, after 24 h of low CO2 treatment, less
SPS activity was recovered by the 20 min. treatment. The cytosolic
protein synthesis inhibitor cycloheximide prevented the slow
recovery of SPS activity, but did not affect the rapid recovery of
SPS. We conclude that the effect of water stress on SPS activity
was a consequence of the inhibition of photosynthesis caused by
stomatal closure. Responses of Phaseolus vulgaris SPS to light were
similar to the response to low CO2 in that the effects were most
pronounced under Vmax assay conditions. This is the first report of
this type of light response of SPS in a dicotyledonous species.

Phaseolus vulgaris/bean

KEYWORDS: ENZYMES, LIGHT, SUCROSEPHOSPHATE SYNTHASE, WATER STRESS

741  
Vessey, J.K., L.T. Henry, and C.D. Raper Jr. 1990. Nitrogen
Nutrition and Temporal Effects of Enhanced Carbon Dioxide on
Soybean Growth. Crop Science 30:287-294.

Plants grown on porous media at elevated CO2 levels generally have
low concentrations of tissue N and often appear to require
increased levels of external N to maximize growth response. This
study determines if soybean [Glycine max (L.) Merr. 'Ransom'] grown
hydroponically at elevated CO2 requires increases in external NO3(-) concentrations beyond levels that are optimal at ambient CO2 to
maintain tissue N concentrations and maximize the growth response.
This study also investigates temporal influences of elevated CO2 on
growth responses by soybean. Plants were grown vegetatively for 34
d in hydroponic culture at atmospheric CO2 concentrations of 400,
675, and 900 uL/L and during the final 18 d at NO3(-)
concentrations of 0.5, 1.0, 5.0 and 10.0 mM in the culture
solution. At 675 and 900 uL/L CO2, plants had maximum increases of
31 and 45% in dry weight during the experimental period. Plant
growth at 900 uL/L CO2 was stimulated earlier than at 650 uL/L.
During the final 18 d of the experiment, the relative growth rates
(RGR) of plants grown at elevated CO2 declined. Elevated CO2 caused
increases in total N and total NO3(-)-N content and leaf area but
not leaf number. Enhancing CO2 levels also caused a decrease in
root:shoot ratios. Stomatal resistance increased by 2.1- and 2.8-fold for plants at the 675 and 900 uL/L CO2, respectively. Nitrate
level in the culture solutions had no effect on growth or on C:N
ratios of tissues, nor did increases in CO2 levels cause a decrease
in N concentration of plant tissues. Hence, increases in NO3(-)
concentration of the hydroponic solution were not necessary to
maintain the N status of the plants or to maximize the growth
response to elevated CO2.

soybean/Glycine max

KEYWORDS: ALLOCATION, CARBON:NITROGEN RATIO, CONDUCTANCE,
CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, HYDROPONIC
CULTURE, NITROGEN, NUTRITION, RHIZOSPHERE, ROOT:SHOOT RATIO

742  
Vu, J.C.V., L.H. Allen Jr., and G. Bowes. 1987. Drought Stress and
Elevated CO2 Effects on Soybean Ribulose Bisphosphate Carboxylase
Activity and Canopy Photosynthetic Rates. Plant Physiology 83:573-578.

Soybean (Glycine max [L.] cv Bragg) was grown at 330 or 660
microliters CO2 per liter in outdoor, controlled environment
chambers. When the plants were 50 days old, drought stress was
imposed by gradually reducing irrigation each evening so that
plants wilted earlier each succeeding day. On the ninth day, as the
pots ran out of water CO2 exchange rate (CER) decreased rapidly to
near zero for the remainder of the day. Both CO2-enrichment and
drought stress reduced the total (HCO3(-)/Mg(++)-activated)
extractable ribulose-1,5-bisphosphate carboxylase (RuBPCase)
activity, as expressed on a chlorophyll basis. In addition, drought
stress when canopy CER values and leaf water potentials were
lowest, reduced the initial (nonactivated) RuBPCase activity by 50%
compared to the corresponding unstressed treatments. This suggests
that moderate to severe drought stress reduces the in vivo
activation state of RuBPCase, as well as lowers the total activity.
It is hypothesized that stromal acidification under drought stress
causes the lowered initial RuBPCase activities. The Km(CO2) values
of activated RuBPCase from stressed and unstressed plants were
similar; 15.0 and 12.6 micromolar, respectively. RuBP levels were
10 to 30% lower in drought stressed as compared to unstressed
treatments. However, RuBP levels increased from near zero at night
to around 150 to 200 nanomoles per milligram chlorophyll during the
day, even as water potentials and canopy CERs decreased. This
suggests that the rapid decline in canopy CER cannot be attributed
to drought stress induced limitations in the RuBP regeneration
capability. Thus, in soybean leaves, a nonstomatal limitation of
leaf photosynthesis under drought stress conditions appears due, in
part, to a reduction of the in vivo activity of RuBPCase. Because
initial RuBPCase activities were not reduced as much as canopy CER
values, this enzymic effect does not explain entirely the response
of soybean photosynthesis to drought.

soybean/Glycine max

KEYWORDS: CANOPY PHOTOSYNTHESIS, RIBULOSE 1,5-BISPHOSPHATE,
RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS, WATER STATUS, WATER
STRESS

743  
Vu, J.C.V., L.H. Allen Jr., and G. Bowes. 1989. Leaf
Ultrastructure, Carbohydrates and Protein of Soybeans Grown under
CO2 Enrichment. Environmental and Experimental Botany 29:141-147.

Soybeans (Glycine max [L.] Merr. cv Bragg) grown under 800 uL CO2
per liter showed increases of 37, 205, 108, 33, 22 and 31% in
specific leaf weight, starch, sucrose, reducing sugars, chlorophyll
and soluble protein, respectively, over control plants at 330 uL
CO2 per liter. CO2 enrichment caused an increase in leaf thickness,
due to an increased number of palisade cells, but no major
alterations in chloroplast ultrastructure. The extra starch formed
under CO2 enrichment was distributed as slightly larger starch
grains among more and larger chloroplasts and more mesophyll cells,
rather than as more starch grains per chloroplast. The Km(CO2) of
ribulose bisphosphate carboxylase was unchanged by growth at high
CO2, similarly there was little effect on the activity of this
enzyme. The increase in starch storage sites, together with the
maintenance of ribulose bisphosphate carboxylase activity, enable
soybeans to continue to exhibit high photosynthetic rates
throughout the growth period.

soybean/Glycine max

KEYWORDS: ANATOMY, CARBOHYDRATES, PIGMENTS, PROTEINS, RIBULOSE
BISPHOSPHATE CARBOXYLASE, SPAR UNITS

744  
Vugts, H.F. 1993. The Need for Micrometeorological Research of the
Response of the Energy Balance of Vegetated Surfaces to CO2
Enrichment. Vegetatio 104/105:321-328.

A Penman-Monteith equation has been use to evaluate a change in
canopy resistance on the evapotranspiration of a savannah and
agricultural area in Botswana. After a short introduction, some
problems concerning the K-theory of 'first order closure' are
indicated when one uses it for transport modelling within and above
a canopy. The Penman-Monteith equation was used to calculate the
canopy resistance for a savannah vegetation and sorghum under the
same environmental conditions. After that, by changing the stomatal
resistance due to an increase of the CO2 content, the change in the
evapotranspiration was estimated. Finally some recommendations for
future research are given and an outline of a proposed FACE
experiment is presented.

KEYWORDS: CONDUCTANCE, EVAPOTRANSPIRATION, MODELING

745  
Wallick, K., and T.M. Zinnen. 1990. Basil Chlorosis: a
Physiological Disorder in CO2-enriched Atmospheres. Plant Disease
74:171-173.

Basil (Ocimum basilicum) grown commercially in a hydroponic
facility under high-pressure sodium lights in a CO2-enriched
atmosphere developed a distinct interveinal chlorosis. Attempts to
transmit the disease mechanically or by grafting to unaffected,
greenhouse-grown basil and certain other plant species failed.
Affected basil that was transferred from the hydroponic facility to
a greenhouse and grown in potting mix produced new, chlorosis-free
leaves. Under experimental conditions, basil became chlorotic in
1,000 ppm CO2, but not when in ambient CO2. This was true whether
the basil was grown hydroponically or in pots, or under fluorescent
or high-pressure sodium lights. Electron microscopy revealed no
detectable pathogens, but large starch grains were observed in
chloroplasts of chlorotic leaves. Elevated CO2 concentrations
apparently induced basil chlorosis.

Ocimum basilicum/basil

KEYWORDS: CARBOHYDRATES, HYDROPONIC CULTURE, PIGMENTS

746  
Wang, Y.-P., R.M. Gifford, G.D. Farquhar, and S.C. Wong. 1991.
Direct Effect of Elevated CO2 on Canopy Leaf Area Development of a
Wheat Crop from Sowing to Anthesis. IN: Climatic Variation and
Change: Implications for Agriculture in the Pacific Rim; 1989 June
20-28 and 1990 September 24-28; University of California, Davis,
USA and University of Melbourne, Australia, The Public Service
Research and Dissemination Program, University of California,
Davis, USA; and the Faculty of Agriculture, University of
Melbourne, Australia, pp. 19-26.

A simple model of wheat canopy leaf area development from sowing to
anthesis was developed and tested. The model was used to analyse
the sensitivity of canopy leaf area development to double present
carbon dioxide concentration in the atmosphere at different
temperature patterns, which were simulated by adding 0 to 3C to
the controlled temperature pattern. It is concluded that the direct
beneficial effect of elevated carbon dioxide (680 mmol/mol) will
counterbalance the detrimental effect of a 3C rise in daily mean
air temperature when a crop is grown under a condition of 680
mmol/mol carbon dioxide concentration without water stress and
nutrient deficiency.

Triticum aestivum/wheat

KEYWORDS: GRASSES, GROWTH STAGES, LEAF AREA DEVELOPMENT, MODELING,
SIMULATION, TEMPERATURE

747  
Ward, D.A. 1987. The Temperature Acclimation of Photosynthetic
Responses to CO2 in Zea mays and Its Relationship to the Activities
of Photosynthetic Enzymes and the CO2-concentrating Mechanism of C4
Photosynthesis. Plant, Cell and Environment 10:407-411.

Associations between photosynthetic responses to CO2 at rate-saturating light and photosynthetic enzyme activities were compared
for leaves of maize grown under constant air temperatures of 19, 25
and 31C. Key photosynthetic enzymes analysed were ribulose
bisphosphate (RuBP) carboxylase, phosphoenolpyruvate (PEP)
carboxylase, NADP-malic enzyme and pyruvate, Pi dikinase. Rates of
CO2-saturated photosynthesis were similar in leaves developed at
19C and 25C but were decreased significantly by growth at 31C.
In contrast, carboxylation efficiency differed significantly
between all three temperature regimes. Carboxylation efficiency was
greatest in leaves developed at 19C and decreased with increasing
temperature during growth. The changes of carboxylation efficiency
were highly correlated with changes in the activity of pyruvate, Pi
dikinase (r=0.95), but not with other photosynthetic enzyme
activities. The activities of these latter enzymes, including that
of RuBP carboxylase, were relatively insensitive to temperature
during growth. The sensitivity of quantum yield to O2 concentration
was lower in leaves grown at 19C than in leaves grown at 31C.
These observations support the novel hypothesis that variation in
the capacity for CO2 delivery to the bundle sheath by the C4 cycle,
relative to the capacity for net assimilation by the C3 cycle, can
be a principal determinant of C4 photosynthetic response to CO2.

Zea mays/corn

KEYWORDS: C4, CARBOXYLATION EFFICIENCY, ENZYMES,
PHOSPHOENOLPYRUVATE CARBOXYLASE, QUANTUM REQUIREMENT, RIBULOSE
BISPHOSPHATE CARBOXYLASE, TEMPERATURE

748  
Warrick, R.A., R.M. Gifford, and M.L. Parry. 1986. CO2, Climatic
Change and Agriculture. IN: The Greenhouse Effect, Climatic Change,
and Ecosystems, Vol. 29 (B. Bolin, B.R. Doos, J. Jager, and R.A.
Warrick, eds.), Scientific Committee on Problems of the
Environment, John Wiley and Sons, Chichester, England, pp. 393-473.

A 'doubling' of ambient CO2 concentrations has a positive effect on
growth and yield of major food and fibre crops. These may range
from 10% to 50% for C3 plants to 1% to 10% for C4 plants. Globally,
the potential benefits of CO2-enhanced yields might well be
unevenly distributed because of the differences in where C3 and C4
crops are grown. The positive growth and yield response from
elevated CO2 levels is obtained under most environmentally
stressful as well as optimal conditions. Thus both the core and the
margins of crop regions could benefit from increased CO2 relative
to current yield levels. In relative terms, the growth and yield
response is actually higher under some stressful environmental
conditions, like moisture stress. In absolute terms, yield response
to increased CO2 concentrations is greatest under good growing
conditions. In many developing countries where soil nutrient
shortage is a chronic problem, the full benefits of enhanced yields
may not be realized, particularly if phosphorus is deficient. As
yet, the regional patterns of climatic change cannot be forecast
reliably. This presents the major obstacle to predicting actual
crop yield and production impacts from climate change. However, in
crop impact analyses, employing GCM-derived crop-climate models, a
number of studies have found that, in the absence of managerial
adjustments or direct CO2 effects: for the core areas of the North
American and European mid-latitude grain regions, the probable
effect of an instantaneous increase in average temperatures would
be to decrease crop yields (3%-17% for 2C). The negative impact of
higher temperature on grain yield derives from associated increases
in evapotranspiration, and from accelerated rates of plant
development and a shortening of the period of yield formation.
Increases in precipitation would tend to offset the reduction in
grain yield from warming; decreases in precipitation would
accentuate them. The impacts of climate warming at the margins of
production could be less than, greater than, or in the opposite
direction from those observed at the core areas. Few systematic
studies of the impacts of possible changes in climate have been
conducted for the tropics and sub-tropics. At all latitudes, the
potential for severest adverse (or most beneficial) impacts of
climatic change on crops may, in fact, be located in the marginal
areas, variously defined. The impacts of climatic change in
marginal areas of agriculture might well be expected to elicit
spatial shifts in crop areas or practices -- the concern of the
'marginal-spatial approach' to impact assessment. Shifts in crop
boundaries could be on the order of hundreds of kilometres per C
change. Spatial readjustment, of course, is only one way in which
agriculture could respond to increasing CO2 and climatic change.
Other response capability is internal to agriculture: feedback
mechanisms can help to self-regulate the system to environmental
change over time. The question, how much? is addressed by
'agricultural sector analyses'. One approach is to link models in
a sequential fashion to identify, estimate and integrate the
'cascade' of impacts which may occur at the regional scale. At
national and international scales, global models that focus on
agricultural production, consumption and trade are one means of
examining the interactions within the entire system. Based on
limited applications, it can be suggested that: A large proportion
of any potential adverse effects on yields and production as a
result of gradual change in climate can be absorbed through policy
and market feedback mechanisms. The disruption from single extreme
years could cause over-reaction in the system with oscillating
impacts in subsequent years. The impacts of climatic change on
production in one region could be transferred to another over time
through the network of global market and trade. The general lesson
from agricultural sector analyses is that close attention needs to
be paid to the dynamics of the system. Furthermore, the response of
the system depends critically on the assumed rate of environmental
change. (Abridged)

KEYWORDS: AGRICULTURAL SECTOR ANALYSIS, AGRICULTURE, CLIMATE
CHANGE, CROP IMPACT ANALYSIS, ENVIRONMENTAL INTERACTIONS, GCM'S,
MARGINAL-SPATIAL ANALYSIS, MODELING, PHYSIOLOGICAL CO2 RESPONSES,
REVIEW, SCALING, TEMPERATURE, YIELD

749  
Warrick, R.A., H.H. Shugart, M.J. Antonovsky, J.R. Tarrant, and
C.J. Tucker. 1986. The Effects of Increased CO2 and Climatic Change
on Terrestrial Ecosystems. IN: The Greenhouse Effect, Climatic
Change, and Ecosystems, Vol. 29 (B. Bolin, B.R. Doos, J. Jager, and
R.A. Warrick, eds.), Scientific Committee on Problems of the
Environment, John Wiley and Sons, Chichester, England, pp. 363-392.

There are no firm grounds for believing that the net effects of
increased CO2 and climatic change will be adverse rather than
beneficial. At the extreme, some assessments like the Global 2000
Report to the President (U.S. Council on Environmental Quality and
Department of State, 1980) see future changes in climate coinciding
with deteriorating conditions in agriculture, forests and other
resources, and thus paint a very gloomy picture indeed. In
contrast, Simon and Kahn (1984) examine the same issues and in a
strongly optimistic tone, reach just the opposite conclusions. In
fact, at a global scale the uncertainties that are involved in both
sets of analyses are large enough to accommodate both views. If, in
this (and subsequent) chapters, we tend to emphasize the potential
negative impacts, it is only because those are the ones which are
of most immediate concern to society and which the scientific
community should hope to identify and predict. The list of possible
adverse consequences of climate-related ecosystem changes is long
and speculative, and the following represent a sample.
Conservation. There are many natural parks and reserves that are
refuges for rare and endangered plant and animal species. Often
these parks occupy a relatively small area in a setting of non-park
land. If an environmental change made such parks unsuitable as
habitats for these species, it is uncertain whether alternative
refuges could be found or whether it would even be possible to
transport species to new sites. The risk of widespread extirpation
of rare species (particularly those with local distributions) could
be high as a result of climatic change. Forestry. Forestry as a
predictive science used in a management context is highly dependent
on data or local knowledge of forest response to specific
management treatments. Under a sufficiently large change in
climate, this local knowledge base would have to be used outside
its calibration range and the consequences of management actions
would be less certain. Related ecological processes. The global
pattern of many of the ecological processes in natural systems
could be altered if the climate changed. Insect pests, pathogenic
organisms and wildfire frequencies could all change. While the
prediction of such changes is highly uncertain, their potential
impacts are quite large. Hydrological systems. The impact of
climatic change on regional ecosystems (particularly forests) could
alter the hydrological characteristics of watersheds. Decreases in
transpiration rates from the direct effects of increased CO2 on
vegetation might increase runoff, for instance, and enhance the
effects of precipitation increases or offset the effects of
precipitation decreases (Wigley and Jones, 1985). Changes in
flooding and river flow rates could have pronounced effects on the
rivers themselves, on the ecosystems adjoining the rivers, and on
the various human activities that depend on reliable quantity and
quality of water. If, on the other hand, the impacts of increased
CO2, trace gases and climatic change on agriculture, forests and
other ecosystems prove, on balance, favourable, all the better. In
summary, this chapter has set the stage for a more detailed
examination of the effects of increased CO2 and climatic change by
outlining the major issues and dimensions of the problem in the
global context, with an emphasis on agriculture and forest
ecosystems. For both agriculture and forests the basic questions
are similar: How would crop yields or crop types or forest
composition be altered, particularly at the margins of production
or at ecological transition zones? How might these effects,
integrated over time and space, change global patterns of forests
or agricultural production, taking into consideration the
interactive natural and human processes that make both systems very
dynamic? In order to derive meaningful, credible answers, it is
necessary to interface scenarios of environmental change with
research procedures or models capable of testing the sensitivity of
the systems. What approaches are available? How have they been used
and what questions have been asked of them? What have we learned so
far from their specific applications to problems of increased CO2
concentrations and climatic change?

KEYWORDS: ADVANCED VERY HIGH RESOLUTION RADIOMETER, AGRICULTURE,
CLIMATE CHANGE, CO2 ENRICHMENT STUDIES, ECOSYSTEM LEVEL CO2
RESPONSES, FOREST, HYDROLOGY, REMOTE SENSING, REVIEW

750  
Weinstein, D.A. 1992. Use of Simulation Models to Evaluate the
Alteration of Ecotones by Global Carbon Dioxide Increases.
Ecological Studies: Analysis and Synthesis 92:379-383.

In the series analytic: Landscape boundaries: Consequences for
biotic diversity and ecological flows/edited by A.J. Hansen and F.
de Castri.

KEYWORDS: MODELING, SIMULATION

751  
Wheeler, R.M., and T.W. Tibbitts. 1989. Utilization of Potatoes for
Life Support Systems in Space. IV. Effect of CO2 Enrichment.
American Potato Journal 66:25-34.

Potatoes (Solanum tuberosum L.) cvs. Norland and Russet Burbank
were grown in solid stands in separate controlled environment rooms
at two CO2 levels, 365 umol/mol (ppm) and 1000 umol/mol. Rooms were
maintained under continuous fluorescent light (450 umol/s/m2 PPF),
16 C and 70% relative humidity. Norland plants were grown for 110
days and Russet Burbank plants for 126 days. CO2 assimilation rates
(net photosynthetic rates) of exposed, upper canopy leaves were
measured at weekly intervals beginning at 21-days-age for Norland
and 28-days-age for Russet Burbank. Elevation of CO2 increased CO2
assimilation rates of Norland leaves by approximately 24% but
decreased rates of Russet Burbank leaves by approximately 12%.
Assimilation rates of Norland leaves under the high CO2 decreased
as plants matured so that their rates were similar to rates under
the low CO2 levels after 70-days-age. Assimilation rates of Russet
Burbank leaves under high CO2 remained depressed in comparison to
low CO2 plants throughout the period of measurements. Yield data
showed only marginal benefits from CO2 enrichment: tuber dry weight
increased 2% for Norland and 12% for Russet Burbank, total plant
dry weight was increased 6% for Norland and 4% for Russet Burbank.
The best productivity obtained in this study (21.9 g tuber dry
wt/m2/day from Norland at 1000 umol/mol of CO2) indicates that the
dietary energy needs of one human in space could be supplied from
34 m2 of potatoes.

Solanum tuberosum/potato

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES,
HARVEST INDEX, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION,
TUBERS

752  
Wheeler, R.M., T.W. Tibbitts, and A.H. Fitzpatrick. 1991. Carbon
Dioxide Effects on Potato Growth under Different Photoperiods and
Irradiance. Crop Science 31:1209-1213.

Carbon dioxide concentration can exert a strong influence on plant
growth, but this influence can vary depending on irradiance. To
study this, potato plants (Solanum tuberosum L.) cultivars
'Norland', 'Russet Burbank', and 'Denali' were grown in controlled-environment rooms at different levels of CO2 and irradiance. Carbon
dioxide levels were maintained either at 350 or 1000 umol/mol and
applied in combination with 12- or 24-h photoperiods at 400 or 800
umol/m2/s photosynthetic photon flux. Air temperatures and relative
humidity were held constant at 16C and 70%, respectively, and
plants were harvested 90 d after planting. When averaged across all
cultivars, CO2 enrichment increased tuber yield and total plant dry
weight by 39 and 34%, respectively, under a 12-h photoperiod at 400
umol/m2/s; 27 and 19% under 12 h at 800 umol/m2/s; 9 and 9% under
24 h at 400 umol/m2/s. It decreased dry weights by 9 and 9% under
24 h at 800 umol/m2/s. Tuber yield of Denali showed the greatest
increase (21%) in response to increased CO2 across all irradiance
treatments, while tuber yields of Russet Burbank and Norland were
increased 18 and 9%, respectively. The results show a pattern of
greater plant growth from CO2 enrichment under lower PPF and a
short photoperiod.

Solanum tuberosum/potato

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LIGHT, PHOTOPERIOD

753  
Whipps, J.M. 1985. Effect of CO2-concentration on Growth, Carbon
Distribution and Loss of Carbon from Roots of Maize. Journal of
Experimental Botany 36:644-651.

The effects of three ranges of CO2 concentration on growth, carbon
distribution and loss of carbon from the roots of maize grown for
14 d and 28 d with shoots in constant specific activity 14-CO2 are
described.  Increasing concentrations of CO2 led to enhancement of
plant growth with the relative growth rate (RGR) of the roots
affected more than the RGR of the shoots.  Between 16% and 21% of
total net fixed carbon (defined as 14C retained in the plant plus
14C lost from the root) was lost from the roots at all CO2
concentrations at all times but the amounts of carbon lost per unit
weight of plant decreased with time.  Possible mechanisms to
account for these observations are discussed.

maize/Zea mays/corn

KEYWORDS: 14C, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS,
RESPIRATION, RHIZOSPHERE, ROOT:SHOOT RATIO, ROOTS, SOIL
MICROORGANISMS

754  
Whiting, G.J., E.L. Gandy, and D.C. Yoch. 1986. Tight Coupling of
Root-associated Nitrogen Fixation and Plant Photosynthesis in the
Salt Marsh Grass Spartina alterniflora and Carbon Dioxide
Enhancement of Nitrogenase Activity. Applied and Environmental
Microbiology 52:108-113.

The coupling of root-associated nitrogen fixation and plant
photosynthesis was examined in the salt marsh grass Spartina
alterniflora. In both field experiments and hydroponic assay
chambers, nitrogen fixation associated with the roots was rapidly
enhanced by stimulating plant photosynthesis. A kinetic analysis of
acetylene reduction activity (ARA) showed that a five-to sixfold
stimulation occurred within 10 to 60 min after the plant leaves
were exposed to light or increased CO2 concentrations (with the
light held constant). In field experiments, CO2 enrichment
increased plant-associated ARA by 27%. Further evidence of the
dependence of ARA on plant photosynthate was obtained when activity
in excised roots was shown to decrease after young greenhouse
plants were placed in the dark. Seasonal variation in the ARA of
excised plant roots from field cores appears to be related to the
annual cycle of net photosynthesis in S. alterniflora.

Spartina alterniflora

KEYWORDS: AQUATIC PLANTS, GRASSES, HALOPHYTES, NITROGEN FIXATION,
NITROGENASE ACTIVITY, RHIZOSPHERE, SALT MARSH

755  
Williams, M.L., D.G. Jones, R. Baxter, and J.F. Farrar. 1992. The
Effect of Enhanced Concentrations of Atmospheric CO2 on Leaf
Respiration. IN: Molecular, Biochemical and Physiological Aspects
of Plant Respiration (H. Lambers and L.H.W. Van der Plas, eds.),
SPB Academic Publishing, The Hague, pp. 541-545.

KEYWORDS: RESPIRATION

756  
Williams, W.E., K. Garbutt, and F.A. Bazzaz. 1988. The Response of
Plants to Elevated CO2. V. Performance of an Assemblage of
Serpentine Grassland Herbs. Environmental and Experimental Botany
28:123-130.

Six species of herbs from the serpentine grassland of Jasper Ridge
Nature Preserve (Stanford, California) -- Microseris sp., Plantago
erecta, Micropus Californicus, Agoseris heterophylla, Layia
platyglossa and Lasthenia glabrata -- were grown individually and
in competitive arrays, under three levels of CO2: 350, 500 and 700
uL/L. CO2 affected the biomass of some species in the individually-grown plants but none in the competitive arrays. Here, in contrast
to some previous studies, total community biomass was not
significantly affected by CO2 in either condition. In every species
where CO2 had a statistically significant effect on nitrogen
content, higher CO2 resulted in lower nitrogen content. Competition
appeared to decrease the effects of CO2. Our results suggest that
in this community, competitive networks and adaptations to a low-resource habitat may strongly damp the effects of CO2. These
results contrast with our previous work on annuals of a higher
stature system and agree with recent results on Arctic tundra
species.

Agoseris heterophylla/Lasthenia glabrata/Layia platyglossa/Micropus
Californicus/Microseris sp./Plantago erecta

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, GRASSES, GROWTH, NITROGEN,
SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS

757  
Williams, W.E., K. Garbutt, F.A. Bazzaz, and P.M. Vitousek. 1986.
The Response of Plants to Elevated CO2. IV. Two Deciduous-forest
Tree Communities. Oecologia 69:454-459.

Tree saplings, two groups of three species from each of two
deciduous tree communities, were grown in competition at three CO2
concentrations and two light levels. After one growing season,
biomass was measured to assess the effect of CO2 on community
structure, and nitrogen and phosphorus concentrations were measured
for leaves, stems, and roots of all trees. Gas-exchange
measurements were made on the same species grown under the same CO2
concentrations. Photosynthetic capacity (rate of photosynthesis at
saturating CO2 and light) tended to decline as CO2 concentration
increased, but differences were not statistically significant.
Stomatal conductance declined significantly as CO2 increased.
Nitrogen and phosphorus concentrations generally declined as CO2
increased, but there were some unexpected patterns in roots and
stems. CO2 concentration did not significantly affect the overall
growth of either community after one season, but the relative
biomass of each species changed in a complex way, depending on CO2,
light level and community.

Carya ovata/hickory/Liriodendron tulipifera/tulip poplar/Quercus
rubra/red oak/Platanus occidentalis/sycamore/Acer
saccharinum/silver maple/Fraxinus lanceolata/green ash

KEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, CONDUCTANCE, FOREST, LEAF
PHOTOSYNTHESIS, LIGHT, NITROGEN, NUTRITION, PHOSPHORUS, SPECIES
COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, TREES

758  
Willits, D., M. Peet, M. Depa, J. Kuehny, and P. Nelson. 1990.
Modulation of Nutrient Uptake in Chrysanthemum by Irradiance, CO2,
Season and Developmental Stage. IN: Proceedings of a Symposium,
Mechanisms of Plant Perception and Response to Environmental
Stimuli; 1989 August 6-10; Arlington, Virginia, Monograph No. 20
(T.H. Thomas and A.R. Smith, eds.), British Society for Plant
Growth Regulation, pp. 59-65.

Leaf tissue concentrations of most elements decreased in
chrysanthemum as growth rates were increased by irradiance or CO2.
Data from six experiments were fit to linear models of relative
accumulation rate of nutrients (RAR) on relative growth rate (RGR),
with and without considering changing plant age and environmental
factors affecting growth rate. For most elements, RAR was linearly
related to RGR with a slope approximating 1 and an intercept
approximating 0. Closer examination of these relationships
revealed, however, that chrysanthemum possesses the ability to
modify its nutrient uptake rate to match its internally regulated
needs and that these needs appear to change with maturity. In
addition to the maturity effect, a growth effect was discovered
which seems to be related to the effect of RGR on RAR, independent
of maturity. The mechanism by which the plant is correcting RAR as
a function of maturity and growth is not known.

chrysanthemum

KEYWORDS: GREENHOUSE, GROWTH ANALYSIS, NUTRITION

759  
Willits, D.H., P.V. Nelson, M.M. Peet, M.A. Depa, and J.S. Kuehny.
1992. Modeling Nutrient Uptake in Chrysanthemum as a Function of
Growth Rate. Journal of the American Society of Horticultural
Science 117:769-774.

The results of six experiments conducted over 3 years were analyzed
to develop a relationship between nutrient uptake rate and growth
rate in hydroponically grown Dendranthema x grandiflorum (Ramat.)
Kitamura, cv. Fiesta. Plants subjected to two levels of CO2 and
three levels of irradiance in four greenhouses were periodically
analyzed for growth and the internal concentration of 11 mineral
elements. The resulting data were used to determine relative
accumulation rate and relative growth rate, which were included in
linear regression analyses to determine the dependence of uptake on
growth. The regression equations were significant, with a slight
trend toward nonlinearity in some elements. This nonlinearity seems
to be related to the aging of the plant and suggests a process in
the plant capable of controlling uptake rate, perhaps as a result
of changes in the rate of formation of different types of tissues.

Dendranthema grandiflorum/Chrysanthemum morifolium

KEYWORDS: BORON, CALCIUM, COPPER, FLOWER PRODUCTION, GREENHOUSE,
GROWTH ANALYSIS, GROWTH RATE, HORTICULTURAL CROPS, HYDROPONIC
CULTURE, IRON, LIGHT, MAGNESIUM, MANGANESE, MODELING, NITROGEN,
NUTRITION, PHOSPHORUS, POTASSIUM, SENESCENCE, SULFUR, TEMPERATURE,
ZINC

760  
Willits, D.H., P.V. Nelson, M.M. Peet, M.A. Depa, and J.S. Kuehny.
1992. Nutrient Uptake in Chrysanthemum as Affected by Light, CO2
Level and Age. IN: ASAE Meeting; 1992 June 21-24; Charlotte, North
Carolina, American Society of Agricultural Engineers, St. Joseph,
Michigan.

Data from six chrysanthemum growth studies were analyzed and the
relative accumulation rate (RAR) of eleven mineral elements
modeled. The plants were grown hydroponically under 3 different
light levels and 2 different CO2 levels. RAR was found to depend
primarily on relative growth rate (RGR) but a significant
dependence on age was observed, suggesting that nutrient uptake
rate may be controlled by the quantity and type of tissue being
formed. Light and CO2 were found to have no effect on RAR
independent of that on RGR.

Dendranthema grandiflorum/Chrysanthemum morifolium

KEYWORDS: BORON, CALCIUM, COPPER, GREENHOUSE, GROWTH ANALYSIS,
HYDROPONIC CULTURE, IRON, LIGHT, MAGNESIUM, MANGANESE, MODELING,
NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM, SULFUR, ZINC

761  
Willits, D.H., and M.M. Peet. 1989. Predicting Yield Responses to
Different Greenhouse CO2 Enrichment Schemes: Cucumbers and
Tomatoes. Agricultural and Forest Meteorology 44:275-293.

Data from six years of carbon dioxide (CO2) enrichment studies at
North Carolina State University were analyzed in an attempt to
develop predictive relationships for plant responses to different
enrichment schemes and CO2 levels (600-5000 uL/L). Cucumbers
(Cucumis sativus L.) and tomatoes (Lycopersicon esculentum Mill.)
were enriched using: (i) closed-loop cooling to extend enrichment
periods beyond that generally practicable and (ii) elevated CO2
levels to compensate for short enrichment times normally
encountered in conventional enrichment. Yields of nine cultivars of
cucumber and seven of tomato, from both ground bed and bag culture,
were regressed against solar energy, number of enrichment hours,
fractional enrichment time, CO2 set point concentration (i.e.,
target concentration), and actual daily CO2 concentration. Absolute
yields for cucumber were found to be strongly related to the solar
energy received and, to a lesser degree, the number of enrichment
hours. CO2 concentration, either set point or actual, was
significant only when included in quadratic form. The relationship
developed suggests that the optimum concentration is inversely
related to the length of the enrichment period and that the product
of the number of enrichment hours and the set point concentration
should equal 14,400 uL-h/L. Absolute yields for tomato were also
highly dependent upon solar energy, and to a lesser degree, either
actual CO2 concentration, number of enrichment hours, or fractional
enrichment time. Weight gain advantages for cucumber were found to
be a linear function of fractional enrichment time (enrichment time
divided by solar daylength), reaching a maximum value of 54% when
continuously enriched during daylight hours. Weight gain advantages
for tomato were found to be a non-linear function of fractional
enrichment time with values of fractional enrichment time less than
0.5 producing little or no gain.

cucumber/Cucumis sativus/tomato/Lycopersicon esculentum

KEYWORDS: CO2 ENRICHMENT DURATION, COMMERCIAL USE OF CO2, CULTIVAR
RESPONSES, GREENHOUSE, HORTICULTURAL CROPS, LIGHT, MODELING, YIELD

762  
Wittwer, S.H. 1985. Carbon Dioxide Levels in the Biosphere: Effects
on Plant Productivity. Critical Reviews in Plant Sciences 2:171-198.

Human society is now inadvertently conducting a great biological
and environmental experiment, the outcome of which is not known.
Atmospheric carbon dioxide (CO2) is increasing at the rate of 1.5
parts per million (ppm) per year. It has risen from 315 ppm to 340
ppm in the past 25 years -- a 9% increase. Because CO2 is among the
factors which can limit the growth of plants, the increase may be
beneficial. An increase in plant growth due to 'fertilization' of
extra CO2 has not been measured, but a 5 to 10% increase may
already have occurred. Current data indicate that plants growing at
higher than normal CO2 levels are more tolerant of water,
temperature, light and atmospheric pollutant stresses. There are
effects on carbon metabolism, plant growth and development,
microbial activity, and terrestrial and aquatic plant communities.
The current rising level of atmospheric CO2 represents a dramatic
change in a resource base and can affect the total biological
productivity of the earth. A global change in a fundamental element
of all plant life mandates the establishment of a research agenda
for the assessment of unexplored frontiers. Increasing levels of
atmospheric CO2 will likely have major effects on food and the
production of other renewable resources in the decades to come.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, COMMERCIAL USE OF CO2,
CROPS, ENVIRONMENTAL INTERACTIONS, PHYSIOLOGICAL CO2 RESPONSES,
REVIEW

763  
Wittwer, S.H. 1986. Worldwide Status and History of CO2 Enrichment
-- an Overview. IN: Status and CO2 Sources, Vol. I (H.Z. Enoch and
B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops,
CRC Press, Inc., Boca Raton, Florida, pp. 3-15.

Historical records indicate that the beneficial effects of elevated
levels of atmospheric CO2 were observed in greenhouses about 200
years ago. Interest and practice in its use in greenhouses for crop
production in Western Europe preceded that in North America.
Widespread use in England and Germany occurred in the mid 1930s and
then diminished. Sources of CO2 were neither reliable nor suitable.
A re-awakening of interest occurred in Western Europe in the 1960s
with both vegetable crops and flowers accompanied by an unusual set
of circumstances which prompted almost immediate widespread use and
acceptance. More recently -- the late 1970s and early 1980s --
there has been a remarkable re-awakening of interest in the
potential benefits of elevated atmospheric levels of CO2 because of
its global atmospheric increase and the flood of reports relating
to the presumed indirect effects on climate change. Human society
is now inadvertently conducting a great biological and possibly an
environmental experiment, the outcome of which is not known. It
appears that the direct biological effects of elevated levels of
atmospheric CO2 may go beyond the now well established increased
yields and earlier maturation observed for greenhouse crops, grown
at double or triple the ambient atmospheric level. Significant
beneficial effects beyond those of improved growth and dry matter
production include increased water use efficiency, and greater
resilience to the environmental stresses of low light intensities,
both high and low temperatures, soil moisture deficiencies, and air
pollutants. The concerns with respect to adverse CO2 induced
climate change, must now be balanced by a historical and current
record of the many benefits accrued from direct biological effects
on plant growth as witnessed with crops grown in greenhouses and
their greater resistance to environmental stresses.

KEYWORDS: COMMERCIAL USE OF CO2, ENVIRONMENTAL INTERACTIONS,
HORTICULTURAL CROPS, PHYSIOLOGICAL CO2 RESPONSES, REVIEW, TREES

764  
Wittwer, S.H. 1990. Implications of the Greenhouse Effect of Crop
Productivity. HortScience 25:1560-1567.

KEYWORDS: AGRICULTURE, CLIMATE CHANGE, COMMERCIAL USE OF CO2,
PHOTOSYNTHESIS, REVIEW, WATER STRESS, WUE

765  
Wong, S.C. 1990. Elevated Atmospheric Partial Pressure of CO2 and
Plant Growth. II. Non-Structural Carbohydrate Content in Cotton
Plants and Its Effect on Growth Parameters. Photosynthesis Research
23:171-180.

Cotton plants were grown in late spring under full sunlight in
glasshouses containing normal ambient partial pressure of CO2 (32
+/- 2 Pa) and enriched partial pressure of CO2 (64 +/- 1.5 Pa) and
at four levels of nitrogen nutrition. Thirty-five days after
planting, the total dry weights of high CO2-grown plants were 2- to
3.5-fold greater than plants grown in normal ambient CO2 partial
pressure. Depending on nitrogen nutrition level, non-structural
carbohydrate content (mainly starch) in the leaves of plants grown
in normal CO2 was between 4 and 37% of the total leaf dry weight
compared to 39 to 52% in the leaves of high CO2-grown plants.
Specific leaf weight calculated using total dry weight was 1.6 to
2-fold greater than that based on structural dry weight. In high
CO2-grown plants the amount of non-structural carbohydrate
translocated from the leaves at night was between 10 and 20% of the
level at the end of the photoperiod. This suggests that the plant
was unable to utilize all the carbohydrate it assimilated in
elevated CO2 atmosphere. While there was a 1.5-fold enhancement in
the rate of CO2 assimilation in plants grown in 64 Pa CO2, there
was, however, some evidence to suggest that the activities of other
metabolic pathways in the plants were not stimulated to the same
extent by the enriched CO2 atmosphere. This resulted in massive
accumulation of non-structural carbohydrate, particularly at low
level of nitrogen nutrition.

cotton/Gossypium hirsutum

KEYWORDS: ALLOCATION, CARBOHYDRATES, GREENHOUSE, GROWTH ANALYSIS,
LEAF PHOTOSYNTHESIS, NITROGEN, NUTRITION, ROOT:SHOOT RATIO

766  
Wong, S.C., P.E. Kriedemann, and G.D. Farquhar. 1992. CO2 x
Nitrogen Interaction on Seedling Growth of Four Species of
Eucalypt. Australian Journal of Botany 40:457-472.

Four eucalypt species were selected to represent two ecologically
disparate groups which would be expected to contrast in seedling
vigour and in the nature of growth responses to CO2 x nitrogen
supply. Eucalyptus camaldulensis and E. cypellocarpa were taken as
examples of fast-growing species with a wide distribution, that
develop into large trees. By contrast, E. pauciflora and E
pulverulenta become smaller trees, and show a more limited
distribution. Seedlings were established in pots (5 L) of a loamy
soil and supplied with nutrient solution containing either 1.2 or
6.0 mM NO3(-) in both ambient (33 Pa) and CO2-enriched (66 Pa)
greenhouses. Analysis of growth response to treatments (2x2
factorial) was based on destructive harvest of plants sampled on
four occasions over 84 days for E. camaldulensis and E.
cypellocarpa, and 100 days for E. pulverulenta and E. pauciflora.
A positive CO2 x N interaction on plant dry mass and leaf area was
expressed in all species throughout the study period. In E.
camaldulensis and E. cypellocarpa, plant mass was doubled by high
N at 33 Pa CO2, compared with a three to four-fold increase at 66
Pa to reach 34 g by final harvest. In E. pulverulenta and E.
pauciflora, slower growth resulted in about 50% less mass at a
given age, but relative increases due to CO2 and N were of a
similar order. A distinction can be made between N and CO2 effects
on growth processes as follows. When trees were grown on low N,
elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf
and whole plant levels. On high N, leaf NUE was increased in E.
camaldulensis and E. cypellocarpa, but decreased in E. pulverulenta
and E. pauciflora. Whole plant NUE showed no consistent response to
elevated CO2 when plants were supplied high N. Net assimilation
rate (NAR) was increased by elevated CO2 in all species on either
N treatment. Moreover, high N increased NAR under either CO2
treatment in all species. There was a positive N x CO2 interaction
on NAR in E. camaldulensis and E. cypellocarpa, but not in E.
pulverulenta and E. pauciflora. Growth indices for E. camaldulensis
and E. cypellocarpa species, and especially E. camaldulensis,
generally exceeded those for E. pulverulenta and E. pauciflora in
terms of NAR, leaf NUE, N-enhancement and CO2 effects on leaf area
and biomass, and non-structural carbohydrate content of foliage.

Eucalyptus camaldulensis/Eucalyptus cypellocarpa/Eucalyptus
pauciflora/Eucalyptus pulverulenta

KEYWORDS: ALLOCATION, CARBOHYDRATES, FAMILY RESPONSES, GREENHOUSE,
GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, NITROGEN, NUTRITION

767  
Wong, S.C., and C.B. Osmond. 1991. Elevated Atmospheric Partial
Pressure of CO2 and Plant Growth. III. Interactions between
Triticum aestivum (C3) and Echinochloa frumentacea (C4) during
Growth in Mixed Culture under Different CO2, N Nutrition and
Irradiance Treatments, with Emphasis on Below-ground Responses
Estimated using the [delta] 13C Value of Root Biomass. Australian
Journal of Plant Physiology 18:137-152.

Wheat (Triticum aestivum L.), a C3 species, and Japanese millet
(Echinochloa frumentacea Link), a C4 species, were grown in pots in
monoculture and mixed culture (2 C3:1 C4 and 1 C3:2 C4) at two
ambient partial pressures of CO2 (320 and 640 ubar), two
photosynthetic photon flux densities (PPFDs) (daily maximum 2000
and 400 umol/m2/s) and two levels of nitrogen nutrition (12 mM and
2 mM NO3). Growth of shoots of both components in mixed culture was
measured by physical separation, and the proportions of root
biomass due to each component were calculated from [delta] 13C
values of total root biomass. In air (320 ubar CO2) at high PPFD
and with high root zone-N, the shoot biomass of C3 and C4
components at the first harvest (28 days) was in proportion to the
sowing ratio. However, by the second harvest (36 days) the C4
component predominated in both mixtures. Under the same conditions,
but with low PPFD, C3 plants predominated at the first harvest but
C4 plants had overtaken them by the time of the second harvest.
Elevated atmospheric CO2 (640 ubar) stimulated shoot growth of
Triticum in 15 of 16 treatment combinations and the stimulation was
greatest in plants provided with low NO3. Root growth of the C3
plants was generally stimulated by elevated CO2, but was only
occasionally sensitive to the presence of C4 plants in mixed
culture. However, growth of the C4 plants was often sensitive to
the presence of C3 plants in mixed culture. In mixed cultures,
elevated CO2 plants stimulated growth of C4 plants at high PPFD,
high-N and in all low-N treatments but this was insufficient to
offset a marked decline in shoot growth with increasing proportion
of C3 plants in mixed cultures. The unexpected stimulation of
growth of C4 plants by elevated CO2 was correlated with more
negative [delta] 13C values of C4 root biomass, suggesting a
partial failure of the CO2 concentrating mechanism of C4
photosynthesis in Echinochloa under low-N. These experiments show
that for these species nitrogen was more important than light or
elevated pCO2 in determining the extent of competitive interactions
in mixed culture.

Triticum aestivum/wheat/Echinochloa frumentacea/Japanese millet

KEYWORDS: C3, C4, GREENHOUSE, GROWTH, ISOTOPE DISCRIMINATION,
LIGHT, NITROGEN, NUTRITION, PLANT-PLANT INTERACTIONS, ROOT:SHOOT
RATIO, ROOTS

768  
Wong, S.-C. 1993. Interaction between Elevated Atmospheric Partial
Pressure of CO2 and Humidity on Plant Growth: Comparison between
Cotton and Radish. Vegetatio 104/105:211-221.

Cotton plants (Gossypium hirsutum L. var Deltapine 90) and radish
plants (Raphanus sativus L. var Round Red) were grown under full
sunlight using a factorial combination of atmospheric CO2
concentrations (350 umol/mol and 700 umol/mol) and humidities (35%
and 90% RH at 32C during the day). Cotton plants showed large
responses to increased humidity and to doubled CO2. In cotton
plants, the enhanced dry matter yield due to doubled CO2
concentration was 1.6-fold greater at low humidity than at high
humidity. Apart from the direct effect of elevated CO2 level on
photosynthesis, the greater effect of doubled CO2 concentration on
dry matter yield at low humidity was probably due to: (1) increased
leaf water potential caused by reduction of transpiration resulting
from the negative CO2 response of stomata to increased CO2
concentration the consequence being greater leaf area expansion;
(2) reduction of CO2 assimilation rate at low humidity and normal
CO2 concentration as a result of humidity response of stomata
causing reduction of intercellular CO2 concentration. In contrast,
apart from the very early stage of development, radish plants do
not respond to increased humidity but had a relatively large
response to doubled CO2 concentration. Furthermore, due to the
determinate growth pattern as well as having a prominent storage
root, the extra photoassimilate derived at doubled CO2 level is
allocated to the storage root.

Gossypium hirsutum/cotton/Raphanus sativus/radish

KEYWORDS: CONDUCTANCE, GREENHOUSE, GROWTH ANALYSIS, HUMIDITY, LEAF
AREA DEVELOPMENT, STOMATA, VPD, WATER STATUS

769  
Wong, S.-C., and F.X. Dunin. 1987. Photosynthesis and Transpiration
of Trees in a Eucalypt Forest Stand: CO2, Light and Humidity
Responses. Australian Journal of Plant Physiology 14:619-632.

Exchange of water vapour and CO2 was measured on a small group of
trees in a 12-year-old regenerating forest dominated by Eucalyptus
spp. in Kioloa State Forest, south-eastern New South Wales. The
trees were growing in a weighing lysimeter (10.3 m2 ground area)
with the dominant tree about 10 m high. A 12 m high enclosure made
of polyethylene film was erected to enclose the trees on the
lysimeter. Air was impelled in from the bottom of the enclosure by
four fans at a total flow rate of 4.6 m3/s. Air samples for
infrared gas analysers were taken 1, 4, 7 and 10 m above the
ground. Pure CO2 (up to 1000 litres/min) was injected to obtain the
response of rates of photosynthesis and transpiration at various
levels of CO2 in the enclosure environment. At normal ambient
partial pressure of CO2, the photosynthetic rate of the canopy (28
umol/m2 ground area/s) was found to be saturated at about half of
full sunlight. At midday, the foliage in the layers 1-4 m, 4-7 m
and 7-10 m from the ground level contributed 10.7, 44.3, and 34% of
the total carbon assimilated by the canopy, respectively. Canopy
conductance was reduced with increasing vapour pressure difference
between leaves and the air on the basis that internal partial
pressure of CO2 was decreased. Light intensity required to saturate
photosynthesis increased with increasing ambient partial pressure
of CO2. At 680 ubar ambient partial pressure of CO2 and at
saturating light intensity, there was a 50% increase in
photosynthetic rate and a 30% reduction in transpiration rate,
resulting in a reduction in transpiration ratio of 80%. The
apparent quantum yield derived at 340 and 680 ubar CO2 was 0.049
and 0.071, respectively. The light compensation point also
decreased at higher ambient partial pressure of CO2.

Eucalyptus spp.

KEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, FOREST, HUMIDITY,
LIGHT, QUANTUM REQUIREMENT, TRANSPIRATION

770  
Woodrow, L., and B. Grodzinski. 1987. Photosynthetic Gas Exchange,
Photoassimilate Partitioning, and Development in Tomato under CO2
Enrichment. IN: Progress in Photosynthesis Research, Vol. III (J.
Biggens, ed.), Martinus Nijhoff Publishers, Dordrecht, pp.
III.9.653-III.9.656.

tomato/Lycopersicon esculentum

KEYWORDS: AMINO ACIDS, CARBOHYDRATES, ETHYLENE, GREENHOUSE,
HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS, METABOLITES,
PARTITIONING, RESPIRATION, TRANSPIRATION

771  
Woodrow, L., and B. Grodzinski. 1993. Ethylene Exchange in
Lycopersicon esculentum Mill. Leaves during Short-and Long-term
Exposures to CO2. Journal of Experimental Botany 44:471-480.

The effects of long-term and transient exposure to elevated CO2
concentrations on photosynthetic gas exchange and ethylene release
by tomato leaves were investigated. The net CO2 assimilation rate
was enhanced when leaf tissue grown at ambient (35 Pa CO2) levels
was assayed at 100 Pa CO2. Leaf tissue grown at high (130 Pa) CO2
exhibited a lower net CO2 assimilation rate at high CO2 levels than
leaf tissue grown at ambient (35 Pa) CO2. This decrease in CO2
exchange rate in response to growth at high CO2 is typical of C3
species. Rates of endogenous and 1-aminocyclopropane-1-carboxylic
acid (ACC)-stimulated ethylene release from leaf tissue were
enhanced by exposure to elevated CO2 levels whether the leaf tissue
had been grown at ambient or enriched CO2 levels. The data
demonstrate that CO2 enhanced C2H4 release from leaf tissue in
response to both short-term perturbations in CO2 concentration and
long-term growth and development under high CO2. Prolonged growth
at elevated CO2 concentrations induced a higher endogenous rate of
C2H4 release relative to that of leaf tissue grown at lower CO2
levels. Leaf tissue from all leaf positions of plants grown at high
CO2 consistently evolved more C2H4 than corresponding tissue from
ambient-grown plants when assayed under standardized conditions.
Endogenous (ACC) tissue contents and rates of ACC-stimulated
ethylene release were also higher at all leaf positions in CO2-enriched tissue. Thus the higher rates appeared to be due to both
higher endogenous precursor (ACC) levels in the tissue and greater
ACC to C2H4 conversion capacity. Growth at elevated CO2 levels
resulted in a persistent increase in the rate of endogenous C2H4
release in leaf tissue. The capacity for increased ethylene release
in response to CO2 did not decline after prolonged growth at high
CO2.

tomato/Lycopersicon esculentum

KEYWORDS: ETHYLENE, LEAF PHOTOSYNTHESIS, MORPHOLOGY, SUNLIT
CONTROLLED ENVIRONMENT CHAMBERS

772  
Woodward, F.I. 1986. Ecophysiological Studies on the Shrub
Vaccinium myrtillus L. Taken from a Wide Altitudinal Range.
Oecologia 70:580-586.

Observations have been made on the gas exchange and morphology of
Vaccinium myrtillus taken from altitudes of 200 m, 610 m and 1,100
m along an altitudinal gradient in central Scotland. Under
saturating irradiance, optimum temperatures and a range of vapour
pressure deficits, photosynthetic rate and stomatal conductance
increased with the altitude of origins of the populations.
Correlated with these increases was an increase in the adaxial
stomatal density with altitude. This response to altitude could be
simulated in controlled conditions, by growing plants in a CO2
concentration below ambient, similar to that expected at altitude.
Plant height decreased with altitude, a feature which was
maintained in cultivation. Stem rigidity declined with altitude, in
a manner which is predicted to limit the reproductive capacity of
the population from 1,100 m in high wind speeds. Total leaf
nitrogen increased with altitude. The nitrogen economy of the shoot
is discussed in terms of nitrogen availability for stems and leaves
and its control over maximum rates of photosynthesis, competitive
ability and reproductive capacity.

Vaccinium myrtillus

KEYWORDS: ALTITUDE, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
LEAF PHOTOSYNTHESIS, MORPHOLOGY, NITROGEN, PRE-INDUSTRIAL CO2
CONCENTRATION, STOMATAL DENSITY

773  
Woodward, F.I. 1987. Stomatal Numbers Are Sensitive to Increases in
CO2 from Pre-industrial Levels. Nature 327:617-618.

Recent measurements of atmospheric CO2 levels in ice cores have
shown that global CO2 has increased by about 60 umol/mol over the
past 200 years. Evidence for the response of plants in the field to
this change in CO2 levels is here presented in the form of a
significant change in stomatal density -- an anatomical response of
considerable ecophysiological importance. A 40% decrease in density
of stomata was observed in herbarium specimens of leaves of eight
temperate arboreal species collected over the last 200 years. This
decline was confirmed for some of the species observed as herbarium
specimens by experiments under controlled environmental conditions.
In these an increase in the mole fraction of CO2 from 280 umol/mol
to the current ambient level of 340 umol/mol was found to cause a
decrease in stomatal density of 67%. Experiments have shown that
the combination of this previously unreported response of stomatal
density to the level of CO2 with the known responses of stomatal
aperture, cause water use efficiency to be much lower than expected
at low CO2 and over a wide range of humidities.

Acer pseudoplatanus/sycamore maple/Quercus robur/Rhamnus
catharticus/Rumex crispus/curly dock

KEYWORDS: HERBARIUM SPECIMENS, PRE-INDUSTRIAL CO2 CONCENTRATION,
STOMATAL DENSITY, STOMATAL INDEX

774  
Woodward, F.I. 1990. Global Change: Translating Plant
Ecophysiological Responses to Ecosystems. Tree 5:308-311.

The physiological responses of plants to elevated CO2 have been
incorporated into most models of ecosystem function under changed
climate. These responses are now well documented, and recent work
demonstrates that they can be readily included in ecosystem models.
Simulations show that the effects of elevated CO2 levels on
transpiration and gas exchange will increase the sensitivity of
community structure (particularly of forests) to climate change.

KEYWORDS: CLIMATE CHANGE, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST,
MODELING, PHOTOSYNTHETIC ACCLIMATION, REVIEW, SCALING, SIMULATION,
TRANSPIRATION

775  
Woodward, F.I. 1993. Plant Responses to Past Concentrations of CO2.
Vegetatio 104/105:145-155.

The influence of recent historical changes in atmospheric CO2 have
been investigated by two methods: 1, the responses of leaf
development and physiology as indicated by leaves stored in
herbaria and 2, by investigating the differential growth responses
of populations originating from naturally different CO2
concentrations. Herbarium leaves indicate that stomatal density and
leaf nitrogen have decreased over the last 150 to 200 years, while
water use efficiency, estimated from leaf delta 13 and historical
measurements of climate, has increased. Natural populations of
Boehmeria cylindrica were found growing at sites, in Florida, with
CO2 mole fractions varying naturally from 350 umol/mol to 505
umol/mol. Plants were grown in the controlled environment, using
seeds originating from populations occurring in the different CO2
mole fractions. Plants from the different ambient CO2 mole
fractions showed different rates of growth and different non-linear
responses of the shoot to root ratio in response to changes in the
CO2 mole fraction from 350 to 675 umol/mol. The proposal that
plants originating from high altitude will show greater
stimulations of growth with an increase in CO2, than plants from
low altitude, was rejected in experiments which simulated the
atmospheric pressure at altitudes of 0 and 2000 m at CO2 mole
fractions of 350 and 700 umol/mol and on populations of Plantago
major originating from altitudes of 0 and 3335 m.

Plantago major/broadleaf plantain/Boehmeria cylindrica

KEYWORDS: ALTITUDE, CONTROLLED ENVIRONMENT CHAMBERS, ISOTOPE
DISCRIMINATION, POPULATION LEVEL CO2 RESPONSES, PRE-INDUSTRIAL CO2
CONCENTRATION, STOMATA, WUE

776  
Woodward, F.I., and F.A. Bazzaz. 1988. The Response of Stomatal
Density to CO2 Partial Pressure. Journal of Experimental Botany
39:1771-1781.

Experiments on a range of species of tree, shrub and herb have
shown that stomatal density and stomatal index increase as the
partial pressure of CO2 decreases over the range from the current
level of 34 Pa to 22.5 Pa. Stomatal density responds to the reduced
partial pressure of CO2 in a simulation of high altitude (3000 m),
when the CO2 mole fraction is unchanged. When the partial pressure
of CO2 is increased from 35 to 70 Pa stomatal density decreases
slightly, with a response to unit change in CO2 which is about 10%
of that below 34 Pa. Measurements of gas exchange on leaves which
had developed in different CO2 partial pressures, but at low
saturation vapour pressure deficits in the range of 0.7 to 0.9 kPa,
indicated lower photosynthetic rates but higher stomatal
conductances at reduced CO2 partial pressures. Experiments on
populations of Nardus stricta originating from altitudes of 366 m
and 810 m in Scotland, indicated genetic difference in the response
of stomatal density to CO2 in pressures simulating altitudes of sea
level and 2000 m. Plants from the higher altitude showed greater
declines in stomatal density when the CO2 partial pressure was
increased.

Nardus stricta/Geum urbanum/Rumex crispus/curly dock/Acer
pseudoplatanus/sycamore maple/Quercus robur/Rhamnus
catharticus/Amaranthus retroflexus/Ambrosia artemisiifolia/Setaria
faberii

KEYWORDS: ALTITUDE, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
LEAF PHOTOSYNTHESIS, STOMATAL DENSITY, STOMATAL INDEX, VPD

777  
Woodward, F.I., G.B. Thompson, and I.F. McKee. 1991. The Effects of
Elevated Concentrations of Carbon Dioxide on Individual Plants,
Populations, Communities and Ecosystems. Annals of Botany 67
(Supplement 1):23-28.

Changes in the atmospheric concentration of CO2, over periods of
millennia, are positively correlated with the temperature of the
world. It is expected that this positive correlation will be
manifested in the future, warmer 'greenhouse world' with higher
concentrations of CO2. The predicted changes in temperature and
precipitation are expected to cause significant changes in the
distribution patterns of the world's terrestrial vegetation
(Woodward and McKee, 1991). In addition to this indirect effect,
CO2 influences plants directly and an increase in the concentration
of CO2 may increase the rate of photosynthesis in plants with the
C3 pathway of fixation. Experimental observations often differ in
the degree and length of this stimulation, reflecting the stronger
impact of other photosynthetic limitations. Where photosynthetic
stimulation does occur there is a general decrease in leaf protein,
which may stimulate rates of leaf herbivory. The well established
and associated increase in the C/N ratio of individual leaves
should reduce rates of leaf decomposition. However the few
community experiments at elevated CO2 suggest little change in the
rate of nutrient cycling in communities. Stomatal opening is
generally reduced as CO2 concentration increases. This feature
scales up through to the community level, however, it appears that
the total volume of water used by a community is unlikely to alter
with CO2 alone, because plants tend to develop leafier canopies.
This change, plus enhanced rates of root development, indicate a
greater potential for carbon sequestration by terrestrial
ecosystems. Monthly observations of atmospheric CO2 concentration
above the tundra over the last 14 years indicate these expected
increases in the rates of CO2 drawdown by the northern ecosystems
of the tundra and the boreal and temperate deciduous forests.
However, some of this change may be due to interactions with the
warmer climate of the 1980s and perhaps an increased aerial supply
of pollutant nitrogen.

KEYWORDS: C3, C4, CANOPY PHOTOSYNTHESIS, CARBON:NITROGEN RATIO,
COMMUNITY LEVEL CO2 RESPONSES, CONDUCTANCE, ECOSYSTEM LEVEL CO2
RESPONSES, HERBIVORY, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC
ACCLIMATION, PHYSIOLOGICAL CO2 RESPONSES, POPULATION LEVEL CO2
RESPONSES, REPRODUCTION, REVIEW, SCALING, WUE

778  
Wray, S.M. 1987. Competitive Interactions of Two Old-field
Perennials, Aster pilosus and Andropogon virginicus under Carbon-dioxide Enrichment. Doctoral Dissertation, Duke University,
Dissertation Abstracts Vol. 48:05-B, p.1232 (180 pp.).

Differential response of species to CO2 enrichment may change
future community structure in natural ecosystems. In old fields of
the North Carolina Piedmont, aster (Aster pilosus Willd., C3) is
usually the dominant perennial two years after abandonment.
Broomsedge (Andropogon virginicus L., C4) outcompetes and replaces
aster during the next several years. When grown individually, aster
responds positively to CO2 enrichment, whereas broomsedge does not.
Thus it was hypothesized that the competitive interaction between
these species would change if the atmospheric CO2 concentration was
increased. Aster and broomsedge were grown in simplified de Wit
replacement series experiments in the Duke Phytotron at 350, 500
and 650 uL/L CO2. The suppression of broomsedge by aster was always
greater with CO2 enrichment so that broomsedge grown with aster had
69% less dry weight than in monoculture at 650 uL/L CO2. Aster had
49% more dry weight when grown with broomsedge than in monoculture
at 650 uL/L CO2. Broomsedge was more drought tolerant than aster
and under ambient conditions had a higher water use efficiency.
However, under water-limited conditions, broomsedge was not a
stronger competitor than aster. With CO2 enrichment aster comprised
75% of total pot biomass under both water-limited and well-watered
conditions. There could also be competition between established
broomsedge and a second generation of aster seedlings in old
fields. In the Phytotron when broomsedge was grown for six weeks
before aster emerged, aster seedlings did not suppress the growth
of broomsedge even with CO2 enrichment. These studies have shown
that competitive interactions between these old-field perennials
change under CO2 enrichment when grown in a controlled environment.
Future increases in atmospheric CO2 concentration may slow the rate
of succession in old fields under both drought and nondrought
conditions. However, aster will not necessarily eliminate
broomsedge from the perennial herbaceous community as broomsedge
ultimately will reach a size where competition with aster seedlings
does not delay its growth. It is hoped that these studies will
contribute to the understanding of the dynamics of community
structure in the face of environmental change.

Aster pilosus/aster/Andropogon virginicus/broomsedge

KEYWORDS: C3, C4, CONTROLLED ENVIRONMENT CHAMBERS, OLD FIELD
COMMUNITIES, SPECIES COMPETITION, SUCCESSIONAL COMMUNITIES, WATER
STRESS

779  
Wray, S.M., and B.R. Strain. 1986. Response of Two Old Field
Perennials to Interactions of CO2 Enrichment and Drought Stress.
American Journal of Botany 73:1486-1491.

Aster pilosus Willd. (aster, C3) and Andropogon virginicus L.
(broomsedge, C4) were grown in growth chambers at 26/20 C day/night
temperatures with a PPFD of 1,000 umol/s/m2. Water was withheld for
a 2-wk drought period under three CO2 concentrations (approximately
380, 500, and 650 uL/L). There were significant effects of CO2
enrichment on aster so that drought stress did not occur in plants
grown with CO2 enrichment. Non-watered plants with CO2 enrichment
had greater leaf water potentials, greater photosynthetic rates,
and greater total dry wt than non-watered plants grown at 380 uL/L
CO2. The response of broomsedge to drought was the same in all CO2
treatments and there was no significant interaction of CO2
enrichment and drought. The decreased severity of drought stress
and the increased growth of aster with CO2 enrichment may increase
its competitive ability during droughts, allowing it to persist for
longer periods during succession in abandoned fields.

Aster pilosus/aster/Andropogon virginicus/broomsedge

KEYWORDS: C3, C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS,
LEAF PHOTOSYNTHESIS, SUCCESSIONAL COMMUNITIES, WATER STATUS, WATER
STRESS

780  
Wray, S.M., and B.R. Strain. 1987. Competition in Old-field
Perennials under CO2 Enrichment. Ecology 68:1116-1120.

Differential response of individual species to increasing
atmospheric CO2 concentrations may change community structure in
natural ecosystems. Some species of old-field annuals show
increases in competitive potential under exposure to increased CO2
concentrations so that their relative contribution to community
production increases. Species with the C3 photosynthetic pathway
typically increase, whereas species with the C4 photosynthetic
pathway decrease in size and absolute contribution to community
production (Bazzaz and Carlson 1984, Zangerl and Bazzaz 1984).
Aster pilosus (aster), a species with the C3 photosynthetic
pathway, is often the dominant perennial in fields 2-3 yr after
abandonment. Andropogon virginicus (broomsedge), a grass species
with the C4 photosynthetic pathway, outcompetes and replaces aster
during the next several years (Keever 1950). When grown
individually, aster increases in size, whereas broomsedge does not
increase under CO2 enrichment (Wray and Strain 1986). Thus, the
present competitive interaction between these species could change
if the atmospheric CO2 concentration continues to increase. A
simplified de Wit Replacement Series (de Wit 1960, Harper 1977) was
used to study the competitive interaction between aster and
broomsedge under three CO2 regimes.

Aster pilosus/aster/Andropogon virginicus/broomsedge

KEYWORDS: C3, C4, CONTROLLED ENVIRONMENT CHAMBERS, OLD FIELD
COMMUNITIES, SPECIES COMPETITION, SUCCESSIONAL COMMUNITIES

781  
Wray, S.M., and B.R. Strain. 1987. Interaction of Age and
Competition under CO2 Enrichment. Functional Ecology 1:145-149.

Typically, Andropogon virginicus L. (broomsedge, C4) replaces Aster
pilosus Willdenow (aster, C3) in old-field succession in the North
Carolina Piedmont, USA. The current work was designed to see how
this situation may change under elevated CO2 concentrations in the
future. Aster and broomsedge were grown in a modified deWit
Replacement Series under 350, 500 and 650 uL/L CO2. Aster was added
to the pots 6 weeks after broomsedge emerged and all plants were
harvested 6 weeks after aster emerged. The C4 species, broomsedge,
did not respond to CO2 enrichment, but leaf area and dry weight of
the C3 aster were greater at 650 than at 350 uL/L CO2. Aster did
not suppress established broomsedge plants at any CO2 level. After
6 weeks broomsedge reached a size where competition with aster
seedlings did not delay its growth in controlled environments.
Future increases in atmospheric CO2 concentrations may slow the
rate of succession in old fields, but will not necessarily
eliminate broomsedge from the composition of the perennial
herbaceous community.

Andropogon virginicus/broomsedge/Aster pilosus/aster

KEYWORDS: C3, C4, CONTROLLED ENVIRONMENT CHAMBERS, OLD FIELD
COMMUNITIES, SPECIES COMPETITION, SUCCESSIONAL COMMUNITIES

782  
Wullschleger, S.D., and R.J. Norby. 1992. Respiratory Cost of Leaf
Growth and Maintenance in White Oak Saplings Exposed to Atmospheric
CO2 Enrichment. Canadian Journal of Forest Research 22:1717-1721.

Atmospheric CO2 enrichment reportedly reduces respiration of mature
leaves in a number of woody and herbaceous perennials. It has yet
to be determined, however, whether these reductions reflect changes
in maintenance respiration alone or whether CO2 might affect growth
respiration as well. This possibility was examined in white oak
(Quercus alba L.) seedlings that had been planted directly into the
ground within open-top chambers and exposed to ambient, ambient +
150 uL/L, and ambient + 300 uL/L CO2 concentrations over a 3-year
period. In the spring of 1992, respiration rates were measured
repeatedly during leaf expansion, and the growth and maintenance
coefficients were determined using a two-component model. Specific
respiration rates (mg CO2/g/h) were consistently lower for leaves
of CO2-enriched saplings than for leaves of ambient-grown saplings.
Partitioning these reductions in leaf respiration to either the
growth or maintenance coefficients indicated a strong effect of CO2
on both components. The growth coefficient for leaves exposed to
the ambient CO2 treatment was 964 mg CO2/g compared with 849 and
664 mg CO2/g for leaves from the two elevated CO2 concentrations,
respectively. The maintenance coefficient was similarly reduced
from a control rate of 114 mg CO2/g/d to below 65 mg CO2/g/d for
leaves exposed to CO2 enrichment. Our results quantitatively
describe the magnitude by which growth and maintenance respiration
are affected by CO2 enrichment and as such should provide useful
information for the future modeling of this phenomenon.

Quercus alba/white oak

KEYWORDS: OPEN-TOP CHAMBERS, RESPIRATION, TREES

783  
Wullschleger, S.D., R.J. Norby, and C.A. Gunderson. 1992. Growth
and Maintenance Respiration in Leaves of Liriodendron tulipifera L.
Exposed to Long-term Carbon Dioxide Enrichment in the Field. New
Phytologist 21:515-523.

Specific respiration rate (SRR) was mathematically partitioned into
its growth and maintenance components for leaves of yellow-poplar
(Liriodendron tulipifera L.) after 3 yr of CO2 enrichment in open-top field chambers. Despite the absence of a CO2 effect on
individual leaf expansion or specific growth rate (SGR), increasing
the CO2 concentration to ambient +150 or +300 cm3/m3 decreased SRR
by 28 to 45% compared with ambient-grown controls. These lower leaf
respiration rates were correlated with reduced leaf nitrogen
concentrations. As described by the two-component model of growth
and maintenance respiration, SRR was a linear function of SGR.
Ambient-grown leaves had a growth respiration coefficient of 704 mg
CO2/g dry mass compared with 572 and 570 mg CO2/g for leaves grown
at the two higher CO2 concentrations. Leaves from the elevated CO2
treatments had an average maintenance respiration coefficient of 88
mg CO2/g dry mass/d compared with 135 mg CO2/g/d for leaves from
the ambient treatment. Incorporating these growth and maintenance
coefficients into a leaf growth simulation model indicated that
total respiration would be reduced by 21 to 26% for a leaf exposed
to +150 or +300 cm3/m3 CO2 throughout its 50-d lifespan compared
with one grown at ambient CO2 conditions. Reductions in total
respiration were dominated by a lower rate of maintenance
respiration, while the contribution of a lower specific rate of
growth respiration was largely offset by a greater dry mass for
leaves grown at elevated CO2 concentrations. Although reductions in
the respiratory loss of carbon could be beneficial, respiration is
unlikely to decrease without a concomitant decrease in other
metabolic processes. Whether these reductions are beneficial or
detrimental to the long-term growth of plants exposed to elevated
CO2 remains unresolved.

Liriodendron tulipifera/tulip poplar/yellow poplar

KEYWORDS: GROWTH ANALYSIS, MODELING, NITROGEN, OPEN-TOP CHAMBERS,
RESPIRATION, TREES

784  
Wullschleger, S.D., R.J. Norby, and D.L. Hendrix. 1992. Carbon
Exchange Rates, Chlorophyll Content, and Carbohydrate Status of Two
Forest Tree Species Exposed to Carbon Dioxide Enrichment. Tree
Physiology 10:21-31.

Seedlings of yellow-poplar (Liriodendron tulipifera L.) and white
oak (Quercus alba L.) were exposed continuously to one of three CO2
concentrations in open-top chambers under field conditions and
evaluated after 24 weeks with respect to carbon exchange rates
(CER), chlorophyll (Chl) content, and diurnal carbohydrate status.
Increasing the CO2 concentration from ambient to +150 or +300 uL/L
stimulated CER of yellow-poplar and white oak seedlings by 60 and
over 35%, respectively, compared to ambient-grown seedlings. The
increases in CER were not associated with a significant change in
stomatal conductance and occurred despite a reduction in the
amounts of Chl and accessory pigments in the leaves of plants grown
in CO2-enriched air. Total Chl contents of yellow-poplar and white
oak seedlings grown at +300 uL/L were reduced by 27 and over 55%,
respectively, compared with ambient-grown seedlings. Yellow-poplar
and white oak seedlings grown at +300 uL/L contained 72 and 67%
more morning starch, respectively, than did ambient-grown plants.
In contrast, yellow-poplar and white oak seedlings grown at +300
uL/L contained 17 and 27% less evening sucrose, respectively, than
did plants grown at ambient CO2 concentration. Diurnal starch
accumulation and the subsequent depletion of sucrose contributed to
a pronounced increase in the starch/sucrose ratio of plants grown
in CO2-enriched air. All seedlings exhibited a substantial
reduction in dark respiration as CO2 concentration increased, but
the significance of this increase to the carbohydrate status and
carbon economy of plants grown in CO2-enriched air remains unclear.

Liriodendron tulipifera/yellow poplar/tulip poplar/Quercus
alba/white oak

KEYWORDS: CARBOHYDRATES, CI:CA, CONDUCTANCE, DIURNAL CYCLE, LEAF
PHOTOSYNTHESIS, OPEN-TOP CHAMBERS, PARTITIONING, PIGMENTS,
RESPIRATION, TREES

785  
Yacoub, A.S., and C.H.M. van Bavel. 1991. Relationships Between
Stomatal Resistance and CO2 Level Around and Inside Leaves of
Greenhouse Tomatoes. HortScience 26:72.

tomato/Lycopersicon esculentum

KEYWORDS: CI:CA, CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS

786  
Yandell, B.S., A. Najar, R. Wheeler, and T.W. Tibbitts. 1988.
Modeling the Effects of Light, Carbon Dioxide, and Temperature on
the Growth of Potato. Crop Science 28:811-818.

This study examined the effects of light, temperature and carbon
dioxide on the growth of potato (Solanum tuberosum L.) in a
controlled environment in order to ascertain the best growing
conditions for potato in life support systems in space. 'Norland'
and 'Russet Burbank' were grown in 6-L pots of peat-vermiculite for
56 d in growth chambers at the University of Wisconsin Biotron.
Environmental factor levels included continuous light (24-h
photoperiod) at 250, 400, and 550 umol/m2/s PPF; constant
temperature at 16, 20, and 24C; and CO2 at approximately 400, 1000
and 1600 uL/L. Separate effects analysis and ridge analysis
provided a means to examine the effects of individual environmental
factors and to determine combinations of factors that are expected
to give the best increases in yields over the central design point.
The response surface of Norland indicated that tuber yields were
highest with moderately low temperature (18.7C), low CO2 (400
uL/L) and high light (550 umol/m2/s PPF). These conditions also
favored shorter stem growth. Russet Burbank tuber yields were
highest at moderately low temperature (17.5C), high CO2 (1600
uL/L) and medium light (455 umol/m2/s PPF). Models generated from
these analyses will be used to project the most efficient
conditions for growth of potatoes in closed ecological life support
systems (CELSS) in space colonies.

Solanum tuberosum/potato

KEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS,
ENVIRONMENTAL INTERACTIONS, LIGHT, TEMPERATURE, YIELD

787  
Yelle, S., R.C. Beeson Jr., M.J. Trudel, and A. Gosselin. 1989.
Acclimation of Two Tomato Species to High Atmospheric CO2. I. Sugar
and Starch Concentrations. Plant Physiology 90:1465-1472.

Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon
chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations
(330 or 900 microliters per liter) for 10 weeks. Tomato plants
grown at 900 microliters per liter contained more starch and more
sugars than the control. However, we found no significant
accumulation of starch and sugars in the young leaves of L.
esculentum exposed to high CO2. Carbon exchange rates were
significantly higher in CO2-enriched plants for the first few weeks
of treatment but thereafter decreased as tomato plants acclimated
to high atmospheric CO2. This indicates that the long-term decline
of photosynthetic efficiency of leaf 5 cannot be attributed to an
accumulation of sugar and/or starch. The average concentration of
starch in leaves 5 and 9 was always higher in L. esculentum than in
L. chmielewskii (151.7% higher). A higher proportion of
photosynthates was directed into starch for L. esculentum than for
L. chmielewskii. However, these characteristics did not improve the
long-term photosynthetic efficiency of L chmielewskii grown at high
CO2 when compared with L. esculentum. The chloroplasts of tomato
plants exposed to the higher CO2 concentration exhibited a marked
accumulation of starch. The results reported here suggest that
starch and/or sugar accumulation under high CO2 cannot entirely
explain the loss of photosynthetic efficiency of high CO2-grown
plants.

Lycopersicon esculentum/tomato/Lycopersicon chmielewskii

KEYWORDS: ACCLIMATION, CARBOHYDRATES, GREENHOUSE, HYDROPONIC
CULTURE, LEAF PHOTOSYNTHESIS, PARTITIONING

788  
Yelle, S., R.C. Beeson Jr., M.J. Trudel, and A. Gosselin. 1989.
Acclimation of Two Tomato Species to High Atmospheric CO2. II.
Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase and
Phosphoenolpyruvate Carboxylase. Plant Physiology 90:1473-1477.

Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon
chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations
(330 or 900 microliters per liter) for 10 weeks. The elevated CO2
concentrations increased the initial ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco) activity of both species for the
first 5 weeks of treatment but the difference did not persist
during the last 5 weeks. The activity of Mg2+-CO2-activated Rubisco
was higher in 900 microliters per liter for the first 2 weeks but
declined sharply thereafter. After 10 weeks, leaves grown at 330
microliters per liter CO2 had about twice the Rubisco activity
compared with those grown at 900 microliters per liter CO2. The two
species showed the same trend to Rubisco declines under high CO2
concentrations. The percent activation of Rubisco was always higher
under high CO2. The phosphoenolpyruvate carboxylase (PEPCase)
activity measured in tomato leaves averaged 7.9% of the total
Rubisco. PEPCase showed a similar trend with time as the initial
Rubisco but with no significant difference between nonenrichment
and CO2-enriched plants. Long-term exposure of tomato plants to
high CO2 was previously shown to induce a decline of photosynthetic
efficiency. Based on the current study and on previous results, we
propose that the decline of activated Rubisco is the main cause of
the acclimation of tomato plants to high CO2 concentrations.

Lycopersicon esculentum/tomato/Lycopersicon chmielewskii

KEYWORDS: ACCLIMATION, ENZYMES, GREENHOUSE, HYDROPONIC CULTURE,
LEAF PHOTOSYNTHESIS, PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE
BISPHOSPHATE CARBOXYLASE

789  
Yelle, S., R.C. Beeson Jr., M.J. Trudel, and A. Gosselin. 1990.
Duration of CO2 Enrichment Influences Growth, Yield, and Gas
Exchange of Two Tomato Species. Journal of the American Society of
Horticultural Science 115:52-57.

Lycopersicon esculentum Mill. cv. Vedettos and Lycopersicon
chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations
(330 or 900 umol/m3) for 10 weeks. The elevated CO2 concentration
increased the relative growth rate (RGR) of L. esculentum and L.
chmielewskii by 18% and 30%, respectively, after 2 weeks of
treatment. This increase was not maintained as the plant matured.
Net assimilation rate (NAR) and specific leaf weight (SLW) were
always higher in CO2-enriched plants, suggesting that assimilates
were preferentially accumulated in the leaves as reserves rather
than contributing to leaf expansion. Carbon dioxide enrichment
increased early and total yields of L. esculentum by 80% and 22%,
respectively. Carbon exchange rates (CER) increased during the
first few weeks, but thereafter decreased as tomato plants
acclimated to high atmospheric CO2. The relatively constant
concentration of internal CO2 with time suggests that reduced
stomatal conductance under high CO2 does not explain lower
photosynthetic rates of tomato plants grown under high atmospheric
CO2 concentrations. Leaves 5 and 9 responded equally to high CO2
enrichment throughout plant growth. Consequently, acclimation of
CO2-enriched plants was not entirely due to the age of the tissue.
After 10 weeks of treatment, leaf 5, which had been exposed to high
CO2 for only 10 days, showed the greatest acclimation of the
experiment. We conclude that the duration of exposure of the whole
plant to elevated CO2 concentration, rather than the age of the
tissue, governs the acclimation to high CO2 concentration.

Lycopersicon esculentum/tomato/Lycopersicon chmielewskii

KEYWORDS: ACCLIMATION, CO2 ENRICHMENT DURATION, CONDUCTANCE,
GREENHOUSE, GROWTH ANALYSIS, HYDROPONIC CULTURE, LEAF
PHOTOSYNTHESIS, NAR, YIELD

790  
Yelle, S., A. Gosselin, and M.-J. Trudel. 1987. Effect of
Atmospheric CO2 Concentration and Root-zone Temperature on Growth,
Mineral Nutrition, and Nitrate Reductase Activity of Greenhouse
Tomato. Journal of the American Society of Horticultural Science
112:1036-1040.

Tomato plants (Lycopersicon esculentum Mill. cvs. Vendor and
Carmelo) were exposed to two CO2 levels (330 or 800 uL/L) and five
root-zone temperatures (12, 18, 24, 30, or 36C). The
enhancement of shoot growth from CO2 enrichment increased with
root-zone temperature (RZT) to 30C. Enhancement of root growth
decreased. The response to high CO2 level was larger with 'Vendor'
than 'Carmelo'. A concentration of 800 uL/L of CO2 increased N and
K uptake by 58% and 45% respectively. The largest P uptake was
obtained with plants grown at 800 uL/L CO2 and 36 RZT. Leaf NO3
concentration decreased at 800 uL/L of CO2 and at a RZT of 12. At
low RZT, CO2 enrichment increased growth but did not increase the
translocation of NO3 to the leaf. There was no significant
relationship between nitrate reductase activity (NRA) and leaf NO3
content, implying that the 'inactive NO3' (which does not affect
NRA) was at higher levels in leaves exposed to 330 uL/L CO2 than in
those exposed to 800 uL/L CO2. There was also a decrease in N
concentration of leaves subjected to 800 uL/L CO2, possibly caused
by a reduction of NO3 transport toward leaves rather than a
decrease in NO3 reduction within leaves. Therefore, the best
response to CO2 enrichment at 30 appears to be related to
increased NO3 translocation.

Lycopersicon esculentum/tomato

KEYWORDS: CULTIVAR RESPONSES, GREENHOUSE, HYDROPONIC CULTURE,
NITRATE REDUCTASE, NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM,
ROOTS, TEMPERATURE

791  
Yelle, S., A. Gosselin, and M.-J. Trudel. 1987. Effets a Long Terme
de l'Enrichissement Carbone sur la Tomate de Serre Cultivee avec ou
sans Eclairage d'Appoint. Canadian Journal of Plant Science 67:899-907.

Tomato (Lycopersicon esculentum Mill. 'Vedettos') was grown under
three different concentrations of atmospheric CO2 (330, 900 and
1500 ppm) and two lighting intensities (natural and natural plus 30
W/m2 PAR) provided by high-pressure sodium lights (HPS). Results
show a reduction in CO2 efficiency after eight weeks of enrichment.
The higher the CO2 concentration, the more serious is this
reduction. Our results show the potential of CO2 enrichment and
supplementary lighting as well as their synergetic effect on
productivity (yield increases of 32, 73 and 122%, respectively).
Supplementary lighting does not compensate for the reduction of CO2
efficiency. Concentrations of 900 and 1500 ppm increased the
plants' water-use efficiency. In French.

Lycopersicon esculentum/tomato

KEYWORDS: GREENHOUSE, HYDROPONIC CULTURE, LEAF PHOTOSYNTHESIS,
LIGHT, WUE, YIELD

792  
Zeroni, M., and J. Gale. 1988. Response of Sonia Roses to
Continuous Daytime CO2 Supplementation under Controlled Environment
Conditions. Australian Journal of Agricultural Research 39:863-870.

Rose plants (Rosa hybrida cv. Sonia, Syn. Sweet Promise) were
placed in growth chambers under conditions resembling winter in a
controlled environment greenhouse in the desert: mild temperature,
high incident photosynthetic photon flux density (PPFD), high air
humidity and 10.5 h daylength. Concentrations of CO2 in the air
were maintained throughout the day at 320, 600 or 1200 uL/L with
approximately 350 L/L at night. Plant growth (length, fresh and dry
weight), development (breaks, blindness), flower yield and flower
quality (flower bud diameter, fresh weight and cane length) indices
were monitored throughout three consecutive flowering cycles. CO2
supplementation caused an increase in leaf resistance to water
vapour diffusion, accompanied by a reduction in the rate of
transpiration per unit leaf area. Total leaf area increased at
higher CO2 concentrations. Water use per plant did not change.
Plant water potentials increased with rising CO2 concentrations.
Growth, development, flower yield and flower quality were greatly
enhanced in the CO2-enriched atmosphere. The response of growth and
development to CO2 supplementation tended to decrease slightly with
time when calculated per branch, but increased when calculated per
plant. Flower yield and quality did not change with time. The
highest CO2 treatment resulted in a sustained, approximately 50%
increase in yield, and doubling of the above quality indices
throughout the three growth cycles.

Rosa hybrida/rose

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, FLOWER
PRODUCTION, HORTICULTURAL CROPS, WATER STATUS

793  
Zeroni, M., and J. Gale. 1989. Response of 'Sonia' Roses to
Salinity at Three Levels of Ambient CO2. Journal of Horticultural
Science 64:503-511.

The effect of prolonged exposure of plants to a combination of both
salinity and high CO2 concentration ([CO2]) is not easy to predict.
The purpose of this work was to contribute to the clarification of
this question for roses. 'Sonia' rose plants were placed in growth
chambers for three consecutive flowering cycles, under conditions
simulating winter in a controlled environment greenhouse in the
desert. Plants were grown at three levels of [CO2] and four levels
of salinity. Plants died or stopped growing when treated with 3,436
g/m3 salt. Subsequently, the highest concentration used was 2,577
g/m3 total soluble salt. Salinity tolerance increased at high
[CO2]. Some combinations of CO2 and salt gave higher yields than
those obtained with CO2 alone, due to a decrease in blindness. This
suggests that salt, in the presence of high [CO2], changed the
distribution of assimilates. Under high [CO2], salinity did not
change plant water potential, but leaf diffusion resistance to
water vapour (r) increased. The r did not correlate well with the
measured rates of transpiration. This suggests that the r of leaves
of different ages react differently to the combination of salinity
and high [CO2]; evidently, the leaves used to measure r were not
representative of the entire plant.

Rosa hybrida/rose

KEYWORDS: CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, FLOWER
PRODUCTION, HORTICULTURAL CROPS, SALT STRESS, WATER STATUS

794  
Ziska, L.H., and J.A. Bunce. 1993. Inhibition of Whole Plant
Respiration by Elevated CO2 as Modified by Growth Temperature.
Physiologia Plantarum 87:459-466.

Plants of alfalfa (Medicago sativa) and orchard grass (Dactylus
glomerata) were grown in controlled environment chambers at two CO2
concentrations (350 and 700 umol/mol) and 4 constant day/night
growth temperatures of 15, 20, 25 and 30C for 50-90 days to
determine changes in growth and whole plant CO2 efflux (dark
respiration). To facilitate comparisons with other studies,
respiration data were expressed on the basis of leaf area, dry
weight and protein. Growth at elevated CO2 increased total plant
biomass at all temperatures relative to ambient CO2 but the
relative enhancement declined (P </= 0.05) as temperature
increased. Whole plant respiration (Rd) at elevated CO2 declined at
15 and 20C in D. glomerata on an area, weight or protein basis and
in M. sativa on a weight or protein basis when compared to ambient
CO2. Separation of Rd into respiration required for growth (Rg) and
maintenance (Rm) showed a significant effect of elevated CO2 on
both components. Rm was reduced in both species but only at lower
temperatures (15C in M. sativa and 15 and 20C in D. glomerata).
The effect on Rm could not be accounted for by protein content in
either species. Rg was also reduced with elevated CO2; however no
particular effect of temperature was observed, i.e., Rg was reduced
at 20, 25 and 30C in M. sativa and at 15 and 25C in D. glomerata.
For the two perennial species used in the present study, the data
suggest that both Rg and Rm can be reduced by anticipated increases
in atmospheric CO2; however, CO2 inhibition of total plant
respiration may decline as a function of increasing temperature.

orchardgrass/Dactylis glomerata/Medicago sativa/alfalfa

KEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, RESPIRATION, TEMPERATURE

795  
Ziska, L.H., B.G. Drake, and S. Chamberlain. 1990. Long-term
Photosynthetic Response in Single Leaves of a C3 and C4 Salt Marsh
Species Grown at Elevated Atmospheric CO2 in Situ. Oecologia
83:469-472.

Mono-specific communities of the C3 sedge, Scirpus olneyi and the
C4 grass, Spartina patens, were exposed to normal ambient or
elevated CO2 (ca. 680 uL/L) throughout the 1987 and 1988 growing
seasons in open-top field chambers located on a tidal marsh. Single
stems of C3 plants grown in ambient or elevated CO2 showed an
increased photosynthetic rate when tested at elevated CO2 for both
seasons. This increase in photosynthetic response in the C3 species
was maintained throughout the 1987 and 1988 growing season. The
stimulation of photosynthesis with elevated CO2 appeared to
increase as temperature increased and decreased as photosynthetic
photon flux (PPF) increased. Analysis of the photosynthetic
response of the C3 species during the 1988 season indicated that
significant differences in light-saturated photosynthetic rate
between ambient and elevated CO2 conditions continued until
October. In contrast to the C3 sedge, the C4 grass showed no
significant photosynthetic increase to elevated CO2 except at the
beginning of the 1988 season.

Spartina patens/Scirpus olneyi

KEYWORDS: C3, C4, GRASSES, LEAF PHOTOSYNTHESIS, OPEN-TOP CHAMBERS,
SALT MARSH, SEDGES

796  
Ziska, L.H., K.P. Hogan, A.P. Smith, and B.G. Drake. 1991. Growth
and Photosynthetic Response of Nine Tropical Species with Long-term
Exposure to Elevated Carbon Dioxide. Oecologia 86:383-389.

Seedlings of nine tropical species varying in growth and carbon
metabolism were exposed to twice the current atmospheric level of
CO2 for a 3 month period on Barro Colorado Island, Panama. A
doubling of the CO2 concentration resulted in increases in
photosynthesis and greater water use efficiency (WUE) for all
species possessing C3 metabolism, when compared to the ambient
condition. No desensitization of photosynthesis to increased CO2
was observed during the 3 month period. Significant increases in
total plant dry weight were also noted for 4 out of the 5 C3
species tested and in one CAM species, Aechmea magdalenae at high
CO2. In contrast, no significant increases in either photosynthesis
or total plant dry weight were noted for the C4 grass, Paspallum
conjugatum. Increases in the apparent quantum efficiency (AQE) for
all C3 species suggest that elevated CO2 may increase
photosynthetic rate relative to ambienbt CO2 over a wide range of
light conditions. The response of CO2 assimilation to internal Ci
suggested a reduction in either the RuBP and/or Pi regeneration
limitation with long term exposure to elevated CO2. This experiment
suggests that: (a) a global raise in CO2 may have significant
effects on photosynthesis and productivity in a wide variety of
tropical species, and (2) increases in productivity and
photosynthesis may be related to physiological adaptation(s) to
increased CO2.

Ananas comosus/pineapple/Aechmea magdalenae/Pharus
latifolia/Paspallum conjugatum/Manihot esculentum/cassava/Ficus
obtusifolia/Psychotria limonensis/Tabebuia rosea/Acacia mangium

KEYWORDS: ALLOCATION, C3, C4, CAM, CARBOXYLATION EFFICIENCY, LEAF
AREA DEVELOPMENT, LEAF PHOTOSYNTHESIS, LIGHT, OPEN-TOP CHAMBERS,
QUANTUM REQUIREMENT, ROOT:SHOOT RATIO, TROPICAL PLANTS, WUE

797  
Ziska, L.H., and A.H. Teramura. 1992. CO2 Enhancement of Growth and
Photosynthesis in Rice (Oryza sativa). Modification by Increased
Ultraviolet-B Radiation. Plant Physiology 99:473-481.

Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were
grown at ambient (360 microbars) and elevated CO2 (660 microbars)
from germination through reproduction in unshaded greenhouses at
the Duke University Phytotron. Growth at elevated CO2 resulted in
significant decreases in nighttime respiration and increases in
photosynthesis, total biomass, and yield for both cultivars.
However, in plants exposed to simultaneous increases in CO2 and
ultraviolet-B (UV-B) radiation, CO2 enhancement effects on
respiration, photosynthesis, and biomass were eliminated in IR-36
and significantly reduced in Fujiyama-5. UV-B radiation simulated
a 25% depletion in stratospheric ozone at Durham, North Carolina.
Analysis of the response of CO2 uptake to internal CO2
concentration at light saturation suggested that, for IR-36, the
predominant limitation to photosynthesis with increased UV-B
radiation was the capacity for regeneration of ribulose
bisphosphate (RuBP), whereas for Fujiyama-5 the primary
photosynthetic decrease appeared to be related to a decline in
apparent carboxylation efficiency. Changes in the RuBP regeneration
limitation in IR-36 were consistent with damage to the
photochemical efficiency of photosystem II as estimated from the
ratio of variable to maximum chlorophyll fluorescence. Little
change in RuBP regeneration and photochemistry was evident in
cultivar Fujiyama-5, however. The degree of sensitivity of
photochemical reactions with increased UV-B radiation appeared to
be related to leaf production of UV-B-absorbing compounds.
Fujiyama-5 had a higher concentration of these compounds than IR-36
in all environments, and the production of these compounds in
Fujiyama-5 was stimulated by UV-B fluence. Results from this study
suggest that in rice alterations in growth or photosynthesis as a
result of enhanced CO2 may be eliminated or reduced if UV-B
radiation continues to increase.

Oryza sativa/rice

KEYWORDS: CARBOXYLATION EFFICIENCY, CI:CA, FLUORESCENCE,
GREENHOUSE, LEAF PHOTOSYNTHESIS, PIGMENTS, REPRODUCTION,
RESPIRATION, UV-B RADIATION, YIELD

798  
Ziska, L.H., and A.H. Teramura. 1992. Intraspecific Variation in
the Response of Rice (Oryza sativa) to Increased CO2 -
Photosynthetic, Biomass and Reproductive Characteristics.
Physiologia Plantarum 84:269-276.

Two rice (Oryza sativa L.) cultivars of contrasting morphologies,
IR-36 and Fujiyama-5, were exposed to ambient (360 uL/L) and
ambient plus 300 uL/L CO2 from time of emergence until ca 50% grain
fill at the Duke University Phytotron, Durham, North Carolina.
Exposure to increased CO2 resulted in about a 50% increase in the
photosynthetic rate for both cultivars and photosynthetic
enhancement was still evident after 3 months of exposure to a high
CO2 environment. The photosynthetic response at 5% CO2 and the
response of CO2 assimilation (A) to internal CO2 (Ci) suggest a
reallocation of biochemical resources from RuBP carboxylation to
RuBP regeneration. Increases in total plant biomass at elevated CO2
were approximately the same in both cultivars, although differences
in allocation patterns were noted in root/shoot ratio. Differences
in reproductive characteristics were also observed between
cultivars at an elevated CO2 environment with a significant
increase in harvest index for IR-36 but not for Fujiyama-5. Changes
in carbon allocation in reproduction between these two cultivars
suggest that lines of rice could be identified that would maximize
reproductive output in a future high CO2 environment.

Oryza sativa/rice

KEYWORDS: ALLOCATION, CULTIVAR RESPONSES, FLUORESCENCE, GREENHOUSE,
LEAF PHOTOSYNTHESIS, OXYGEN, REPRODUCTION, RESPIRATION