bluuebunny/crossref_metadata_2025 huggingface dataset:
Sinking and suspended particles in the South-west Pacific
Authors: Kawahata Hodaka , Ohta Hidekazu
Published: September 2002

Sinking and suspended particles were sampled
at Sites 11 and 12 in the Coral Sea, characterized by low seasonal variation
in sea surface temperature (SST), and at Site 13 in the central Tasman Sea
with a high range of seasonal SST variation. Sinking particles obtained at
Site 12 had low annual mean total mass and organic matter (OM) fluxes with
high carbonate content. Mean total mass flux at Site 13 was lower than those
obtained around the same latitude of the boreal central Pacific. More
carbonate-dominated and opal-depleted plankton communitygenerally
characterized the sinking particles in the low to mid latitude of the austral
western Pacific. To understand the relationship between sinking and suspended
particles, suspended particles were taken in the upper 300 m of the water
column. C Organic /N atomic ratios in the suspended
particles were generally 7–8, indicating that living organisms
contributed a significant proportion. Although organic carbon (OC) flux by
sinking particles at Site 13 was more than three times higher than that at
Site 12 during May–June 1995, the total particle OC standing stock in
the top 100 m was similar from 15ºS to 35ºS, indicating that OM is
more recycled at the oligotrophic site 12, whereas higher new production
yielded higher export production in the middle latitude site 13.
Comparison of dynamic models to predict the concentration of a photochemical tracer in the upper ocean as a function of depth and time
Authors: Kettle A. J.
Published: September 2002

Three one-dimensional upper-ocean
boundary-dynamics models are used to predict the concentration of a
short-lived natural photochemical tracer (CO) as a function of time and depth.
The models are coupled with parameterizations of the production and
destruction rates of the tracer using chemical rate constants from published
experimental studies. The model predictions of the upper-ocean [CO]
do not agree closely with the measured concentrations obtained during one
expedition, probably mostly because of errors in the rate constants used in
the chemical model (published values of the
in situ rate constants show much
variability). An optimization scheme is described to find the values of the
production and destruction rate constants that minimize the difference
betweenthe modelled and measured upper-ocean [CO], and the
uncertainty is assessed by Monte Carlo simulation. Using the optimized
estimates of the chemical production and destruction rate constants, the
simulated upper-ocean [CO] shows close agreement among the three
models. It is still difficult to quantitatively determine which of the models
is the best description for observed tracer concentrations because of
weaknesses in the existing in situ data sets.
Impact of mortality, possibly due to herpesvirus, on pilchard Sardinops sagax stocks along the south coast of Western Australia in 1998-99
Authors: Gaughan D. J. , Mitchell R. W. , Blight S. J.
Published: September 2002

During progression of a mass mortality of Australian pilchards in late 1998
and early 1999, quantities of dead pilchards on the sea-surface, sea-floor and
along beaches were estimated in three regions along southern Western Australia
(WA) by use of transects. Total mortality was estimated at 17 590, 11193 and
144.4 t for Esperance, Bremer Bay and Albany respectively. Mortality rates at
Esperance and Bremer Bay were similar at 74.5% and 64.7%
respectively, with a mean of 69.6%. In contrast, estimated mortality at
Albany was only 2.4%. Although the difference in total mortality
between regions is probably related to differences in stock size, as
determined by simulation models, the much lower estimate for Albany is
probably an artefact of an over-estimated pilchard biomass and not due to
large differences in actual mortality rates. Variability in estimates of both
pilchard biomass and quantities killed resulted in a wide range of estimated
mortality rates, with lower estimates for Esperance and Bremer Bay of
28.0% and 22.9% respectively. This represents a significant
decline in the breeding stock of WA pilchards. If the impact was closer to the
mean (69.6%), then pilchard stocks in WA are severely depressed.
SDS-insoluble glutenin polymer formation in developing grains of hexaploid wheat: the role of the ratio of high to low molecular weight glutenin subunits and drying rate during ripening
Authors: Carceller Jean-Luc , Aussenac Thierry
Published: September 2002

The accumulation of polymeric proteins and the changes in molecular size
distribution of these proteins were followed during grain filling and/or
premature desiccation. The accumulation behavior of polymeric proteins and
their constituent polypeptides (high and low molecular weight glutenin
subunits, HMW-GS and LMW-GS) was determined by reversed phase-high performance
liquid chromatography using a NaI/propanol purification procedure. With
this new extraction and separation procedure, we have demonstrated that there
was a coordinated initiation of storage protein biosynthesis, even if the
accumulation rate varied greatly between the two main classes of proteins
(i.e. monomeric and polymeric fractions). Moreover, the glutenin subunit
composition was largely modified during glutenin accumulation. Both the
HMW-GS/LMW-GS and HMW-GS-x/HMW-GS-y ratios increased significantly
during the whole cell enlargement phase (from 16 to 37 d after anthesis). By
applying premature grain desiccation during this physiological phase, we
demonstrated that the polymerization index (SDS-insoluble polymers/total
polymers) of the glutenin polymers was closely related to the
HMW-GS/LMW-GS ratio of these proteins. An increase in the relative
proportion of HMW-GS in glutenins caused the proportion of SDS-insoluble
polymers to rise during grain desiccation. From these studies, it appears that
the modification of the desiccation rate (grain desiccation at a constant
temperature with variable relative humidity levels) induced a parallel
modification of the glutenin insolubilization rate but did not affect the
polymerization index of the glutenins at maturity.
Photoprotection in chilling-sensitive and -resistant plants illuminated at a chilling temperature: role of the xanthophyll cycle in the protection against lumen acidification
Authors: Xu Chang-Cheng , Li Liangbi , Kuang Tingyun
Published: September 2002

The role of the xanthophyll cycle in the
protection against photoinhibition of photosystem II (PSII) induced by
chilling in moderate light was investigated in leaves of eight species or
varieties of higher plants differing widely in chilling sensitivity. The
extent of photoinhibition measured as the increase in the slowly reversible
fluorescence quenching (qI) was
found not to correlate with the overall amount of zeaxanthin formed during
photo-inhibitory treatment. On the other hand, a strong, positive correlation
existed between qI and the rate
difference between the development of the rapidly relaxing, DpH-dependent
quenching component (qf) and the
formation of zeaxanthin (DR) across all examined species
or varieties. There was also found to be a weaker, negative correlation
between qI and the rate of
zeaxanthin formation. Ascorbate feeding markedly increased the resistance to
chilling-induced photoinhibition mainly by increasing the rate of zeaxanthin
formation and therefore by decreasing DR. The possible
implications of the present findings in explaining the mechanistic basis for
the reversible, sustained photo-inhibition are discussed. It is suggested that
the xanthophyll cycle may play a critical role in the protection of the
thylakoid lumen against over-acidification and the resulting photoinhibition
of PSII reaction centers.
Contrasting seed germination responses to red and far-red light in Leptospermum scoparium and Melicytus ramiflorus
Authors: Herron Helen , Clemens John , Greer Dennis H.
Published: September 2002

Effects of red light (R) and far-red light (FR), and selected photon flux
densities (PFD) of photosynthetically active radiation (PAR) on seed
germination in the photoblastic, primary colonising species
Leptospermum scoparium J. R. et G. Forst. and the late
secondary successional Melicytus ramiflorus J. R. et G.
Forst. were studied. A continuous R dose response curve
forL. scoparium germination was developed, unifying data
from experiments using long-term exposure to PAR with those following
short-term exposure to R. The threshold R dose needed to effect germination
was ~0.1 mmol m –2 , and the response was
saturated at 1000 mmol m –2 . Stimulation of
germination by R was reversed by a subsequent exposure to FR. These features
are consistent with a low-fluence response mediated by phytochrome B. FR
reversal of germination was achieved at a dose two orders of magnitude lower
than that of R required to induce initial germination. However, when both R
and FR were provided simultaneously, the FR dose needed to even partially
inhibit germination (34% compared to > 95% in controls) was
two orders of magnitude higher than the R dose (R:FR ratio = 0.007).
Germination in L. scoparium was also stimulated in up to
12% of seed upon diurnal exposure to FR, or by green light (~2 mol m
–2 ), indicating a very-low-fluence response
mediated by phytochrome A also operating in this species. In contrast, seed
germination in M. ramiflorus was
relatively unresponsive to R, and secondary dormancy was induced by high PFD
(515 mol m –2 s –1 ).
Fractionation of carbonic anhydrase activity in Gracilaria sp. (Rhodophyta) and Enteromorpha intestinalis (Chlorophyta): changes in the extracellular activity in response to inorganic carbon levels
Authors: Andría Jesús R. , Vergara Juan J. , Pérez-Lloréns J. Lucas
Published: September 2002

The presence of different carbonic anhydrase (EC 4.2.1.1) activities has been
investigated in the intertidal macroalgae Gracilaria sp.
and Enteromorpha intestinalis (L.) Nees by using
fractionation techniques. Activities, measured potentiometrically, were
recorded for all fractions in both species, including those containing
proteins associated with chloroplast membranes. In
Gracilaria sp., most of the total activity was present
in the soluble fraction, while similar activities were obtained for all
fractions in E. intestinalis. By using inhibitors with a
different capacity to enter the cell (acetazolamide and 6-ethoxyzolamide,
inhibitors of external and total activity, respectively), a surface-accessible
location was indicated for a high proportion of the soluble activity obtained
in Gracilaria sp. In
E. intestinalis, the inhibitor assays showed a
substantial dependence of photosynthesis on intracellular activity. The
short-term regulation of the extracellular activity in response to inorganic
carbon availability was also examined in both macroalgae. Rapid repression
(after 2 h) of the activity was recorded when Gracilaria
sp. was transferred from limited to replete carbon conditions, while a fairly
constant activity was recorded for E. intestinalis. In
contrast, an increase of external activity was obtained for both macroalgae
after being transferred to carbon-limited conditions, this response being more
pronounced in E. intestinalis. Our results suggest the
occurrence of a species-specific carbonic anhydrase system.
Chlorophyll degradation in heat-treated Chlorella pyrenoidosa. A flow cytometric study
Authors: Tzeng Shainnfer , Hsu Ban-Dar
Published: September 2002

The process of chlorophyll degradation of
Chlorella pyrenoidosa was studied by flow cytometry
using intrinsic chlorophyll fluorescence as the gauge. The small vegetative
cells of a synchronous culture were subjected to a heat pre-treatment
(46.5ºC for 1 h in the dark) and cultured again under continuous
illumination thereafter. The cellular chlorophylls vanished within about 24 h
after the heat pre-treatment in two distinguishable stages, which corresponded
to the two major stages of the present model for chlorophyll degradation. It
was found that, although both stages were light-dependent, they differed in
several aspects. The first stage of degradation, in which the whole cell
population uniformly converted its chlorophylls into pheopigments, started
immediately after light-on during recultivation, and continued even after
light-off for a long period (~60 h), indicating that all cells responded to
light without delay, and the process continued once triggered. The second
stage of degradation, in which cells opened their chlorophyll macrocycles and
lost their green color, did not start until after about 8 h of illumination,
and each individual cell actually entered this process at a somewhat different
time (8–24 h). In addition, the conversion of each cell was fast, but
the process in the population as a whole stopped whenever illumination was
off. This indicates that the second stage proceeds in a random mode, and that
light must be present during the conversion of each cell. It was also found
that the process of pigment breakdown could be turned on by illumination as
low as 4 mol m –2 s –1
, but was abolished by a period of dark treatment, suggesting that light
played a triggering role, and the ‘signal’ for chlorophyll
degradation set up by the heat pre-treatment was automatically canceled after
a certain time without light triggering.
Effects of leaf age on internal CO2 transfer conductance and photosynthesis in tree species having different types of shoot phenology
Authors: Hanba Yuko T. , Miyazawa Shin-Ichi , Kogami Hiroyuki , Terashima Ichiro
Published: September 2002

We examined the changes in leaf anatomy and some physiological characteristics
during leaf expansion and maturation. Three deciduous tree species having
different types of shoot phenology, maple (Acer mono
Maxim.; ‘flush’ type), alder
(Alnus japonica(Thunb.) Steud.; ‘successive’
type), and Japanese poplar (Populus maximowiczii A.
Henry; ‘successive’ type), were studied. Leaf CO
2 assimilation rate at high irradiance
(P max) and CO
2 transfer conductance inside the leaf
(g i) varied significantly with
leaf development. There were strong positive relationships between
P max) and g
i for all of the species. The variations in
g i were partly related to those
in the surface area of chloroplasts facing the intercellular airspaces, while
some other factors that related to liquid phase conductance may also
contribute to the variation in g i
. The developments of mesophyll cells were accompanied by the concomitant
increase in chloroplast and Rubisco content in Alnus and
Populus (successive types).
Effects of temperature and nitrogen nutrition on the accumulation of gliadins analysed by RP-HPLC
Authors: Daniel Catherine , Triboï Eugen
Published: September 2002

The gliadin content and composition at harvest play a critical role in
governing wheat flour properties and uses. The effects of two major
environmental factors, temperature and nitrogen (N) supply, on gliadin
accumulation were studied using a sequential extraction method coupled with
RP–HPLC separation, in order to understand the variations observed at
harvest. The thermal effects after anthesis were studied at canopy level in
transparent climate tunnels in 1997 and 1998 under natural light. The N
effects were studied in field experiments in 1997. An increase in temperature
after anthesis induced an increase in the rate of gliadin accumulation per
day, and a decrease in the duration of accumulation in days. The effects of
the temperature were greater on the α, β-gliadins than on the
ω- and γ-gliadins. Increased N nutrition increased the rate and
duration of accumulation both in days and degree-days (˚Cd). The level of
N nutrition before anthesis governed the effects of N supply at anthesis. The
accumulation of ω-gliadins was relatively more affected by the N supply
than the α-, β- and γ-gliadins. The final composition of
gliadins was a function of the rate of accumulation and of the duration of
synthesis, determined by the dates of onset and cessation of synthesis. We
concluded that the dynamic allocation of N between different gliadin
fractions, described in terms of thermal time, could be useful for modelling
gliadin content and composition of wheat.
Structure and function of plasmodesmata
Authors: Blackman Leila M. , Overall Robyn L.
Published: September 2002

Little is known about the molecular architecture of plasmodesmata. Electron
micrographs of plasmodesmata, although showing remarkably consistent features,
do not reveal the dynamic nature of plasmodesmata. In addition, the generally
accepted size exclusion limit of plasmodesmata of 1 kDa as determined by the
microinjection of fluorescent probes, is not an accurate measure of the size
of molecules that can move from cell to cell. In some cases, plasmodesmata
allow the non-selective movement of proteins up to 50 kDa, whereas others
allow the selective transport of proteins such as transcription factors.
Insights to the molecular architecture of plasmodesmata and the mechanism of
cell-to-cell transport can be gained by the examination of the type of
molecules and conditions under which selective and passive movement of
molecules occurs.
Modeling the current-voltage characteristics of charophyte membranes. III. K+ state of Lamprothamnium
Authors: Beilby Mary J. , Shepherd Virginia A.
Published: September 2002

The K + state of salt-tolerant charophyte
Lamprothamnium papulosum (Wallr.) J. Gr., acclimated to
0.5 seawater (SW) containing 4.5 mM K + , was
investigated by exposing the cells to a range of [K
+ ] o from 0 to 45.0
mM . The current–voltage (I/V) characteristics were modeled as a sum
of four different transporter currents: the large conductance K
+ channel current, inward and outward K
+ rectifier currents and linear background current.
The first three transporters were fitted with the Goldmann-Hodgkin-Katz (GHK)
model. The potential difference (PD) dependence of the population of open
channels was simulated by Boltzmann probability distribution. The linear
background current exhibited reversal PD independent of lsqb;K
+ ] o and the
background conductance decreased as lsqb;K +
] o increased. The combined channel number and
permeability parameter, N K P K ,
was in a similar range for all three K +
transporters. The N K P K
parameter of the large conductance K + channel
reached a maximum at lsqb;K + ]
o concentration of 9 mM , decreasing at 45 mM . The
modeled large conductance K + channel revealed a
strong asymmetry of the I/V profile in response to change of outside and
inside K + concentrations. This behaviour was
exploited to estimate the rise of cytoplasmic K +
concentration at the time of the hypotonic effect. The cytoplasmic K
+ concentration range giving the best fit to the
data in steady-state was 28–65 mM .
Use of the15N natural abundance technique for the quantification of the contribution of N2 fixation to sugar cane and other grasses
Authors: Boddey Robert M. , Polidoro José Carlos , Resende Alexander S. , Alves Bruno J. R. , Urquiaga Segundo
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
The use of the 15N natural abundance technique to
quantify contribution of biological nitrogen fixation (BNF) to any plant is
based on the observation that N derived from soil is generally slightly
different [usually higher in 15N abundance
(δ15N‰)] than that of the air. Plants
or micro-organisms growing solely on BNF generally accumulate N with
15N isotopic abundance lower than that of the air (i.e.
δ15N‰ is negative), while plants obtaining
all N from the soil generally show a positive δ15N‰ signal. The
technique is applied by estimating the 15N abundance of
the putative ‘N2-fixing’ crop and analysing
the 15N abundance of neighbouring
non-N2-fixing reference plants. However, often there are
such large variations in the N derived from the soil by different
non-N2-fixing plants that in natural ecosystems it is
often impossible to even distinguish plants that are benefiting form BNF, let
alone quantity this contribution. The reasons why soil derived N can vary so
widely, especially in natural ecosystems, are briefly discussed and a sampling
strategy is described to assess possible BNF inputs to sugar cane plants in
commercial plantations in Brazil. The results suggest that in nine of the 11
sites studied, BNF inputs were significant ranging from 25 to 60% of N
assimilated.
Research note: On the intermediate steps between the O and P steps in chlorophyll a fluorescence rise measured at different intensities of exciting light
Authors: Tomek Pavel , Lazár Dusan , Ilík Petr , Naus Jan
Published: September 2002

It is known that the characteristic O–I–P transient of the fast
chlorophyll a fluorescence rise (FR) detected under low
intensity of exciting light, changes to the O–J–I–P
(O–I 1 –I 2 –P)
transient under higher intensity of exciting light. In this work, we extend an
application of the mathematical model of FR [Lazár
et al. (1997)l
Pesticide Biochemistry and Physiology
57, 200–210], involving photosystem II
(PSII) heterogeneity and simulating the O–J–I–P transient,
for modeling of FR under different intensities of exciting light. Our
simulations qualitatively agree well with experimental FR curves obtained with
wheat leaves. The simulations demonstrate that the first step after the O
fluorescence level (the I step and the J step under lower and higher
intensities of exciting light, respectively) is caused mainly by the
accumulation of reduced QA electron acceptors without
reduction of subsequent electron acceptors. The first step appears at shorter
times with increasing intensity of exciting light as reported previously
[Strasser et al. (1995)
Photochemistry and Photobiology 61,
32–42]. Our simulations also demonstrate, in accordance with
previous publications, that the O–I phase in FR detected under low
intensity of exciting light, reflects mainly the accumulation of Q
A – in the Q
B-non-reducing PSII centers and partly also the
accumulation of Q A – in the
Q B -reducing PSII centers. In our model, the
accumulation of Q A – in the
Q B -non-reducing PSII centers gradually shifts with
increasing intensity of exciting light to shorter times and participates in
the formation of the O–J phase; this is also supported by measurements
of FR with wheat leaves treated with
3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU). Under high
intensity of exciting light, the O–J phase in FR also markedly reflects
the accumulation of Q A – in
the Q B -reducing PSII centers. Our simulations also
support the previously reported suggestion of Strasser’s group that the
I step in FR obtained under high intensity of exciting light (in the position
of the I step detected under lower intensity of exciting light) appears mainly
owing to the accumulation of the Q A
–Q B
2– and Q
A–Q BH
2f orms.
Ammonium transport: unifying concepts and unique aspects
Authors: van Dommelen Anne , de Mot René , Vanderleyden Jos
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
Ammonium uptake by cells has been studied for more than a century, but only
recently a family of ammonium transporters (Mep/Amt) with 10–12
transmembrane domains has been defined. These proteins are probably
ubiquitous, since homologues have been found in the major kingdoms of living
organisms. Plants as well as yeast and some archaebacteria have multiple
Mep/Amt paralogues, which can be distinguished by their affinity for
ammonium and the ammonium analogue methylammonium. Most ammonium transporters
are induced in nitrogen-starving conditions, both in prokaryotes and plants.
In Saccharomyces cerevisiae,
Escherichia coli and
Azospirillum brasilense Mep/Amt proteins where shown
to be necessary for growth when the external concentration of the diffusive
ammonium form (NH3) becomes limiting. Ammonium
transporters also play an important role in pseudohyphal differentiation in
yeast and efficient symbiotic interaction between
Rhizobium etli and its host plant. In most bacteria,
NH4+ transport appears to be
a uniport mechanism driven by the membrane potential, but, depending on the
organism, a different mode of ammonium uptake may be operating. Current
knowledge offers the basis to investigate further the physiological role of
ammonium transporters in the natural habitat of organisms and their importance
in plant–bacteria interactions.
Physiological control of phosphate uptake and phosphate homeostasis in plant cells
Authors: Mimura Tetsuro
Published: September 2002

Inorganic phosphate (Pi) uptake systems across the plasma membrane of plant
cells have been extensively investigated. Physiological studies have
established that Pi is transported into plant cells via co-transport with
H+ , and in some plants with Na
+ , using the driving force provided by the
electrogenic H + pump in the plasma membrane.
Molecular studies have identified many genes for Pi transporters and are
providing insights into the mechanisms of genetic control of Pi transport.
There still remain, however, questions as to how Pi uptake systems are
regulated at the physiological level. We have found that Pi uptake induces
cytoplasmic acidification, and, conversely, that inducing cytoplasmic
acidification causes the cytoplasmic Pi concentration to decrease. Both of
these responses affect the operation of the H +
-pump. These phenomena are discussed in relation to a possible mechanism for
the physiological control of Pi uptake by plant cells.
Prospects for using soil microorganisms to improve the acquisition of phosphorus by plants
Authors: Richardson Alan E.
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
Microorganisms play an important role in the acquisition and transfer of
nutrients in soil. For phosphorus (P), soil microorganisms are involved in a
range of processes that affect P transformation and thus influence the
subsequent availability of P (as phosphate) to plant roots. In particular,
microorganisms can solubilize and mineralize P from inorganic and organic
pools of total soil P. In addition, microorganisms may effectively increase
the surface area of roots. Also, the microbial biomass itself contains a large
pool of immobilized P that potentially is available to plants. Given that most
soils are deficient in plant-available P and that P fertilizer represents a
significant cost for agricultural production throughout the world, there is
interest in using soil microorganisms as inoculants to mobilize P from poorly
available sources in soil. Although potential clearly exists for developing
such inoculants, their widespread application remains limited by a poor
understanding of microbial ecology and population dynamics in soil, and by
inconsistent performance over a range of environments. Furthermore, promotion
of growth of plants in soil, as a consequence of microbial inoculation, may
not necessarily be associated with characteristics such as P solubilization,
which are manifest under laboratory conditions.
Effect of salinity on water relations and growth of wheat genotypes with contrasting sodium uptake
Authors: Rivelli Anna Rita , James Richard A. , Munns Rana , Condon A. G. (Tony)
Published: September 2002

Four wheat genotypes with contrasting degrees of Na+ exclusion were selected to see if low Na+ uptake had an adverse effect on water relations or growth rates during exposure to saline conditions. Plants were grown in supported hydroponics with and without 150 mM NaCl, and sampled for measurements of water relations, biomass, stomatal conductance, and ion accumulation. After 4 weeks exposure to salt, biomass was reduced in all genotypes to a similar extent (about 50%), with the effect of salinity on relative growth rate confined largely to the first week. There was little difference between genotypes in the effect of salinity on water relations, as indicated by their relative water content and estimated turgor. Osmotic adjustment occurred in all genotypes, with one of the low-Na+ genotypes having the greatest adjustment. In the low-Na+ genotypes, osmotic adjustment depended on higher K+ and high organic solute accumulation. Stomatal conductance of all genotypes was reduced by saline conditions, but the reduction was greater in the low-Na+ genotypes. These genotypes also showed a larger fall in the value of carbon isotope discrimination measured in expanding leaves, indicating a greater transpiration efficiency when exposed to saline conditions. Chlorophyll fluorescence measurements failed to indicate damage to photochemical pathways in either high- or low-Na+ genotypes. These data indicate that selecting lines with low Na+ accumulation for the purpose of improving salt tolerance is unlikely to introduce limitations for osmotic adjustment.
Starch synthesis in potato tubers transformed with the wheat genes for ADPglucose pyrophosphorylase
Authors: Vardy Kathryn A. , Emes Michael J. , Burrell Michael M.
Published: September 2002

The aim of this work was to study the role of ADPglucose pyrophosphorylase (AGPase) in starch biosynthesis of non-photosynthetic organs. Agrobacterium tumefaciens was used to transform potato plants (Solanum tuberosum L. cv. Desire�) with the wheat AGPase genes (AGP-S and AGP-L, coding for the small and large subunits, respectively). Neither of these genes contains a recognisable plastid targeting sequence. Southern analysis and analysis of starch content identified four lines that contained both wheat sequences. Immunoblotting indicated that, in the tubers, three lines expressed the wheat small subunit (AGP-S), but AGP-L cross-reacting protein was not apparent. The fourth transgenic line had reduced AGPase activity. AGPase activity in the AGP-transgenic tubers ranged from 15 to 165% of that found in β-glucuronidase (GUS) control lines.
Inorganic carbon acquisition and its energization in eustigmatophyte algae
Authors: Huertas I. Emma , Colman Brian , Espie George S.
Published: September 2002

The eustigmatophyceans are primitive unicellular algae that represent the most
basal group of ochrophytes. They are believed to be obligate photoautotrophs,
occurring mainly in freshwater and soil but with some marine representatives.
The freshwater eustigmatophytes Monodus subterraneus and
Vischeria stellata, and the marine eustigmatophyte
Nannochloropsis gaditana, have been studied by mass
spectrometry with respect to their characteristics for inorganic carbon (Ci)
uptake. A CO2 concentrating mechanism was found in all
three, but an external carbonic anhydrase (CA) was not detected. The
acquisition of Ci from the external medium was based on the active transport
of HCO3–,
CO2, or both. In particular,
N. gaditana was able to use
HCO3– exclusively as an
exogenous carbon source for photosynthesis, with this
HCO3– being subsequently
converted to CO2 by an intracellular CA for
photosynthetic fixation. A unique characteristic of this species was its
capacity to transport HCO3–
during prolonged periods of time in the dark. In contrast,
M. subterraneus utilized CO2 alone
through an active transport process, whereas
V. stellataexhibited the capacity to transport both
HCO3– and
CO2. The uptake of CO2 also
continued in the dark in V. stellatacells. Regardless of
the Ci species taken up, transport was abolished by anoxia and by inhibitors
of mitochondrial respiration. These results indicate that that the supply of
Ci for photosynthetic CO2 fixation is partly dependent
upon mitochondrial activity in these primitive eukaryotes.
Influence of nitrogen supply on the photoprotective response of Neoregelia cruenta under high and low light intensity
Authors: Fernandes Janaina , Chaloub Ricardo M. , Reinert Fernanda
Published: September 2002

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001.
We investigated preference for nitrogen source and the influence of ammonium nitrate on leaf pigment content, crassulacean acid metabolism (CAM) activity, and the efficiency of PSII in Neoregelia cruenta (R.Graham) L.B. Smith, a CAM bromeliad of major ecological importance to restinga (coastal sand ridge plains) environments. Plants showed a preference for ammonium over nitrate in a 24-h experiment where plants were exposed to 15NH4NO3 or NH415NO3. Mature individuals of N. cruenta were exposed to 95 and 20% full sunlight, and treated with 5 mm NH4NO3 or tap water only. After 4 months under the different treatments we found that nitrogen uptake and carotenoid content were independent of light exposure. Total chlorophyll decreased under nitrogen limitation and high light. Net titratable acid accumulation was not influenced by light or nitrogen regimes. Plants under low light showed consistently high photochemical efficiency of PSII (Fv/Fm) throughout the day. In contrast, plants under high light and nitrogen limitation showed a significant decline in Fv/Fm around midday, which recovered by the end of the light period. This decline in Fv/Fm was attributed to increased non-photochemical quenching. Our findings that plants under high light and with high nitrogen behave similarly to shade plants were unexpected. They suggest that the high light, high nitrogen leaves used a greater portion of the light absorbed in PSII antennae for photochemistry than the high light, low nitrogen plants. High nitrogen content in the leaves of N. cruenta appears to protect this CAM bromeliad against photoinhibition.
Strong responses of growth and photosynthesis of five C3 pasture species to elevated CO2 at low temperatures
Authors: Laing William A. , Greer Dennis H. , Campbell Bruce D.
Published: September 2002

Five cool-season C3 pasture species (Bromus willdenowii Kunth, Festuca arundinacea Schreb, Lolium multiflorum Lam., Lolium perenne L. and Trifolium repens L.) were grown at a constant temperature of 12°C to assess effects of elevated CO2 on growth and photosynthesis. Plants were grown at either 350 or 700 μmol mol–1 CO2 for 42-56 d, after which they were destructively harvested to assess biomass. At the same time, leaf gas exchange was measured at 12°C for each species at both CO2 concentrations. Photosynthetic response to CO2, that is the A/Ci curve, was also measured. Results showed all species responded to elevated CO2 at low temperature by increasing total biomass, relative to that at ambient CO2, from 105 to 158%. T. repens and B. willdenowii had the smallest response, and the two Lolium species had the greatest response. Photosynthesis also responded strongly to elevated CO2 at low temperature, increasing on average by 40%. Only small growth CO2 effects occurred with the A/Ci curves, with lower CO2-saturated photosynthesis only for L. perenne and T. repens grown at elevated CO2. The photosynthetic response to CO2 was not correlated with the growth response. However, the product of photosynthesis and leaf area, that is carbon supply, was highly correlated with the growth rate, and growth CO2 had a marked effect. Results suggest T. repens responded poorly to elevated CO2 at low temperature because of a low capacity to fix carbon, while both Lolium species responded strongly at low temperature because of a high capacity to fix CO2. Changes to photosynthetic model parameters are now required to account for growth temperature effects on the CO2 response.
Changes in sourcesink relations during development influence photosynthetic acclimation of rice to free air CO2 enrichment (FACE)
Authors: Seneweera Saman P. , Ghannoum Oula , Conroy Jann P. , Ishimaru Ken , Okada Masumi , Lieffering Mark , Kim Han Yong , Kobayashi Kazuhiko
Published: September 2002

Relationships between photosynthetic acclimation and changes in the balance between source-sink supply and demand of carbon (C) and nitrogen (N) were tested using rice (Oryza sativa L. cv. Akitakomachi). Plants were field-grown in northern Japan at ambient CO2 partial pressure [p(CO2)] or free air CO2 enrichment (FACE; p(CO2) ~ 26-32 Pa above ambient) with low, medium or high N supplies. Leaf CO2 assimilation rates (A) and biochemical parameters were measured at 32-36 (eighth leaf) and 76-80 (flag leaf) d after transplanting, representing stages with a contrasting balance between C and N supply and demand in sources and sinks. Acclimation due to FACE was pronounced in flag leaves at each N supply. This was not fully accounted for by reductions in leaf N concentrations, because A/N and Vcmax/N were lower in FACE-grown flag leaves. Acclimation did not occur in the eighth leaf, and A/N and Vcmax/N was not significantly increased in FACE-grown leaves. Soluble protein / sucrose and amino acid / sucrose concentrations decreased under FACE, whereas sucrose phosphate synthase protein levels increased. At flag leaf stage, there was a discrepancy between the demand and supply of N, which was resolved by enhanced leaf N remobilization, associated with the lower Rubisco concentrations under FACE. In contrast to the early growth stage, enhanced growth of rice plants was accompanied by increased plant N uptake in FACE. We conclude that photosynthetic acclimation in flag leaves occurs under FACE because there is a large demand for N for reproductive development, relative to supply of N from root uptake and remobilization from leaves.
Aquaporins in the plasma membrane of leaf callus protoplasts of Actinidia deliciosa var. deliciosa cv. Hayward
Authors: Qiu Quan-Sheng , Wang Ze-Zhou , Zhang Nang , Cai Qi-Gui , Jiang Rong-Xi
Published: September 2002

The water transport activity of Actinidia deliciosa
protoplasts was determined using a cell imaging system. Results showed that
the protoplast volume increased swiftly when placed in a hypoton-ic medium,
and also increased with an increase in medium osmotic gradients. The osmotic
water permeability coefficient
(Pf) values were 0.118 ×
10–3, 0.121 ×
10–3, and 0.133 ×
10–3 cm s–1 when the
osmotic gradients were 75, 100, and 125 mosmol, respectively. The water
transport activity of protoplas-ts could be inhibited by
HgCl2 and stimulated by amphotericin B. Moreover,
ZnCl2 and ZnSO4 had a significant
inhibitory effect on the water transport activity of the protoplasts. Our
results indicate that the Actinidia deliciosa
protoplasts had properties typical of aquaporins, suggesting that aquaporins
were present at the plasma membrane.
Seasonal fluctuations in photoprotective (xanthophyll cycle) and photoselective (chlorophylls) capacity in eight Mediterranean plant species belonging to two different growth forms
Authors: Kyparissis Aris , Drilias Periklis , Manetas Yiannis
Published: September 2002

Xanthophyll cycle components and their pool
sizes were seasonally examined in eight Mediterranean plant species from two
different growth forms (drought semi-deciduals and evergreen sclerophylls), in
an attempt to correlate possible fluctuations in the above parameters with
potentially photoinhibitory conditions. The xanthophyll cycle was common in
all species examined and was functional throughout the year. In
semi-deciduals, the maximum midday values for conversion state, defined as the
ratio (zeaxanthin + antheraxanthin)/(violaxanthin + zeaxanthin
+ antheraxanthin), and the maximum xanthophyll pool sizes, expressed on a
Chl basis, were recorded during the dry summer, indicating that the period of
water shortage may be the most demanding for a high photoprotective potential.
However, the data suggests that sclerophylls may also need a high
photoprotective potential during winter, since the xanthophyll pool sizes were
equally high during both summer and winter. Corresponding spring and autumn
values were low. Furthermore, winter pre-dawn conversion state values were the
highest recorded amongst all species studied, indicating that the mildly low
winter temperatures may be a considerable stress factor for these plants. It
is assumed that by preserving high concentrations of zeaxanthin and
antheraxanthin overnight, sclerophylls retain high energy dissipation activity
early in the morning, when minimum temperatures, coinciding with high photon
fluence rates, are likely to drive the photosynthetic apparatus to potentially
harmful overexcitation. Of significance may be the fact that almost all
species show a minimum in chlorophyll content during the summer. In this way,
overexcitation is alleviated and the photoprotective action of carotenoids per
chlorophyll molecule is enhanced.
The disappearance kinetics of Lhcb polypeptides during dark-induced senescence of leaves
Authors: Rosiak-Figielek Beata , Jackowski Grzegorz
Published: September 2002

A set of polyclonal antibodies in conjunction
with immunoblot technique and integrating densitometry has been used to
positively identify and quantify Lhcb 1-6 polypeptides in barley
(Hordeum vulgare L.) leaves in which senescence
processes were induced by detachment and dark incubation for 0–6 d. A
considerable hetero-geneity with regard to disappearance kinetics on a
chlorophyll basis during the course of senescence has been foundamong
individual Lhcbs. Lhcb 2/1 (the heavier of two polypeptides representing
barley Lhcb2) and Lhcb3 exhibited the most rapid disappearance kinetics and
decreased to 20 and 42% of their initial levels, respectively, after 6
d of dark incubation. Lhcb 1, 4 and 6 levels were maintained through the
senescence, at a level very similar to that of fresh leaves, while Lhcb
2/2 (the lighter of two polypeptides representing barley Lhcb 2) and Lhcb
5 were the most stable of all Lhcbs — their relative abundance increased
after 6 d of dark incubation of the leaves to 181 and 120%,
respectively, of the value detected in fresh leaves.
Electrokinetic properties of thylakoids in in vitro cultured Gypsophila paniculata plants
Authors: Doltchinkova Virjinia R. , Georgieva Katia , Kapchina-Toteva Veneta , Polle Juergen
Published: September 2002

In vitro cultured
Gypsophila paniculata L. plants were used as a model to
evaluate the effect of some cytokinins and anticytokinins on thylakoid surface
charge. Influence of the cytokinins
N-6-furfurylaminopurine (kinetin) and
N1-(2-chloro-4-pyridyl)-N2-phenylurea
(4-PU-30), cytokinin antagonists
2-chloro-4-cyclobutylamino-6-ethylamino-1,3,5-triazine and
N-(4-pyridyl)-O-(4-chlorophenyl)
carbamate on the pigment content, surface charge density (s ), fluorescence
induction kinetics and millisecond-delayed light emission was studied. Our
results showed that the chlorophyll
(a+b) content significantly
decreased after the 1st and the 2nd month of
G. paniculata growth in the presence of the cytokinins
kinetin and 4-PU-30. In our model system, cytokinins enhanced the number of
open lateral buds and, as a consequence, more shoots per explant. Hence,
chlorophyll synthesis was not inhibited but so-called ‘dilution of the
pigments’ was available. Anticytokinins inhibited the formation of more
than one shoot, and the chlorophyll content was not influenced significantly.
The phenylurea cytokinin 4-PU-30 and anticytokinins increased the
electrophoretic mobility, zeta potential and surface charge density of
thylakoids after a longer time of treatment. Making thylakoid membranes more
negatively charged, phenylurea cytokinin and anticytokinins increased the
aggregation of the complexes and the energization of the membrane. Our results
showed that plant growth regulators decreased the primary photochemical
activity of photosystem II (estimated by the ratio
Fv/Fm)
and delayed fluorescence intensity in the 1st month. However, no significant
changes were observed in these parameters in the 2nd month.
Drought responses of Eucalyptus microtheca provenances depend on seasonality of rainfall in their place of origin
Authors: Li Chunyang , Berninger Frank , Koskela Jarkko , Sonninen Eloni
Published: September 2002

We exposed seedlings of 12
Eucalyptus microtheca F. Muell. provenances to
well-watered and water-stressed growing conditions in a greenhouse experiment
and investigated the effects of drought on various plant properties in the
provenances. We found significant variation in total biomass, height, root
mass/foliage area ratio,foliage area/stem cross sectional area ratio,
specific leaf area (SLA), water-use efficiency (WUE) and carbon isotope
composition (d 13 C) among the provenances. The observed
inter-provenance variation was more pronounced in the water-stressed treatment
than in the well-watered one. Drought increased root mass/foliage area
ratio, foliage area/stem cross sectional area ratio, WUE, d
13 C and decreased total biomass, height, transpiration
and SLA. We also analysed relationships between plant properties and climate
of native habitats of the provenances and found that most properties were
strongly correlated with mean driest quarter rainfall. The correlation was
positive for total biomass, height, transpiration and SLA and negative for
root mass/foliage area ratio, foliage area/stem cross sectional area
ratio, WUE and d 13 C. Finally, we evaluated the
intra-specific variation in foliage area/stem cross sectional area ratio
in the context of tree hydraulic architecture: provenances from dry areas and
trees grown under drought stress had more foliage per stem area ratio.
However, their transpiration and the length of their hydraulic pathway were
smaller and therefore the root to leaf water potential gradient might be
smaller in these trees.
Spatial distributions and net deposition rates of Fe, Mn and Zn in the elongating leaves of wheat under saline soil conditions
Authors: Hu Yuncai , von Tucher Sabine , Schmidhalter Urs
Published: September 2002

In this study, we quantified the spatial distributions of Fe, Mn and Zn and
their net deposition rates in the elongating and mature zones of leaf 4 on the
main stem of spring wheat (Triticum aestivum L.) on a
millimetre scale during its linear growth phase under saline soil conditions.
Plants were grown in an illitic-chloritic silty loam with 0 and 120 mМ
NaCl in growth chambers. The sampling was conducted on the 3rd day after leaf
4 emerged during the photoperiod. The patterns of spatial distributions of Fe,
Mn and Zn concentrations (mmol kg–1 FW) in the
growing leaves were distinct. Salinity affected the distri-bution pattern of
Fe concentration on the FW basis, whereas it did not affect those of the Zn
and Mn. The distribution patterns of Fe and Mn differed from those for N, P,
K, Ca and Mg found in a previous study, whereas the distribution pattern of Zn
was similar to those of Mg, P and N. The spatial distribution of the net
deposition rates (mmol kg–1 FW
h–1) in both treatments demonstrated the strongest
sink for the micronutrients in the elongation zone, and their net deposition
rates were enhanced by 120 mМ NaCl at the middle of the elongation zone.
From the results, we conclude that the inhibition of leaf growth of wheat is
probably not due to the effect of salinity on Fe, Mn and Zn in leaves.