bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon isotope discrimination during photosynthesis and dark respiration in intact leaves of Nicotiana sylvestris: comparisons between wild type and mitochondrial mutant plants
Authors: Duranceau Muriel , Ghashghaie Jaleh , Brugnoli Enrico
Published: September 2002

Leaf gas-exchange, carbon isotope discrimination (D) during photosynthesis,
carbon isotope composition (d13 C) of leaf dry matter,
leaf carbohydrates and ‰ d13 C of dark
respiratory CO 2 were measured both in wild type (WT)
and in a respiratory mutant of Nicotiana sylvestris
Spegazz. plants. The mutation caused a dysfunction of complex I of the
respiratory chain which has been described in detail by Gutierres
et al. 1997, PNAS,
94, 3436. The aim of this work was to verify if this
mutation has an influence on carbon isotope discrimination during
photosynthesis and dark respiration. Another objective was to study the
possible effect of respiratory fractionation on the isotopic composition of
dry matter and on the discrimination measured on-line, in comparison with the
expected D based on the model developed by Farquhar
et al. 1982, AJPP,
9, 121. On-line D measured on leaves during
photosynthesis was lower in the mutants (16.5‰ 0.9) than in the WT
(20.1‰ 0.6), mainly due to lower conductance to CO
2 diffusion (both across stomatal pores and in the
gaseous and liquid phases across the mesophyll) in the mutants. No
statistically significant difference in the fractionation during dark
respiration was observed between WT and mutant plants. However, respiratory CO
2 was enriched in 13 C compared to
sucrose and glucose by about 2–3 and 2.5–4‰, respectively.
The enrichment in 13 C (about 2‰) observed in
leaf metabolites and leaf organic matter in the mutants compared to the WT can
be explained by differences in .during photosynthesis. However, the
fractionation in the whole-leaf organic matter of both WT and mutant plants
was higher (more depleted in 13C) than expected based on
the .values obtained with on-line measurements during photosynthesis. The
observed discrimination during dark respiration, releasing
13 C-enriched CO 2 , may partly
explain the higher fractionation in the remaining leaf organic matter compared
to the overall discrimination during photosynthesis, as measured on-line.
Response of oxidative metabolism to the application of carbendazim plus boron in tobacco
Authors: García Pablo C. , Rivero Rosa M. , López-Lefebre Luis R. , Sánchez Esteban , Ruiz Juan M. , Romero Luis
Published: September 2002

In view of the essential role of oxidative process in the development of
pathogen resistance in plants, the aim of the present study was to determine
the individual effect of a fungicide, as well as to determine the combined
effect of the fungicide and boron (B) on superoxide dismutase (SOD), guaiacol
peroxidase (GPX), catalase (CAT), and ascorbate peroxidase (APX) activities
and H 2 O 2 levels in tobacco
plants (Nicotiana tabacum L. cv. Tennessee 86). The
fungicide applied was carbendazim (carb) at a concentration of 2.6 mM . Boron
was applied as H 3 BO 3 at: 1.6 mM
(B1), 4 mM (B2), 8 mM
(B3), 16 mM (B4), 32 mM
(B5), and 64 mM (B6). The results
indicated that foliar application of carbendazim by itself does not increase
SOD, GPX, CAT or APX activities or H2
O2 foliar accumulation. The combined application of
carbendazim and B increased SOD, GPX, CAT, and APX activities, especially in
carb-B3 and carb-B4 . This effect
may signify an additional tolerance mechanism to pathogenic infection, given
the participation of these enzymes in the early phases of the
plant–pathogen interactions.
Comparative analysis of mitochondrial citrate synthase gene structure, transcript level and enzymatic activity in acidless and acid-containing Citrus varieties
Authors: Sadka Avi , Dahan Esther , Or Etti , Roose Mikeal L. , Marsh Kenneth B. , Cohen Lidya
Published: September 2002

Most citrus (Citrus L. spp.) fruits accumulate a
considerable amount of citric acid in the vacuoles of the juice sac cells. As
part of research aimed to understand the mechanism of acid accumulation, we
compared the gene structures and transcript levels of citrate synthase in sour
lemon (high acid, C. limon (L.) Burm.),
‘Shamouti’ orange (moderate acid,
C. sinensis (L.) Osbeck) and sweet lime (acidless,
C. limmetioides Tan.). Southern analyses suggested that
a single gene for citrate synthase was present in the genomes of all three
Citrus varieties. The gene structures seemed to be very
similar, with minor differences in Shamouti orange. Overall, the transcript
levels of citrate synthase were similar in sweet lime and sour lemon, and
about 2-fold lower in Shamouti orange. The enzymatic activity of citrate
synthase was compared between sour lemon and sweet lime. In sour lemon, the
specific activity of the enzyme was induced early in fruit development and, in
parallel with the increase in acid content, reached a maximal level, and did
not diminish significantly towards fruit maturation; the pattern and level of
activity detected during sweet lime fruit development were similar. These
results suggest that the difference in acid accumulation between acidless and
acid-containing fruits may not be attributed to changes in the activity of
citrate synthase.
Ripening of 'Red Rosa' plums: effect of ethylene and 1-methylcyclopropene
Authors: Dong Li , Zhou Hong-Wei , Sonego Liliane , Lers Amnon , Lurie Susan
Published: September 2002

‘Red Rosa’, a Japanese type plum, was treated with 0.1 ppm
1-methylcyclopropene (1-MCP) for 20 h at 20˚C at harvest and then held at
20˚C for ripening together with untreated fruit, or placed at 0˚C
storage for 5 weeks. Another batch of plums were exposed to 15 ppm ethylene
during storage at 0˚C. Fruits ripening directly after 1-MCP treatment had
lower ethylene production and softened more slowly than untreated fruits.
Following storage, both the ethylene-treated and 1-MCP-treated fruits were low
in ethylene production and softened more slowly than untreated fruits. They
also showed lower exo-polygalacturonase (exo-PG) and endo-glucanase (EGase)
activities. Respiration rates, pectin esterase (PE) and endo-PG activities
were similar in 1-MCP-treated and control fruits. Cell wall enzyme activities
were different amongst the treatments, but did not correlate with the
differences in fruit softening. 1-Aminocyclopropane–1-carboxylic acid
(ACC) oxidase (ACO) activity was highest in ethylene treated fruit during
ripening after storage, while the mRNA abundance was highest in control fruit
at removal from storage. ACC synthase (ACS) activity was higher in control and
1-MCP-treated fruit than in ethylene-treated during ripening after storage,
and message abundance was highest at removal from storage in control fruit.
ACC content was highest in fruits at removal from storage. The results are
discussed in terms of the role of ethylene in ripening of ‘Red
Rosa’ plums.
Leaf anatomical characteristics associated with shoot hydraulic conductance, stomatal conductance and stomatal sensitivity to changes of leaf water status in temperate deciduous trees
Authors: Aasamaa Krõõt , Sõber Anu , Rahi Märt
Published: September 2002

Some anatomical characteristics in leaves relating to hydraulic conductance
and stomatal conductance were examined in six temperate deciduous tree
species. The fourth power of the radius of the conducting elements in xylem
(r4) and the area of mesophyll and
epidermal cells per unit length of leaf cross-section
(u) were high in leaves with high hydraulic conductance
(L). Stomatal conductance (gs) and
stomatal sensitivity to an increase in leaf water potential
(si) correlated positively with
the length of stomatal pore (l), but negatively with the
guard cell width (z) and the length of the dorsal side
of the guard cells (ld). Stomatal
sensitivity to a decrease in leaf water potential
(sd) correlated negatively with l
and positively with z and
ld. The anatomical characteristics
associated with hydraulic conductance
(r4 and u)
and those associated with stomatal conductance and sensitivity to changes of
leaf water potential (l, z and
ld) were correlated. We conclude
that hydraulic conductance may depend on anatomical characteristics of xylem,
mesophyll and epidermis, and stomatal conductance and its sensitivity to
changing water potential may depend on anatomical characteristics of stomata.
The correlation of shoot hydraulic conductance with stomatal conductance and
its sensitivity may be based largely on the correlation between the anatomical
characteristics of the water conducting system and stomata in these trees.
Possible involvement of condensed tannins in aluminium tolerance of Lotus pedunculatus
Authors: Stoutjesdijk Peter A. , Sale Peter W. , Larkin Philip J.
Published: September 2002

We investigated the distribution of aluminium (Al) in the root tips of the
Al-tolerant forage legume,Lotus pedunculatus Cav., a
species that also accumulates condensed tannin (proanthocyanidin) in the roots
and leaves. Clonal cuttings were grown in low ionic-strength nutrient
solutions containing Al at levels that were either stimulatory or inhibitory
(5–60µM ). The X-ray microanalysis of
treated root apices revealed Al deposits at all Al concentrations. In
freeze-fractured root samples from high Al concentrations (30 and 60 M ),
deposits were found very close to the root tip. These deposits were
predominantly composed of Al, phosphorus (P) and silicon (Si). At low Al
concentrations (10 µM ), epoxy-embedded root samples were examined and
Al deposits were also found near the meristematic areas. At lower
concentrations (10 µM ), Al was found associated with P. In all
osmium-fixed samples from high and low Al concentrations, Al was generally
found in association with osmium-binding vacuoles. Because of the established
high affinity of osmium for condensed tannin, the hypothesis is developed that
condensed tannins possibly bind and detoxify Al in the root apices of
L. pedunculatus.
Research Note: Boron deficiency affects early infection events in the pea-Rhizobium symbiotic interaction
Authors: Redondo-Nieto Miguel , Rivilla Rafael , El-Hamdaoui Abdelaziz , Bonilla Ildefonso , Bolaños Luis
Published: September 2002

The effects of the deprivation of boron (B) on
Rhizobium–legume signaling and preinfection events
have been investigated in pea (Pisum sativum L. cv.
Argona). The capacity of root exudates to induce the activity of nodulation
genes was modulated by B nutrition in the host plant. Exudates derived from
B-deficient pea plants led to a low level of nod-gene
expression that could be correlated with poor root hair curling. However,
inoculation of B-deficient plants with bacteria grown in the presence of the
nod-gene inducing hesperetin, restored root hair
curling. The attachment of bacteria to roots was also diminished in plants
grown in the absence of the micronutrient, and it was not recovered by
hesperetin. Both phenomena provoked a reduction in nodulation of more than
50%. Furthermore, infection thread development was arrested at very
early stages, and cell invasion by endocytosis was precluded, leading to
almost empty of bacteria B-deficient nodules.
Cold-induced photoinhibition and foliar pigment dynamics of Eucalyptus nitens seedlings during establishment
Authors: Close Dugald C. , Beadle Chris L. , Hovenden Mark J.
Published: September 2002

The effects of cold-induced photoinhibition on chlorophyll and carotenoid
dynamics and xanthophyll cycling in Eucalyptus nitens
(Deane and Maiden) Maiden were assessed between planting and 32 weeks after
planting. The seedlings were fertilised or nutrient-deprived (non-fertilised)
before planting and shaded or not shaded after planting. The experimental site
was 700 m a.s.l., which is considered marginal for establishment of
E. nitens plantations in Tasmania due to low mean annual
minimum temperatures. Low temperature–high light conditions caused a
reduction in variable to maximal chlorophyll fluorescence ratio
(F v /F
m ), which was more pronounced in non-fertilised than in
fertilised seedlings. Shadecloth shelters alleviated this depression. Except
in shaded fertilised seedlings, F
v /F m
did not recover to the level before planting until after 20 weeks. Total
chlorophyll content was initially reduced in shaded treatments but
subsequently increased with increasing temperatures and
F v /F
m. Total xanthophyll content and xanthophylls per unit
chlorophyll remained relatively constant in fertilised seedlings but decreased
in non-fertilised seedlings within 2 weeks after planting. Total xanthophyll
and xanthophylls per unit chlorophyll subsequently recovered in non-shaded,
non-fertilised seedlings with increasing temperatures and
F v /F
m. Diurnal [yield and non-photochemical quenching
(NPQ) and seasonal (F v
/F m) variation in chlorophyll
fluorescence parameters were not reflected in xanthophyll cycling during the
period of most severe photoinhibition. This result may indicate that
chlorophyll–xanthophylls protein complexes form in winter-acclimated
E. nitens foliage as have been demonstrated to occur in
Eucalyptus pauciflora Sieb. ex Spreng. (Gilmore and Ball
2000,
Proceedings of the National Academy of Sciences USA
97, 11098–11101).
Structures and expression patterns of two cDNA clones encoding S-adenosyl-L-methionine synthetase from the root nodule of Elaeagnus umbellata
Authors: Lee Sang Ho , Kim Ho Bang , An Chung Sun
Published: September 2002

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000
Two cDNA clones encoding S-adenosyl-L-methionine
synthetase (SAMS) were isolated from the root nodule cDNA library of
Elaeagnus umbellata Thunberg and analysed on the basis
of deduced amino acid sequence and expression pattern. Two
EuSAMS clones shared 75–84% identity at the
nucleotide level, and 85–95% identity at the amino acid level,
with the other plant SAMS genes. Genomic Southern
hybridization revealed the presence of more than two copies of
SAMS genes in the genome of
E. umbellata. Reverse transcriptase-mediated polymerase
chain reaction (RT–PCR) analysis showed EuSAMS1
transcripts were more abundant than those of EuSAMS2.
Similar to the expression pattern of other plant SAMS
genes, both genes were expressed at higher levels in root than in leaf. During
nodule development, expression of both genes was increased, with the highest
level at 6–8 week after inoculation, and decreased rapidly thereafter.
In situ hybridization analysis also showed both
SAMS transcripts in the meristem zone, the infected
cells of the fixation zone and in the central vascular system of root nodules.
However, EuSAMS2 transcripts were strongly detected in
the prefixation zone, whereas EuSAMS1 transcripts were
hardly detected. These results suggest different regulatory mechanisms for the
two genes in the root nodule. The expression pattern of
SAMS genes in the root nodule may correlate mostly with
cell wall synthesis, polyamine biosynthesis and other methylation-mediated
functions.
Carbon metabolism in developing spears of two asparagus (Asparagus officinalis) cultivars with contrasting yield
Authors: Guo Jianmin , Jermyn William A. , Turnbull Matthew H.
Published: September 2002

To assess the relative importance of sucrose-cleaving enzymes in the
regulation of carbon accumulation in developing asparagus spears (growing
shoots), we investigated spear elongation, carbohydrate accumulation and
enzyme activities of acid invertase (AI), neutral invertase (NI) and sucrose
synthase (SS) in two asparagus (Asparagus officinalis
L.) cultivars with contrasting yield. The greater elongation rate measured in
the high-yielding cultivar ASP-69 was associated with a significantly higher
hexose accumulation (P < 0.05) in spear tissue in
comparison with the low-yielding cultivar ASP-03. However, sucrose content was
similar in the two cultivars, suggesting a more efficient machinery for
transport and catalysis of carbohydrate in spears of ASP-69. Biochemical
evidence indicated that the greater elongation rate in ASP-69 was associated
with a significantly higher AI activity (P < 0.05) in
the elongation zone, whereas SS activity was not significantly different
between the two cultivars. There was little NI activity detected in either
cultivar. These results strongly suggest that it is AI, and not SS or NI, that
is an important determinant of the difference in sucrose metabolism between
the two asparagus cultivars in metabolising imported sucrose in the elongation
region, which in turn plays a part in regulating the import of sucrose into
spear tissue. The profile of sucrose-cleaving enzyme activities along spear
sections indicated that SS was the dominant enzyme in both the tip and base of
spears, whereas AI was the dominant enzyme in the elongation zone. Apart from
sucrose-cleaving enzymes, the associated biochemical processes for structure
and component synthesis in spear tissues also contributed to the regulation of
carbohydrate accumulation. It is most likely that carbohydrate metabolism in
the developing spears is a whole spear property influenced by sucrose
degradation (AI and SS activity) and its utilisation in building spear
structure and storage materials. The overall data substantiate the conclusion
that changes in the activity of sucrose-cleaving enzymes are correlated with
sink functions in developing spears.
Cellular localisation and function of a sucrose transporter OsSUT1 in developing rice grains
Authors: Furbank Robert T. , Scofield Graham N. , Hirose Tatsuro , Wang Xin-Ding , Patrick John W. , Offler Christina E.
Published: September 2002

We previously reported the cloning and tissue-specific expression of a gene
encoding a sucrose/proton symporter in rice
(Oryza sativa L.), OsSUT1 (Hirose
et al. 1997,
Plant Cell Physiology38,
1389–1396). This gene is expressed at high levels in the filling grain,
leaf sheath and stem. Expression in these tissues occurred only after heading
i.e. during the development of the reproductive structure as a major sink. In
this paper, we report localisation of the transcript and protein to specific
cells in the filling rice grain by in situ hybridisation
with a probe from theOsSUT1 cDNA, and immunolocalisation
of OsSUT1 and proton-pumping ATPase
(H+-ATPase). An OsSUT1 cDNA
probe recognises a transcript of approximately 2.4 kb, and the SUT1 antibody
recognises a protein of approximately 55 kDa in total membrane protein
extracts from the filling grain, leaf sheath and stem. In the developing
grain, OsSUT1 is expressed at low levels before heading,
with expression reaching a peak approximately ten days after emergence of the
panicle from the sheath. Transcript is then present throughout seed
development, with expression falling substantially after about 25 days
post-heading. Both transcript and protein are localised to the aleurone cells
of the developing grain, and are also detected in the maternal tissue,
particularly the nucellus, vascular parenchyma tissue and the nucellar
projection. Tissue slices from filling rice grain showed high rates of sucrose
uptake that were inhibited by pCMBS. The role of OsSUT1
in sucrose transport to the filling grain endosperm is discussed.
Photosynthetic and anatomical characteristics in the C4crassulacean acid metabolism-cycling plant Portulaca grandiflora
Authors: Guralnick Lonnie J. , Edwards Gerald , Ku Maurice S. B. , Hockema Brandon , Franceschi Vince
Published: September 2002

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001.
Portulaca grandiflora (Lind.) is a succulent species with C4 photosynthesis and crassulacean acid metabolism (CAM) cycling in leaves, and CAM-idling type photosynthesis in stems. We investigated the level and localization of carbon fixation enzymes and photosynthetic activity of leaves and stems of P. grandiflora under well-watered and drought conditions. As CAM activity increased during water stress, the leaf water-storage tissue collapsed, presumably transferring water to the bundle sheath and mesophyll cells, and so maintaining the C4 photosynthetic pathway. Tissue prints indicated an increase in phosphoenolpyruvate carboxylase (PEPC) in the water-storage tissue of leaves and the cortex of stems. Immunoblot analyses after 10 d of water stress showed that leaves had a slight decrease in the proteins of the C4-CAM pathway, while at the same time a new isoform of NADP-malic enzyme (NADP-ME) appeared. In contrast, the stem showed increases in proteins of the CAM pathway when water stressed. Under water stress, diurnal fluctuation in acidity in leaves was not accompanied by a net gain or loss of CO2 at night, and there was sustained, but decreased, fixation of CO2 during the day, characteristic of CAM cycling. High gross rates of O2 evolution were maintained during the day under water stress, suggesting induction of alternative electron sinks. With induced diurnal fluctuations in acidity in stems, there was no net carbon gain during the day or night. These results demonstrate, for the first time, that the stem of P. grandiflora is an inducible CAM-idling tissue. Our results also indicate that the C4 and CAM pathways operate independently of one another in P. grandiflora.
Two CO2 uptake systems in cyanobacteria: four systems for inorganic carbon acquisition in Synechocystis sp. strain PCC6803
Authors: Shibata Mari , Ohkawa Hiroshi , Katoh Hirokazu , Shimoyama Masaya , Ogawa Teruo
Published: September 2002

The cyanobacterium Synechocystis sp. strain PCC6803
possesses two CO2 uptake systems; one constitutive,
dependent on NdhD3/NdhF3/CupA (Sll1734), and one low-CO2 inducible,
dependent on NdhD4/NdhF4/CupB (Slr1302). Homologues of these genes are
present in pairs in most cyanobacterial strains.
Synechocystis PCC6803 also possesses two types of
HCO3– transporters; an
ATP-binding cassette (ABC)-type transporter encoded by the
cmp operon, and a novel sodium-dependent transporter
encoded byslr1512(sbtA) that plays
a central role in HCO3–
uptake. Mutants impaired for one of these four inorganic-carbon acquisition
systems did not show mutant phenotype. Mutants inactivated for both
CO2 uptake systems were unable to grow at pH 7.0 in air,
although they grew normally at pH 9.0 in air. Additional inactivation of the
SbtA-type HCO3– transporter abolished growth at pH 9.0 in air. A
fragment containing the promoter region of ndhF3 fused
to the coding region of luxAB was inserted into a neutral
site of the ΔndhD4 mutant to construct
apF3-lux/ ΔndhD4 strain. The luminescence
intensity of this strain was low in high-CO2 grown
cells, and was increased about 100 times after acclimation to air.
Inactivation of the pF3-lux/ ΔndhD4 strain
with a transposon-tagging library enabled us to isolate mutants incapable of
acclimation to low CO2.
Hyperaccumulation of manganese in the rainforest tree Austromyrtus bidwillii (Myrtaceae) from Queensland, Australia
Authors: Bidwell Sjaan D. , Woodrow Ian E. , Batianoff George N. , Sommer-Knudsen Jens
Published: September 2002

Throughout the world, over 400 species of plants are known to accumulate large quantities of metals in their shoots (`hyperaccumulators'), but of these, relatively few accumulate manganese (Mn). We have identified for the first time an Australian native hyperaccumulator of Mn, Austromyrtus bidwillii (Benth.) Burrett (Myrtaceae). Concentrations of Mn up to 19 200 µg g-1 were measured in dried leaves of this rainforest tree, and young bark was found to contain up to 26 500 µg g-1 Mn. Approximately 40% of the Mn in the leaves is readily extracted with water, suggesting that some of the Mn is associated with water-soluble compounds such as organic acids. Organic acids present in appreciable amounts in leaf extracts of A. bidwillii were identified and quantified by HPLC and gas chromatography-mass spectrometry. The following organic acids (in order of concentration) were present: succinic > malic ≥ malonic > oxalic >> citric acid. The concentration of total organic acids was on average 123 000 µg g-1 dry tissue, which amounted to approximately three times the molar equivalent of Mn and two times the molar equivalent of total cations (Mn, Mg and Ca), demonstrating that organic anions were in excess. The Mn remaining after water extraction ((61 ± 3.9%) could be extracted with 0.2M HCl, suggesting that a significant portion of the Mn is associated with the cell wall (perhaps replacing Ca) or is present as other insoluble compounds.
Resistance is useful: diurnal patterns of photosynthesis in C3 and crassulacean acid metabolism epiphytic bromeliads
Authors: Maxwell Kate
Published: September 2002

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001
Diurnal patterns of photosynthesis in response to environmental variables were investigated in an obligate C3 and a facultative C3-crassulacean acid metabolism (CAM) bromeliad species. A midday depression of photosynthesis occurred in both C3 groups, mediated as a decrease in stomatal conductance in response to increased vapour pressure difference. The response was associated with a reduction in Rubisco activation state during the period of maximum photon flux density. In contrast, the switch to CAM resulted in a strong shift in the pattern of Rubisco carbamylation, with full enzyme activation delayed until the midday period. For the first time it is demonstrated that the pattern of Rubisco activation differs between C3 and CAM plants of the same species under identical conditions. Despite large differences in Rubisco content between C3 and CAM plants, neither the amount of Rubisco or enzyme activity is thought to be limiting for photosynthesis, and it is suggested that Rubisco may function as a nitrogen store. Extreme CO2 diffusion limitation resulted in low rates of atmospheric CO2 assimilation that were associated with high rates of photosynthetic electron transport, and it is likely that photorespiration constitutes a significant electron sink over the entire diurnal course. Leaf morphological and physiological adaptations to drought stress are necessary for the epiphytic lifestyle but limit CO2 assimilation and confound the likelihood of high productivity.
Mechanistic interpretation of carbon isotope discrimination by marine macroalgae and seagrasses
Authors: Raven John A. , Johnston Andrew M. , Kübler Janet E. , Korb Rebecca , McInroy Shona G. , Handley Linda L. , Scrimgeour Charlie M. , Walker Diana I. , Beardall John , Vanderklift Mathew , Fredriksen Stein , Dunton Kenneth H.
Published: September 2002

The literature, and previously unpublished data from the authors’
laboratories, shows that the δ13C of organic
matter in marine macroalgae and seagrasses collected from the natural
environment ranges from –3 to –35‰. While some marine
macroalgae have δ13C values ranging over more than
10‰ within the thallus of an individual (some brown macroalgae), in
other cases the range within a species collected over a very wide geographical
range is only 5‰ (e.g. the red alga
Plocamium cartilagineum which has values between
–30 and –35‰). The organisms with very negative
δ13C (lower than –30‰) are mainly
subtidal red algae, with some intertidal red algae and a few green algae;
those with very positive δ13C values (higher than
–10‰) are mainly green macroalgae and seagrasses, with some red
and brown macroalgae. The δ13C value correlates
primarily with taxonomy and secondarily with ecology. None of the organisms
with δ13C values lower than –30‰
have pyrenoids. Previous work showed a good correlation between
δ13C values lower than –30‰ and the
lack of CO2 concentrating mechanisms for several species
of marine red algae. The extent to which the low
δ13C values are confined to organisms with
diffusive CO2 entry is discussed. Diffusive
CO2 entry could also occur in organisms with higher
δ13C values if diffusive conductance was
relatively low. The photosynthesis of organisms with
δ13C values more positive than –10‰
(i.e. more positive than the δ13C of
CO2 in seawater) must involve
HCO3- use.
Calcification and inorganic carbon acquisition in coccolithophores
Authors: Berry Lorraine , Taylor Alison R. , Lucken Uwe , Ryan Keith P. , Brownlee Colin
Published: September 2002

A number of species of coccolithophorid phytoplankton precipitate calcite
inside intracellular vesicles (coccolith vesicles). They can form vast blooms
under certain conditions, and account for major fluxes of inorganic carbon
(Ci) to the ocean floor. The functions of calcification have been debated for
many years, and a role in carbon acquisition has been proposed by several
workers. The precipitation of calcite from
HCO3- involves the production of
protons that can potentially be used to facilitate the use of external
HCO3- as a photosynthetic
substrate. For this function to be feasible, certain criteria must be met.
HCO3- (rather than
CO32–) should be the
external substrate for calcification, photosynthesis should be facilitated by
HCO3- in calcifying cells when
CO2 availability is limiting, and the transport of Ci
and Ca2+ to the site of calcification should be
energetically and kinetically feasible. Considerable evidence exists for
HCO3- as the substrate for
calcification in coccolithophores. However, evidence for a direct role for
calcification in supply of Ci for photosynthesis is less clear. The
environmental factors that regulate calcification are still uncertain but
appear to be related as much to the availability of nutrients as
CO2. Transport of Ci to the intracellular site of
calcification and removal of H+ from the coccolith
vesicle appear to present few energetic or kinetic constraints. However, the
large sustained transcellular fluxes of Ca2+
required for calcification probably occur via a pathway that does not involve
diffusion across the cytoplasm.
Nitrogen nutrition during ontogeny of hemiepiphytic Clusia species
Authors: Wanek Wolfgang , Arndt Stefan K. , Huber Werner , Popp Marianne
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 the nitrogen (N) nutrition of Clusia osaensis, C. peninsulae and C. valerii during the seedling, epiphytic and hemiepiphytic phase in a lowland tropical forest in Costa Rica in order to elucidate nutritional adaptations of different plant growth stages to their habitat. Although all Clusia individuals were non-mycorrhizal, excised roots of seedlings, but also of epiphytic and hemiepiphytic stages, showed a distinct preference for glycine uptake. The shift in main rooting site from canopy soil to terrestrial soil was not reflected by changes in uptake rate or preference, although N availability and the composition of the available N pool changed significantly. High foliar N concentrations indicated that epiphytic seedlings seemed to be sufficiently supplied with N by maternal seed resources and canopy soils. With development, the epiphytic plants of Clusia may face N limitation due to higher N demands with increasing growth and restricted resources in the tree crowns. 15N natural abundance data indicate that epiphytes mainly accessed atmospheric and, to a lesser extent, canopy soil N sources and, after becoming terrestrially anchored, in the hemiepiphytic life stage exploited the larger nutrient reservoir of the ground soil. In consequence, Clusia species did not show an adaptation to the different N availability situations that they experienced whether canopy or ground-rooted.
Impact of root morphology on metabolism and oxygen distribution in roots and rhizosphere from two Central Amazon floodplain tree species
Authors: De Simone Oliviero , Haase Karen , Müller Ewald , Junk Wolfgang J. , Gonsior Guido , Schmidt Wolfgang
Published: September 2002

Adaptation to prolonged flooding was investigated using cuttings of two tree species from the Central Amazon white-water floodplain (V�rzea). Morphological features and oxygen distribution patterns were correlated with metabolic changes under hypoxia, such as alterations in alcohol dehydrogenase (ADH) activity and adenylate energy charge (AEC) of root cells. Salix martiana (Leyb.) was able to react to hypoxic growth conditions with formation of adventitious roots rich in lysigenous aerenchyma, which facilitates root aeration by longitudinal oxygen transport and rhizosphere oxidation by radial oxygen loss (ROL). The oxygen concentration on the surface of adventitious roots of S. martiana reached 2-3 mg O2 L–1. The low resistance to gas exchange in Salix roots was reflected by low ADH activities, which ranged between 0.03-0.1 μmol NADH mg –1 min–1, and AEC values of 0.8-1 under hypoxic conditions. Adventitious roots were also formed by Tabernaemontana juruana ([Markgr.] Schumann ex. J.F. Macbride) during growth under low-oxygen conditions, although at a later stage. The gas-space continuum in roots of T. juruana was less pronounced, resulting in a 10-fold lower oxygen concentration in the root cortex under oxygen stress compared with adventitious roots of Salix. The lower oxygen content was reflected in 6-fold higher ADH activities and decreased AEC values. ROL occurred only at the non-suberized root tip, suggesting that the suberized hypodermis functions as a barrier against gas exchange between the root and the rhizosphere. These findings indicate that different strategies of adaptation to low oxygen levels are realized in the two species under investigation that occur naturally in the same ecosystem but inhabit different elevation sites.
Environmental, hormonal and circadian regulation of crassulacean acid metabolism expression
Authors: Taybi Tahar , Cushman John C. , Borland Anne M.
Published: September 2002

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001.
Expression of crassulacean acid metabolism (CAM) is characterized by the extreme plasticity observed within and between species. Switches between C3 photosynthesis and CAM, and subsequent 24-h patterns of day/night CO2 uptake, are tightly controlled by a variety of environmental and metabolic factors that optimize the response of CAM plants to the most challenging environments over seasonal and daily time scales. Regulation of the genes and enzymes involved in CAM and connected metabolic pathways occurs at a number of levels (transcriptional through to post-translational). Such multiple levels of control are considered to be the key to the photosynthetic plasticity of CAM. Here, we review some of the primary environmental and hormonal factors controlling CAM plasticity in different CAM-inducible species, with emphasis on the regulatory signalling circuits responsible for this control. We also examine the inherent circadian regulation of the pathway, mainly in the context of the diel regulation of phosphoenolpyruvate carboxylase and the dedicated kinase that modulates its activity. We then consider the role of secondary signals, with emphasis on changes in cytosolic [Ca2+]i and the downstream signalling pathways, based on studies conducted on Mesembryanthemum crystallinum L. Besides representing an important metabolic adaptation, CAM provides an intriguing paradigm for studying the complex signalling mechanisms that control and coordinate the expression of genes under a variety of short- and long-term environmental perturbations.
NMR study of low subcellular pH during the development of cherry tomato fruit
Authors: Rolin Dominique , Baldet Pierre , Just Daniel , Chevalier Christian , Biran Marc , Raymond Philippe
Published: September 2002

Changes in metabolites (organic acids, sugars and amino acids) and subcellular
pH were studied during fruit development of cherry tomato
(Lycopersicon esculentum Mill. var.
cerasiformae). Fructose and glucose were the major
sugars, whereas citrate and malate the two major organic acids. At different
stages of fruit development, vacuolar and cytoplasmic pH changes were followed
by in vivo 13C and
31P NMR spectroscopy. Fruit compartments had a
cytoplasmic pH around 7.1 as early as the cell-divi-sion and -expansion
stages. The vacuolar pH measured by in vivo
13C NMR spectroscopy decreased from 4.5 to 3.6.
Concomitantly, strong accumulation of γ-aminobutyric acid (GABA) was
observed during the first 15 days after anthesis and glutamate decarboxylase
(GAD) activity increased 10-fold during the first 8 days of development. The
relationships between organic acid biosynthesis and storage, GABA produc-tion,
and subcellular pH changes during development of cherry tomato fruit are
discussed.
Effects of ageing and salicylate on beetroot mitochondria
Authors: Potter Felicity Johnson , Bennett Ellen , Wiskich Joseph T.
Published: September 2002

Root tissue slices of
Beta vulgaris were aged by aerated mixing for 5 d in 0.1
mM CaSO4 solution with and without 0.5 mM salicylate (pH
7.0). Mitochondria, isolated from treated and fresh beetroot tissue, were
investigated, and the activities of the NAD(P)H oxidising pathways of the
mitochondrial inner and outer membranes, together with the activity of the
alternative pathway, were measured. From these we determined which
non-phosphorylating pathways of mitochondrial respiration were induced by the
treatments. The presence of salicylate in the ageing treatment was shown to
increase the activity of the alternative pathway as well as the level of
alternative oxidase protein. This increase was above that seen in the ageing
treatment alone. Investigation of the other non-phosphorylating pathways of
mitochondrial respiration indicated that while they also increased during
ageing, they were not specifically affected by salicylate treatment. The
specific induction of the alternative pathway increased activity by almost
4-fold from the fresh tissue and 2-fold from the aged tissue rates.
Application of commercially available, low-cost, miniaturised NIR spectrometers to the assessment of the sugar content of intact fruit
Authors: Walsh Kerry B. , Guthrie John A. , Burney Justin W.
Published: September 2002

Recent decreases in costs, and improvements in performance, of silicon array
detectors open a range of potential applications of relevance to plant
physiologists, associated with spectral analysis in the visible and short-wave
near infra-red (far-red) spectrum. The performance characteristics of three
commercially available ‘miniature’ spectrometers based on silicon
array detectors operating in the 650–1050-nm spectral region (MMS1 from
Zeiss, S2000 from Ocean Optics, and FICS from Oriel, operated with a Larry
detector) were compared with respect to the application of non-invasive
prediction of sugar content of fruit using near infra-red spectroscopy (NIRS).
The FICS–Larry gave the best wavelength resolution; however, the narrow
slit and small pixel size of the charge-coupled device detector resulted in a
very low sensitivity, and this instrumentation was not considered further.
Wavelength resolution was poor with the MMS1 relative to the S2000 (e.g. full
width at half maximum of the 912 nm Hg peak, 13 and 2 nm for the MMS1 and
S2000, respectively), but the large pixel height of the array used in the MMS1
gave it sensitivity comparable to the S2000. The signal-to-signal standard
error ratio of spectra was greater by an order of magnitude with the MMS1,
relative to the S2000, at both near saturation and low light levels.
Calibrations were developed using reflectance spectra of filter paper soaked
in range of concentrations (0–20% w/v) of sucrose, using a
modified partial least squares procedure. Calibrations developed with the MMS1
were superior to those developed using the S2000 (e.g. coefficient of
correlation of 0.90 and 0.62, and standard error of cross-validation of 1.9
and 5.4%, respectively), indicating the importance of high signal to
noise ratio over wavelength resolution to calibration accuracy. The design of
a bench top assembly using the MMS1 for the non-invasive assessment of
mesocarp sugar content of (intact) melon fruit is reported in terms of light
source and angle between detector and light source, and optimisation of math
treatment (derivative condition and smoothing function).
Role of starch in carbon translocation and partitioning at the plant level
Authors: Geiger Donald R. , Servaites Jerome C. , Fuchs Mark A.
Published: September 2002

Endogenous regulation of translocation and of
carbon partitioning, major factors for integrating plant function, depend on
diurnal regulation of starch synthesis and mobilization. Regulated diurnal
cycling of transitory starch provides a steady carbon supply to sink growth
and avoids potentially adverse high sugar levels. Carbon availability from
starch affects development and alters carbon availability with respect to
nitrogen. Along with sugar sensing, the level and turnover of starch are
involved in endogenous regulation in response to carbohydrate status. Despite
their key roles in plant metabolism, mechanisms for endogenous regulation of
starch synthesis and degradation are not well characterized. Time course
studies with labeled carbon reveal endogenous diurnal regulation of starch
metabolism, by which sucrose synthesis from starch and newly-fixed carbon are
mutually regulated in support of translocation at night, under low light, and
during periods of water stress. Even under steady irradiance, which supports
photosynthesis at midday levels, starch synthesis begins gradually and slows
under an end-of-day circadian regulation that anticipates the dark period.
Studies with Arabidopsis mutants identified two
requisite components of starch mobilization, endoamylase, and glucose
transport across the chloroplast inner envelope. Time course studies of
carbohydrate levels and labeling studies of plant-level carbon metabolism in
mutant plants with impaired ability to mobilize starch identified steps in
starch mobilization that support diurnal regulation of translocation.
Endogenously regulated exit of glucose across the chloroplast membrane appears
to regulate starch mobilization.
Characterisation of a methionine-rich storage protein cDNA from perilla (Perilla frutescens) seeds
Authors: Jin Un-Ho , Jin Byung-Rae , Lee Jin-Woo , Cho Young-Su , Kwon O-Chang , Kim Young-Kil , Chung Chung-Han
Published: September 2002

We have cloned and characterised a cDNA
(PrLeg) coding for a methionine-rich storage protein,
which is reported for the first time in perilla
(Perilla frutescens (L.) Britt. var. Japonica) seeds,
homologous to the 11S legumin-like storage proteins. The most significant
feature of the PrLeg precursor protein is that it has the highest content of
methionine residues among the 11S legumin-like storage proteins examined so
far. Another feature is that the deduced amino acid sequences of the PrLeg
protein are phylogenetically close to the sequence groups derived from
evolutionally ancient states of the 11S legumin-like storage proteins, or from
gymnospermous seed storage proteins, such as Magnolia,
Asarum, Dioscorea,
Cryptomeria, Metasequoia and
Ginkgo. In contrast, with the exception of sesame,
relatively low phylogenetic relationships are determined between the PrLeg
sequence group and those derived from crop plants, such as soybean, pea, broad
bean, rape, pumpkin, rice, coffee and citrus. Southern blot analysis suggests
that there may be several copy numbers of thePrLeg genes
and their seed-specific expression patterns at the transcriptional level were
confirmed by northern hybridisation analysis.
The role of biomass allocation in the growth response of plants to different levels of light, CO2, nutrients and water: a quantitative review
Authors: Poorter Hendrik , Nagel Oscar
Published: September 2002

The allocation of biomass to different plant
organs depends on species, ontogeny and on the environment experienced by the
plant. In this paper we first discuss some methodological tools to describe
and analyse the allocation of biomass. Rather than the use of shoot:root
ratios, we plead strongly for a subdivision of biomass into at least three
compartments: leaves, stems and roots. Attention is drawn to some of the
disadvantages of allometry as a tool to correct for size differences between
plants. Second, we tested the extent to which biomass allocation of plants
follows the model of a ‘functional equilibrium’. According to this
model, plants respond to a decrease in above-ground resources with increased
allocation to shoots (leaves), whereas they respond to a decrease in
below-ground resources with increased allocation to roots. We carried out a
meta-analysis of the literature, analysing the effect of various environmental
variables on the fraction of total plant biomass allocated to leaves (leaf
mass fraction), stem (stem mass fraction) and roots (root mass fraction). The
responses to light, nutrients and water agreed with the (qualitative)
prediction of the ‘functional equilibrium’ theory. The notable
exception was atmospheric CO2, which did not affect
allocation when the concentration was doubled. Third, we analysed the
quantitative importance of the changes in allocation compared to changes in
other growth parameters, such as unit leaf rate (the net difference between
carbon gain and carbon losses per unit time and leaf area), and specific leaf
area (leaf area: leaf biomass). The effects of light,
CO2 and water on leaf mass fractions were small compared
to their effects on relative growth rate. The effects of nutrients, however,
were large, suggesting that only in the case of nutrients, biomass allocation
is a major factor in the response of plants to limiting resource supply.
Modification of rhizosphere pH by the symbiotic legume Aspalathus linearis growing in a sandy acidic soil
Authors: Muofhe Mmboneni L. , Dakora Felix. D.
Published: September 2002

Aspalathus linearis is a N2-fixing
legume used for tea production, and grows in highly acidic soils (pH
3–5.3) of the Cederberg mountains in South Africa. Field and glasshouse
studies revealed significantly higher pH in rhizosphere than non-rhizosphere
soils. However, when six non-legume species were studied in adjacent fields,
there were no differences in pH between rhizosphere and non-rhizosphere soils.
The culture of A. linearis plants in sterile Leonard
jars similarly showed a marked increase of 2.8 pH units in the nutrient
solution bathing the roots of inoculated (nodulated) plants, compared to 1.5
pH units in uninoculated control. The uptake and reduction of
NO3– by plants fed 2 mM
NO3– also raised the
rhizosphere pH by 3.5 units, a value comparable to that of the nodulated
plants. The use of titrimetric methods showed that
OH– and
HCO3– were the components of
alkalinity in the nutrient solution bathing roots of
A. linearis, and were directly responsible for the
increase in rhizosphere pH. These findings suggest that the ability to raise
rhizosphere pH is an adaptative feature of this legume symbiosis that
overcomes the adverse effects of low pH in enhancing nutrient acquisition and
reducing trace element toxicity.
The influence of elevated CO2 on the activities of antioxidative enzymes in two soybean genotypes
Authors: Pritchard Seth G. , Ju Zhenlin , van Santen Edzard , Qiu Jiansheng , Weaver David B. , Prior Stephen A. , Rogers Hugo H.
Published: September 2002

The effects of elevated compared to current atmospheric
CO2 concentration (720 and 365 L L
–1 , respectively) on antioxidative enzymatic
activities of two soybean (Glycine max (L.) Merr.)
genotypes (R and S) grown in open-top field chambers were investigated.
Enzymatic activities of leaves collected 40, 47, 54 and 61 d after planting
were measured. Elevated CO2 significantly decreased
activities of superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC
1.11.1.7), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APOD, EC
1.11.1.7), gluta-thione peroxidase (GPOD, EC 1.11.1.9) and glutathione
reductase (GR, EC 1.6.4.2) in both genotypes. The activi-ties of
dehydroascorbate reductase (DAR, EC 1.8.5.1) and monodehydroascorbate
reductase (MDAR, EC 1.1.5.4.) increased in genotype S, but decreased in
genotype R under elevated CO2. Elevated
CO2 decreased rubisco activity and rubisco, chlorophyll,
carotenoids and total soluble protein contents in both genotypes. Results
indicate that constitutive antioxidative enzymatic activities may decrease in
a high-CO2 world. Significant CO2
¥ genotype interactions, however, suggest that there may be key genotypic
differences in response patterns, potentially conferring differential
resistance to biotic and abiotic stress.