bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light acclimation, CO2 response and long‐term capacity of underwater photosynthesis in three terrestrial plant species
Authors: Vervuren P. J. A. , Beurskens S. M. J. H. , Blom C. W. P. M. 
Published: March 2003

ABSTRACTTo characterize underwater photosynthetic performance in some terrestrial plants, we determined (i) underwater light acclimation (ii) underwater photosynthetic response to dissolved CO2, and (iii) underwater photosynthetic capacity during prolonged submergence in three species that differ in submergence tolerance: Phalaris arundinacea, Rumex crispus (both submergence‐tolerant) and Arrhenatherum elatius (submergence‐intolerant). None of the species had adjusted to low irradiance after 1 week of submergence. Under non‐submerged (control) conditions, only R. crispus displayed shade acclimation. Submergence increased the apparent quantum yield in this species, presumably because of the enhanced CO2 affinity of the elongated leaves. In control plants of the grass species P. arundinacea and A. elatius, CO2 affinities were higher than for R. crispus. The underwater photosynthetic capacity of R. crispus increased during 1 month of submergence. In P. arundinacea photosynthesis remained constant during 1 month of submergence at normal irradiance; at low irradiance a reduction in photosynthetic capacity was observed after 2 weeks, although there was no tissue degeneration. In contrast, underwater photosynthesis of the submergence‐intolerant species A. elatius collapsed rapidly under both irradiances, and this was accompanied by leaf decay. To describe photosynthesis versus irradiance curves, four models were evaluated. The hyperbolic tangent produced the best goodness‐of‐fit, whereas the rectangular hyperbola (Michaelis‐Menten model) gave relatively poor results.
Three new osmotic stress‐regulated cDNAs identified by differential display polymerase chain reaction in rapeseed leaf discs
Authors: Deleu C. , Coustaut M. , Niogret M.‐F. , Larher F. 
Published: March 2003

ABSTRACTPlant osmotic stress responses are associated with changes in gene expression. Osmotic stress‐regulated genes (OR genes) have been isolated by various approaches such as differential screening of cDNA libraries or by complementation. We have used differential display of mRNA to isolate partial cDNAs corresponding to transcripts differentially expressed in leaf discs from osmotically stressed rapeseed. The cloning and the sequencing of three OR genes (MC12, MC43 and MC24) isolated by this method are reported here. Differences in corresponding mRNA levels during the first hours of stress were confirmed by Northern blot analysis. The deduced amino acid sequence of the MC12 and MC43 clones, for which mRNA accumulation was detected under osmotic stress, shows significant similarities to saccharopine dehydrogenase and linker histone H1‐3 genes, respectively. Furthermore these up‐ regulated genes are induced by ABA. The nucleotide sequence of MC24 shows strong homology with a chloroplast gene (rps12) encoding a ribosomal protein. mRNA hybridization with MC24 led to a multiple banding pattern resulting from maturation of polycistronic precursor transcripts. Levels of different sized transcript hybridizing with MC24 decreased during osmotic stress, suggesting that rps12 chloroplast gene is down‐regulated by osmotic stress. Interestingly, up‐regulation of a gene encoding an enzyme involved in lysine catabolism suggests that products from this pathway could be of interest for the adaptation of rapeseed leaf explants subjected to osmotic upshock in vitro. This discovery opens new insights into metabolic adjustment mechanisms under stress.
Diffusion and reaction of oxygen in the central tissue of ureide‐producing legume nodules
Authors: Thumfort P. P. , Layzell D. B. , Atkins C. A. 
Published: March 2003

ABSTRACTPrevious simulation models for the diffusion and reaction of oxygen in legume nodules were based on infected cells and neglected adjacent uninfected cells. This study uses a three‐dimensional model of the central zone of legume nodules made up of the two cell types represented by a geometrically defined, space‐filling, binary combination of polyhedra, each with bevelled edges to allow for a network of intercellular gas spaces. The model predicted a distinctively compartmentalized distribution of [O2] between uninfected and infected cells; with high O2 concentrations for an uninfected cell being consistent with, and necessary for, efficient operation of uricase and ureide synthesis and low O2 concentrations across most of the infected cell providing a suitable environment for N2‐fixation. Compartmentalization of O2 also predicted significant O2 fluxes between cell types, compromising maintenance of low [O2] in infected cells, as well as high [O2] in uninfected cells. The results predict that there might be significant resistance to O2 diffusion across the cell : cell interface due to the plasmalemma and cell walls.
Manganese application alleviates the water deficit‐induced decline of N2 fixation
Authors: Vadez V. , Sinclair T. R. , Serraj R. , Purcell L. C. 
Published: March 2003

ABSTRACTWater deficit is a very serious constraint on N2 fixation rates and grain yield of soybean (Glycine max Merr.). Ureides are transported from the nodules and they accumulate in the leaves during soil drying. This accumulation appears responsible for a feedback mechanism on nitrogen fixation, and it is hypothesized to result from a decreased ureide degradation in the leaf. One enzyme involved in the ureide degradation, allantoate amidohydrolase, is manganese (Mn) dependent. As Mn deficiency can occur in soils where soybean is grown, this deficiency may aggravate soybean sensitivity to water deficit. In situ ureide breakdown was measured by incubating soybean leaves in a 5 mol m−3 allantoic acid solution for 9 h before sampling leaf discs in which remnant ureide was measured over time. In situ ureide breakdown was dramatically decreased in leaves from plants grown without Mn. At the plant level, allantoic acid application in the nutrient solution of hydroponically grown soybean resulted in a higher accumulation of ureide in leaves and lower acetylene reduction activity (ARA) by plants grown with 0 mol m−3 Mn than those grown with 6·6 mol m−3 Mn. Those plants grown with 6·6 mol m−3 Mn in comparison with those grown with 52·8 mol m−3 Mn had, in turn, higher accumulated ureide and lower ARA. To determine if Mn level also influenced N2 fixation sensitivity to water deficit, a dry‐down experiment was carried out by slowly dehydrating plants that were grown in soil under four different Mn nutritions. Plants receiving no Mn had the lowest leaf Mn concentration, 11·9 mg kg−1, and had N2 fixation more sensitive to water deficit than plants treated with Mn in which leaf Mn concentration was in the range of 21–33 mg kg−1. The highest Mn treatments increased leaf Mn concentration to 37·5 mg kg−1 and above but did not delay the decline of ARA with soil drying, although these plants showed a significant increase in ARA under well‐watered conditions.
Protection against the photo‐induced inactivation of the photosystem II complex by abscisic acid
Authors: Saradhi P. Pardha , Suzuki I. , Katoh A. , Sakamoto A. , Sharmila P. , Shi D.‐J. , Murata N. 
Published: March 2003

ABSTRACTTo examine the effect of abscisic acid (ABA) on the photo‐induced inactivation of the photosystem II (PSII) complex, a suspension culture of Chlamydomonas reinhardtii was treated with ABA for 24 h in darkness and then, after removal of ABA, the cells were exposed to strong light at a photon flux density of 2000 μmol m−2 s−1 at various temperatures. The activity of PSII, as estimated in terms of chlorophyll fluorescence and the evolution of oxygen, decreased significantly during the exposure of cells to the strong light, and the extent of the photo‐induced decrease in PSII activity was much greater at lower temperatures. Irrespective of temperature, the decrease in PSII activity in ABA‐treated cells was significantly smaller than that in control cells. Moreover, the recovery of PSII activity from the photo‐inactivated state in ABA‐treated cells was significantly faster than that in control cells. The recovery of PSII activity in both ABA‐treated and control cells was almost entirely prevented by the presence of chloramphenicol. These results indicate that ABA protects the PSII complex in C. reinhardtii against photo‐induced inactivation by accelerating the recovery of this complex.
Strategy differences of two potato species in response to nitrogen starvation. Do plants have a genetic switch for nitrogen signalling?
Authors: Davies Corinne S. 
Published: March 2003

ABSTRACTSurvival responses to nitrogen starvation are well known in micro‐organisms but little studied in plants. To construct a framework for study of the plant responses, we investigated the strategy differences of tubers from two closely related potato species. Solanum tuberosum conserves tuber nitrogen by inhibiting shoot growth, but S. phureja mobilizes tuber nitrogen to grow shoots, flowers and seeds. Genetic analysis of progeny from S. phureja–haploid S. tuberosum crosses uncovered segregation of a single dominant gene for the S. tuberosum inhibition strategy. Within S. tuberosum, haploid progeny closely resembled their tetraploid parents, suggesting strong genetic control of the inhibition. Growth of the inhibited shoots was proportional to sub‐optimal levels of added nitrate, and was triggered by exogenous gibberellic acid (GA3). These observations support the notion that potato plants can closely tie shoot growth to ambient nitrogen levels – probably by a root–shoot nitrogen signal transduction pathway, and that this can be overridden by emergency mobilization of nitrogen reserves, perhaps by GA signalling from the tuber. Furthermore, genes for such developmental switches can be identified by classical genetic analysis of closely related species, such as S. tuberosum and S. phureja, that exhibit opposite survival strategies.
Effects of light on respiration and oxygen isotope fractionation in soybean cotyledons
Authors: Ribas‐Carbo M. , Robinson S. A. , Gonzàlez‐Meler M. A. , Lennon A. M. , Giles L. , Siedow J. N. , Berry J. A. 
Published: March 2003

ABSTRACTLight effects on electron flow through the cyanide‐resistant respiratory pathway, oxygen isotope fractionation and total respiration were studied in soybean (Glycine max L.) cotyledons. During the first 12 h of illumination there was an increase in both electron partitioning through the alternative pathway and oxygen isotope fractionation by the alternative oxidase. The latter probably indicates a change in the properties of the alternative oxidase. There was no engagement of the alternative oxidase in darkness and its fractionation was 27‰. In green cotyledons 60% of the respiration flux was through the alternative pathway and the alternative oxidase fractionation was 32‰. Exposing previously illuminated tissue to continuous darkness induced a decrease in the electron partitioning through the alternative pathway. However, this decrease was not directly linked with the low cellular sugar concentration resulting from the lack of light because 5 min of light every 12 h was sufficient to keep the alternative pathway engaged to the same extent as plants grown under control conditions.
Heat‐induced protection against death of suspension‐cultured apple fruit cells exposed to low temperature
Authors: Wang C. Y. , Bowen J. H. , Weir I. E. , Allan A. C. , Ferguson I. B. 
Published: March 2003

AbstractDeath of suspension‐cultured apple fruit cells (Malus domestica Borkh. cv. Braeburn), resulting from exposure to low temperature (1 °C), was reduced by a prior 1 h/38 °C treatment. Pre‐heated chilled cells produced less ethylene, indicating lower chilling injury. Heat treatment resulted in increased transcripts for a low molecular weight (hsp17) and a 70 kDa heat shock protein (hsp), but expression weakened within 24 h following the transfer of cells to 25 °C. When cells were instead transferred to 1 °C after heat, elevated hsp gene expression persisted for up to 3 d. Flow cytometric analysis of apple cell protoplasts showed that the 1 °C treatment resulted in a subpopulation of protoplasts undergoing cell death, not observed with the 38 °C pre‐treatment. Chromatin condensation did not occur with the heat treatments. These results suggest that heat‐induced reduction of cell death at low temperatures may involve persistence of hsps, and low‐temperature susceptibility is less likely to be associated with programmed cell death. All cells do not respond in the same way, their tolerance being associated with different states of metabolism or of the cell cycle.
Will rising CO2 protect plants from the midday sun? A study of photoinhibition of Quercus myrtifolia in a scrub‐oak community in two seasons
Authors: Hymus G. J. , Dijkstra P. , Baker N. R. , Drake B. G. , Long S. P. 
Published: March 2003

AbstractOver a large part of the photoperiod, light energy absorbed by upper canopy leaves saturates photosynthesis and exceeds the energetic requirements for light‐saturated linear electron flow through photosystem II (JPSII), so that photoinhibition results. From a theoretical consideration of the response of light‐saturated photosynthesis to elevated atmospheric CO2 partial pressure (pCO2) it may be predicted that, where light‐saturated photosynthesis is Rubisco‐limited, an increase in pCO2 will stimulate JPSII. Therefore, the proportion of absorbed quanta dissipated photochemically will increase and the potential for photoinhibition of photosynthesis will decrease. This was tested by measuring modulated chlorophyll a fluorescence from Quercus myrtifolia Willd. growing in the field in open‐top chambers, at either current ambient or elevated (ambient + 35 Pa) pCO2 on Merritt Island, Florida, USA. During spring and summer, light‐saturated photosynthesis at current ambient pCO2 was Rubisco‐limited. Consistent with theoretical prediction, JPSII was increased and photoinhibition decreased by elevated pCO2 in spring. In the summer, when growth had largely ceased, an acclimatory decrease in the maximum Ribulose 1,5 bisphosphate saturated carboxylation capacity (Vc max) removed the stimulation of JPSII seen in the spring, and photoinhibition was increased in elevated pCO2. It is concluded that, for Q. myrtifolia growing in the field, the effects of elevated pCO2 on JPSII and photoinhibition will reflect seasonal differences in photosynthetic acclimation to elevated pCO2 in a predictable manner.
The identification of a pollen‐specific LEA‐like protein in Lilium longiflorum
Authors: Mogami N. , Shiota H. , Tanaka I. 
Published: March 2003

AbstractA novel pollen‐specific LEA‐like protein, LP28, was detected in Lilium longiflorum using two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE). Immunoblot analysis using antiserum raised against LP28 revealed that the protein was not found in somatic tissues or uninucleate microspores, but accumulated gradually in developing pollen following microspore mitosis. Furthermore, LP28 was abundant in germinated pollen after hydration. The cDNA clone corresponding to LP28 encoded a putative protein of 238 amino acids with a calculated molecular mass of 24·2 kDa and a pI of 4·7. The amino acid sequence is highly hydrophilic except for the N‐terminal hydrophobic signal peptide. The sequence has similarities with group 3 LEA (late embryogenesis abundant) proteins. Immunocytochemical analyses demonstrated that LP28 was mainly found in cytoplasmic granules of the vegetative cell until pollen maturation, but after hydration it appeared in the elongating pollen tube wall. LP28 might be a unique pollen‐specific protein that is transported to the pollen tube wall after germination. Therefore, it is assumed that LP28 plays a role not only in pollen maturation, but also in the growth of the pollen tube, which penetrates the stylar matrix.
Increases of 3‐phosphoglyceric acid in potato plants through antisense reduction of cytoplasmic phosphoglycerate mutase impairs photosynthesis and growth, but does not increase starch contents
Authors: Westram A. , Lloyd J. R. , Roessner U. , Riesmeier J. W. , Kossmann J. 
Published: March 2003

AbstractA full‐length cDNA encoding cytosolic phosphoglycerate mutase (PGAM; E.C. 5.4.2.1) from potato (Solanum tuberosum L.) was isolated. RNA blots indicated that the accumulation of PGAM transcript was similar in all organs studied. Transgenic potato plants with either constitutive, or tuber‐specific, decreases in PGAM expression were created. Constitutive reduction of enzyme activity of down to 25% of the control resulted in increased 3‐PGA contents of up to 30% in leaves, but also led to reduced growth rates, probably due to a reduction of photosynthetic activity. Soluble carbohydrates and starch in leaves were reduced, and the tuber yield of the plants was lowered. Plants with 30% of the wild‐type PGAM activity in leaves and 55% in tubers showed reduced amounts of starch in tubers also. Tuber‐specific reduction of PGAM expression in transgenic potato plants had no effect on starch metabolism and tuber yield, although the 3‐PGA level was increased. This indicates that 3‐PGA concentrations in potato tubers are not important for regulating ADP‐glucose pyrophosphorylase activity in the production of starch under some environmental conditions.
Altered metabolic fluxes result from shifts in metabolite levels in sucrose phosphorylase‐expressing potato tubers
Authors: Fernie A. R. , Tiessen A. , Stitt M. , Willmitzer L. , Geigenberger P. 
Published: March 2003

AbstractAs reported in a previous paper (Plant, Cell and Environment 24, 357–365, 2001), introduction of sucrose phosphorylase into the cytosol of potato results in increased respiration, an inhibition of starch accumulation and decreased tuber yield. Herein a more detailed investigation into the effect of sucrose phosphorylase expression on tuber metabolism, in order to understand why storage and growth are impaired is described. (1) Although the activity of the introduced sucrose phosphorylase was low and accounted for less than 10% of that of sucrose synthase its expression led to a decrease in the activities of enzymes of starch synthesis relative to enzymes of glycolysis and relative to total amylolytic activity. (2) Incubation of tuber discs in [14C]glucose revealed that the transformants display a two‐fold increase of the unidirectional rate of sucrose breakdown. However this was largely compensated by a large stimulation of sucrose re‐synthesis and therefore the net rate of sucrose breakdown was not greatly affected. Despite this fact major shifts in tuber metabolism, including depletion of sucrose to very low levels, higher rates of glycolysis, and larger pools of amino acids were observed in these lines. (3) Expression of sucrose phosphorylase led to a decrease of the cellular ATP/ADP ratio and energy charge in intact growing tubers. It was estimated that at least 30% of the ATP formed during respiration is consumed as a result of the large acceleration of the cycle of sucrose breakdown and re‐synthesis in the transformants. Although the absolute rate of starch synthesis in short‐term labelling experiments with discs rose, starch synthesis fell relative to other fluxes including respiration, and the overall starch content of the tubers was lower than in wild‐type tubers. (4) External supply of amino acids to replace sucrose as an osmoticum led to a feed‐back inhibition of glycolysis, but did not restore allocation to starch. (5) However, an external supply of the non‐metabolizable sucrose analogue palatinose – but not sucrose itself – stimulated flux to starch in the transformants. (6) The results indicate that the impaired performance of sucrose phosphorylase‐expressing tubers is attributable to decreased levels of sucrose and increased energy consumption during sucrose futile cycling, and imply that sucrose degradation via sucrose synthase is important to maintain a relatively large sucrose pool and to minimize the ATP consumption required for normal metabolic function in the wild type.
Growth responses of yellow‐poplar(Liriodendron tulipifera L.) exposed to 5 years of O3 aloneor combined with elevated CO2
Authors: Rebbeck J. , Scherzer A. J. 
Published: March 2003

AbstractField‐grown yellow‐poplar (Liriodendron tulipifera L.) werefumigated from May to October in 1992–96 within open‐topchambers to determine the impact of ozone (O3) aloneor combined with elevated carbon dioxide (CO2) on saplinggrowth. Treatments were replicated three times and included: charcoal‐filteredair (CF); 1 × ambient ozone (1 × O3);1·5 × ambient ozone (1·5 × O3);1·5 × ambient ozone plus 350 p.p.m.carbon dioxide (1·5 × O3 + CO2)(target of 700 p.p.m. CO2); and open‐air chamberlessplot (OA). After five seasons, the total cumulative O3 exposure (SUM00 = sumof hourly O3 concentrations during the study) rangedfrom 145 (CF) to 861 (1·5 × O3) p.p.m. × h (partsper million hour). Ozone had no statistically significant effecton yellow‐poplar growth or biomass, even though total root biomasswas reduced by 13% in the 1·5 × O3‐exposedsaplings relative to CF controls. Although exposure to 1·5 × O3 + CO2 hada stimulatory effect on yearly basal area growth increment aftertwo seasons, significant increases in shoot and root biomass (∼ 60% increaserelative to all others) were not detected until the fifth season.After five seasons, the yearly basal area growth increment of saplingsexposed to 1·5 × O3 + CO2‐air increasedby 41% relative to all others. Based on this multi‐yearstudy, it appears that chronic O3 effects on yellow‐poplargrowth are limited and slow to manifest, and are consistent withprevious studies that show yellow‐poplar growth is not highly responsiveto O3 exposure. In addition, these results show thatenriched CO2 may ameliorate the negative effects of elevatedO3 on yellow‐poplar shoot growth and root biomass underfield conditions.
Photosystem II energy use,non‐photochemical quenching and the xanthophyll cycle in Sorghumbicolor grown under drought and free‐air CO2 enrichment(FACE) conditions
Authors: Cousins A. B. , Adam N. R. , Wall G. W. , Kimball B. A. , Pinter P. J. , Ottman M. J. , Leavitt S. W. , Webber A. N. 
Published: March 2003

AbstractThe present study was carried out to test the hypothesis thatelevated atmospheric CO2 (Ca) will alleviate over‐excitationof the C4 photosynthetic apparatus and decrease non‐photochemicalquenching (NPQ) during periods of limited water availability. Chlorophyll a fluorescencewas monitored in Sorghum bicolor plants grown under a free‐aircarbon‐dioxide enrichment (FACE) by water‐stress (Dry) experiment.Under Dry conditions elevated Ca increased the quantum yield ofphotosystem II (φPSII) throughout the day throughincreases in both photochemical quenching coefficient (qp)and the efficiency with which absorbed quanta are transferred toopen PSII reaction centres (Fv′/Fm′).However, in the well‐watered plants (Wets) FACE enhanced φPSIIonly at midday and was entirely attributed to changes in Fv′/Fm′. Underfield conditions, decreases in φPSII under Dry treatmentsand ambient Ca corresponded to increases in NPQ but the de‐epoxidation stateof the xanthophyll pool (DPS) showed no effects. Water‐stress didnot lead to long‐term damage to the photosynthetic apparatus asindicated by φPSII and carbon assimilation measuredafter removal of stress conditions. We conclude that elevated Caenhances photochemical light energy usage in C4 photosynthesisduring drought and/or midday conditions. Additionally,NPQ protects against photo‐inhibition and photodamage. However,NPQ and the xanthophyll cycle were affected differently by elevatedCa and water‐stress.