bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamma‐ray‐induced changes in the synthesis of tomato pericarp protein
Authors: FERULLO J.‐M. , NESPOULOUS L. , TRIANTAPHYLIDÈS C. 
Published: April 2006

ABSTRACTThe application of massive doses of gamma rays (1–8 kGy) to mature green cherry‐tomato fruits led to a transient fall in pericarp tissue protein metabolism within 6h. A separate 3 kGy treatment resulted in the appearance of certain transcripts and proteins, and a reduction in the abundance of others. At the same dose, protein synthesis regained the control level within 24 h, and in addition a new set of proteins was induced. Gamma‐induced proteins (referred to as GIPs) were divided into three groups, depending on the time‐course of their induction. Group 1 GIPs were synthesized only during the first few hours following treatment, whereas group 2 GIPs were synthesized for at least 48 h. Group 3 GIPs were progressively induced when the control level of synthesis was restored. These results demonstrated that, despite its deleterious effects on DNA and cell structures, irradiation induced an active response in plant tissue. Comparative experiments suggest that the majority of group 1 GIPs might belong to the heat shock protein family. GIPs might play a role in the protection and repair of cellular structures, or may be implicated in physiological disorders triggered by irradiation.
Regulation of the expression of photosynthetic nuclear genes by CO2 is mimicked by regulation by carbohydrates: a mechanism for the acclimation of photosynthesis to high CO2?
Authors: VAN OOSTEN J.‐J. , WILKINS D. , BESFORD R. T. 
Published: April 2006

ABSTRACTThe abundance of transcripts of cab‐7 and cab‐3C, which code for the chlorophyll a/b binding proteins of the light‐harvesting complexes I and II, respectively, and the abundance of transcripts of Rca, which encodes Rubisco activase, were reduced in tomato plants exposed to high CO2 for up to 9d, whereas the abundance of mRNA from psa A–psa B and psb A, which encode the proteins of the core complex of PSI and the D1 protein of PSII, respectively, and the abundance of glycolate oxidase, which is involved in photorespiration, were not affected. However, the abundance of the transcript for the B subunit of ADP‐glucose pyrophosphorylase was increased after 1 d at elevated CO2. The chlorophyll a/b ratio decreased significantly over 9 d of exposure to elevated CO2. The responses of the nuclear genes to high CO2 were enhanced when leaves were detached so as to deprive them of any major sink. The responses of these transcripts to high CO2 were mimicked when sucrose or glucose was supplied to the leaf tissue, whereas acetate or sorbitol had no effect. Carbohydrate analyses of leaves grown in high CO2 or supplied with sucrose revealed that major increases occurred in the amount of glucose and fructose.Based on these and other published data, a molecular model involving the repression or activation of the transcription of nuclear genes coding for chloroplast proteins by photosynthetic end‐products is proposed to account for photosynthetic acclimation to high CO2 in tomato plants and other species.
Anaerobiosis‐mediated early transcriptional and translational responses in rice (Oryza sativa L.) coleoptiles and roots
Authors: BREVIARIO D. , GIANÍ S. , MORELLO L. , CORAGGIO I. 
Published: April 2006

ABSTRACTTo study the transcriptional and translational responses that occur in rice (Oryza sativa L., cv. Arborio) coleoptiles and roots during the first hours of anoxia, we analysed the patterns of in vitro translational products and in vivo labelled newly synthesized proteins obtained from both organs grown in the presence or absence of O2. Analysis of the protein pattern obtained from nuclear‐enriched sub‐cellular fractions showed the enhancement of the synthesis of several proteins with molecular weights of 67–62, 54 and 34 kD. In the cytoplasmic‐enriched subcellular fractions, we found that the synthesis of polypeptides of relatively low molecular weight (13–16 kD) was strongly induced by anaerobiosis. In vitro translation analysis showed that this enhancement was mainly due to a rapid increase in the level of the corresponding mRNA species. These low‐molecular‐weight translational products were already detected after 1h of anoxia in both rice roots and rice coleoptiles, but remained undetectable in aerobically grown organs. Additional anaerobic‐specific transcriptional and translational changes were also observed. In particular, a specific reduction in the level of mRNAs coding for polypeptides of 38 kD occurred in both roots and coleoptiles after only 1 h of anoxia.
Decreased ribulose‐1,5‐bisphosphate carboxylase/oxygenase in transgenic tobacco transformed with ‘antisense’rbcS.VIII. Impact on photosynthesis and growth in tobacco growing under extreme high irradiance and high temperature
Authors: KRAPP A. , CHAVES M. M. , DAVID M. M. , RODRIQUES M. L. , PEREIRA J. S. , STITT M. 
Published: April 2006

ABSTRACTWild‐type and antisense rbcS tobacco (Nicotiana tabacum) plants were grown in a glasshouse in midsummer in Portugal with an irradiance of 1500–2000 μmol m−2s−1 and daytime temperatures of 30–35 °C. The Rubisco content of the transformants was lower by 35, 80 and over 90% than that of the wild‐type. Gas exchange was measured over three separate days. There was a near‐linear relation between Rubisco content and photosynthetic rate during the period of high irradiance, allowing a flux control coefficient of 0.83–0.89 to be estimated. The relation deviated slightly from linearity, because the internal CO2 concentration (c;) was higher in the transformants than in the wild‐type (190 and 275 μmol mol−1 in plants with 35 and 80% less Rubisco, respectively, compared with 175 μmol mol−1 for wild‐type), compensating to some extent for the decreased Rubisco content. This increase in ci occurred because the stomatal conductance (g) remained unaltered or was even higher in plants with decreased Rubisco, despite the lower rate of CO2 assimilation. As a consequence, water use efficiency declined. The decreased rate of photosynthesis was not accompanied by a stoichiometric decrease in apparent growth rate. These results are discussed in relation to earlier studies of the plant set in growth cabinets. It is concluded that tobacco can adjust over a wide range of growth conditions to avoid a onesided limitation by Rubisco, but that in extreme environmental conditions this capacity to adapt is exhausted.
The pH‐dependent yield threshold of the cell wall in a glycerinated hollow cylinder (in vitro system) of cowpea hypocotyl
Authors: OKAMOTO H. , OKAMOTO A. 
Published: April 2006

ABSTRACTIn order to determine whether the pH‐dependent yield threshold of the cell wall still exists in an in vitro system, an extensometer was devised to enable the perfusion of any experimental solution through the hollow cylinder of a hypocotyl segment excised from a cowpea seedling. Stress‐strain experiments on glycerinated hollow cylinders revealed the existence of a definite yield threshold (y) of the cell wall in this in vitro system. The y value decreased reversibly with acidification (pH 4) to the same extent as the decrease of the yield threshold obtained in vivo (Y) with auxin‐induced growth acceleration of hypocotyl segments. Heat treatment of the glycerinated hollow cylinder completely inhibited the decrease in y with acidification. The increase in the extensibility of the cell wall with acidification was inhibited significantly but not completely by heat treatment. These results support strongly the ‘acid growth’ theory and provide evidence that the acid‐induced decrement of the yield threshold is mediated by an enzymatic reaction of a wall‐binding protein. The combination of in vitro and in vivo studies presented here provides a basis for the establishment of a molecular theory on the nature of the growth parameters Y and Ф which control the yielding of the cell wall.
Root xylem transport of amino acids in the root hemiparasitic shrub Olax phyllanthi (Labill) R.Br. (Olacaceaea) and its multiple hosts
Authors: PATE J. S. , WOODALL G. , JESCHKE W. D. , STEWART G. R. 
Published: April 2006

ABSTRACTThe amino acid compositions of the root xylem saps of Olax phyllanthi and a range of its common hosts were examined in native coastal heath in Western Australia and in pot cultures of Olax reliant on single hosts. When hosts specializing in the xylem transport of one major solute (asparagine, glutamine, histidine, arginine or proline) were exploited, the endophytic tissue of haustoria and the xylem sap of Olax showed much lower proportions of this than of other solutes, suggesting pronounced metabolic transformation prior to xylem loading by the parasite. However, the xylem sap of Olax did partly reflect the compositions of its hosts; for example, djenkolic acid and pipecolic acid were present when Olax was parasitic on species of Acacia, and levels of citrulline and aspartic acid were higher than normal when it exploited hosts transporting large amounts of these compounds. Back‐flow of S‐ethenyl cysteine, a novel amino acid specific to Olax, was observed to another root hemiparasite (Exocarpos sparteus) in native habitat and to certain non‐parasitic hosts in water‐stressed pot cultures. Haustoria exhibited high levels of glutamine synthetase but showed appreciable in vivo nitrate reductase activity only when on hosts with high xylem levels of nitrate.
The effects of CO2, temperature and their interaction on the growth and yield of carrot (Daucus carota L.)
Authors: WHEELER T.R. , MORISON J. I. L. , ELLIS R.H. , HADLEY P. 
Published: April 2006

ABSTRACTStands of carrot (Daucus carota L.) were grown in the field within polyethylene‐covered tunnels at a range of soil temperatures (from a mean of 7·5°C to 10·9°C) at either 348 (SE = 4·7) or 551 (SE = 7·7) μmol mol−1 CO2. The effect of increased atmospheric CO2 concentration on root yield was greater than that on total biomass. At the last harvest (137d from sowing), total biomass was 16% (95% CI = 6%, 27%) greater at 551 than at 348 μmol mol−1 CO2, and 37% (95% CI = 30%, 44%) greater as a result of a 1°C rise in soil temperature. Enrichment with CO2 or a 1°C rise in soil temperature increased root yield by 31% (95% CI = 19%, 45%) and 34% (95% CI = 27%, 42%), respectively, at this harvest. No effect on total biomass or root yield of an interaction between temperature and atmospheric CO2 concentration at 137 DAS was detected. When compared at a given leaf number (seven leaves), CO2 enrichment increased total biomass by 25% and root yields by 80%, but no effect of differences in temperature on plant weights was found. Thus, increases in total biomass and root yield observed in the warmer crops were a result of the effects of temperature on the timing of crop growth and development. Partitioning to the storage roots during early root expansion was greater at 551 than at 348 μmol mol−1 CO2. The root to total weight ratio was unaffected by differences in temperature at 551 μmol mol−1CO2, but was reduced by cooler temperatures at 348 μmol mol−1 CO2. At a given thermal time from sowing, CO2 enrichment increased the leaf area per plant, particularly during early root growth, primarily as a result of an increase in the rate of leaf area expansion, and not an increase in leaf number.
Effects of low temperature on lateral diffusion in plasma membranes on maize (Zea mays L.) root cortex protoplasts: relevance to chilling sensitivity
Authors: KOSTER K. L. , TENGBE M. A. , FURTULA V. , NOTHNAGEL E. A. 
Published: April 2006

ABSTRACTThe effects of temperature on the lateral diffusion of fluorescent phospholipids, sterols and proteins in the plasma membranes of maize root cortex protoplasts were monitored using fluorescence photobleaching recovery (FPR). Diffusion parameters were measured in two cultivars of maize having different chilling tolerance. Hydrodynamic theory predicts that the diffusion coefficient, D, should increase with increasing temperature. In the more chilling‐tolerant cultivar, however, D for all three probes was nearly insensitive to temperature. In the more chilling‐sensitive cultivar, D was also insensitive to temperature over the range from 12 to 21°C, but D for the lipid probes tended to be higher and more variable at lower temperatures. The proportion of probe molecules free to diffuse in the membrane was less than 1 for all probes, and increased significantly with increasing temperature for the protein probe. These results, taken together, support the concept that the plasma membrane contains domains having differing diffusional characteristics. Temperature effects on membrane diffusion are moderated by the existence of these domains to limit significant changes. The observed tendency for higher diffusion coefficients at low temperatures in the chilling‐sensitive cultivar may correlate to morphological changes observed with protoplasts of that cultivar at low temperatures.
Loss of intracellular glycerol from Dunaliella by electroporation at constant osmotic pressure: subsequent restoration of glycerol content and associated volume changes
Authors: SHARIATI M. , LILLEY R. McC. 
Published: April 2006

ABSTRACTThe effect of electroporation on Dunaliella tertiolecta at constant osmotic pressure (or water activity) was investigated. The following metabolic and physiological parameters were determined: extracellular and intracellular glycerol content, soluble protein content, photosynthetic oxygen evolution, mitochondrial oxygen uptake, cell volume and cell density. Electroporation conditions are described that released about 10% of intracellular glycerol to the external medium with minimal apparent effects on metabolism. Glycerol release originated from most cells rather than by total rupture of a small proportion of cells. Cell volume, measured on motile cells by video microscopy, reduced by 23% immediately after electroporation. Cell density did not increase. The uptake of mannitol, the major solute in the electroporation medium, was less than 20% of glycerol release. Following electroporation, the intracellular glycerol content and the cell volume both returned to pre‐electroporation values after about 30min. Because the cells were maintained at constant external osmotic pressure throughout the procedure, it is concluded that the regulatory mechanism responsible for setting the intracellular glycerol content does not sense external osmotic pressure per se. These findings are consistent with a mechanism that senses a parameter linked directly to cell volume to set the intracellular glycerol content.
Modelling forest response to increasing CO2concentration under nutrient‐limited conditions
Authors: KIRSCHBAUM M. U. F. , KING D. A. , COMINS H. N. , MCMURTRIE R. E. , MEDLYN B. E. , PONGRACIC S. , MURTY D. , KEITH H. , RAISON R. J. , KHANNA P. K. , SHERIFF D. W. 
Published: April 2006

ABSTRACTThe growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of essential nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO2concentration, but it is uncertain whether this will translate into increased growth in the longer term under nutrient‐limited conditions. An analytical model to address this question was developed by Comins & McMurtrie (1993,Ecological Applications3, 666–681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assumptions and allowed a more confident prediction of expected growth responses to CO2enrichment under nutrient‐limited conditions.The analysis indicated that conclusions about the CO2sensitivity of production were strongly influenced by assumptions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration proportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing CO2concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growth response to changing CO2concentration. On the other hand, predictions were only slightly affected by: (1) assumptions about the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the effects of nitrogen status on specific leaf area or (3) leaf longevity; (4) carbon allocation between different plant parts; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification of the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO2sensitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single‐leaf photosynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen‐limited conditions can respond to increasing atmospheric CO2concentration with considerable increases in growth.
Adaptation of the tonoplast V‐type H+‐ATPase of Mesembryanthemum crystallinum to salt stress, C3–CAM transition and plant age
Authors: RATAJCZAK R. , RICHTER J. , LÜTTGE U. 
Published: April 2006

ABSTRACTPlants of the facultative halophyte and CAM species Mesembryanthemum crystallinum L. (Aizoaceae) were stressed for 8 d with 400 mol m−3 NaCl in the root medium. NaCl was then removed from the substratum, and the plants were watered again with NaCl‐free solution. A second set of plants was maintained as controls. A small degree of CAM, as indicated by day‐night changes in malate levels, was expressed during ageing of the plants. Salinity‐stress‐dependent CAM induction was reversible by the removal of salt, as indicated by similar Δ malate levels in previously salt‐stressed plants and in non‐stressed plants on day 19 of the experiment. Tonoplast vesicles were isolated from leaves during the time‐course of stress application, stress removal and ageing. Parameters of the tonoplast H+‐ATPase were correlated to the application of salinity, the expression of CAM and ageing. It was concluded, first, that a pronounced increase in the amount of tonoplast H+‐ATPase is related to salinity per se and a smaller increase to ageing; secondly, that there is an increase in the specific activity of the enzyme related to ageing; thirdly, that the induction of two new polypeptides with molecular masses of 32 and 28 kDa is correlated in time with the expression of CAM, and, fourthly, that the two new polypeptides are part of the tonoplast H+‐ATPase holoenzyme.
The influence of nitrogen availability on carbon and nitrogen storage in the biennial Cirsium vulgare (Savi) Ten. II. The cost of nitrogen storage
Authors: MONSON R.K. , SCHULZE E.‐D. , FREUND M. , HEILMEIER H. 
Published: April 2006

ABSTRACTThe cost of nitrogen storage to current growth was examined in relation to N availability in the biennial Cirsium vulgare. Plants were grown outdoors, in sand culture, with continuous diel drip irrigation of fertilization medium containing one of five different N concentrations. Plants grown at the highest N concentration stored twice as much N in their tap roots as did plants grown at the lowest N concentration. In high‐N‐grown plants, the storage of N reserves occurred during the period of maximum growth, at the same time as tap‐root production. At the time of maximum biomass, stored N was also at a maximum. During the period following maximum biomass, no additional storage of N occurred. This pattern was observed despite frequent late‐season leaf senescence which resulted in a large pool of potentially mobile N which could have been stored at no cost to growth. In low‐N‐grown plants, the production of tap‐root storage tissue and the filling of that tissue with stored N were staggered. Tap‐root production and growth occurred during the period of maximum growth, as in the high‐N‐grown plants. However, filling of the storage tissue with N occurred late in the growing season, when the pool of mobile N from senescent leaves was large. The utilization of this late‐season N source occurred with little or no cost to growth, and this N is labelled, according to previous definitions, as ‘accumulated’. The costs of storing N in plants of the different N treatments were calculated using two models based on different growth constraints. In one model, the cost of N storage was represented as lost growth due to allocation of N to storage, rather than to the photosynthetic shoot (i.e. growth was assumed to be limited by carbon acquisition). In the second model, the storage cost was calculated as lost growth due to allocation of N to storage, rather than to the nitrogen‐acquiring fine‐root system (i.e. growth was assumed to be limited by nitrogen acquisition). In both models, the total cost of N storage was predicted to decrease as N availability decreased due to smaller storage pool sizes in plants of the low‐N treatments. The cost of filling the tap root with stored N as a percentage of the total storage cost was also reduced as N availability decreased due to the occurrence of late‐season accumulation. By relying, at least in part, on late‐season accumulation, plants grown at the lowest three levels of N availability reduced total storage costs by 15 to 22%. The results demonstrate that plants are capable of adjusting their storage patterns in response to low nitrogen availability such that the costs of storage are reduced.
Comparison of electric and growth responses to excision in cucumber and pea seedlings. I. Short‐distance effects are a result of wounding
Authors: STAHLBERG R. , COSGROVE D. J. 
Published: April 2006

ABSTRACTThe local electric response to stem excision in both pea epicotyls and cucumber hypocotyls is a depolarization of the cells in the wound area. If we define wound area as the region of local depolarization, we find that it extends for approximately 10 mm from the cut or wound site in pea epicotyls, whereas it can reach up to 40 mm in cucumber hypocotyls. The wound‐induced depolarization in pea cells is transient, reaching its maximal amplitude within 1–2 min, whereas in cucumber cells this depolarization is more sustained. A third difference between wound responses in pea and cucumber is the intermittent appearance of spikes, i.e. very short, rapidly reverted depolarizations which frequently accompany the basic depolarization in cucumber but not in pea cells. These spikes can propagate in both directions along the hypocotyl axis. The cause of the different responses of pea and cucumber cells is unknown. A possible explanation might be found in different degrees of electrical cell coupling in the two species. This possibility was investigated in cucumber hypocotyls by measuring the cell input resistance (Rin) of epidermal cells at various axial distances from the cut. Shorter distances increase the likelihood of shunting the cell membrane resistance through the shortened symplastic path to the cut surface. With a series of cuts made at decreasing distances from the measured site, cell depolarization increased without comparable changes in Rin. Two conclusions were drawn. Firstly, wound‐induced depolarizations are not brought about by shunting of the cell resistance in the wound area. Secondly, the depolarization is probably not carried by ion channels but may be caused by an inhibition of proton pump activity. Parallel to its depolarizing effect on the membrane potential, excision led to a severe and sustained decline in the cucumber hypocotyl growth rate only when carried out sufficiently close to the growing region (45 mm from the hook). Similar excision in pea epicotyls failed to change the growth rate. Both electrical and growth data support the concept that the high and sustained responsiveness of cucumber seedlings to wounding is caused by a particular sensitivity of their proton pump mechanism.