bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absence of phyB inhibits hypocotyl elongation in dark‐grown Ih cucumber seedlings: an active role for PrB
Authors: SAEFKOW R. L. , ALLISTON T. N. , SHINKLE J. R. 
Published: April 2006

ABSTRACTCucumber (Cucumis sativus L.) seedlings carrying the long hypocotyl (Ih) mutation, which confers a lack of B‐type phytochrome (phyB), were significantly shorter than their near‐isogenic wild‐type counterparts when grown in complete darkness. Relative growth rates determined for 5 mm hypocotyl regions were lower in Ih seedlings in all growing regions, and the zone of elongation was less extensive in Ih hypocotyls. Digital imaging microscopy revealed that the pattern of epidermal cell lengths along the stem axis differed between the Ih mutant and the iso‐genic wild‐type. These findings (and the fact that experiments were conducted under conditions where phytochrome photoconversion to the far‐red‐absorbing form does not occur) suggest that the red‐absorbing form of phyB (PrB) is an active positive regulator of development in etiolated plants.
Asymmetric responses of adaxial and abaxial stomata to elevated CO2: impacts on the control of gas exchange by leaves
Authors: PEARSON M. , DAVIES W.J. , MANSFIELD T.A. 
Published: April 2006

ABSTRACTThe response of adaxial and abaxial stomatal conductance in Rumex obtusifolius to growth at elevated atmospheric concentrations of CO2 (250 μmol mol−1 above ambient) was investigated over two growing seasons. The conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated concentrations of CO2. Elevated CO2 caused a much greater reduction in conductance for the adaxial surface than for the abaxial surface. The absence of effects upon stomatal density indicated that the reductions were probably the result of changes in stomatal aperture. Partitioning of gas exchange between the leaf surfaces revealed that increased concentrations of CO2 caused increased rates of photosynthesis only via the abaxial surface. Additionally, leaf thickness was found to increase during growth at elevated concentrations of CO2. The tendency for these amphistomatous leaves to develop a distribution of conductance approaching that of hypostomatous leaves clearly reduced their maximum photosynthetic potential. This conclusion was supported by measurements of stomatal limitation, which showed greater values for the adaxial surfaces, and greater values at elevated CO2. This reduction in photosynthesis may in part be caused by higher diffusive limitations imposed because of increased leaf thickness. In an uncoupled canopy, asymmetrical stomatal responses of the kind identified here may appreciably reduce transpiration. Species which show symmetrical responses are less likely to show reduced transpirational rates, and a redistribution of water loss between species may occur. The implications of asymmetrical stomatal responses for photosynthesis and canopy transpiration are discussed.
cDNA cloning and characterization of three genes in the Bet v 1 gene family that encode pathogenesis‐related proteins*
Authors: SWOBODA I. , SCHEINER O. , HEBERLE‐BORS E. , VICENTE O. 
Published: April 2006

ABSTRACTBet v 1 isoforms, the major pollen allergens of white birch (Betula verrucosa), show sequence homology to a class of pathogenesis‐related (PR) proteins identified in several other plant species. We recently reported that Bet v 1‐related mRNAs and proteins are induced by microbial pathogens in birch cell suspension cultures, which suggests that these pollen allergens and PR proteins are encoded by the same gene family. However, apart from the genes expressed in pollen, no other Bet v 1 clones have been characterized until now. Here we describe the isolation, by screening with a pollen Bet v 1 cDNA probe, of three full‐length cDNA clones, Bet v 1‐Sc1, Sc2 and Sc3, from a cDNA library prepared from cultured birch cells grown in the presence of Pseudomonas syringae. Sequence analysis indicated that these clones are highly homologous, but different from the genes encoding the pollen isoallergens. Northern blots and RNase protection experiments showed that the three genes are transcriptionally activated, with similar kinetics, in birch cells co‐cultivated with bacteria or fungi, regardless of whether they were pathogenic for birch. Infection of leaves with the fungus Taphrina betulina, a natural pathogen of birch, also led to the coordinated activation of the Bet v 1‐Sc genes, although infection with Fusarium solani did not. These results demonstrate that the Bet v 1 gene family of pollen allergens includes a subset of genes, different from those constitu‐tively expressed in pollen, that are induced in somatic cells upon their interaction with microorganisms. The possible implications of these results for the function of Bet v 1 proteins in the defence reaction against pathogens, as well as for the incidence of Type I allergies, are discussed.
Root architecture in cultivated and wild lettuce (Lactuca spp.)
Authors: JACKSON L. E. 
Published: April 2006

ABSTRACTRoot architecture is described for intact root systems of cultivated (Lactuca sativa L.) and wild (L. serriola L.) lettuce, grown for 5 to 6 weeks in greenhouse pot and cylinder experiments in coarse‐textured soil. L. sativa cv. Salinas and a sclinas line of L. serriola attained the same biomass at 4 to 6 weeks after planting. Root biomass allocation was also similar, but root architecture differed. In the top zone along the tap root (0 to 5 cm), Salinas tended to produce more laterals, a greater total root length, and more external links (segments that originate at a branch point and end in a meristem) than wild lettuce. In the 5 to 55cm zone of the tap root, these measures were greater in the wild species. These patterns of root structure were generally corroborated by a second cylinder study with a different pair of L. sativa and L. serriola. Regressions of root structural traits were made against total root dry weight as a means to compare root architecture independently of the size of the root system. Regressions demonstrated that production of root segments differed between the two species; for example the slope for the regression of summed external link length in the top 0 to 5 cm with total root dry weight was significantly higher for Salinas, indicating that the rate of construction in the top 0 to 5cm was greater for cultivated than for wild lettuce. Yet, from 5 cm depth to the tap root tip, the rate of construction of external link length was greater in L. serriola. For many of these types of regression, r2 and mean slope ± SE suggested that more variation occurred in cultivated than wild lettuce, yet genetic heterogeneity was probably low within the studied taxa. Inadvertent selection may have occurred in the breeding of cultivated lettuce varieties for increased root growth in the surface zone where water and fertilizer are applied, and for greater plasticity in construction of root segments, which might maximize the efficiency of exploitation of soil moisture and nutrients.
Xylem pressure response in maize roots subjected to osmotic stress: determination of radial reflection coefficients by use of the xylem pressure probe
Authors: ZHU J. J. , ZIMMERMANN U. , THÜRMER F. , HAASE A. 
Published: April 2006

ABSTRACTThe absolute pressure in conducting xylem vessels of roots of 2‐week‐old, slowly transpiring intact maize plants (bathed in nutrition medium) was determined to be +0·024 ± 0·044 MPa using the xylem pressure probe. When the roots were subjected to osmotic stress (NaCI, KCI or sucrose), the xylem pressure decreased immediately and became more negative. However, the response of xylem pressure to osmotic stress was considerably attenuated, indicating that the radial reflection coefficients, σ13 of the maize root for these solutes were rather low (between 0·2 and 0·4 depending on the concentration of the osmoticum). The low values of a, may be caused (partly) by unstirred layer effects. In repeated osmoticum/nutrition regimes a complex pattern of changes in xylem pressure was observed which was apparently linked to the interplay between transpiration and (passive and/or active) solute loading of the xylem. These processes were not observed when the roots were subjected to osmotic stress after excision. In this case, a biphasic response was observed comparable to that found for excised roots using the root pressure probe.
The active uptake of carbon dioxide by the marine diatoms Phaeodactylum ticornutum and Cyclotella sp.
Authors: ROTATORE C. , COLMAN B. , KUZMA M. 
Published: April 2006

ABSTRACTMass spectromelry has been used to investigate the uptake of CO2 by two marine diatoms, Phaeodactylum tricornutum and Cyclotella sp. The time course of CO2 formation in the dark after addition of 100 mmol m−3 dissolved inorganic carbon (DIC) to cell suspensions showed that external carbonic anhydrase (CA) was not present in cells of P. tricornutum but was present in Cyclotella sp. In the absence of external CA, or when it was inhibited by 5 mmol m−3 acetazolamide, cells of both species preincubated with 100 mmol m−3 DIG rapidly depleted almost all of the free CO2 (3·2mmol m−31 at pH7·5) from the suspending medium within seconds of illumination and prior to the onset of steady‐state photosynthesis. Addition of bovine CA quickly restored the HCO3−–CO2 equilibrium in the medium, indicating that the initial depletion of CO2 resulted from the selective uptake of CO2 rather than uptake of all DIG species. Transfer of cells to the dark caused a rapid increase in the CO2 concentration in the medium, largely as a result of the efflux of unfixed inorganic carbon from the cells. The measured CO2 uptake rates for both species accounted for 50% of the total DIG uptake at HCO3−–CO2 equilibrium, indicating that HCOHCO3− was also being taken up. These results indicate that both Phaeodactylum tricornutum and Cyclotella sp. have the capacity to transport CO2 actively against concentration and pH gradients.
Respiration and growth of tomato fruit
Authors: GRANGE R.I. , ANDREWS J. 
Published: April 2006

ABSTRACTThe respiration rate and diameter expansion growth of young tomato fruit were measured simultaneously and related to changes in carbon import and plant water status. Respiration rate was directly proportional to the volume expansion rate of fruit growing on isolated plant tops at a positive water potential, whether the growth rate was changed by changing the fruit temperature or by manipulating the source:sink ratio of the plants. From the latter relationship, the maintenance respiration rate was estimated by extrapolation to zero growth and was found to be about 25% of the respiration rate of the average fruit at 21°C. Alternatively, when carbon import was prevented by heat‐ringing the fruit peduncle, the respiration rate of the fruit declined to about 40% of the control rate and remained steady, while the expansion rate then declined steadily to >10% of the control rate. These results show that fruit expansion was not contributing significantly to fruit respiration. Indeed, large fluctuations in fruit expansion rate could also be induced by repeated darkening and illumination of potted plants without a corresponding change in fruit respiration. Most significantly, fruit expansion was considerably reduced when plants were allowed to wilt, hut there was no change in fruit respiration rate unless the fruit peduncle was subsequently heat‐ringed. We conclude that a major part of the respiration of young tomato fruit was determined by the rate of carbon import, or associated processes, and that fruit expansion per se can occur with relatively low respiratory costs.
Developmental regulation of anoxic stress tolerance in maize
Authors: VANTOAI T. T. , SAGLIO P. , RICARD B. , PRADET A. 
Published: April 2006

ABSTRACTAnoxia associated with flooding stress is detrimental to plant growth and productivity. When maize seedlings 2 to 7 d old were exposed to anoxic stress, 3‐d‐old seedlings were found to have much lower tolerance than 2‐d‐old seedlings. Ninety per cent of 2‐d‐old seedlings survived 72 h of anoxic stress compared with 0% of the 3‐d‐old seedlings. Since 2‐d‐old isolated root tips survived anoxic stress better than 3‐d‐old tips, the anoxic tolerance of 2‐d‐old seedlings was independent of the translocation of nutrient reserves from the endosperm to the root. The addition of glucose to the medium improved the anoxia tolerance of 2‐d‐old seedlings by 25% but had no effect on 3‐d‐old seedlings. Acclimation by pre‐cxposure to 4% oxygen and pre‐treatment with 100mmol m−1 abscisic acid (ABA) improved the anoxia tolerance of 3‐d‐old seedlings by 2‐ and 4‐fold, respectively. However, acclimation and ABA treatment had no effect on 2‐d‐old seedlings. The results indicate that anoxia tolerance in maize is develop‐mentally regulated. The mechanism of anoxia tolerance innate to 2‐d‐old seedlings was inducible in 3‐d‐old seedlings by acclimation or treatment with ABA.
Transmembrane potential‐mediated coupling between H+ pump operation and K+ fluxes in Elodea densa leaves hyperpolarized by fusicoccin, light or acid load
Authors: BELLANDO M. , MARRÈ M.T. , SACCO S. , TALARICO A. , VENEGONI A. , MARRÈ E. 
Published: April 2006

ABSTRACTIn isolated Elodea densa leaves, the relationships between H+ extrusion (‐ΔH+), K+ fluxes and membrane potential (Em) were investigated for two different conditions of activation of the ATP‐dependent H+ pump. The ‘basal condition’ (darkness, no pump activator present) was characterized by low values of‐ΔH+ and K+ uptake (ΔK+), wide variability of the −ΔH+/ΔK+ ratio, relatively low membrane polarization and Em values more positive than EK for external K+ concentrations (|K+]o of up to 2mol m−3. A net K+ uptake was seen already at [K+]o below 1 mol m−3, suggesting that K+ influx in this condition was a thermodynamically uphill process involving an active mechanism. When the H+ pump was stimulated by fusicoccin (FC), by cytosol acidification, or by light (the ‘high polarization condition’), K+ influx largely dominated K+ and C− efflux, and the −ΔH+/ΔK+ ratio approached unity. In the range 50 mmol m−3−5 mol m−3 [K+]0, Em was consistently more negative than EK. The curve of K+ influx at [K+]0 ranging from 50 to 5000mmol m−3 fitted a monophasic, hyperbolic curve, with an apparent half saturation value = 0–2 mol m−3. Increasing |K+]0 progressively depolarized Em, counteracting the strong hyperpolarizing effect of FC. The effects of K+ in depolarizing Em were well correlated with the effects on both K+ influx and −ΔH+, suggesting a cause‐effect chain: K+0 influx → depolarization → activation of H+ extrusion. Cs+ competitively inhibited K+ influx much more strongly in the ‘high polarization’ than in the ‘basal’ condition (50% inhibition at [Cs+]/[K+]0 ratios of 1:14 and 1:2, respectively) thus confirming the involvement of different K+ uptake systems in the two conditions. These results suggest that in E. densa leaves two distinct modes of interactions rule the relationships between H+ pump, membrane polarization and K+ transport. At low membrane polarization, corresponding to a low state of activation of the PM H+‐ATPase and to Em values more positive than EK, K+ influx would mainly
Site‐specific isotope fractionation of hydrogen in the biosynthesis of plant fatty acids
Authors: QUEMERAIS B. , MABON F. , NAULET N. , MARTIN G. J. 
Published: April 2006

ABSTRACTThe overall deuterium content of plant lipids has been investigated by isotope ratio mass spectrometry (IRMS), and the site‐specific natural isotope fractionation of hydrogen has been studied by 2H‐NMR at natural abundance (SNIF‐NMR). An analytical strategy has been developed in order to exploit the isotopomeric composition determined in clusters associated with different chemical sites of one or several fatty acid components. The method, which combines spectrometric and chromatographic data, enables isotopic criteria to be directly derived from raw vegetable oils containing in general two saturated and two unsaturated fatty acids. These results provide new information on isotopic fractionation caused by biochemical, physiological and natural environmental effects. Some alternation in the molecular deuterium distribution has been detected which may be related to the mechanism of fatty acid elongation. The successive methylene groups introduced through malonyl CoA are the subjects of different kinetic isotope effects since one of them is exclusively derived from NADH whereas the other has a contribution from pyruvate. A discriminant analysis of the cluster isotopic parameters enables several kinds of botanical precursors to be distinguished. The authenticating performances can be improved by taking into account the influence of climatic effects related to the region in which the plant grew.
The isolation and characterization of novel low‐amylose mutants of Pisum sativum L.
Authors: DENVER K. , BARBER L. M. , BURTON R. , HEDLEY C. L. , HYLTON C. M. , JOHNSON S. , JONES D. A. , MARSHALL J. , SMITH A. M. , TATGE H. , TOMLINSON K. , WANG T. L. 
Published: April 2006

ABSTRACTMutants of Pisum sativum L. with seeds containing low‐amylose starch were isolated by screening a population derived from chemically mutagenized material. In all of the mutant lines selected, the low‐amylose phenotype was caused by a recessive mutation at a single locus designated lam. In embryos of all but one mutant line, the 59 kDa granule‐bound starch synthase (GBSSI) was absent or greatly reduced in amount. The granule‐bound starch synthase activity in developing embryos of the mutants was reduced but not eliminated. These results provide further evidence that amylose synthesis is unique to GBSSI. Other granule‐bound isoforms of starch synthase cannot substitute for this protein in amylose synthesis. Examination of iodine‐stained starch granules from mutant embryos by light microscopy revealed large, blue‐staining cores surrounded by a pale‐staining periphery. In this respect, the low‐amylose mutants of pea differ from those of other species. The differential staining may indicate that the structure of amylopectin varies between the core and peripheral regions.
Water deficit in developing endosperm of maize: cell division and nuclear DMA endoreduplication
Authors: ARTLIP T. S. , MADISON J. T. , SETTER T. L. 
Published: April 2006

ABSTRACTWater deficit severely decreases maize (Zea mays L.) kernel growth; the effect is most pronounced in apical regions of ears. The capacity for accumulation of storage material in endosperms is thought to he partially determined by the extent of cell division and endoreduplication (post‐mitotic nuclear DNA synthesis). To gain a better understanding of the regulatory mechanisms involved, we have examined the effect of water deficit on cellular development during the post‐fertilization period. Greenhouse‐grown maize was subjected to water‐limited treatments during rapid cell division [from 1 to 10days after pollination (DAP)] or rapid endoreduplication (9 to 15 DAP). The number of nuclei and the nuclear DNA content were determined with flow cytometry. Water deficit from 1 to 10 DAP substantially decreased the rate of endosperm cell division in apical‐region kernels, but had little effect on middle‐region endosperms. Rewatcring did not allow cell division to recover in apical‐region endosperms. Water deficit from 9 to 15 DAP also decreased cell division in apical‐region endosperms. Endoreduplication was not affected by the late treatment in either region of the car, but was inhibited by the early treatment in the apical region. In particular, the proportion of nuclei entering higher DN A‐content size classes was reduced. We conclude that cell division is highly responsive to water deficit, whereas endoreduplication is less so. We also conclude that the reduced proportion of nuclei entering higher DNA‐content size classes during endoreduplication is indicative of multiple control points in the mitotic and endoreduplication cycles.
Temperature gradient chambers for research on global environment change. II. A twin‐wall tunnel system for low‐stature, field‐grown crops using a split heat pump
Authors: HADLEY P. , BATTS G. R. , ELLIS R. H. , MORISON J. I. L. , PEARSON S. , WHEELER T. R. 
Published: April 2006

ABSTRACTA temperature gradient chamber (TGC) is described which enables elevated CO2 concentrations and a dynamic temperature gradient to be imposed on field crops throughout their life cycle under standard husbandry. Air is circulated through two double‐walled polyethylene‐covered tunnels connected to a split heat pump system to give a near‐linear temperature gradient along each tunnel. Solar energy gain along each tunnel and exchange with outer tunnel air flow contribute to the temperature gradient and also produce diurnal and seasonal temperature fluctuations corresponding to ambient conditions. Mean temperature gradients of between 3 and 5°C have been recorded throughout the growing seasons of crops of lettuce, carrot, cauliflower and winter wheat. Elevated or present CO2 concentrations are maintained in each of two pairs of tunnels throughout the cropping season using pure CO2 injected through motorized needle valves. This system can realistically simulate aspects of the effects of projected future environmental change on crop growth, development and yield, and in particular tin‐possible interaction of the effects of increased CO2 and temperature.
Temperature gradient chambers for research on global environment change. III. A system designed for rice in Kyoto, Japan
Authors: HORIE T. , NAKAGAWA H. , NAKANO J. , HAMOTANI K. , KIM H. Y. 
Published: April 2006

ABSTRACTSynthesis and validation of crop models for assessment of of the impact of elevated atmospheric CO2 concentration and anticipated global warming on crop production require crop response data obtained under field‐like conditions. The temperature gradient chamber (TGC) with the facility for CO2 enrichment allows the creation of various CO2 and temperature regimes for crops over the entire growth period with relatively inexpensive construction and running costs. The TGC develops a temperature gradient along its longitudinal axis using solar energy during the day and heating at night while maintaining the natural diurnal cycle. The temperature gradient and the CO2 concentration in the TGC are regulated by computer control of the air ventilation rate through the TGC and of the CO2 release rate. Longitudinal gradients of CO2 concentration and water vapour pressure deficit of air in the TGC were generally less than 5% and ±0.2 kPa, respectively.A CO2 enrichment experiment on rice in the TGC showed that a doubling of the CO2 concentration markedly enhanced crop dry matter production. Temperature had less effect on dry matter production, although panicle dry weight was greatly decreased at higher temperature as a result of high‐temperature‐induccd sterility of rice spikelets. Since rice spikclets are most sensitive to high temperature at the moment of flowering, and their flowering habit is highly synchronized with the diurnal courses of environmental conditions, the TGC is a useful tool in understanding rice responses to changes in atmosphere and temperature.