bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosynthate partitioning in diploid and autotetraploid barley (Hordeum vulgare)
Authors: Sicher Richard C. , Kremer Diane F. , Harris William G. , Baenziger P. Stephen 
Published: April 2006

Net rates of carbon assimilation per unit leaf area by fully expanded, vegetative leaves of diploid (2x) and autotetraploid (4x) barley (Hordeum vulgare L. cultivars OAC‐21 and Brant) were not significantly different (90% level) when measured under controlled environment conditions with air levels of CO2 and either 2 or 20% O2. Leaf thickness increased with ploidy so that net photosynthetic rates measured on single leaves were lower for 4x than 2x barley varieties when compared on a dry or fresh weight basis. Rates of 14CO2 fixation by isolated mesophyll protoplasts prepared from seedlings were also lower for 4x than 2x varieties [about 108 and 125 μmol (mg ChI)−1 h−1, respectively]. Carbohydrate accumulation in leaves of 5‐weekold plants averaged 28% (2x) and 47% (4x) of the total photosynthetic weight gain during the first 9 h of the light period. Estimated photoassimilate export from leaves was 15% (OAC‐21) and 38% (Brant) lower for 4x compared to 2x isolines. The sucrose and oligofructan content of 4x compared to 2x leaves increased as a result of decreased photosynthate transport.Total tiller dry weight of plants raised in a glasshouse was greater for 4x than 2x barley varieties at ear emergence, but tiller height decreased with increasing ploidy. The nonstructural carbohydrate content of the inflorescence, leaves and lower stem organs was significantly (P≤ 0.01) higher in 4x than in 2x lines at this sampling. During the first 15 days of grain development total tiller dry weight increased by 46% (2x) compared to 8% (4x) when the results of both varieties were averaged together. The dry weight gain of the ear during this period was about 60 to 80% lower for 4x compared to 2x isolines. The nonstructural carbohydrate content of the inflorescence was also about 24% (Brant) and 51% (OAC‐21) lower for 4x as compared to 2x plants 15 days post ear emergence. The above results suggested that photosynthate partitioning in autotetraploid barley was sink‐limited.
Arginase activity in the cotyledons of soybean seedlings
Authors: Matsubara Shyuichiro , Suzuki Yonezo 
Published: April 2006

The germination of soybean (Glycine max L. cv. Akita) seeds is accompanied by increased arginase activity in the cotyledons, and the enzyme is predominantly (84% for 5‐day‐old seedlings) recovered in the mitochondrial fraction (co‐purifies with succinate dehydrogenase) where it is located inside the inner membrane. When dry cotyledons from which the axis and testa have been removed surgically are imbibed for 6 h in water and maintained on filter paper during the subsequent incubation, there is little increase in mitochondrial arginase activity. However, if similar dry cotyledons are rinsed for 1 min after the sterilization of 3 min and maintained on filter paper from the beginning, the increase in enzyme activity is similar to that in the intact seedling. Thus the embryonic axis is not essential for the development of arginase in soybean cotyledon although the enzyme development was enhanced by the presence of the axis under the same conditions of incubation.The addition of actinomycin D, 6‐methylpurine and cycloheximide early in the incubation period strongly inhibits the development of mitochondrial arginase activity in the cotyledons, but chloramphenicol does not. However, actinomycin D and 6‐methylpurine had little effect on enzyme development when added after 2 days of incubation. These results suggest that arginase is synthesized in the cytosol and then transported into the mitochondria, while mRNA for arginase synthesis is produced for a limited time only during early germination.
Relative rates of delivery of xylem solute to shoot tissues: Possible relationship to sequential leaf senescence
Authors: Neumann Peter M. , Stein Zipporah 
Published: April 2006

The rates of delivery of regulatory solutes such as cytokinins and mineral ions from the roots to competing shoot tissues can influence rates of metabolism and development. A 15 min pulse of a synthetic xylem mobile and phloem‐immobile solute, acid fuchsin, was used to quantify relative rates of solute delivery to competing organs on excised transpiring bean shoots (Phaseolus vulgaris L. cv. Contender) at different stages of development. Stem, flower and fruit tissues received comparatively low rates of solute delivery. The relative rate of solute delivery to newly opened leaves was initially low, but increased during rapid leaf expansion and then declined progressively as the leaves exceeded 70% of their final area.The relative rate of solute delivery to tissues of the basal primary leaves declined progressively from 2 weeks onwards. This decline appeared to be caused by progressive internally regulated increases in both stomatal resistances and hydraulic resistances to xylem flow up to and into the leaf blade. Thus combined abaxial and adaxial stomatal resistance values in the primary leaves (Rs) increased from 3 to ≥ 7 s cm−1 between 2 and 5 weeks. Similarly, mean values for the connection resistances (Rc) to hydraulic flow into the primary leaves rose from 7 to 13 TPa · s · m−1 between 2 and 4 weeks. In the same period pathway resistance from stem to primary leaf petioles (Rp), as determined by direct pressure flow assay, increased from 7 to 15 TPa · s · m−1.Senescence‐associated declines in protein and chlorophyll levels in the primary leaves were initiated in parallel with, or after, declines in relative rates of solute delivery. The provision of extra illumination at the basal leaf level between 2 and 5 weeks did not prevent declines in chlorophyll and soluble protein or increases in stomatal resistance. We suggest that internally programmed changes in the hydraulic architecture of the plant progressively divert xylem‐transported root supplies of nutrients and cytokinins from basal to more apical leaves and thus regulate the progressive senescence of leaves from the base upwards.
The effect of bacterial strain and temperature changes on the nitrogenase activity of Lotus pedunculatus root nodules
Authors: Pankhurst C. E. , Layzell D. B. 
Published: April 2006

After 40 days of growth at 25°C, Lotus pedunculatus cav., cv. Maku plants infected with Rhizobium loti strain NZP2037 displayed similar relative growth rates but had twice the nodule mass and only one third the whole plant dry weight of plants infected with Bradyrhizobium sp. (Lotus) strain CC814s. In the NZP2037 symbiosis, the rate of CO2 evolution (per g dry weight of nodulated root) was 1.6 times as high as that in the CC814s symbiosis while the rate of C2H2 reduction (per g dry weight of nodule) was only 48% of that in the CC814s symbiosis. Studies of the effect of short term temperature changes on the gas exchange characteristics (CO2 and H2 evolution, C2H2 reduction) of these symbioses revealed wide differences in the optima for C2H2 reduction. Nodules infected with NZP2037 displayed maximal C2H2 reduction rates [157 μmol (g dry weight nodule)−1 h−1] at 12°C, whereas nodules infected with CC814s were optimal at 30°C [208 μmol (g dry weight nodule)−1 h−1]. These short term studies suggested that differences in temperature optima for N2 may have partially accounted for the poorer effectivity, at 25°C, of strain NZP2037 when compared with strain CC‐814s.The relative efficiency [RE = 1 – (H2 evolution/C2H2 reduction)] of N2 fixation varied widely with temperature in the two symbioses, but there was a general trend toward higher RE with lower temperatures. The ratio of CO2 evolution: C2H2 reduction (mol/mol) in nodulated roots infected with CC814s was constant (ca 10 CO2/C2H2) between 5°C and 30°C, whereas in plants infected with NZP2037 it reached a minimal value of 3.3 CO2/C2H2 at 10°C and was 19 CO2/C2H2 at the growing temperature (25°C).
Anion‐sensitive ATPase activity and proton transport in isolated vacuoles of species of the CAM genus Kalanchoë
Authors: Jochem Petra , Rona Jean‐Pierre , Smith J. Andrew C. , Lüttge Ulrich 
Published: April 2006

Vacuoles were isolated from leaves of Kalanchoë daigremontiana Hamet et Perrier de la Bathie, and the ionic sensitivity of the vacuolar ATPase was studied in vacuole homogenates desalted on Sephadex G‐25. The ATPase activity was dependent on the presence of divalent cations (Mg2+≥ Mn2+≥ Ca2+, Co2+; Zn2+ had no effect). Mg2+‐dependent ATPase activity was stimulated by anions (Cl− > malate2+, HCO−3), with maximal stimulation at concentrations above 50 mM. Mg2+‐Dependent activity was inhibited by NO−3 above 2 mM, but no saturation was observed up to 100 mM. No stimulation by K+ or Na+ was detected; stimulation by NH+4 was abolished by 0.01% (w/v) Triton X‐100, suggesting that the NH+4 effect was due to the permeability of vacuolar membrane vesicles to NH3.Trans‐tonoplast electrical potentials (Δψ) and intra‐vacuolar pH were measured with glass microelectrodes and antimony covered glass micro‐pH‐electrodes, respectively. Free vacuofes isolated from Kalanchoë tubiflora (Harv.) Hamet were slightly positive with respect to the suspension medium. This Δψ was insensitive to the protonophore FCCP and depolarized by about 4 mV on addition of 50 mM KCl, still remaining about +5 mV. Upon addition of 7 mM Mg‐ATP, vacuoles showed an FCCP‐sensitive increase of Δψ from +9.2 ± 2.8 (13) to +17.8 ± 3.7 (12) mV [given as x̄± sd (n)] and an internal acidification from pH 5.4 ± 0.2 (11) to pH 4.3 ± 0.4 (12). Mg‐ADP and ATP without Mg2+ had no effect on Δψ.It is concluded that the H4 pumping at the tonoplast is due to the functioning of the anion‐sensitive vacuolar ATPase and that this is an essential part of the mechanism of nocturnal acid accumulation in CAM.
Effects of nitrogen nutrition and root medium water potential on growth, nitrogen uptake and osmotic adjustment of rice
Authors: Yambao E. B. , O'Toole J. C. 
Published: April 2006

The effects of nitrogen (N) nutrition on growth, N uptake and leaf osmotic potential of rice plants (Oryza sativa L. ev. IR 36) during simulated water stress were determined. Twenty‐one‐day‐old seedlings in high (28.6 × 10 −4M) and low (7.14 × 10 4M) N levels were exposed to decreased nutrient solution water potentials by addition of polyethylene glycol 6000. The roots were separated from the solution by a semi‐permeable membrane. Nutrient solution water potential was −0.6 × 105 Pa and was lowered stepwise to −1 × 105, −2 × 105, −4 × 105 and −6 × 105 Pa at 2‐day intervals. Plant height, leaf area and shoot dry weight of high and low nitrogen plants were reduced by lower osmotic potentials of the root medium. Osmotic stress caused greater shoot growth reduction in high N than in low N plants. Stressed and unstressed plants in 7.14 × 104M N had more root dry matter than the corresponding plants in 28.6 × 104M N. Dawn leaf water potential of stressed plants was 1 × 105 to 5.5 × 105 Pa lower than nutrient solution water potential. Nitrogen‐deficient water‐stressed plants, however, maintained higher dawn leaf water potential than high nitrogen water‐stressed plants. It is suggested that this was due to higher root‐to‐shoot ratios of N deficient plants. The osmotic potentials of leaves at full turgor for control plants were about 1.3 × 105 Pa higher in 7.14 × 10−4M than in 28.6 × 10−4M N and osmotic adjustment of 2.6 × 105 and 4.3 × 105 Pa was obtained in low and high N plants, respectively. The nitrogen status of plants, therefore, affected the ability of the rice plant to adjust osmotically during water stress.Plant water stress decreased transpiration and total N content in shoots of both N treatments. Reduced shoot growth as a result of water stress caused the decrease in amount of water transpired. Transpiration and N uptake were significantly correlated. Our results show that nitrogen content is reduced in water‐stressed plants by the integrated effects of plant water stress per se on accumulation of dry matter and transpiring leaf area as well as the often cited changes in soil physical properties of a drying root medium.
Effect of plant density on the uptake and distribution of 14C in the field bean, Vicia faba
Authors: Crompton Hilary J. , Hill‐Cottingham D. G. , Hudd G. A. , Lloyd‐Jones C. P. 
Published: April 2006

Whole bean plants, ev. Cockfield, grown in pots crowded or well‐spaced (50 or 10 plants m2, respectively) were treated with 14CO2 at the pod‐fill stage (25 modes) and the radioactivity in each leaf was determined after 30 min. With spaced plants the uptake was greatest in the mid‐stem leaves and was proportional to leaf area. In contrast, 70% of the total assimilation took place in the upper six leaves of crowded plants and there was a steady decrease down the stem.When 14CO2 was fed to single leaves of similar crowded plants the resultant distribution of labelled assimilates varied with the position of the treated leaf. After 6 h, 67% of the 14C fixed by a mid‐stem leaf (node 13) was recovered from the beans, whereas 76% of that from an upper leaf (node 23) had accumulated along the stem. Due to the shading of mid‐stem leaves at the higher planting densities, seed yield becomes increasingly dependent upon re‐distribution of assimilates from stem to beans.
Leaf expansion as related to plant water availability in a wild and a cultivated sunflower
Authors: Sobrado M. A. , Rawson H. M. 
Published: April 2006

This study aimed to determine if two species of sunflower, Helianthus annus L. cv. Hysun 31 (cultivated, single‐stemmed genotype) and Helianthus petiolaris Nuttall ssp. fallax (wild, many‐hranched genotype) differed in the response of leaf growth to water deficits. Earlier published studies, concerned only with H. annuus, failed to reveal differences in the response of sunflowers to water stress. Plants of the two species were paired in large containers of soil and grown under high radiation in a glasshouse. One batch of plants was irrigated and the other allowed to dry so that predawn leaf water potentials declined at an average of 0.072 MPa day−1. The dry batch was rewatered when predawn leaf water potentials reached −0.85 MPa.The stress imposed was sufficient to curtail leaf growth so that plants in the dry treatment had only 60% of the leaf area of irrigated plants at the onset of rewatering. Both species were affected by stress to the same relative extent, though their leaf areas at this stage differed 7‐fold. Both genotypes also recovered to the same degree in the long term, finally having leaf areas and gross dry matter distribution patterns which were indistinguishable from plants which were irrigated throughout. However, water stress resulted in different distribution patterns of leaf area: H. annuus produced larger leaves at the top of its single stem which compensated for the reduced area in lower leaves, whereas H. petiolaris compensated in the leaves on its branches. Leaves which emerged after the time of stress were most able to compensate in area subsequently. For example, those leaves of H. annuus which emerged one week after stress‐relief were more than three times larger than comparable leaves on plants irrigated continuously. Leaf expansion rates were affected earlier in the stress cycle than leaf conductance in H. annuus, but not in H. petiolaris. But as with other plant responses to water stress, the differences between the two species were small.
Development of pH sensitivity of sucrose uptake during ageing of Vicia faba leaf discs
Authors: Lemoine Remi , Delrot Serge , Auger Evelyne 
Published: April 2006

Uptake of [U‐14C]‐sucrose (40 mM) by fresh and aged peeled leaf discs of broad bean (Vicia faba L. cv. Aguadulce) has been studied. In fresh discs, uptake was nearly insensitive to external pH, whereas the pH response of absorption in discs aged for 12 h was bell‐shaped, with an optimum between pH 5 and 6. At this pH, uptake was nearly twice that in fresh tissue. The passive (insensitive to carbonyl cyanide m‐chlorophenylhydrazone and to cold treatment) uptake was the same in fresh or aged discs. The development of pH sensitivity of absorption did not appear when ageing was performed in the presence of 10−HM cycloheximide or 5.7 × 10−5M actinomycin D. Similarly, when the tissues were treated with 10−3M spermidine for 2 h after excision and then aged for 10 h, the development of the pH‐sensitive uptake system was inhibited. Ca2+ (10−2M) supplied together with spermidine prevented the inhibiting effect of spermidine. The appearance of the pH‐sensitive system was also markedly reduced if ageing took place in the presence of 10−3M aminoethoxyvinylglycine. Autoradiographs from fresh discs and from discs aged with or without the inhibitors suggest that pH sensitivity developed more intensively in the parenchyma than in the veins.The results suggest some caution when using excised leaf discs for studies on sucrose uptake and phloem loading. Development of pH sensitivity of uptake may require the synthesis of both DNA‐dependent RNA and protein and could be related to ethylene metabolism.
The role of the chloroplast coupling factor in the inactivation of thylakoid membranes at low temperatures
Authors: Santarius Kurt A. 
Published: April 2006

Thylakoids isolated from spinach leaves (Spinacia oleracea L. cv. Monatol) were exposed to variable low temperatures under non‐freezing conditions. After incubation, changes in the activities of several photochemical reactions and physical properties of the membranes were measured at room temperature.Cyclic photophosphorylation was strictly dependent on the temperature and the electrolyte concentration: decrease in temperature and increase in NaCl concentration enhanced membrane damage. Inactivation of photophosphorylation was accompanied by stimulation of non‐cyclic electron transport, increase in proton permeability and decrease in δpH. When dicyclohexylcarbodiimide was added, the proton gradient became completely restored. The temperature‐ and salt‐dependent breakdown of photophosporylation was closely related to the release of the chloroplast coupling factor (CF1) from the membranes. The addition of Mg2+, very low concentrations of ATP or ADP, or higher concentrations of low‐molecular‐weight polyols prior to temperature treatment prevented thylakoid damage.The data indicate that inactivation of photophosphorylation of thylakoids at low temperatures is determined to a considerable extent by the cold lability of the CF1. As a consequence, it must be concluded that damage of biomembranes caused by freezing is not due solely to changes resulting from the ice formation but additionally by temperature‐dependent alterations of cold‐labile proteins. Moreover, the data explain the mechanism of non‐colligative cryoprotection of isolated thylakoid membranes.
Differences in the response of sunflower (Helianthus annuus) subjected to flooding and drought stress
Authors: Wample Robert L. , Thornton Robert K. 
Published: April 2006

Wample, R. L. and Thornton, R. K. 1984. Differences in the response of sunflower (Helianthus annuus) subjected to flooding and drought stress.Comparison of drought‐ and flood‐stressed sunflower plants (Helianthus annuus L. hybrid 894) showed some similarities in response but differences in the mechanisms responsible for the responses to stress. Drought–stressed plants showed typical reductions in leaf water potential with increasing stress accompanied by increased leaf resistance. Photosynthesis declined while photorespiration increased after 48 and 96 h of drought stress. A primary reason for reduced photosynthesis in drought‐stressed plants was increased stomatal resistance. No significant 0change in leaf water potential or in leaf resistance in flooded plants was found in this study. However, photosynthesis declined in a manner similar to that in drought‐stressed plants and photorespiration showed only a transient increase at 48 h. Dark respiration was significantly higher at 48 and 96 h but the magnitude of the increase cannot account for the reduction in photosynthesis. Since the photosynthetic rate of flooded plants declined while stomata remained open, an effect at a more fundamental level is suggested and is thought to be related to disruption of carbohydrate transport.
Phénolamides et induction florale de Cichorium intybus dans différentes conditions de culture en serre ou in vitro
Authors: Martin‐Tanguy Josette , Margara Jacques , Martin Claude 
Published: April 2006

Phenolamides and floral induction of Cichorium intybus in different conditions of culture in glass‐room or in vitro.Three complexes between phenols and amines (phenolamides) have been found in Cichorium intybus L., a plant with an absolute requirement of vernalisation followed by long days for flowering. Upon hydrolysis, these complexes (A, B and C) liberate aromatic amines whose exact identification is in progress, but which are closely related to dopamine, tyramine and serotonin, respectively.In a first series of experiments, phenolamides were studied in the buds of plants grown in the greenhouse under varying conditions. Only buds from plants which flower in long days contained large amounts of these compounds. Much smaller amounts were found in buds at the end of vernalisation (at 2–4°C) before long‐day treatment as well as in buds kept in the vegetative state after vernalisation by being grown in short days (8 h light) or in total darkness. In a second series of experiments, phenolamides were studied in bud‐forming calli induced in vitro on explants of tuberised root. After sixteen days of culture in continuous light, large quantities of phenolamide were found in the buds and calli of the upper part of the explant, while the lower part which never produces buds contained much less.Buds formed under continuous light produce inflorescences in approximately one month. Various other culture conditions make it possible to maintain the explants in the vegetative state. This can be obtained by short‐day conditions, or otherwise under continuous illumination by decreasing the sugar or increasing the NAA levels in the medium. After 13 days of culture, the phenolamide levels were much lower under all of these conditions, than under conditions favourable to floral induction. Compound C is absent or present in trace amounts in vegetative buds. The significance of the differences observed between floral and vegetative buds is supported by the sensitivity of the analytical techniques used.The accumulation of phenolamides in tissues of Cichorium intybus appears to be closely linked to floral induction. Under continuous light it begins very early in young buds and even in the calli that bear these buds.