bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possibilities and constraints in the regeneration of trees from cotyledonary needles of Picea abies in vitro
Authors: Bornman Chris H. 
Published: April 2006

Although use of embryonic or seedling tissues for mass clonal micropropagation in vitro in conifer reforestation programmes is questionable, there is a potential application in the regeneration of plants from scarce and costly seed derived from controlled pollination. In addition, in vitro culture shortens considerably the lag phase in numbers during the initial stages of vegetative propagation via rooted cuttings. Successive steps of the present technique are described whereby cotyledonary needles (secondary explants) were subcultured on a hormone‐free medium after administration of cytokinin or auxin to 14‐day‐old seedling (primary) explants of Picea abies. For bud induction, N6‐benzyladenine (BA) was applied either as a short‐duration (3 h), high‐concentration (125 μM) pulse or by vacuum infiltration and incubation in a BA‐containmg (5 μM) infusion medium. Induced adventitious shoots were elongated with the aid of far‐red light and rooted in vivo after a long‐duration (12 h), high‐concentration (625 μM) application of indolebutyric acid. Pulse and infusion treatments resulted in the induction of greater numbers of adventitious buds (average of 12 per needle) over a three to four week shorter culture period than was the case with the conventional inclusion of growth regulators in the agarified medium. No exogenous auxin was required in the bud‐induction programme; its inclusion even at nanomolar levels promoted histo‐ rather than morphogenesis. In cotyledonary needles, to the primary explants of which BA was applied as a pulse or by infusion, the cell divisions which gave rise to the meristemoids from which adventitious buds were produced, appeared to commence mainly in undifferentiated hypodermal layer cells but also in the mesophyll immediately below. By contrast, where BA was incorporated in the agarified medium the first divisions occurred mainly in cells of the epidermal layer.A number of factors affected plantlet regeneration, for instance seed variability, age of seedlings, and mode of application of growth substances. It should also be accepted that the xeromorphic nature of the conifer leaf might impose physiological and morphological constraints on its culture in vitro that could militate against easy morphogenic manipulation. It is deemed essential that the current mean ratio of regenerated plants to cotyledonary needles of 1:1 be increased 10 to 20 fold in order to approach commercial feasibility.
Influence of light on phosphoenol pyravate carboxylase in sorghum leaves
Authors: Vidal Jean , Godbillon Guy , Gadal Pierre 
Published: April 2006

Upon greening of sorghum leaves (Sorghum vulgare Pers. cv. INRA 450) under white light illumination, phosphoenolpyruvate carboxylase activity increases. 17 times; at the same time, a new isoform of the enzyme appears.The aim of the present work has been to identify the process responsible for the appearance of this isoform. Greening. of the leaves in the presence of D2O did not lead to a significant increase in the buoyant density of the enzyme. On the other hand, cycloheximide was a powerful inhibitor of the rise in PEP carboxylase activity. In order to clarify these conflicting data a procedure based on the immunoprecipitation of the enzyme and its quantification by gel electrophoresis was developed in order to estimate the amount of enzyme in leaf tissue. The results clearly demonstrate that light triggers an increased synthesis of the enzyme protein during greening of sorghum leaves.
Effect of bovine serum albumin on membrane potential in plant mitochondria
Authors: Diolez Philippe , Moreau François 
Published: April 2006

The membrane potential in highly coupled potato (Solanum tuberosum L.) mitochondria, as measured by changes in safranine absorbance, was significantly increased by addition of bovine serum albumin. Purification of potato mitochondria on Percoll, in removing 50% of free unsaturated fatty acids, decreased the BSA‐de‐pendent membrane potential. The effect of added linoleic acid and of the natural accumulation of fatty acids during aging was studied. The response of membrane potential to addition of bovine serum albumin appeared to be directly correlated to the amount of free unsaturated fatty acids. Aging in vitro, in releasing free fatty acids, decreased respiratory control and ADP:O ratios and collapsed the membrane potential. During 2–3 h of incubation, addition of BSA completely restored membrane potential and oxidative phosphorylation.It is concluded that both in fresh and in aged potato mitochondria the effect of bovine serum albumin on oxidative phosphorylation can be ascribed to an effect on membrane permeability to ions. BSA, in binding free unsaturated fatty acids, restored maximal membrane potential. The bovine serum albumin‐dependent membrane potential appears to be a sensitive criterion of the functional integrity of the inner mitochondrial membrane.
Transplanting shock in white spruce; effect of cold‐storage and root pruning on water relations and stomatal conditioning
Authors: Blake T. J. 
Published: April 2006

White spruce [Piceae glauca(Moench) Voss] seedlings were pre‐conditioned by cold storage and root pruning and a study was made of the effects of conditioning on root regeneration and stomatal adaptation following transplanting.Root pruning (0 to 75% of the initial root area) of dormant seedlings immediately prior to transplanting did not confer any detectable physiological advantage in either cold‐stored or freshly‐lifted seedlings. Transpiration rates and stomatal resistance were not greatly affected by root pruning in the 6 week period after planting and root pruning did not greatly alter the response to drought.Cold‐stored seedlings appear better able to avoid transplanting shock and an early drought despite delayed root growth as evidenced by a) a delay in flushing of new shoot growth and b) pre‐conditioning of the stomatal apparatus which reduced water loss after planting and when moisture was limiting. Seedlings freshly‐lifted in the spring did not show these adaptive responses and their stomata were poorly adapted to reduce water loss in the post‐planting period after a drought.
Effets physiologiques de ľ atrazine à doses sublétales sur Lemna minor, VII. Incorporation ?acétate‐l,2‐[14C] dans les groupes de lipides et leurs acides gras
Authors: Grenier Gilles , Beaumont Gaston 
Published: April 2006

Physiological effects of sublethal doses of atrazine on Lemna minor. VII. 1,2‐[14C] acetate incorporation into the groups of lipids and their fatty acids.The lipids and the fatty acids of ten‐day old duckweed (Lemna minor L.), cultivated aseptically in mineral solution containing sublethal concentrations of 0,10 and 0,50 ppm (0.46 and 2.3 μM, respectively) of atrazine, were analyzed by thin‐layer chromatography and gas‐liquid radiochromatography after 1,2‐[14C] acetate feeding. Sublethal concentrations of atrazine increased the incorporation of radioactivity in total lipids, diacylgalactosylglycerol (DGG), diacyldigalactosylglycerol (DDG), sul‐folipids (SL), phosphatidylglycerol (PG), diacylglycerol (DAG) and triacylglycerol + steroll esters (TAG+SE). The incorporation of acetate‐1,2‐[14C] decreased in phos‐phatidylcholine (PC) and in phosphatidylethanolamine (PE) in the presence of atrazine. The radioactivity increased in total Transic‐hexadecenoic, linoleic and α ‐linolenic acids while it decreased in the other fatty acids. This indicates that the sublethal concentrations of atrazine stimulate the desaturation of fatty acids of L. minor. The radioactivity was strongly incorporated in the α ‐linolenic acid of DGG in the presence of atrazine. The specific radioactivity of α‐linolenic acid was greater in DAG than in PG > TAG + SE > PC > PE > DGG > SL > DDG and it increased in all groupd of lipids analyzed under the influence of sublethal doses of atrazine. The labelling of Translchexadecenoic acid of PG and its specific radioactivity increased in the presence of atrazine. These changes suggest that the sublethal concentrations of atrazine stimulate especially the lipid metabolism of the chloroplasts of L. minor and they could explain the increase in the number of grana per chloroplast in treated L. minor. The results are discussed in relation to the biosynthesis of galactolipids.
Synthèses ?acides nucléiques et de protéines au cours de ľinitiation de bourgeons adventifs sur des explantats de Cichorium intybus cultivés in vitro
Authors: Vasseur Jacques , Roger Véronique 
Published: April 2006

Synthesis of nucleic acids and proteins during initiation of vegetative buds from explants of Cichorium intybus cultivated in vitro.Explants of 6 mm diameter and 2 mm thickness from roots of Cichorium intybus L. (var. WitIoof cv. “Zoom”), grown in vitro in the presence of kinetin (l0–6M), produced only buds. By comparing the histological events and the biochemical modifications which occurred during the neoformation of buds, it is possible to distinguish two distinct phases. The first phase starts immediately after the excision of the explants and continues for 30 h, when the mitotic index is at its highest. This corresponds to a phase of cellular activation, which is characterized by early synthesis of RNA, permitting the synthesis of proteins necessary for duplication of DNA and cell divisions. The second period starts after 30 h and ends after approximately 72 h of culture, at which time the first bud meristematic nodules were detected. This is a preparatory phase for organogenesis and above all related to synthesis of RNA and proteins.
Quantitative and qualitative changes in cell wall polysaccharides in relation to growth and cell wall loosening in Lactuca sativa hypocotyls
Authors: Katsu Noriko , Kamisaka Seiichiro 
Published: April 2006

The correlation between hypocotyl elongation, cell wall loosening and changes in cell wall polysaccharides was studied using intact lettuce seedlings grown in the dark or in light together with gibberellic acid (GA) and/or 5‐fluorodeoxyuridine (FUDR). The following results were obtained:1) The production of pectic, hemicellulosic and cellulosic polysaccharides look place in parallel with hypocotyl elongation, which was substantially affected by different growth conditions.2) The mole percentage sugar composition of pectic and hemicellulosic polysaccharides changed in response to dark, light, GA, or FUDR treatments.3) The amounts of xylose and glucose in hemicellulosic polysaccharides and those of galactosc, rhumnose and uronic acid in pectic polysaccharides increased in parallel with hypocotyl elongation.4) Statistical analysis of the quantitative relationship between sugars composing polysaccharides revealed that the uronic acid content changed in parallel with those of rhamnose and galactose in pectic polysaccharides, and the content of xylose varied in parallel with those of fucose and glucose.5) The content of hemicellulosic polysaccharides was correlated with cell wall loosening represented by a decrease in the minimum stress‐relaxation time. Changes in the stress‐relaxation time value were correlated with those in the content of araltinose and galactose in hemicellulosic polysaccharides.Based on these results, the relationship between hypocotyl elongation, changes in cell wall polysaccharides, and cell wall loosening is discussed with respect to the effect of GA and FUDR on hypocotyl elongation.
A malate‐oxaloacetate shuttle linking cytosolic fatty acid α‐oxidation to the mitochondrial electron transport chain in uncoupled fresh potato slices
Authors: Wu Shu‐yi , Laties George G. 
Published: April 2006

The possible existence of a malonate‐sensitive dicarboxylate‐mediated electron shuttle between microsomal NAD‐linked fatty acid α‐oxidation and the mitochondrial electron transport chain in uncoupled fresh potato slices was investigated. Uncoupled slice respiration is inhibited by benzylmalonate and butylmalonate, inhibitors of dicarboxylate transport into mitochondria. Uncoupled slice respiration is also inhibited by rotenone, an indication of intramitochondrial NADH oxidation. Since fatty acid α‐oxidation per se is rotenone insensitive, rotenone and benzylmalonate inhibition of the oxidation of carboxyl‐labeled myristate in slices points to a dicarboxylic acid shuttle linking microsomal fatty acid a‐oxidation with intramitochondrial NADH dehydrogenase.Malonute inhibits both respiration and 14CO2, release from carboxyl‐labeled myristate in fresh uncoupled slices, as do inhibitors of dicarboxylate transport. Mitochondrial studies show that malonate inhibits malate oxidation but not malate dehydrogenase per se. Furthermore, malonate inhibits malate transport more severely than malate oxidation. Accordingly, mulonate inhibition of uncoupled slice respiration in the absence of tricarboxylic acid cycle activity is attributed to its interference with mitochondrial malate transport, and its consequent curtailment of a putative malate‐OAA shuttle linked to cytosolic NAD‐mediated fatty acid α‐oxidation.
Thigmomorphogenesis: membrane lipid and protein changes in bean plants as affected by mechanical perturbation and Ethrel
Authors: Erner Y. , Jaffe M. J. 
Published: April 2006

When bean plants (Phaseolus vulgaris L. cv. Red Cherokee Bush) are mechanically perturbed by rubbing, their stem elongation is inhibited and the stem thickness increases. The decrease in cell elongation and the increase in lateral cell divisions, which are partially responsible for this syndrome, were correlated with a decrease in the tree fatty acids and in the phospholipids of the membranes of microsomal fractions of first and second internodes of mechanically stimulated plants. This was true even though only the first internode was mechanically stimulated.Of the microsomal free fatty acids, mechanical perturbation induced an increase in myristic acid and large decreases in stearic, oleic, linoleic and linolenic acids. It also reduced the unsaturated:saturated ratio of the fatty acids. It induced a decrease in phosphatidyl choline but an increase in phosphatidyl ethanolamine. When the fatty acids were cleaved from the microsomal phospholipids, mechanical perturbation caused only a slight decrease in the unsaturated:saturated ratio and no significant changes in the double bond index.Mechanical perturbation induced an increase in the total microsomal protein and of membrane‐associated latent IDPase. However, the activity of membrane‐associated KCN‐insensitive NADPH cytochrome‐c reductase was decreased by mechanical perturbation.Treatment of the first internode with exogenous Ethrel produced results that were very similar in all respects to those obtained by mechanical perturbation. The factors inducing hardening against frost and drought, as achieved by mechanical perturbation and Ethrel treatment, are not only related to sterols or the polar head‐groups of phospholipids but may also be related to the protein components, and all may have an effect on the fluidity of a bilayer membrane model. These data support the hypothesis that ethylene mediates thigmomorphogenesis and that mechanical perturbation of the first internode results in the acropetal transport of a translocatable thigmomorphogenetic factor.
Effects of pH, NADH, succinate and malate on the oxidation of glycine in spinach leaf mitochondria
Authors: Bergman Anders , Ericson Ingentar 
Published: April 2006

The effect of external pH on several reactions catalyzed by glycine decarboxylase in spinach leaf mitochondria was investigated. Glycine‐dependent oxygen consumption showed a pH optimum at 7.6, whereas the release of CO2 and NH3 from glycine in the presence of oxaloacetate both showed pH maxima at 8.1. Glycine‐dependent reduction of 2,6‐dichlorophenolindophenol. on the other hand showed a pH optimum at 8.4. It is concluded that these three reactions have different rate‐limiting steps. The rate of the glycine‐bicarbonate exchange reaction catalyzed by glycine decarboxylase showed no optimum in the pH range investigated, pH 7–9, but increased with decreasing pH. This suggests that CO2 may be the true substrate in this reaction.The oxidation of glycine inhibited the oxidation of both malate, succinate and external NADH since the addition of malate, succinate or NADH to mitochondria oxidizing glycine in state 3 resulted in a rate of oxygen consumption which was lower than the sum of the rates when the substrates were oxidized individually. The addition of malate, succinate or NADH did not, however, decrease the rate of CO2 or NH, release from glycine. It is suggested that the preferred oxidation of glycine by‐spinach leaf mitochondria may constitute an important regulatory mechanism for the function of leaf mitochondria during photosynthesis.
Purification and properties of NADP‐dependent glutamate dehydrogenase from Sphaerostilbe repens
Authors: Balton Bernard , Msatef Yamina 
Published: April 2006

NADP‐dependent glutamate dehydrogenase (EC 1.4.1.4) extracted from Sphaerostilbe repens was purified to homogeneity by using ammonium sullate fractionation hydroxyapatite and DEAE‐cellulose column chromatography and, finally, preparative polyacrylamide gel electrophoresis. The turnover number of the enzyme for the amination reaction was about 66000 mol substrate transformed min‐1 (molecule of GDH)‐1. Molecular weight of the native enzyme was estimated to be 280000 dalton by polyacrylamide gradient gel electrophoresis. The same technique in the presence of sodium dodecyl sulfatc gave a single protein band that corresponded to the subunit molecular weight of 48000 dalton. Thus, it is concluded that NADP‐GDH is composed of six identical polypeptidic chains.The pH optimums were 6.9 and 8.4 for the forward and reverse reactions respectively. The NADP‐GDH lost practically none of its activity for ten days at 4°C and for 15 h at room temperature, but was inactivated by higher temperatures. Thiol compounds such as 2‐mercaptoethanol and dithiolhrcitol protected the enzyme from rapid inactivation. The Michaelis constants for GDH were 0.64, 0.049. 0.043 and 5.5 mM for α‐ketoglutaratc. NADPH, NADP and glutamate, respectively. The enzyme had a negative cooperativity for ammonium (Hill number of 0.66), and its Km value increased from 2.6 to 21.2 mM when the ammonium concentration exceeded 16 mM. The deamination reaction was highly sensitive to inhibition by ammonium, while the amination reaction was only slightly inhibited by glutamate. These results, considered together with the Km values, indicate that the NADP‐GDH in Sphaerostilbe repens is primarily concerned with glutamate biosynthesis.
The effect of triacontanol on growth, photosynthesis and photorespiration in Chlamydomonas reinhardtii and Anacystis nidulans
Authors: Haugstad May , Ulsaker Liv Kari , Ruppel Anneke , Nilsen Stein 
Published: April 2006

Chlamydomonas reinhardtii Dangerad 11–32(90) (−), which exhibits C3 properties, and Anacystis nidulans (Strain no. UTEX 625), which exhibits C4 properties, were used to study the effects of triacontanol on growth, photosynthesis and photorespiration. Photosynthetic rate was measured as CO2 uptake and the O2 inhibition of photosynthesis was used as a measure of photorespiration. Triacontanol dissolved in chloroform and dispersed in Tween‐20 and triacontanol colloidally dispersed in an aqueous solution of sodium tallow alkyl sulfate were tested. Chlamydomonas cultures increased significantly in cell number after 4 days, and in chlorophyll content after 3 days of treatment with 2.3 × 10−8 M TRIA in chloroform/Tween‐20. In cultures of Anacystis the chlorophyll content became significantly higher 3 days after treatment with 2.3 × 10−9 M TRIA and the cell number was noticeably higher than the controls.CO2 uptake by triacontanol‐treated Chlamydomonas cultures was about the same in both 2 and 21% O2, and the O2 inhibition was significantly reduced as compared with the controls. Photosynthesis in Anacystis was O2‐insensitive under the experimental condition used. When Anacystis was treated with triacontanol there was no change in the rate of CO2 uptake and no change in the O2 sensitivity of its CO2 uptake. It appears that triacontanol affects some process which regulated the balance between photosynthesis and photorespiration, but other processes which result in increased growth are probably also affected.
5‐Oxo‐prolinase activity in tobacco suspension cultures: Regulation by sulfate nutrition
Authors: Rennenberg Heinz , Polle Andrea , Grundel Ina 
Published: April 2006

In heterotrophic and photoheterotrophic tobacco (Nicotiana tabacum L., var. Samsun) suspensions cultured with growth‐limiting amounts of sulfate, 5‐oxo‐prolinase activity declines at the same time as the growth rate of the cells decreases. However, 5‐oxo‐prolinase activity is reduced to a greater extent than growth. As a result, the specific activity of 5‐oxo‐prolinase also declines when sulfur is scarce. The decrease in both growth and 5‐oxo‐prolinase activity can be prevented by adding sulfate to the suspensions during exponential growth. Addition of sulfate after the exponential growth phase restored neither growth nor 5‐oxo‐prolinase activity. These observations show that 5‐oxo‐prolinase activity in tobacco cells is regulated by the sulfate supply in the medium. Such a regulation is an essential prerequisite, but not a proof, for a role of 5‐oxo‐prolinase as the rate‐limiting factor in glutathione degradation.During exponential growth the average specific activity of 5‐oxo‐prolinase in heterotrophic tobacco cells is twice as high as in photoheterotrophic cells. This difference is consistent with the idea that green cells are equipped for glutathione synthesis and export, and chloroplast‐free cells for uptake and degradation of this peptide.
Patterns of ammonium absorption and acetylene reduction during soybean developmental growth
Authors: Marcus‐Wyuer Lynn , Rains D.W. 
Published: April 2006

Nodulated and unnodulated soybean plants (Glycine max (L.) Merr. cv. Amsoy 71) were grown in nutrient solution either lacking or containing N. Nodulated plants, dependent on N2 fixation, exhibited a generalized N‐stress and were less vigorous than unnodulated plants dependent on inorganic N assimilation.Starting at preflowering throughout mid pod‐filling, NH4+ absorption, expressed on the basis of root dry weight, was determined for intact nodulated and unnodulated plants in short‐term kinetic experiments. Depletion of NH4+ was measured from the liquid phase of a mist chamber. Maximum NH4+ absorption occurred for both nodulated and unnodulated plants during vegetative growth. A pattern of progressive decrease in NH4+ absorption was similar in nodulated and unnodulated plants, however. NH4+ absorption was consistently greater in unnodulated plants. Simultaneous measurements of C2H2 reduction from the gas phase of the mist chamber revealed and 41‐day‐old plants, corresponding to late flowering and early pod‐filling.