bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and functional relationships in developing Pinus silvestris chloroplasts
Authors: LEWANDOWSKA MARY , ÖQUIST GUNNAR 
Published: April 2006

AbstractThe light dependent chloroplast development of dark grown seedlings of Pinus silvestris L. was followed by analyses of chlorophyll content, chlorophyll a/b ratios, chlorophyll/P700 ratios, chlorophyll‐protein complexes and structural changes.Low‐temperature fluorescence emission spectra of isolated chloroplasts and separation of sodium dodecyl sulphate solubilized chlorophyll‐protein complexes by gel electrophoresis showed that the chlorophyll‐protein complexes of photosystem 1 (P700‐CPa), photosystem II (PS II‐CPa) and the light‐harvesting complex LH–CPa/b were present in dark grown seedlings. The low‐temperature fuoorescence emission maxima of isolated P700–CPa and PS II–CPa shifted towards longer wavelengths during greening in light, indicating a light induced change of the chlorophyll organisation in the two photosystems. Illumination caused LH–CPa/b to increase relative to P700–CPa, whereas the ratio between LH–CPa/b and PS II–CPa remained essentially constant. Analyses of low‐temperature fluorescence spectra with or without 0.01 M Mg2+ showed that the Mg2+ controlled distribution of excitation energy into PS I was activated upon illumination of the seedlings.The photosynthetic unit size, as defined by the chlorophyll/P700 ratio, did not change over a 96 h illumination period, although the chlorophyll content increased about 6–fold during that time. This result and the constant electron transport rate per unit chlorophyll and time during chlorophyll accumulation provided evidence for a sequential development of the photosynthetic units when illuminating dark grown pine cotyledons. Electron micrographs showed that exposure of dark grown seedlings to light for 2 h caused the prolamellar body to disappear and grana to form. These changes occurred prior to substantial accumulation of chlorophyll or change in the ratio between LH–CPa/b and P700–CPa. However, both the water‐splitting system of photosystem II and the Mg2+ controlled redistribution of excitation energy was activated during this period.
Kinetic studies of a (Na++ K++ Mg2+)ATPase in sugar beet roots. III. A proposed model for the (Na++ K+) activation and its significance for field properties
Authors: LINDBERG SYLVIA 
Published: April 2006

AbstractA microsomal (Na++ K++ Mg2+)ATPase preparation from sugar beet roots was used. The activation by simultaneous addition of Na+ and K+ at different levels was examined in terms of steady state kinetics. The observed data can be summarized in the following way:1. The apparent affinity between the enzyme and the substrate MgATP depends on the ratio between Na+ and K+. At low Na+ concentration (below 5 mM), the apparent Km decreases with increasing concentrations of K+ (1–20 mM). At 5 mM Na+, the K+ level does not change the apparent Km, while at Na+ levels above 10 mM, the apparent Km between enzyme and substrate increases with increasing concentration of K+.2. When the MgATP concentration is kept constant, homotropic cooperativity (concerning one type of ligand) and heterotropic cooperativity (concerning different types of ligands) exist in the activation by Na+ and K+. The Na+ binding is cooperative with different Km values and Hill coefficients (n) in the presence of low and high concentration of K+. At low Na+ level (< 5 mM). a negative cooperativity exists for Na+ (nNa < 1) which is more pronounced in the presence of high [K+]. When the concentration of Na+ is raised the negative cooperativity disappears and turns into a positive one (nNa > 1).Only K+ binding in the presence of low [Na+] shows cooperativity with a Hill coefficient that reflects changes from negative to positive homotropic cooperativity with increasing concentrations of K+ (nK < 1 → nK > 1). In the presence of [Na+] > 10 mM, the changes in nk are insignificant.3. A model is proposed in which one or two different K sites and one or two Na sites control the catalytic activity, with multiple interactions between Na+, K+ and MgATP.4. In the presence of Na+ (< 10 mM), K+ is probably bound to two K sites, one of which translocates K+ through the membrane by an antiport Na+/K+ mechanism. This could be connected with an elevated K+ uptake in the presence of Na+ and could therefore explain some field properties of sugar beets.
Interaction of light and auxin in regulation of rooting in pea stem cuttings
Authors: ELIASSON LENNART 
Published: April 2006

AbstractIrradiation of the base internode of stem cuttings of Pisum sativum L. with white light during the rooting period resulted in the formation of fewer roots. IBA applied to the rooting solution for 4 days counteracted this inhibition even at low concentrations. IBA stimulated rooting, also, in cuttings grown under low irradiance where availability of photosynthetic products is probably the limiting factor for rooting. IAA, however, did not reverse the inhibition of rooting, resulting from unfavourable light conditions, at concentrations lower than 10−5M, but 10−4M IAA had a similar action to IBA. Under light conditions giving good root formation IAA over a concentration range from 10−7M to 10−5M decreased the number of roots formed.It is hypothesized that light prevents the action of endogenous auxin, or low exogenous concentrations of IAA, in the root‐forming process while the synthetic auxin IBA is fully active in irradiated tissues.
Photoactivation of the latent O2‐evolving center in chloroplasts isolated from dark‐grown spruce seedlings
Authors: OKU TATSUO , TOMITA GIITI 
Published: April 2006

AbstractThe latent O2‐evolving center in chloroplasts isolated from spruce [Picea abies (L.) Karst.] seedlings grown in the dark was readily activated by pre‐illuminating the chloroplast suspension with weak white light. The photoactivation depended on pH with the optimum at pH 7–8, and was strongly stimulated by ascorbic acid. The optimal stimulation was also obtained at pH 7–8. The temperature dependence of the photoactivation suggested the involvement of some dark reaction in the activation process.
Comparison of acetylene‐reduction and nitrogen‐15 techniques for the determination of nitrogen fixation by field bean (Vicia faba) nodules
Authors: HUDD G. A. , LLOYD‐JONES C. P. , HILL‐COTTINGHAM D. G. 
Published: April 2006

AbstractField bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station, and grown in sand culture supplied with a complete nutrient solution which included nitrate at either 1.5 or 6.0 mM. Nodules were detached from the roots at intervals during plant development and their rates of nitrogen fixation estimated by both acetylene reduction and 15N gas technique.There was a constant relationship, independent of nitrate supply, between the results obtained by these two methods at all samplings. The amounts of acetylene reduced divided by a factor of 5.75 gave the amount of true nitrogen fixation; this factor is about twice the theoretical value. It is suggested that this discrepancy arose because, with acetylene, all the electrons available to the nitrogenase were used to form ethylene, whereas during normal fixation only about half the electron supply was used to fix nitrogen, the remainder having been consumed in the production of hydrogen gas.
The influence of nitrate supply on nitrogen fixation during growth of the field bean Vicia faba in sand
Authors: HILL‐COTTINGHAM D. G. , LLOYD‐JONES C. P. 
Published: April 2006

AbstractField bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station and grown in sand culture supplied with 15N‐labelled nitrate at two concentrations. Plants were sampled at intervals throughout their growth for 15N and total N analysis. The rate of nitrate uptake was almost uniform up to pod‐fill and was proportional to the nitrate concentration. Nodule weight was slightly depressed by the larger nitrate concentration at all samplings, and there was a corresponding reduction in the amount of atmospheric nitrogen fixed. However, at harvest the bean seeds from plants given most nitrate contained slightly more total N, as the enhanced nitrate uptake outweighed the reduction in fixation.
Effect of kinetin and abscisic acid on the distribution of 2‐amino (1‐14C) isobutyric acid in leaves of Zea mays
Authors: FENNER RUDOLF , DÖRFFLING KARL 
Published: April 2006

Abstract2‐Amino (1‐14C) isobutyric acid (AIB) was applied to the leaf tips of thirteen‐day‐old primary leaves of Zea mays L. cv. Goldprinz. Simultaneously, the leaves were treated in the basal region with solutions of kinetin (KN), abscisic acid (ABA) and mixtures of both hormones. The distribution of the radioactive material was determined after 72 h. Treatment with KN caused an accumulation of radioactive material at the point of application (KN spot). In comparison to controls, the leaf zones between the KN spot and the leaf tip contained lower amounts of radioactive material. Treatment with ABA caused a pattern of distribution opposite to that induced by KN. The ABA point of application (ABA spot) was depleted of radioactive material, whereas the leaf area between the ABA spot and the leaf tip showed enhanched levels of radioactive AIB. The effect of ABA was reduced by application of ABA and KN in equimolar amounts. The results are discussed in relation to the possible role of ABA in hormone‐directed transport processes.
Development of photosynthetic electron transport in Pinus silvestris
Authors: LEWANDOWSKA MARY , ÖQUIST GUNNAR 
Published: April 2006

AbstractPhotosynthetic electron transport activity has been measured in chloroplasts isolated from dark‐grown seedlings of Pinus silvestris L. and in chloroplasts isolated from seedlings subjected to illumination for periods of up to 48 h. Activities of photosystem 2, photosystem 1 and photosystem 2 plus 1 have been measured. Chloroplasts isolated from dark‐grown seedlings showed significant electron transport activity through both photosystems and through the entire electron transport chain from water to NADP. Illumination of the seedlings for only 5 min markedly promoted photosystem 2 activity. The artificial electron donor, diphenylcarbazide. promoted activity in chloroplasts from dark‐grown seedlings and in chloroplasts from seedlings illuminated for up to 30 min. In comparison to photosystem 2 and overall electron transport from water to NADP, photosystem 1 activity increased only slightly during illumination. Measurements of electron transport and fluorescence kinetics have confirmed that photosynthetic electron transport capacity is limited on the water splitting side of photosystem 2 in dark‐grown seedlings, whereas the primary and secondary electron acceptors of photosystem 2 are fully synthesized and functioning in darkness.Polyethylene glycol must be used as a protective agent when isolating photoactive chloroplasts from secondary needles of conifers. However, the presence of polyethylene glycol, when isolating chloroplasts from dark‐grown pine cotyledons, caused a total inhibition of the activity of photosystem 2. The failure of others to show a substantial electron transport activity in chloroplasts from dark‐grown Pinus silvestris might depend on their use of polyethylene glycol in the preparation medium and/or on their use of suboptimal reaction conditions for the electron transport measurements.
Starch and prolamin level in single and double high‐lysine barley mutants
Authors: KREIS MARTIN , DOLL HANS 
Published: April 2006

AbstractAt maturity the high‐lysine barley (Hordeum vulgare L.) Ris0 mutants 1508, 527 and 29 kernels contained about 20% less starch and twice as much free sugars as the parent varieties Bomi and Carlsberg II. An enhanched effect on starch reduction and free sugar accumulation was observed during kernel development when the single mutants 527 and 29 are combined with the mutant 1508. At maturity, kernels of the double mutants 527/1508 and 29/1508 contained, respectively, 68 and 43% less starch than Bomi.The double mutant 29/1508 kernel had a slightly lower prolamin content than mutant 1508 which is the most prolamin‐deficient single mutant. In the double mutant 527/1508, however, an almost complete suppression of prolamin synthesis was observed during kernel development. The percentage of lysine in the seed proteins of the double mutants was about the same as in the most extreme single mutant 1508.Based on the additive effect of the individual high‐lysine genes in the double mutants, it is concluded that the influences of these genes on prolamin and starch synthesis are independent.
Water stress and root formation in pea cuttings
Authors: RAJAGOPAL VELAMOOR , ANDERSEN A. SKYTT 
Published: April 2006

AbstractThe stock plants of pea (Pistum sativium L. cv. Alaska) grown for 11 days at 16 W m−2 38 W m−2 were subjected to different degrees of moisture stress, simulated with polyethyleneglycol (PEG, 6000) for different periods. The cuttings were made at the end of stress treatments, planted in perlite and allowed to root in a mist propagation chamber.The number of adventitious roots formed on the cuttings from non‐stressed plants was significantly higher under low (16 W m−2) than under high (38 W m−2) irradiance. However, under the influence of short duration stress the number of roots increased significantly under high but not under low irradiance. There was significantly poor rooting after prolonged stress under both irradiances.The leaf osmotic potential ψπ showed a greater reduction with increasing degree and duration of stress at 38 W m−2 than at 16 W m−2. The differential rooting behaviour as a result of stress levels and irradiances is discussed in the light of available literature on adventitious root formation.
Frost‐induced phospholipid changes in cold‐acclimated and non‐acclimated rape leaves
Authors: SIKORSKA ELŻBIETA , KACPERSKA‐PALACZ ALINA 
Published: April 2006

AbstractFreezing and thawing of winter rape leaves was found to cause a marked decrease of total phospholipid content in general, and that of phosphatidyl choline in particular. In the highly injured leaves the decrease of phosphatidyl choline was irreversible, and it was accompanied by a marked increase of phosphatidic acid. In the slightly damaged leaves no phosphatidic acid accumulation was detected, irrespective of phosphatidyl choline decrease. Instead of phosphatidic acid, the phosphatidyl glycerol or an unidentified P‐containing lipid increased after thawing in leaves hardened to the first (Tk50=−8°C) or to the second (Tk50=−13.5°C) level, respectively. Frost hardening was found to promote phospholipid recovery after freezing and to increase phospholipid content, including that of phosphatidyl choline and phosphatidyl ethanolamine. Possible association of frost hardening with modified phospholipase‐D properties is suggested.
Effect of root formation on 14C‐glycine uptake and incorporation into protein by attached and excised cotyledons of Helianthus annuus
Authors: MOHAMMAD A. M. S. , YOUSIF A. E. 
Published: April 2006

AbstractRoot formation was found to extend the life‐span of excised cotyledons of Helianthus annuus L. markedly. Excised cotyledons of 12‐day‐old plants attained longer life‐span, higher root number and total root length than cotyledons excised before or after 12 days. Protein content of attached cotyledons reached a maximum level 12 days after the commencement of germination followed by a decrease. Cotyledons excised 8 days after sowing showed maximum level of protein content 44 days after excision followed by a decrease. The increase was correlated with the full development of roots. The incorporation of 14C‐glycine into protein followed a pattern similar to the protein content, both in attached and detached cotyledons.
Somatic hybrid plants of Nicotiana glauca and Nicotiana tabacum obtained by protoplast fusion
Authors: EVANS DAVID A. , WETTER LESLIE R. , GAMBORG OLUF L. 
Published: April 2006

AbstractSomatic hybrid plants were produced by fusion of protoplasts from cell cultures of the Nicotiana tabacum L. sulfur mutant Su/Su and from leaf mesophyll of Nicotiana glauca Graham. After fusion the N. glauca protoplasts failed to survive under the selected culture condition. From the hybrid cells light green shoots were produced. The hybrid plants exhibited intermediate characters between parental species with respect to leaf morphology, trichome density, floral structure and flower color. The chromosome number of 25 hybrid plants was 2n = 72 and both N. glauca and N. tabacum chromosomes were identified in the hybrids. Results of isoenzyme analysis showed bands of both parents and a specific (hybrid) band for aspartate amino‐transferase. Small subunit fraction‐1‐protein of somatic hybrids also consisted of the sum of N. glauca and N. tabacum bands. Leaf spot formation associated with the Su locus of N. tabacum was observed in somatic hybrids.
Cytoplasmic male sterility in barley
Authors: AHOKAS H. 
Published: April 2006

AbstractThe maternal male sterile barley msm1 with or without a dominant gene, Rfmla, which restores male fertility, was studied. Determined with SDS‐PAGE, the polypeptide pattern in the anthers of unrestored msm1 plants remains juvenile in the middle of anther development, two major zones being absent or weak. At the stage when anther development stops in msm1 plants, the anther proteins appear to be hydrolyzed to short‐chain peptides. Restored plants, heterozygous for the restorer gene, Rfmla, behaved like the near‐isogenic normal barley, cv. Adorra. The total leaf protein pattern of young leaf tissue and the chloroplastidic membrane protein pattern are normal in msm1 cytoplasm when studied with this technique.Chlorophyll b is unnecessary for restoration by Rfmla, though the restored plants have a lower chlorophyll a/b ratio than an unrestored plant in the mature stem leaf.Mature stem leaf pieces of unrestored msm1 plants were induced to senesce with 20 mM NaCl solution. This senescence was inhibited by exogenous kinetin. Leaf pieces of restored msm1 plants or those of near‐isogenic normal barley behaved in the same way in the NaCl solution as in distilled water. Many features of the physiology of restored plants can be explained as the functions of cytokinins.Kernels of male sterile plants have a more rapid root elongation at germination than near‐isogenic normal barley.
Effects of canavanine on IAA‐ and fusicoccin‐stimulated cell enlargement, proton extrusion and potassium uptake in maize coleoptiles
Authors: COCUCCI M. C. , ROSA S. DALLA 
Published: April 2006

AbstractIn maize coleoptiles (Zea mays F1 XL 640A, cv. Dekalb) canavanine and cycloheximide strongly and simultaneously inhibit cell elongation, H+ extrusion and K+ uptake, induced by IAA. They inhibit also, although to a much lesser degree, the same phenomena induced by fusicoccin. Cycloheximide severely depresses the incorporation of leucine into proteins, while canavanine leaves leucine incorporation almost unchanged. The data confirm that elongation, H+ extrusion and K+ uptake can be regarded as correlated processes; they also support the view that normal protein synthesis is essential for IAA‐induced growth, while this requirement is only partial in growth stimulated by fusicoccin.
Fractionation by centrifugation of leaf proteins from Brassica napus, Brassica oleracea, Helianthus annuus and Atriplex hortensis as a function of pH and temperature
Authors: LUNDBORG TOMAS 
Published: April 2006

AbstractChlorophyll‐free leaf protein concentrates for human consumption can be produced after separation of the chlorophyll‐associated protein from the rest of the leaf protein. This protein separation was studied in four plant species using heat fractiona‐tion. Press juice was prepared on a laboratory scale from field grown Atriplex hortensis, Brassica napus. Brassica oleracea and Helianthus annuus. Some further experiments were made with greenhouse grown plant material. After adjustment of pH to values between 4.0 and 8.0 the press juice was heated in water baths at 20, 35, 40, 45, 50, 55 and 60°C with or without 20 min holding time at appropriate temperature. Thereafter the juices were briefly centrifuged at 2500g. The protein content of the sediment was determined and the colour of the supernatant was observed.The species showed different protein sedimentation patterns, especially at neutral and weakly alkaline pH. Brassica napus had rapidly sedimenting proteins, low temperature was sufficient for complete sedimentation of chlorophyll‐associated proteins and gave a high percentage of the total press juice protein as chlorophyll‐free protein. Atriplex hortensis had slowly sedimenting proteins irrespective of temperature, required high temperature for complete sedimentation of chlorophyll‐associated proteins and gave a low percentage chlorophyll‐free proteins. Brassica oleracea and Helianthus annuus showed intermediated properties. Reasons for these differences among the species are discussed.
Light effects on root formation in aspen and willow cuttings
Authors: ELIASSON LENNART , BRUNES LAILA 
Published: April 2006

AbstractThe effect of light on rooting of leafy cuttings of aspen (Populus tremula × tremuloides) and a willow hybrid (Salix caprea × viminalis) was investigated under controlled conditions in water culture. Two levels of irradiance were used, 40 and 8 W m−2. The lower level gave the best rooting of aspen cuttings, both when applied to the stock plants before the cuttings were taken and when given to the cuttings during the rooting period. Irradiation of the cutting base during the rooting period inhibited rooting almost completely in aspen and decreased the number of roots formed in the Salix hybrid.Net photosynthesis in the cuttings of Salix decreased considerably after excision and increased again after formation of roots. Indirect evidence indicated that photosynthesis was even more affected in aspen cuttings. The possible roles of carbohydrates and inhibitors in the light effects are discussed.
Galactose, aspartate crossway and rhythm inhibition in Aspergillus niger
Authors: JEREBZOFF STEPHAN , JEREBZOFF‐QUINTIN SIMONE 
Published: April 2006

AbstractWhen the glucose/K+ balance in the medium is favourable to rhythm expression in Aspergillus niger Van Tieghem, galactose has an inhibitory effect on amplitude but not on period length of the rhythm. Galactose is active when its level reaches 1/10 of that of glucose.On liquid media a small quantity of glucose is necessary to start growth on galactose. Under these conditions U14C‐galactose is rather slowly metabolized. After 6 h of feeding on the labelled galactose medium, this sugar is converted into glucose, which is used both for the synthesis of compounds derived from C3 and C4 units and for synthesis of polysaccharides and perhaps small peptides. The labelling of the macromolecules always remains low. The insoluble carbohydrates of the mycelium are little affected by the type of sugar supplied to the fungus.The metabolism on galactose differs from the metabolism on glucose mainly in a decrease of the free asparagine pool and a simultaneous equivalent increase of the free aspartate pool; such an effect could not be correlated with an increase of the aspartate aminotransferase activity. Supply of aspartate but not of gluta‐mate into the agar medium inhibits the rhythm amplitude. So, the damping effect of galactose on the rhythm might be at least partly due to its effect on the regulation of the aspartate cross‐way.