bluuebunny/crossref_metadata_2025_split huggingface dataset:
Passive and Active Components of Chloride Absorption in the Bark and the Wood of Citrus Roots
Authors: ALTMAN A. 
Published: April 2006

AbstractThe characteristics of chloride absorption by the tap root of citrus (Citrus spp.) seedlings were compared in isolated disks of the bark and in segments of the wood. Analysis of elution curves of the isotope following saturation of the tissue shows that there are at least two components of the chloride absorption system: one typical of the free space (“passive”) and the other of the non‐free space (“active”). These two components are present in the bark only, while the wood has essentially the characteristics of a free space absorption (the slow component of the efflux being less evident). The nature of the bark as an actively collecting tissue for chloride from 10 mM Na36Cl, in contrast to the wood, was established on the basis of uptake curves. Examination of the uptake in the bark of 3 citrus varieties revealed considerable differences with regard to the magnitude of the two components of chloride absorption. These findings are discussed in relation to the role of the cortex and the stele in the transport of ions.
On Extraction and Quantitation of Plant Peroxidase Isoenzymes
Authors: LEE T. T. 
Published: April 2006

AbstractPeroxidase in tobacco callus tissue differed in extract‐ability depending on the subcellular distribution of the enzyme. Based on extractability it consisted of four fractions: freely soluble and less freely soluble in phosphate buffer, KCl‐soluble, and insoluble. The latter two fractions were un‐extractable by a phosphate buffer alone. The different fractions contained varied proportions of peroxidase isoenzymes. The extractability of indoleacetic acid oxidase was similar. A medium of high ionic strength is essential for quantitative extraction of peroxidase and indoleacetic acid oxidase isoenzymes.For quantitation of isoperoxidase activity on polyacryl‐amide gel following electrophoretic separation, benzidine and o‐dianisidine were better hydrogen donors than guaiacol and pyrogallol. The optimum pH was 4.5, but a citrate buffer was inhibitory. The optimum conditions included an acetate buffer at pH 4.5, a substrate concentration of 0.03 %, benzidine as the hydrogen donor, and a 3‐minute treatment with 7 % acetic acid after staining. The color intensity of the bands remained unchanged for at least three days. With appropriate sample size and reaction time there was a linear relationship between enzyme concentration and activity.
Polyamines Bound to tRNA and rRNA of Eukaryotic Plant Organisms
Authors: BAGNI NELLO , STABELLINI GIORDANO , FRACASSINI DONATELLA SERAFINI 
Published: April 2006

AbstractThe occurrence of polyamines in different RNAs was investigated in view of the importance of these organic cations in RNA function. RNA was extracted at low ionic strength and separated on Sephadex columns.tRNA and rRNA of plants (Spinacia oleracea leaves, etiolated epicotyls of Pisum sativum, and Neurospora crassa mycelia) contain polyamines although in a different ratio than they are found in a complete cell. Contrary to spermine and putrescine, spermidine is always present.The binding of polyamines to tRNA and rRNA is discussed applying the Liquori model to the double stranded regions, where it was possible.Polyamines were also detected in 5S RNA.
Seed and Embryo Germination in Syringa vulgaris and S. reflexa as Affected by Temperature during Seed Development
Authors: JUNTTILA OLAVI 
Published: April 2006

AbstractEffects of controlled temperature conditions during seed development on seed and embryo germination of Syringa vulgaris were studied using vegetatively propagated mother plants. Seeds from mother plants grown at 18–24°C were partially dormant at low (15°C) but not at high (21°C) germination temperature, while seeds from outdoors or from plants grown at 12°C were not dormant at all. Seed dormancy at low temperatures was induced as well when branches from outdoor plants were kept at 18–24°C for the last two‐three weeks before harvesting. The dormancy induced by 24°C during seed development was not broken by keeping branches at 12°C for the last two‐three weeks. In most cases the induced seed dormancy was broken completely by gibberellic acid.Embryo germination at 24 or 15°C was not affected by mother plant temperature. Part of the embryos from plants grown at 24°C were, however, dormant at 9°C. The ability of embryos to germinate in osmoticum was only slightly affected by mother plant temperature.The mechanical resistance of the endosperm was significantly higher in the seeds from plants grown at 24°C than in seeds from 12°C.Both the embryos and the seeds of S. reflexa were dormant at the time of termination of embryo elongation. Experiments with three seed‐propagated mother plants indicated that the water potential of embryos may be reduced by high mother plant temperature.
Cytokinin‐induced Pseudonodules on Alnus glutinosa
Authors: RODRIGUEZ‐BARRUECO C. , DE CASTRO F. BERMUDEZ 
Published: April 2006

AbstractAlder root nodules are capable of atmospheric nitrogen fixation. A differential treatment with kinetin and 2IP (2‐isopentenyl adenine) was applied to the rooting medium of alder plants growing in test tubes containing Crone solution. The experiment led to the formation of a fair number of pseudonodules scattered on the root system of the plants treated with cytokinin levels higher than 0.6 μg/ml. Kinetin had a lowering effect on the overall growth of the plant, whereas the plants treated with 2IP showed no differences in growth as compared to the non‐treated control plants. Histological sections of the pseudonodules show an unorganized tissue originating from the parental root cortex, and the presence of groups of tracheids giving the aspect of unorganized vascular bundles.
Uptake, Cellular Distribution, and Metabolism of 14C‐picloram by Excised Plant Tissues
Authors: SHARMA M. P. , BORN W. H. VANDEN 
Published: April 2006

AbstractExcised soybean (Glycine max (L.) Merr.) hypocotyls, barley (Hordeum vulgare L.) coleoptiles, barley leaf sections, and Canada thistle (Cirsium arvense (L.) Scop.) leaf discs continuously absorbed 14C‐picloram from a buffered solution over a 24 h period. After an 8 h uptake period excised sections released up to 30 % of the absorbed picloram into ‘clean’ buffer solution in a 4 h period. Leaf sections released less than did the other tissues. Uptake of 14C‐picloram by soybean hypocotyl and barley coleoptile sections increased with an increase in temperature from 5 to 35°C. Uptake was promoted by added ATP and sucrose but inhibited by actinomycin D, cycloheximide, and DNP.After differential centrifugation of aqueous extracts of 14C‐picloram‐treated excised tissues more than 95 % of the radioactivity was in the soluble fraction.In excised barley and Canada thistle leaf tissues, 3 days after treatment, part of the 14C‐picloram was conjugated with plant constituents, largely with sugar(s). After acid hydrolysis of ethanol extracts of such tissues only unaltered picloram was detected. In barley coleoptile and soybean hypocotyl sections no conjugation products of 14C‐picloram were detected.
The Inhibition by Cytokinin of Auxin‐Promoted Elongation in Excised Soybean Hypocotyl
Authors: VANDERHOEF LARRY N. , STAHL CATHERINE , SIEGEL NED , ZEIGLER ROBERT 
Published: April 2006

AbstractThe experiments characterize the inhibition by kinetin of auxin‐promoted elongation in excised hypocotyl sections of 3‐day soybean seedlings (Glycine max cv. Hawkeye 63). It was found that concentrations of kinetin above 4.2 μM did not further inhibit auxin‐promoted elongation. Kinetin is as potent an inhibitor of elongation as actinomycin D or cycloheximide. Tissue incubated for 3 or 5 h in the absence of auxin or cytokinin would, upon addition of auxin, exhibit a new growth rate similar to that of tissue grown in auxin for the entire incubation period. Similarly, tissue grown for 3 and 5 h in the presence of auxin would revert to the control rate of elongation upon addition of kinetin. A 10 to 30 min preincubation in kinetin yielded the tissue incapable, for the ensuing 6 h, of increasing its rate of elongation in response to auxin. Zeatin and isopentenyladenine were more potent than kinetin and benzyladenine in the inhibition of elongation. Levels of ethylene produced in the presence of auxin plus cytokinin indicated that it was not involved in this auxin‐cytokinin interaction. Kinetin by itself did not promote elongation; nor did it enhance auxin‐promoted elongation at low auxin concentrations.
Studies of the Biochemical Background to Differences in Glucosinolate Content in Brassica napus L. III. Further Studies to Localize Metabolic Blocks
Authors: JOSEFSSON EGON 
Published: April 2006

AbstractTo localize the metabolic block(s) in the biosynthesis of glucosinolates in the Brassica napus L. cv. Bronowski, 5‐methylthiopentanal oxime‐1‐14C was synthesized and fed to this cultivar and cv. Regina II, which has average levels of glucosinolates. The aldoxime was as efficient as a precursor of 3‐butenylglucosinolate in both cultivars, but less efficient as a precursor of 2‐hydroxy‐3‐butenylglucosinolate in Bronowski. These results suggest that there is a block in the biosynthesis of 3‐butenylglucosinolate in Bronowski that is situated before the synthesis of the intermediate 5‐methylthiopentanal oxime, as well as a block in the hydroxylation step.The silique walls of Bronowski contained increased amounts of total sulphur and inorganic sulphate.
Ozone Alteration of Nitrate Reduction in Soybean
Authors: TINGEY DAVID T. , FITES ROGER C. , WICKLIFF CARLOS 
Published: April 2006

AbstractSoybeans [Glycine max (L.) Merr.] were harvested at various periods after a 2 h exposure to determine the effects of ozone on nitrate reductase and selected metabolites related to nitrate reduction. Ozone initially depressed the concentrations of reducing sugars, amino acids, and nitrate reductase activity. On subsequent days following exposure, amino acid and protein levels were higher than the respective controls while the levels of reducing sugars and nitrate reductase activity returned to control levels. The ozone depression of nitrate reduction was not the result of a direct ozone reaction with the nitrate reductase protein but rather an interference with reactions that supplied the NAD(P)H needed for nitrate reduction.
Synergism between Gibberellin and Auxin in the Growth of Intact Tomato
Authors: GRUNWALD C. , LOCKARD R. G. 
Published: April 2006

AbstractGibberellin A4&7 was more effective than gibberellic acid in increasing shoot elongation when applied to the apex of intact Lycopersicum esculentum seedlings of Tiny Tim, a dwarf cultivar, and Winsall, a tall cultivar. After 14 days, gibberellic acid and gibberellin A4&7 stimulated growth of the dwarf more than the tall tomato. In tall tomato the application of indole‐3‐acetic acid alone (6.1 μg/plant) showed an inhibitory growth effect, but when applied with 17.5 μg per plant of gibberellic acid, it had a synergistic effect at 7 days but not at 14 days. When the auxin concentration was reduced to 0.61 μg per plant a synergistic effect was observed on tall plants at 7 and 14 days between indole‐3‐acetic acid and gibberellic acid. Application of gibberellin A4&7 with auxin did not give a synergistic response in tall or dwarf tomato.
X‐Ray Analysis of Microelements in Seeds of Crambe abyssinica
Authors: v HOFSTEN ANGELICA 
Published: April 2006

AbstractX‐Ray microanalyses were made by scanning electron microprobe on thin sections of seeds of Crambe abyssinica. Linear scan profile and multilinear scan image of X‐ray emissions for magnesium, calcium and sulphur were compared. It was also possible to detect these elements in point analyses in the globoid region in the protein bodies of the seed. Microanalyses were also made with the EDAX system and with EMMA analytical electron microscope.
The Effect of Oxygen on Endogenous Cytokinin Levels and Germination of Leucadendron daphnoides Seed
Authors: VAN STADEN J. , BROWN N. A. C. 
Published: April 2006

AbstractThe soybean callus assay was used to study the effect of high oxygen tensions on the cytokinin levels of Leucadendron daphnoides Meisn. seed, where dormancy is apparently due to the restricting effect of the seed coat on oxygen diffusion to the embryo. High oxygen tensions led to a six‐fold increase in germination compared to seed incubated in air and resulted in significant increases in butanol soluble cytokinins prior to visible germination. It is suggested that the primary effect of oxygen is to increase the rate of respiration and thus, to provide the energy required for the synthesis of butanol soluble cytokinins which leads to cotyledon expansion and subsequent radicle elongation. Present indications are that untreated seeds remain dormant due to low concentrations of butanol soluble cytokinins in their embryos.
Metabolism of Carbon‐14 Labelled Arginine, Citrulline and Ornithine in Intact Apple Stems
Authors: HILL‐COTTINGHAM D. G. , LLOYD‐JONES C. P. 
Published: April 2006

AbstractA study was made of the absorption and metabolism of arginine‐guanido‐14C, citrulline‐carbamyl‐14C and ornithine 1‐14C which had been applied to apple stem internodes by a perfusion technique at intervals throughout the year.The results showed that these amino acids were interconverted according to the Krebs‐Henseleit cycle always in the direction arginine‐ornithine‐citrulline‐arginine. In addition ornithine was degraded by another pathway with loss of CO2. This loss was particularly extensive during the period June to August when labelled proline and glutamic acid were also found. The evidence is consistent with the initial breakdown of ornithine taking place via glutamic semi‐aldehyde.
Auxin Stimulation of Cambial Activity in Pinus silvestris I. The Differential Cambial Response
Authors: CZKOWSKI STEFAN ZAJA 
Published: April 2006

AbstractIsolated stem segments of Pinus silvestris L. produce new xylem in sterile culture for 5 weeks if sucrose and IAA are present in the medium. The response of cambium varies in the course of the season and along the tree stem. The cambium is more sensitive in spring and in the stem portion closer to tree apex than later in the season and closer to the stem base. Spring initiation of cambial activity in adult pine trees under natural conditions could not be correlated with any consistent concentration gradient of natural auxin extracted from the cambial region. Thus, the relation between concentration of auxin and the activity of cambium is complex and involves changes of cambial responsivity. Interaction with gibberellic acid or kinetin and changing concentration of sucrose were studied during the season, but none of these substances alone appeared to be responsible for the observed variation in cambial response to auxin.
Correlative Changes in Endogenous Hormone Levels and Shoot Growth Induced by Short Heat Treatments to the Root
Authors: ITAI CHANAN , BEN‐ZIONI ALIZA , ORDIN LAWRENCE 
Published: April 2006

AbstractHeat treatments of two minutes at 46 to 47°C to root systems of Nicotiana rustica and Phaseolus vulgaris affected roots and shoots. Xylem exudate of Phaseolus was collected, and it was found that heat treatment reduced cytokinin levels and increased abscisic acid levels in the exudate. Shoot and root growth of both species was reduced. Root membrane integrity of Nicotiana was measured and was found to be impaired. It is suggested that the changes in hormone activity due to heat treatment regulate the reduction in shoot growth. Cell wall metabolism and glucosyl transferases making β‐glucans were investigated in Phaseolus leaves. Incorporation of 14C from 14CO2 into wall constituents was slightly inhibited but neither photosynthesis nor extracted β‐glucan synthetases were affected during the first 12 hours after treatment.
Citrate Synthase of Plants: Sensitivity to Sulfhydryl Reagents and Molecular Weight of the Enzyme
Authors: GREENBLATT GERALD A. , SARKISSIAN IGOR V. 
Published: April 2006

AbstractCitrate synthase of wheat (Triticum aestivum L.), bean (Phaseolus vulgaris L.), cauliflower (Brassica oleracea L.), and a marine blue‐green alga (Coccochloris elabens) is inhibited by sulfhydryl binding reagents. The inhibitions are partially reversed by dithiothreitol. Pig heart citrate synthase is only slightly inhibited by the same reagents and this is completely reversed by dithiothreitol.All citrate synthases in this study are inhibited by adenosine triphosphate. The inhibition is relieved by increasing the concentration of acetyl coenzyme A.Citrate synthase of wheat, cauliflower, bean, and pig heart was estimated by gel filtration to have a molecular weight of 100,000 daltons. The Coccochloris citrate synthase was estimated to have a molecular weight greater than 250,000 daltons.The evolutionary implications of these findings are discussed.This enzyme is comparable in size to the 100,000 dalton mammalian enzyme (Singh et al. 1970) making it somewhat larger than the 65,000 dalton mango enzyme (Srere et al. 1971). The PHMB‐treated enzyme also shows changes in its electrophoretic properties (Greenblatt and Sarkissian unpublished).The evidence presented here demonstrates that citrate synthase of various plants is sensitive to sulfhydryl reagents suggesting that sulfhydryl reactivity is a not unusual property of plant citrate synthase. In addition we show that molecular weight as large as or larger than that reported in microbial systems can occur in a blue‐green alga.
Incorporation of Uracil by Synchronous Chlorella
Authors: KNUTSEN GJERT 
Published: April 2006

AbstractLight‐dark synchronized Chlorella fusca was used to study the incorporation of radioactive uracil into the trichloroacetic acid insoluble fraction.In autospores the incorporation measured in darkened cells usually started immediately after uraci addition, and the time course showed three distinct linear phases with abrupt transitions between them. Chromatographic analyses of the radioactive pool components showed that the total amounts of monophosphate, diphosphate and triphosphate nucleotides of uracil did not limit the incorporation and thus did not cause the abrupt rate shifts.In autospores, 5, 9 and 14 h old cells, the initial incorporation rate increased with increasing initial uracil concentration to reach a constant value above 0.5 μ.M. Addition of glucose to the cells increased the incorporation rate over the whole uracil concentration range tested with autospores, but did not influence the rates of the other cells.The incorporation rate varied during the synchronous cycle in a manner which closely resembled the pattern for uptake and degradation rates, with the most pronounced similarity from 9 h onwards.
Cytokinins in Populus×robusta: Qualitative Changes during Development
Authors: HEWETT E. W. , WAREING P. F. 
Published: April 2006

AbstractQualitative changes of cytokinins in leaves of different ages from Populus x robusta (Schneid.) have been determined, together with seasonal changes in cytokinin activity in mature leaves and xylem sap. Chromatography on Sephadex LH‐20 has shown that total cytokinin activity and diversity are at a maximum in expanding leaves. As leaves age, the amount and number of cytokinins decrease, with yellow senescent leaves having only one detectable cytokinin, thought to be a glucoside.Seasonal changes were followed by chromatography of the extracts on paper in butan‐2‐ol: 25 % NH4OH (4:1). Maximum cytokinin levels, due to Fraction Z (Rf 0.5–0.8), in leaves and xylem sap were found in mid‐summer. Prior and subsequent to cessation of shoot elongation growth, fraction Z decreased and fraction N (Rf 0–0.2) increased to predominate in senescent leaves. Removal of the apex resulted in an increase of fraction N in leaves from decapitated plants when compared to similar leaves from intact plants. It is suggested that, once apical sink activity has ceased, cytokinins in the xylem sap are diverted into leaves and converted to a cytokinin glucoside, possibly a storage form of the hormone.
Effect of Water Quality on Relationships Between Cationic Species and Leaf Lipids at Two Different Development Stages in Cotton
Authors: TWERSKY M. , FELHENDLER R. 
Published: April 2006

AbstractLipid and phospholipid content of cotton leaves were measured in plants irrigated with fresh water and brackish water. The correlation between K+ and Na+ in leaf tissue and the changes in total lipids and phospholipids was determined at the vegetative and fruiting stages. Data demonstrated that total lipids and phospholipids can be associated with changes in the K/Na ratio and with the two developmental stages of the cotton plant. Plants irrigated with brackish water had more total phosphate incorporated into the phospholipids in the fruiting stage.
Changes in Polysomes of Black Locust Seedlings during Dehydration‐Rehydration Cycles
Authors: BRANDLE JAMES R. , SCHNARE PAUL D. , HINCKLEY THOMAS M. , BROWN GREGORY N. 
Published: April 2006

AbstractNet assimilation, dark respiration and xylem pressure potential were followed through dehydration‐rehydration cycles in black locust seedlings (Robinia pseudoacacia L.). Sucrose gradient profiles indicated the retention of polysomes during stress. RNase activity declined during dehydration but returned to pre‐stress levels upon irrigation. Comparisons of black locust and corn polysomes during water stress are made.
Role of Pressure in Xylem Transport of Coconut and Other Palms
Authors: MILBURN JOHN A. , DAVIS T. ANTONY 
Published: April 2006

AbstractThe significance of root pressure in the transport of xylem sap has been investigated in Cocos nucifera L. and a few other palms. Despite the fact that excised palm roots can generate considerable pressures in situ, the quantity of water transported is only a small fraction of the demand resulting from transpiration. Most water transport is induced by negative pressure gradients, as in other higher plants. The development of considerable negative pressures has been demonstrated both directly and indirectly.Acoustic detection was used for the first time to monitor cavitation in water‐stressed Cocos leaves. Its detection implies the ready disruption of xylem sap under these tensions. We suggest that root pressure might serve to refill cavitated xylem conduits when water is abundantly available and transpiration practically zero. However, little or no positive pressure could be demonstrated in intact palms subjected to low water stress: experimentally.
The Influence of Varying Light Intensities on the Photo‐transformation of Protochlorophyllide636 in Dark Grown Wheat Leaves Treated with δ‐Aminolevulinic Acid
Authors: SUNDQVIST CHRISTER 
Published: April 2006

AbstractLeaves treated with δ‐aminoievulinic acid accumulate protochlorophyllide636 in large amounts. Due to a continuous conversion of protochlorophyllide636 (nonphototransformable) into protochlorophyllide650 (phototransformable) in weak red light, the photoreduction of protochlorophyllide to chlorophyllide can proceed for at least 20 minutes and results in a chlorophyllide content of the leaves three times higher than that in untreated leaves. The half time for this chlorophyllide accumulation is 55 seconds. A photodestruction of the pigments takes place at high light intensities or if the content of protochlorophyllide636 is high. The conversion of protochlorophyllide636 to chlorophyllide is dependent on the light intensity used for phototransformation of protochlorophyllide550 The conversion of PChlide646 was not limiting for chlorophyllide formation within the range of the light intensity used. The extrapolation of a double reciprocal plot of chlorophyllide formation, rate versus light intensity gives a maximal value of 8.7 μg chlorophyllide per g fresh weight and min. The conversion of protochlorophyllide363 to protochlorophyllide650 is believed to depend on the available sites of an apophotoenzyme.