bluuebunny/crossref_metadata_2025_split huggingface dataset:
Allosteric Properties of Chorismate Mutase from Quercus pedunculata
Authors: GADAL PIERRE , BOUYSSOU HUGUETTE 
Published: April 2006

AbstractChorismate mutase from Quercus pedunculata Ehrh. leaves has been purified by ammonium sulfate precipitation, molecular sieving and hydroxyapatite chromatography. Some results obtained during the purification suggest the presence, in oak, of two isofunctional forms of the enzyme, the one sensitive, the other insensitive to the action of aromatic amino acids. The regulable form exhibits a molecular weight of about 45,000. It is inhibited by tyrosine and by phenylalanine and is activated by tryptophan. In addition to its activating properties, this latter compound, endowed with a great affinity for the enzyme, reverses the inhibition due to the two other amino acids.The H+ concentration of the medium plays an important role in the sensitivity of the enzyme with regard to its effectors. Inhibition by tyrosine and by phenylalanine is maximal at pH 6.5, at which value the two ligands present an identical effect. At alkaline pH values, the rate of inhibition decreases regularly, tyrosine becoming the most effective inhibitor. Activation by tryptophan is particularly acute in a mildly acid medium; at pH 6.5, this effector increases the enzymatic activity threefold. Its action is weak (20% activation) in the optimum pH zone (pH 7.8) and increases towards the more basic pH values. As a result, tryptophan maintains a constant level of enzymatic activity throughout a large pH zone (between 6.5 and pH 9.0). The physiological significance of these results is discussed.
The Growth of the Primary Roots and Root Hairs of Sinapis alba and Lepidium sativus in Triton X‐100
Authors: HAAPALA EVA 
Published: April 2006

AbstractSeeds of Lepidium and Sinapis were germinated and grown for 3 days in different concentrations of Triton X‐100 (0.001–0.1 % v/v). The elongation of the primary root was slightly stimulated by low concentrations. In concentrations above 0.01 %, Triton inhibited root growth and forked root hairs developed. The hairs elongated both at the apex and at the base, exhibited protoplasmic streaming and activity of particulate non‐specific esterase. In contrast the growth of the hypocotyl of both Lepidium and Sinapis diminished steadily in increasing concentrations of Triton. Triton also affected the percentage germination of Lepidium, which increased or decreased according to the concentration used. The changes in root growth and germination and the appearance of branched root hairs in abundance coincide with a change in the detergent solution from monomer to aggregated molecules.
The Uptake and Fractional Distribution of Differentially Labeled Indoleacetic Acid in Light Grown Stems
Authors: DAVIES P. J. 
Published: April 2006

AbstractThe uptake of exogenously applied indoleacetic acid (IAA) by light grown stems of bean (Phaseolus vulgaris L. cv. Red kidney) and pea (Pisum sativum L. cv. Alaska) was examined. The IAA was labeled in the 1 and 2 side chain positions with 14C and the 5 ring position with 3H. The distribution of label in the sections was analyzed by recording the elution into water, ethanol and 1.0 N NaOH, and the amount in the insoluble residue also recorded. Total uptake consisted of a rapid uptake for about 1 h followed by continued uptake at a slower rate for 24 h to give a radioactive concentration in the tissues four to five times, that of the external solution. Most of the radioactivity was initially extractable by water, later by ethanol. With IAA‐2‐14C there was a slow increase in radioactivity in NaOH and residue fractions but with IAA‐1‐14C most of the radioactivity was present in insoluble residue at times longer than 3 h. From the different residue patterns estimates of the extent of decarboxylation of the IAA were made. The radioactivity in the tissues was largely IAA after 1 h and the content increased until 6 h but there after there was little further increase. The water fraction initially contained the most IAA but by 24 h most IAA was found in the NaOH fraction in bean and the ethanol fraction in pea. The NaOH fraction was the only fraction in which the IAA content continually increased.
Wind Flow Characteristics on a Soybean Leaf Compared with a Leaf Model
Authors: PERRIER EUGENE R. , ASTON ALAN , ARKIN GERALD F. 
Published: April 2006

AbstractThe purpose of this paper is to describe momentum boundary layer flow parameters on a soybean leaf [Glycine max (L.) Merrill] at various velocities of the bulk air stream and these data are compared with similar measurements on an artificial leaf. The wind structure is measured at three different bulk air velocitìes (u∞= 39, 148 and 271 centimeters per second) on an individual soybean leaf and is compared to structural effects on an artificial leaf (flat metal plate) in a small closed‐circuit wind tunnel. The boundary layers were homogeneous for the metal plate, but only at the lower velocity for the soybean leaf. The boundary layer thicknesses decrease with increasing bulk air velocity for laminar flow regimes, whereas in the turbulent flow regime the boundary layer thickness greatly increases. The effect of turbulence on the soybean leaf boundary layer made the eddy diffusivities at least three times greater than in the laminar flow regime at the calculated roughness height above the leaf surface. The structure of the leaf boundary layer flow is comparable to that of the metal plate only at the lower bulk air velocity.
Effect of Abscisic Acid on Sucker Development and Callus Formation on Excised Roots of Populus tremulaides
Authors: SCHIER GEORGE A. 
Published: April 2006

AbstractAbscisic acid (ABA) inhibited sucker development and promoted callus formation from cambium exposed at cut ends of excised roots from two clones of trembling aspen, Populus tremuloides Michx. Clonal differences in response to ABA inhibition of sucker outgrowth appeared to be related to the developmental stage of the preexisting shoot primordia. When ABA treatment was followed about a month later by gibberellic acid, ABA inhibition was partially reversed. This is one of few investigations in which both promotive and inhibitory effects of ABA have been demonstrated simultaneously on the same plant part.
On Auxin‐Induced pH Drop and on the Improbability of its Involvement in the Primary Mechanism of Auxin‐Induced Growth Promotion
Authors: ILAN I. 
Published: April 2006

AbstractWhen sunflower hypocotyl segments were floated on a solution containing potassium, auxin brought about a pH drop in the medium. The effect was detectable about 2–3 hours after the application of the auxin, and persisted during the 26 hours of the experiment. When ammonium was applied instead of potassium, an auxin‐induced pH drop was also noted in the first hours of the incubation. Afterwards, the pH of the auxin‐treated medium became higher than that of the control solution. It is suggested that the difference in the action of the auxin in the presence of the two cations is related to the contrast between its effects on their absorption.The data are discussed in relation to the recently proposed hypothesis that auxin‐induced growth promotion is a result of an auxin‐induced pH drop in a cell wall compartment. It is concluded that the results do not support the hypothesis.
The Effect of Cadmium on Electron and Energy Transfer Reactions in Corn Mitochondria
Authors: MILLER R. J. , BITTELL J. E. , KOEPPE D. E. 
Published: April 2006

AbstractThe effects of cadmium on isolated corn shoot mitochondria were determined. In the absence of phosphate cadmium stimulated the oxidation of exogenous NADH optimally at 0.025 mM, but was inhibitory at 0.1 mM and above. The presence of phosphate negated the cadmium stimulation of exogenous NADH oxidation and permitted inhibitions only at higher cadmium concentrations. Succinate or malate + pyruvate oxidation in the absence of phosphate was inhibited to a greater extent by cadmium than when phosphate was present. ADP/O and respiratory control ratios were reduced by cadmium but generally were less sensitive to cadmium than state 4 or minus phosphate respiration. The data suggest that the site of cadmium effect is likely to be early in electron transport. Cadmium had a pronounced effect on mitochondrial swelling under either passive or active conditions. When succinate or exogenous NADH were being oxidized swelling occurred at 0.05 mM cadmium, but with malate + pyruvate the cadmium concentration had to exceed 1.0 mM. Phosphate (2 mM) prevented the swelling. Dithiothreitol, a SH group protector, prevented any effect of cadmium on swelling or respiration which suggests that sulfhydryl groups are likely involved in the cadmium‐membrane interaction.
In vivo Characterization of Nitrate Reductase Activity in Cotton
Authors: BILAL I. M. , RAINS D. W. 
Published: April 2006

AbstractThe in vivo nitrate reductase activity in leaf tissue of cotton (Gossypium hirsutum L.) was characterized. Enzymatic activity was linear with time up to 60 min. The assay for nitrate reductase activity was optimized in leaf slices 400 μm wide incubated in an anaerobic system at 30°C, in a 0.02 M KNO3 medium at pH 7.0 with 1 % propanol. In vivo activity was highest in recently matured leaves at the top of the plant.Both light and nitrate enhanced in vivo enzymatic activity. The activity was highest after 9 hours in the light and then decreased steadily for several more hours even in the presence of light.The nitrate reductase activity was more strongly correlated to the levels of NO3‐N in the culture solution than to the NO3‐N level in the tissue. The utility of this technique in nitrate reductase assay in a tissue containing large amounts of phenolic compounds is discussed.
Studies on the Genetic Control of a Nitrogenase Component in Leguminous Root Nodules
Authors: PHILLIPS DONALD A. , HOWARD ROBERT L. , EVANS HAROLD J. 
Published: April 2006

AbstractAn attempt was made to determine whether Rhizobium or the host legume carries genetic information required for synthesis of the enzyme complex nitrogenase. No rhizobial mutants were found which could reduce N2. Anaerobically‐grown rhizobial cells contained neither component of nitrogenase. Rhizobium strain 32H1 was used to produce root nodules on Vigna sinensis and Phaseolus aureus. Other V. sinensis plants were inoculated with Rhizobium strain 29C2. The iron‐molybdenum component of nitrogenase (fraction I) from these three combinations was purified by DEAE‐cellulose chromatography and preparative electrophoresis. The final sample formed a single band after analytical electrophoresis on polyacrylamide gel. No differences in mobility were observed between the three nitrogenase samples during short periods of analytical electrophoresis. Longer periods of electrophoresis produced degradative products with similar electrophoretic mobilities from each nitrogenase sample. Amino acid analysis of fraction I samples from the three host‐symbiont combinations suggested that the protein from the V. sinensis‐Rhizobium 29C2 combinations was different from the other two samples. These results are interpreted as preliminary evidence that Rhizobium carries the genetic information for fraction I of nitrogenase.
Studies on the Flowering Mechanism in Lemna
Authors: MAENG JUESON , KHUDAIRI A. KARIM 
Published: April 2006

AbstractA nitrogen source was needed for the flowering of Lemna gibba L., a long‐day plant, and L. perpusilla Torr., a shortday plant. The level of endogenous amino acids analyzed by an Amino Acid Analyzer, rose during the first few inductive cycles, but was reduced during later stages of the flowering process. Serine and threonine levels increased during the light period and decreased during the dark period in L. perpusilla. Exogenous serine and threonine added to the culture medium at 10−6M increased the rate of flowering by more than 35% over the controls. Cysteine inhibited flowering, while other amino acids had little or no promotive effect on flowering. Serine and threonine increased flowering rate in L. perpusilla only when added during a dark period of the inductive cycle. The addition of amino acids during a light period not followed by a dark period had no effect on flowering.
Geotropic Curvatures in Roots of Cress (Lepidium sativum)
Authors: IVERSEN TOR‐HENNING 
Published: April 2006

AbstractRoots of cress growing between two agar slices develop an asymmetry in the extreme root tip region after 10 to 20 min of horizontal stimulation. After prolonged stimulation (exceeding 50 min) the asymmetry disappears and after 3 h the curvature is distributed over the entire growing region. The course of the initial stages in the geotropic curvature has been followed by light microscopy and scanning electron microscopy. — When stimulated at an angle of 135° with the gravitational force, the asymmetry in the root tip is clearly visible after 10 min of stimulation.The asymmetry in the root cap can be explained by a difference in the elongation rate of the epidermal cells on the upper and lower sides of the stimulated root. The disappearance of the asymmetry is followed by a second phase in which there is a differential growth of the cortical cells on the two sides of the elongation zone. The average growth rate of cells in the upper half of the apical region during the first 50 min of continuous stimulation is 1.5 μm per min, while the elongation rate of the entire root is 16.2 μm per min. Only small modifications in the elongation rates were observed when stimulated and unstimulated roots were rotated parallel to the horizontal axis of a klinostat at 2 rpm.The ultimate curvature developed after 50 min is unaffected by stimulation times exceeding the reaction time which for cress roots has been found to be about 5 min.The two phases in the development of geotropic curvature are discussed in view of the statolith theory.
Gibberellin‐like Substances from Norway Spruce (Picea abies)
Authors: DUNBERG ARNE 
Published: April 2006

AbstractBy use of methanol extraction, two different consecutive partition procedures, repeated polyvinylpyrrolidone column chromatography, silicic acid partition column chromatography and the dwarf rice, lettuce, and barley half‐seed bioassays, several gibberellin‐like substances were detected in elongating shoots of Picea abies (L.) Karst. No significant differences in the content of gibberellin‐like substances could be detected between juvenile and mature trees. The shoot axes were found to contain fewer gibberellin‐like substances than the needles.
Formation of Proteinase Inhibitors in Developing Barley Grain
Authors: KIRSI MARKKU 
Published: April 2006

AbstractAssays have been made of the activities of trypsin inhibitors and Aspergillus‐proteinase inhibitors in developing grains of barley (Hordeum vulgare L.) grown under controlled conditions. Trypsin inhibitor activity appeared early in the development, reaching a near‐maximal value 24 days after anthesis, but Aspergillus‐proteinase inhibitors were synthesized quite late in the development. A half‐maximal value was attained about 25 days subsequent to anthesis. The corresponding half‐maximal value for all the proteins synthesized was about 16 days.The trypsin inhibitor present in developing grains appeared to be immunologically identical with the endospermal inhibitor in mature grains.The concentrations of Aspergillus‐proteinase inhibitors varied between different cultivars of barley. Moreover, each cultivar displayed an almost linear relationship between inhibitor activity and the increasing content of total protein. Great differences between different cultivars were also observable with regard to trypsin inhibitor activities. However, the activities in each cultivar were constant, regardless of the total protein content.The author is greatly indebted to Dr. Juhani Mikola for many helpful discussions during the course of the work, and for several valuable suggestions in regard to the manuscript. I also wish to thank Mrs. Marja‐Leena Niku‐Paavola, Lic. Phil., for valuable help in the immunodiffusion experiments, and Miss Outi Karkkainen for skilful technical assistance. This work was supported by grants from the Emil Aaltonen Foundation and from the E. J. Sariola Foundation.
Development of Ascorbate Oxidase Activity and Its Iso‐enzyme Pattern in the Roots of Pea Seedlings
Authors: SUZUKI YONEZO , OGISO KAZUKO 
Published: April 2006

AbstractEarly in the germination of peas, ascorbate Oxidase activity increased markedly in the root and epicotyl, but not in the cotyledons. The activity in the root was suppressed by the administration of 6‐methylpurine, thiouracil, cyclohexi‐mide, thioproline, and phenylthiourea. Although enzyme development was inhibited by phenylthiourea and thioproline, root elongation was not affected by these reagents. As germination progressed, the ascorbate oxidase activity in the extract of the seedling's root could be separated into at least 3 to 7 isoenzymes.
The Effect of Sodium Chloride on the Balance between the C3‐ and C4‐Carbon Fixation Pathways
Authors: SHOMER‐ILAN ADIVA , WAISEL Y. 
Published: April 2006

AbstractYoung leaves of salt‐depleted Aeluropus litoralis Parl. plants show CO2 fixation by the C3‐carbon fixation pathway. No detectable activity of phosphoenol pyruvate (PEP) carboxylase was found. When A. litoralis plants were exposed to a NaCl solution, the leaves showed a high activity of PEP carboxylase as well as a significant CO2 fixation by the C4‐pathway. — Also in Zea mays L. and Chloris gayana Kunth., the presence of NaCl in the medium influences the balance between phosphoenol pyruvate carboxylase and ribulose‐1,5‐diphosphate carboxylase.
α‐Amylase in the Barley Grain Influenced by the Auxin‐Cytokinin Interaction in the Coleoptile
Authors: VERBEEK RITA , VAN ONCKELEN H. A. , GASPAR TH. 
Published: April 2006

AbstractTwo phases are distinguished in the α‐amylase production in barley (Hordeum vulgare) grains. There is an increase in activity extended to the third or fourth day of germination, then a slight decrease follows. This decrease is accelerated by kinetin while it is prevented by IAA applied at the top of the embryo coleoptile. IAA reverses partially the kinetin action. IAA applied in the germination medium has practically no effect. Removal of the coleoptile stops further increase in α‐amylase activity and induces complete insensitivity to hormone treatment.The results indicate that auxin metabolism in the coleoptile participates in the control of α‐amylase evolution in the barley grain and that kinetin could act through auxin metabolism in this coleoptile.
Levels of Indol‐3yl‐acetic acid (IAA), IAA‐oxidase and Peroxidase in Developing Cucumber Seedlings
Authors: ELKINAWY MAHASEN , RAA JAN 
Published: April 2006

AbstractThe level of indol‐3yl‐acetic acid (IAA) in the cotyledons of cucumber seedlings increases in the period 4 to 11 days after germination. In hypocotyls and roots the IAA level decreases. IAA‐oxidase activity of homogenates of cotyledons, hypocotyls and roots decreases with age. The soluble fraction of all three organs contains an IAA‐oxidase, which may be allosteric. It is suggested that this IAA oxidase limits the upper level of IAA in the cell. The cell wall fraction of the three organs contains IAA‐oxidases with conventional kinetics. The function of this IAA oxidase is probably to degrade exogenous IAA.
Oxygen Release from Rice Seedlings
Authors: JOSHI M. M. , IBRAHIM I. K. A. , HOLLIS J. P. 
Published: April 2006

AbstractOxygen release from root systems of individual rice seedlings was measured polarographically employing an oxygen monitor with a Clark electrode. The oxidizing capacity of four rice varieties was correlated with their relative yielding abilities and with their reactions to Straighthead (SH) and Mild Sulfide Disease (MSD). These data support previous findings which link SH and MSD with rice‐toxic levels of soluble sulfides in Gulf Coast (U.S.A.) rice soils containing excess iron.
Effect of Different Osmotic Potentials of Media on Germination of Three Safflower Varieties
Authors: SIONIT N. , KHERADNAM M. , GHORASHY S. R. 
Published: April 2006

AbstractThe effect of osmotic potentials, 0 to −13.5 atm (−1.37 M Pa), on the germination of three safflower varieties (Carthamus tinctorius L.) was studied at a controlled temperature (30±2°C) using a non‐electrolyte substance, polyethelene glycol 6000. The varieties were cv. Ute, cv. Iranian local 3151, and cv. Iranian local 2811. The percent germination of the three varieties averaged over all osmotic potentials were: 86, 77 and 61 for local 3151, local 2811 and “Ute”, respectively. The Ute variety had the highest, and the local 3151 variety had the lowest rate of germination reduction. The variations among the varieties in the percent and rate of germination were due to osmotic effects of the media.
Seasonal Variations in Absorption and Metabolism of Carbon‐14 Labelled Arginine in Intact Apple Stem Tissue
Authors: HILL‐COTTINGHAM D. G. , LLOYD‐JONES C. P. 
Published: April 2006

AbstractAt intervals through the year a study was made of the absorption and metabolism of arginine‐C 14(U) which had been perfused into the wood of apple stem internodes. Absorption was greater during the period May to September than at any other time of the year. The metabolic breakdown of arginine took place only after absorption but the products found varied widely with season. From the analyses it is concluded that arginine is metabolized by the Krebs‐Henseleit cycle at all times of the year, in addition to which during the period from May to August there are other pathways in operation that result in a more extensive breakdown so that all the N in arginine becomes available for new growth.
Utilization of Carbohydrates by Rhynchosporium secalis. I. Growth and Sporulation on Glucose, Galactose, and Galacturonic acid
Authors: OLUTIOLA P. O. , AYRES P. G. 
Published: April 2006

AbstractThe fungus Rhynchosporium secalis (Oud.) Davis grew and speculated in liquid nutrient media that contained glucose, galactose or galacturonic acid, or a pair of those substances, as the sole carbon source. Sporulation was inhibited by high concentrations of glucose and galacturonic acid. Growth and sporulation were greatest on glucose, and least on galactose. Growth was increased when glucose and galacturonic acid were mixed. Nitrogen concentration affected sporulation but not growth.
Auxin Stimulation of Cambial Activity in Pinus silvestris II. Dependence upon Basipetal Transport
Authors: WODZICKI T. J. , WODZICKI ALINA B. 
Published: April 2006

AbstractNatural auxin content has been determined in the cambial region of large Pinus silvestris L. trees at various dates during the year. The tissue was collected from the stem of intact or ring‐barked trees and from stumps remaining after the trees were cut down at breast height in early summer or late autumn. No seasonal decrease of concentration of the extractable auxin in the cambial region could be detected. Decapitation or ring‐barking produced severe reduction in auxin content and arrested cambial division. In the next season the auxin level and the cambial activity remained completely depressed. It is concluded that without tissue continuity in the region external to xylem and without basipetal supply of substances, no mechanism operated by roots or remaining stem tissue near the tree base can ensure a high level of auxin in the cambial region or activate and maintain the cambial division. The activity of extracted pine auxin was found not to be identical with the stimulatory potential of authentic IAA determined by standard bioassays. The possibility of interaction with other extracted substances is discussed.