bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrate Reductase and Nitrite Reductase Activity in Dark‐Grown Radish Seedlings: Relation to the Supply of NADPH
Authors: STULEN INEKE , LANTING L. 
Published: April 2006

AbstractFunctioning of nitrate reductase and nitrite reductase was measured in intact cotyledons from radish seedlings (Raphanus sativus L.) grown in the dark in a nitrate medium. Reduction of nitrate to nitrate did proceed during the whole period of 45 h, whereas the reduction of nitrite in the intact cotyledons dropped abruptly between 20 and 23 h after exposing the roots to nitrate.The activity of the enzymes glucose‐6‐P dehydrogenase (G6PDH) and 6‐P‐gluconate dehydrogenase (6PGDH), measured in cotyledon extracts, showed a sharp decline simultaneously with the drop in nitrite reductase activity of the intact cotyledons. It was concluded that the amount of NADPH generated by the enzymes G6PDH and 6PGDH is not sufficient to allow continuous functioning of nitrite reductase after 20 h in cotyledons of seedlings grown in the dark. Therefore, the results from our experiments point to the functioning of nitrite reductase as the rate limiting step in the reduction pathway of nitrate in the dark.
Enhancement by Low pH of Gibberellin Effects on Dormant Celery Seeds and Embryoless Half‐Seeds of Barley
Authors: PALEVITCH D. , THOMAS T. H. 
Published: April 2006

AbstractThe action of gibberellins on celery (Apium graveolens L.) seed germination and the release of reducing sugars from barley (Hordeum vulgare L.) seed endosperm were enhanced by decreasing the pH of the incubation solution to below the pKa point. In most cases, low pH was obtained by mixing the solution with weak acids such as succinic acid 2.2 dimethylhydrazide (SADH), 2‐chloroethylphosphonic acid (CEPA), or citric acid. However, lowering the pH of the gibberellin solution with strong acid (HCl) also increased markedly the activity of low concentrations of GA4/7. The synergistic action of ethylenediaminetetraacetic acid (EDTA) with gibberellin was not dependent on the pH level of the incubation solution. The response of celery seeds to gibberellins was increased when their distal ends were removed: solution pH and EDTA had no effect on this response.The possible explanations of the synergism between low pH compounds and gibberellins are discussed.
Temperature Response and Effect of Ca2+ and Mg2+ on ATPases from Roots of Oats and Wheat as Influenced by Growth Temperature and Nutritional Status
Authors: KÄHR M. , MØLLER I. MAX 
Published: April 2006

AbstractActivation by Ca2+, Mg2+, Zn2+, or Mn2+ of adenosine triphosphatases in a microsomal fraction from wheat roots depends upon the growth temperature when the plants are grown under low salt conditions, but not when the plants get a full‐strength culture medium. At low ionic strength, cultivation at 25°C gives only half as high activation as cultivation at 18°C or at high ionic strength at both temperatures.Corresponding data for activation of ATPases from oats also show that low ionic strength during growth gives the highest temperature dependence. Low temperature together with low salt conditions during growth gives the highest ATPase activity after stimulation with divalent cations. High growth temperature and full‐strength medium decrease the ATPase activity.Activation energies (Ea) were calculated for the two temperature intervals 35–20°C and 20–5°C. The dominating ATPase stimulation (Ca2+ in wheat, Mg2+ in oats) is characterized by high specific activity combined with a low Ea value.The differences in ATPase activity between oats and wheat can be correlated with different cultivation requirements known from agriculture.
Variations in Zinc Content of Subcellular Fractions from Young and Old Roots, Stems and Leaves of Broad Beans (Vicia faba)
Authors: POLAR E. 
Published: April 2006

Abstract 65Zn labelled seeds of broad beans (Vicia faba L.) germinated and grown in a complete nutrient solution containing the radioisotope were used to investigate the change in the subcellular distribution of this trace element during subsequent development of the labelled seeds. Homogenates of leaves, stems and roots were fractionated into cell‐wall debris, nuclei, chloroplasts, mitochondria, ribosomes and “soluble” fraction. The concentration of the radioisotope in these fractions, expressed as cpm/mg dry weight, was highest in the soluble fraction and in the ribosomes isolated from young tissues. However, as roots and leaves aged, a general decrease in the overall zinc concentration was followed by a similar drop in the concentration of the metal associated with the “soluble” fraction and ribosomes, causing a more or less uniform zinc distribution pattern. On the other hand, there was a general increase in the zinc concentration of the “soluble” and in the particulate fractions of relatively high sedimentation coefficient from older stem samples. Taking also into consideration the dry weight change per unit volume of the tissues under investigation, the relationship between these variations and the metabolism of the plant is discussed.
Anaerobic ATP Levels in the Blue‐Green Alga Anabaena: Dark‐Light Transients and Effects of Light Intensity
Authors: IMAFUKU HIROSHI 
Published: April 2006

AbstractAn enzymatic method was used to determine ATP extracted from anaerobically incubated samples of the blue‐green alga Anabaena variabilis. The dark‐light‐dark transients of the ATP level in the whole cells were studied in the presence and in the absence of 3 (p‐chlorophenyl)‐l.l‐dimethylurea (CMU). When O2 evolution was completely inhibited by CMU, there was no significant difference between the transient under illumination of a low intensity and that of fourfold intensity. On the other hand in the absence of CMU, the ATP level decreased more rapidly after high intensity illumination than after low intensity one. The increase in ATP content during the first 5 s illumination was smaller in the absence of CMU than in the presence of CMU. With or without CMU the increase was saturated at the vicinity of the intensity at which photosynthetic O2 evolution compensates for respiratory O2 consumption. The calculated quantum requirement of cyclic photophosphorylation in vivo was 2.2 quanta per ATP.
Étude conductimétrique des effets de trois auxines sur un parenchyme de réserve
Authors: MEYLAN S. 
Published: April 2006

Abstract Conductimetric study of the effects of three auxins on a storage tissue. The change of conductivity of calibrated disks of potato tuber tissue was measured after a 6 h immersion in a mixed aqueous solution of 1 × 10−3M auxin and 0.2 M mannitol, or pure auxin, or mannitol, of the same concentrations; then measured anew after a l h immersion in 0.1 M KCI. The auxins used were: β‐indolyl‐acetic acid (AIA), α‐naphtyl‐acetic acid (ANA) and β‐naphtoxyacetic acid (ANOX). A final higher conductivity was observed, the effect increasing from AIA to ANA and ANOX. The physiological significance of the results is discussed.
Apical Growth Cessation and Shoot Tip Abscission in Salix
Authors: JUNTTILA OLAVI 
Published: April 2006

AbstractTime course of apical shoot growth and shoot tip abortion in northern ecotypes (lat. 69°39′N, long. 18°37′E) of Salix pentandra and S. caprea have been investigated. In trees more than 15 years old growing under natural climatic conditions apical growth cessation and shoot tip abortion normally occurred in June‐July when the day length still was 24 h. Application of GA3, in spring to the apex effectively delayed growth cessation and shoot tip abortion. Application of kinetin was without effect. First‐year seedlings of both species grew continuously at temperatue of 9 to 24°C in 24 h photoperiod. Short days induced apical growth cessation, but two to four (S. pentandra) or three to five (S. caprea) weeks of 12 h photoperiod were required to stop the elongation growth. The results indicated that the critical photoperiod for apical growth cessation in the used ecotype of S. pentandra was 16 to 18 h at 18°C. Short days had a minor effect only on the formation of apical leaf primordia in small seedlings. Development of axillary buds and radial growth were stimulated by short days when compared with long days. Small seedlings of both species (3 to 8 cm high at the start) formed terminal buds in short days, but in large seedlings (more than about 15 cm high) apical growth cessation was accompanied by shoot tip abortion. Abscisic acid applied to the apex or through a leaf did not induce growth cessation in S. pentandra seedlings grown in continuous light. The growth retardants CCC, B‐9 and Phosphon D reduced growth rate under continuous light and induced shoot tip abortion in some plants. The effect of CCC was counteracted by GA3. Apical growth cessation in short days was significantly delayed by a single GA1 application.
Nitrogen and Cation Nutrition of Three Ecologically Different Plant Species
Authors: INGESTAD TORSTEN 
Published: April 2006

AbstractExperiments on nutrient requirements of the ecologically very different plant species Betula verrucosa Ehrh., Cucumis sativus L., and Vaccinium vitis idaea L. are discussed with regard to the nitrogen and cation nutrition. The nutrient solution technique used allows a strict control of nitrogen source and cation uptake at maximum growth rate.The nitrogen sources were equally efficient except for growth reductions in cucumber at ammonium nutrition. Increase in tissue pH resulting from a high total uptake rate of NH4+ and other cations is probably an important factor in ammonium toxicity. No evidence was found for the concept of “ammonium plants”; but at high nitrate supply to Vaccinium a high cation uptake may account for decrease in growth rate.No large or fundamental differences in cation or anion requirements among the species were found; the difference in ion balance (C — A) in relation to dry matter depends mainly on differences in xeromorphy.In cucumber, the relations between cation and nitrate nutrition are in agreement with models proposed in the literature. Vaccinium and birch have a cation uptake and retention of high efficiency at low nutrient availability and ammonium nutrition indicating independence between cation and nitrate nutrition in these species.The properties found are regarded as significant and functional in relation to the ecological character of the species.
Uptake of 14C‐L‐Glutamic Acid by Daucus carota Cell Suspension in Different Shock Situations
Authors: WAHLSTRÖM DAN , ERIKSSON TAGE 
Published: April 2006

AbstractCell suspension cultures of Daucus carota were shocked by inoculation or by temperature, salts or osmotica in combination with inoculation. Changes in cell vitality were measured by uptake studies with labelled L‐glutamic acid performed during the first 30 min after shock treatment. The cell sample was then collected on filter and counted in a liquid scintillation counter. Inoculation alone caused a marked decrease in uptake. Normal uptake capacity was re‐established within 2 h. Temperatures of 0−20°C as against 27°C gave an additional decrease in uptake. Of the tested osmotica, polyethylene glycol gave the greatest stabilizing effect on the glutamic acid uptake and sucrose the least. The highest uptake rates were obtained with a calcium concentration of 0.10–0.15 mM.
Effects of 2,5‐Dibromo‐3‐methyl‐6‐isopropyl‐p‐benzoquinone (DBMIB) on Light Induced and Glycolytic Phosphate Uptake in Scenedesmus
Authors: SUNDBERG INGRID , TILLBERG JAN‐ERIC , BJÖRKLUND GUN 
Published: April 2006

AbstractThe effects of DBMIB on photophosphorylation and glycolysis in Scenedesmus obtusiusculus Chod. were investigated by measuring the uptake of inorganic phosphate. To analyze the effects of DBMIB on the different energy coupling possibilities in open chain and cyclic photophosphorylation, DBMIB was given to the algae in narrow concentration intervals between 10−6M to 10−4M, either alone, or in combination with DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea) or desaspidin. DBMIB inhibits non‐cyclic as well as cyclic photophosphorylation in Scenedesmus. However, the DCMU resistant photophosphorylation reactions are less sensitive to DBMIB than the open chain photophosphorylating system in non‐DCMU treated cells. Low concentrations of DBMIB even released a part of the DCMU inhibition. Experiments with combinations of DBMIB and desaspidin also indicated that cyclic photophosphorylation is less sensitive to DBMIB than non‐cyclic. The inhibition of DCMU resistant cyclic phosphorylation by DBMIB, which is a competitive inhibitor of quinones, indicated a participation of plastoquinones in this type of energy coupling as well as in the non‐cyclic and DCMU‐sensitive processes. The cyclic and the non‐cyclic photophosphorylation pathways probably use different parts of the plastoquinone pool.For the purpose of the experiments, it was necessary to produce data for the effect of DBMIB (10−6–10−4M) on glycolysis. The highest concentration gave 50% inhibition.
Variations nycthémérales de l'intensité des corrélations entre les cotylédons et leur bourgeon axillaire induites par des traumatismes faits unilatéralement sur l'un des deux cotylédons de Bidens pilosus
Authors: DESBIEZ MARIE‐ODILE 
Published: April 2006

AbstractDifferent methods (physiological, electrophysiological and biochemical) were used in order to show, during a 24 h period, a change in sensitivity of Bidens pilosus seedlings to the pricking of one of the cotyledons. The sensitivity is maximum in the morning and in the evening; it decreases during the light period (day) and the dark period (night). The minimum of the sensitivity occurs in the middle of the day and 3 to 4 h after the beginning of the night.
Reliability of the Indolo‐α‐Pyrone Fluorescence Method for Indole‐3‐acetic Acid Determination in Crude Plant Extracts
Authors: ELIASSON LENNART , STRÖMQUIST LARS‐HELGE , TILLBERG ELISABETH 
Published: April 2006

AbstractIndole‐3‐acetic acid (IAA) contents in plant extracts were determined spectrofluorometrically after conversion of the compound into indolo‐α‐pyrone. The method is sensitive and accurate and showed good reproducibility. The values obtained by this method corresponded well with those obtained with the Avena coleoptile straight‐growth assay.Impurities in extracts often cause various difficulties. Colored compounds influence the readings and may even make indole‐3‐acetic acid determination impossible by strong quenching of the fluorescence light. Insoluble compounds can be formed in the reaction and cause increased opalescence and light scattering which interferes with the fluorescence measurements. The necessities for the method to be reliable are that the insoluble compounds are removed or brought into solution and that the exciting light is sufficiently monochromatic.Indolo‐α‐pyrone is fairly stable in the dark but is rapidly broken down by UV radiation. This decay may be used as a check to see if the measured light represents fluorescence of indolo‐α‐pyrone.
Fatty Acid and Chlorophyll Levels of Coastal Bermudagrass during the Day and during Maturation
Authors: CHAPMAN GLENN W. , ROBERTSON JAMES A. , BURDICK DONALD 
Published: April 2006

AbstractLipids were extracted from fresh, field‐grown coastal bermudagrass (Cynodon dactylon (L.) Pers.) and the fatty acids determined by gas chromatography. Total fatty acid levels (dry weight basis) increased during the day and reached a single maximum at sunset in 2‐week‐old grass; whereas, in older grass, the fluctuations in fatty acid levels showed two maxima. The first maximum occurred 4 h after sunrise and the second maximum occurred at sunset. Total fatty acid levels, based on dry weight, decreased during the first 6 weeks of growth and changed very little after an additional 4 weeks' growth in bermudagrass leaf blades. Chlorophyll levels (dry weight basis) continuously decreased during the entire growth period (10 weeks). Chlorophyll alb ratios increased at sunset in 2‐ and 6‐week‐old grass, but this ratio did not change during the day in subsequent growth stages. The results of these experiments show that stages of maturity affected fatty acid fluctuations during the day as well as total fatty acid and chlorophyll levels in Coastal bermudagrass leaf blades. Chlorophyll alb ratios varied independently of fatty acid levels.
Role of Photosynthetic Electron Transfer in Light Activation of Calvin Cycle Enzymes
Authors: CHAMPIGNY MARIE‐LOUISE , BISMUTH EVELYNE 
Published: April 2006

AbstractThe effect of light in activating fructose‐1,6 biphosphate phosphatase (E.C. 3.1.3.11), sedoheptulose‐1,7, biphosphate phosphatase (E.C. 3.1.3.11), ribulose‐5 phosphate kinase (E.C. 2.7.1.19), ribulose‐1,5 biphosphate carboxylase (E.C. 4.1.1.39) and (NADPH) glyceraldehyde‐3 phosphate dehydrogenase (E.C. 1.2.1.13) in intact spinach chloroplasts in the presence of antimycin A, tetramethylethylenediamine (TMEDA) or chlorophenyl‐1,1‐dimethylurea (CMU) was examined. Antimycin A and TMEDA were added as stimulating agents for photosynthetic electron transfer in intact chloroplasts while CMU was added for its inhibitory characteristics.Light exerted its control through the mediation of the photosynthetic electron transfer. Antimycin A and TMEDA promoted the light activation. CMU nullified the light activation as well as the stimulatory effect of antimycin A and TMEDA.Thus the control by light of the activities of the Calvin cycle enzymes involves a reduced agent formed by the photosynthetic electron transport chain. From the presently available evidence, it seems appropriate to hypothesize that the light activation of the enzymes is not a single mechanism. In fact three types of enzymes can be distinguished: Ru‐5 P kinase and (NADPH) G‐3 P dehydrogenase, maximal activation of which appears within the first minute of illumination and is promoted by antimycin A and by TMEDA; F‐1,6 P2 phosphatase and S‐1,7 P2 phosphatase, ferredoxin‐dependent enzymes, activation of which is slightly slower but is also promoted by antimycin A and by TMEDA; finally Ru‐1,5 P2 carboxylase, activation of which is still slower and characterized by the absence of any response to antimycin A as well as to TMEDA.
Relationship between Water Potential and Leaf and Inflorescence Initiation in Helianthus annuus
Authors: MARC J. , PALMER J. H. 
Published: April 2006

AbstractThe total number of leaves produced by the primary stem of Helianthus annuus L. cv. Pole Star and cv. Peredovik, was reduced from 29 leaves to 21–22 leaves when water stress ranging from −2000 to −3000 kPa was imposed over the period from day 10 to day 20 after sowing, by withholding water from the soil. Extending the stress period by 10 days did not cause any further significant reduction in leaf number. Examination of the shoot apex showed that the leaf initiation rate was depressed by low water potential, the greatest effect occurring in the range 0 to −1000 kPa. It was established that inflorescence initiation commenced about 18 days after planting in control plants and this was delayed by only about 4 days by low water potentials in the range −1000 to −3000 kPa.
The Effects of Dehydration‐Rehydration Cycles on Protein Synthesis of Black Locust Seedlings
Authors: BRANDLE JAMES R. , HINCKLEY THOMAS M. , BROWN GREGORY N. 
Published: April 2006

AbstractProtein synthetic activity of polysomes isolated during dehydration‐rehydration cycles of black locust seedlings (Robiniapseudoacacia L.) was investigated. Polysomes of black locust seedlings were reduced by only 20% during water stress and were capable of incorporating 3H‐leucine into peptide chins. RNase activity increased during stress and declined following irrigation. The presence of a protective mechanism is suggested which, if present in other drought hardy species, could help to explain the ability of these species to withstand various levels of water stress.
Changes in Glycolate Oxidase and Glyoxylate Reductase in Quercus robur Infected by Microsphaera alphitoides
Authors: HEWITT H. G. , AYRES P. G. 
Published: April 2006

AbstractLeaves of Quercus robur L. were infected with conidia of Microsphaera alphitoides Griffon and Maublanc. Crude enzyme extracts of healthy and infected tissue, taken during a 7‐day experimental period, were assayed, using spectrophotometric and manometric techniques, for glycolate oxidase, NAD‐ and NADP‐glyoxylate reductase activities. After 2 days, extracts from infected tissue contained significantly higher activities of glycolate oxidase and NAD‐glyoxylate reductase than extracts from controls, but the activity of NADP‐glyoxylate reductase, after an initial rise, was significantly reduced below that in control extracts. The reduction in glycolate oxidase activity may be partly due to a deficiency in flavin mononucleotide in infected tissue. A possible connection between the reduction in flavoprotein enzyme activity, photorespiration and susceptibility to infection is described.
Environmental Effects on Transpiration and Leaf Water Potential in Avocado
Authors: STERNE RICKIE E. , KAUFMANN MERRILL R. , ZENTMYER GEORGE A. 
Published: April 2006

AbstractA field study was conducted to determine how atmospheric and edaphic conditions influenced the water relations of avocado trees (Persea americana Mill. cv. Bacon). With high and low levels of incident photosynthetically active radiation (PAR, 400–700 nm wave length), and either wet or dry soil, leaf conductance decreased as the absolute humidity difference from leaf to air increased. For any water stress treatment, conductance was higher at high PAR than at low PAR. Both conductance and transpiration were higher in well‐watered trees than in stressed trees, and in prestressed trees levels were intermediate to unstressed and stressed trees. A model for water flux through the soil‐plant‐atmosphere continuum was used to examine the relationship of leaf xylem pressure potential to transpiration in well‐watered trees and in trees stressed by dry soil. There was a close linkage between leaf xylem pressure potential and transpiration in unstressed and previously stressed trees with high or low PAR, i.e. similar potentials occurred with equivalent transpiration regardless of previous treatment or time of day. In stressed trees, xylem pressure potential was lower than in unstressed trees both during the day and night, and at a given transpiration rate the potential was lower after 1400 h than before that time. The model indicated that in stressed trees xylem pressure potential was uncoupled from transpiration, presumably because of altered resistance in the soil‐root portion of the transport system.
Spectral Properties of Juvenile and Adult Leaves of Piper betle and Their Ecological Significance
Authors: BRUNNER U. , ELLER B. M. 
Published: April 2006

AbstractJuvenile and adult leaves of Piper betle L. were shown to have different spectral properties. A computer model was used to calculate the temperature of these leaves taking the energy balance approach. At high values of solar radiation, juvenile leaves with lower absorptivity in the visible and the near infrared show markedly lower temperatures than mature leaves. There is an ecological effect of high and low leaf temperatures on heat load and water stress.