bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Some Chemicals on the Oxygen Evolution and Oxygen Uptake in Isolated Wheat Chloroplasts Irradiated without the Addition of an Oxidant
Authors: EGNÉUS HANS 
Published: April 2006

AbstractThe oxygen exchange, obtained when isolated chloroplasts of Triticum aestivum, wheat, are irradiated without the addition of a Hill oxidant has been investigated using an oxygen electrode. Ascorbate, catalase, 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐p‐benzoquinone(DBMIB), diethyldithio‐carbamate (DEDT), dichlorophenylmethylurea (DCMU), and potassium cyanide were added to the Chloroplasts in order to investigate the oxygen exchange. At least two oxygen uptake reactions, one sensitive to catalase and one catalase‐insensitive, appeared upon irradiation. Hydrogen peroxide was the product of the oxygen uptake in the former process, and water was the reductant. The formation of hydrogen peroxide was probably associated with photosystem I. The other oxygen consuming reaction was found to be insensitive to both catalase and potassium cyanide. After the chloroplasts had been treated with DCMU, it was possible to show that the catalase‐insensitive oxygen uptake was localized in photosystem I, and that a cyclic electron transport system or some endogenous reductant (‐s) acted in the oxygen uptake.Addition of ascorbate or DEDT to the chloroplasts led to an enhanced oxygen uptake in 710 nm light. This was probably due to the effect of these compounds on the superoxide radical ion formed in photosystem I. The stimulated oxygen uptake was only weakly affected by catalase, indicating that hydrogen peroxide was not a product of this oxygen uptake. Addition of DEDT and potassium cyanide inhibited (strongly respectively weakly) the oxygen uptake when photosystem II was functioning. The effect of these compounds was probably due to an inhibition of the electron transport at the plastocyanin.DBMIB inhibited the oxygen uptake reactions and the cooperation between the two photosystems. The cooperation between the photosystems was also studied in DCMU‐treated chloroplasts. The reactions in photosystem II, measured as oxygen evolution, were more inhibited than the coupling between the photosystems.The oxygen “gush” appearing upon irradiation in light of 650 nm was not affected by a DBMIB‐treatment, showing that the oxygen evolution was due to the reduction of plastoquinone. The reoxidation in the dark of the plastoquinone pool was stimulated by DBMIB and potassium cyanide indicating that an oxygen uptake could be associated with plastoquinone.The sites of interaction of oxygen with the electron transport pathways in chloroplasts, and the different reductants for the oxygen consuming reactions are discussed.
Production of Pectinase and Cellulase by Cladosporium cucumerinum with Dissolved Carbohydrates and Isolated Cell Walls of Cucumber as Carbon Sources
Authors: SKARE N. H. , PAUS F. , RAA J. 
Published: April 2006

AbstractThe scab fungus Cladosporium cucumerinum can use pectins and polygalacturonic acid as sole sources of carbon. Cellulose and Ca‐polygalacturonate are not available carbon sources for the fungus. When growing on sucrose or pectin, pectinase is produced. In these cases the production of cellulase is insignificant. On a mixture of pectin and carboxymethylcellulose also cellulase is produced.Both pectinase and cellulase are released into the culture filtrate when the fungus grows on cell walls without ionic proteins, whereas only cellulase is released when cell walls with ionic proteins are the carbon source. Pectinase produced by the pathogen can bind to isolated cell walls. The bound pectinase can be extracted with 1 M NaCl from cell walls without ionic proteins, but not from cell walls with ionic proteins.A water‐extract or 1 M NaCl‐extract of cucumber hypocotyls with visible disease symptoms contains cellulase but no pectinase activity. Lack of pectinase activity in the 1 M NaCl‐extract may be due to inhibition by a component that could be extracted by NaCl from the cucumber cell walls.
Comparative Effects of Indoleacetic Acid and Gibberellic Acid on Growth of Decapitated Etiolated Epicotyls of Pisum sativum cv. Alaska
Authors: DAVIES ERIC , ÖZBAY ORHAN 
Published: April 2006

AbstractMeasurements were made of the growthof the sub‐apical region of decapitated, etiolated epicotyls of Pisum sativum L. cv. Alaska after treatments with indoleacetic acid (IAA), gibberellic acid (GA) and triiodobenzoic acid (TIBA). Growth was measured either at the end of a 2‐day period, at short intervals during growth, or was monitored continuously for 2–3 h using a position‐sensing transducer.In experiments measuring growth after 2 days, high levels (0.1–10 μg/plnat) of IAA caused expansion, whereas similar levels of GA caused elongation. When both hormones were applied together, the effects of IAA were dominant and expansion ensued, even when GA was present at 100 times the amount of IAA. Very low amounts of IAA (0.5–5 ng/plant), however, caused elongation. The elongation elicited by high GA or low IAa was inhibited to a similar extent by TIBA and this inhibition of elongation was associated with an increased expansion at the extreme tip. When application of the hormones was delayed, GA‐induced elongation was reduced considerably, IAA‐induced elongation was lessened somewhat and IAA‐induced expansion was partially converted into elongation.In experiments measuring elongation at short intervals, high levels of IAA caused rapid elongation followed after 3 to 6 h by expnasion. Both GA and low levels of IAA extended the duration of elongation with little apparent effect on the rate of growth. In fast‐growth experiments, low, intermediate and high levels of IAA doubled the rate of elongation with a lag period of about 20 min, whereas GA had at most a very slight stimulatory effect on the growth rate.It is concluded that the main role of GA in this system is to maintain physiological levels of IAA in the growing zone and that the level of IAA present determines whether elongation or expansion will take place.
Regulation of Transpiration in Avena. Responses to Red and Blue Light Steps
Authors: BROGÅRDH TORGNY 
Published: April 2006

AbstractThe transpiration responses of primary Arena leaves to red and blue light steps were investigated. The response to a red light step was a so‐called slow response (with a rise time of about 8 min). The response to a blue light step consisted of both a slow, and a rapid response (with a rise time of about 2 min). CO2‐free air outside the leaf eliminated only the slow response, i.e. in CO2‐free ait the plant responded to blue light steps but not to red ones. A short exposure of red light prior to a blue light step enhanced the rapid response. The same enhancement of the rapid response could be achieved by means of a temporary pretreatment with CO2‐free air. The magnitude of the rapid response was dependent on the blue light irradiance and no threshold effects could be detected. — The experimental results are discussed by means of a model, based on stomatal regulation by, ion transport between the subsidiary cells and the guard cells. It is suggested that the slow transpiration response is due to CO2‐regulation of the stomatal aperture and that the rapid response reflect a CO2‐independent blue light sensitive process, which acts directly on the ion transport through the subsidiary and guard cell membranes.
Sulphate Uptake in Two Mutants of Chlorella vulgaris with High and Low Sulphur Amino Acid Content
Authors: PASSERA CALVINO , FERRARI GIOVANNI 
Published: April 2006

AbstractTwo mutants of Chlorella vulgaris characterized by higher and lower content of sulphur amino acids compared with the wild strain were assayed for the efficiency of the sulphate uptake mechanism. In both mutants uptake exhibited positive cooperation kinetics and was strongly stimulated by sulphate starvation. Stimulation was depressed by cysteine and to a higher extent by methionine. Mutations affected the uptake efficiency concordantly with the level of sulphur amino acids. Addition to the starved strains of sulphate or chromate reduced the induced transport to the lower values of the non‐starved strains. Addition of cycloheximide during the induction period prevented a further enhancement of transport without depressing the attained rate in the low sulphur mutant; it was followed by a rapid fall to the non‐induced rate in the high sulphur mutant.
Sources of Nitrogen Supporting Growth and Embryogenesis in Cultured Wild Carrot Tissue
Authors: WETHERELL D. F. , DOUGALL D. K. 
Published: April 2006

AbstractThis paper seeks to calarify conflicting reports on the nitrogen requirements for in vitro embryogenesis in Daucus carota.Tissue derived from petiole explants of the wild strain of this species were tested with a variety of sources of cellular nitrogen under conditions otherwise favorable for in vitro embryogenesis. The use of very small, sieved and well‐washed inocula reduced the carry‐over of soluble materials with the inoculum. Embryo yield was quantified by direct counting of samples.Nitrate at concentrations ranging from 5 to 95 mM KNO3 supportes only weak growth and very low embryogenesis under the exacting conditions of these experiments. As little as 0.1 mM NH4Cl added to a nitrate medium allows some embryogenesis and 10 mM NH4Cl is near optimal when KNO3 is in the range of 12 to 40 mM concentration. Glutamine, glutamic acid, urea and alanine can individually partially replace NH4Cl as a supplement to KNO3. Glutamine, alanine, and possibly glutamic acid can serve as sole sources of nitrogen supporting both good growth and embryogenesis. It was concluded that a reduced nitrogen source is required, at least as a supplement to nitrate, for rapid growth and for in vitro embryogenesis of cultured wild carrot tissue. The relationship of pH of the culture medium to growth and embryogenesis was explored and optima observed at approximately pH 5.4 for both processes.
The Effect of Metabolic Poisons on ATP Level and on Active Phosphate Uptake in Chlorella pyrenoidosa
Authors: JEANJEAN ROBERT 
Published: April 2006

AbstractInfluence of light and dark aerobic conditions and of various metabolic poisons [3‐(3,4‐dichlorophenyl)1,1‐dimethylurea (DCMU), 2,4‐dinitrophenol (2,4‐DNP), carbonyl cyanide‐m‐chlorophenylhydrazone (m‐CCCP), α,α′bis(hexafluoroacetonyl) acetone (1799), N,N′‐dicyclohexylcarbodiimide (DCCD), sodium azide, fatty acids] on the active phosphate uptake and on the ATP level has been investigated. Cells in the dark have the same level of ATP as in the light though the phosphate transport is decreased. Similar findings are observed with DCMU. Other poisons used inhibit phosphate uptake and decrease ATP level. However their effect is more drastic on phosphate transport than on the ATP level. There is no good correlation between the ATP level and phosphate transport.
Nitrate, Ammonium and Kinetin Effects on Growth and Enzyme Activities of Paul's Scarlet Rose Callus
Authors: CALDAS R. A. , CALDAS L. S. 
Published: April 2006

AbstractFactorial experiments using the three variables nitrate, ammonium, and kinetin at six different concentrations each (nitrate 4.64 to 215 mM; ammonium 2.15 to 100 mM; and kinetin 0.1 to 4.64 mg/l) were set up to measure the effects of each of these factors, and their interactions, on the fresh weight, protein, and enzyme activities of callus of Paul's Scarlet Rose. Optimum fresh weight values were obtained with nitrate at 46.4 mM. Ammonium inhibited growth at concentrations above 2.15 mM, and kinetin had no significant effect. Significant interaction between nitrate and ammonium effects on growth was found. Kinetin did not interact significantly with either nitrate or ammonium to influence the fresh weight. The specific activity of glutamate dehydrogenase (NAD) in the aminating reaction increased with increasing ammonium concentrations to 21.5; at higher concentrations the activity remained high. Glutamine synthetase specific activity was constant over a large range of nitrate and ammonium concentrations, increasing only when nitrate went from 46.4 to 100 mM. Glutamine synthetase was sensitive to the nitrate: ammonium interaction. Specific activity decreased at progressively higher ammonium levels when nitrate concentration increased. No glutamate synthase activity was detected at optimal nitrate concentrations.
Respiration and NADH‐Oxidation of the Roots of Flood‐Tolerant and Flood‐Intolerant Senecio Species as Affected by Anaerobiosis
Authors: LAMBERS HANS 
Published: April 2006

AbstractRespiration was measured under anaerobiosis in the roots of two Senecio species: S. aquaticus Hill, which is flood‐tolerant, and S. jacobaea L., which is flood‐intolerant. NADH‐oxidation under anaerobiosis was measured in roots of S. aquaticus, S. jacobaea and S. vulgaris L., which is also flood‐intolerant.Protein content of S. aquaticus was about 15% higher under anaerobiosis. At 20°C respiration of the roots of S. aquaticus was 50% inhibited under anaerobiosis, while an almost complete inhibition occurred in the roots of S. jacobaea. The activities of nitrate reductase, glutamate dehydrogenase and lactate dehydrogenase were considerably higher in the roots of S. aquaticus grown under anaerobic conditions than in roots grown under aerobic conditions. In S. jacobaea glutamate dehydrogenase activity was lower and in S. vulgaris nitrate reductase was lower and glutamate dehydrogenase activity was higher in roots grown under anaerobic conditions. The possible role of these enzymes for metabolism under anaerobic conditions by oxidizing a surplus of NADH is discussed.Since oxidative phosphorylation is 50% inhibited under anaerobiosis, ATP has to be generated in a different way. It is argued that maintenance of the ATP‐level may be compensated by way of the enzymes mentioned above, in combination with a modified glucose utilization.
Effects of Ethylene and 2,4‐D on the Activity of Cellulase Isoenzymes in Abscission Zones of the Developing Orange Fruit
Authors: GOREN R. , HUBERMAN M. 
Published: April 2006

AbstractThe role of ethylene and 2,4‐D in the abscission process, and the induction of cellulase isoenzymes in the abscission zones of Citrus fruit at two physiological stages of fruit development, were studied using a new staining technique for the detection of cellulase isoenzymes in polyacrylamide gels following electrophoretic separation. Four to seven isoenzymes were detected in the shoot‐peduncle (zone A) and peduncle‐fruit (zone C) abscission zones; at least two of them could be detected at excision time, and of these at least one could not be connected with abscission. In the young fruit, ethylene enhanced and 2,4‐D delayed both abscission and the formation of several isoenzymes. In the older fruit, ethylene enhanced and 2,4‐D delayed the formation of isoenzymes at a time where no abscission occurred any more in zone A. A slower but significant increase in most of the isoenzyme activity detected was also observed in abscission zone A of untreated older fruit explants after excision. These results fully agree with those reported earlier in relation to total cellulase and polygalacturonase activity (Greenberg et al., Physiol. Plant. 34: 1, 1975) tested at the same stages of fruit development. It is suggested, that the generality of the concept that a rise in hydrolytic enzymes in the abscission zone is necessarily followed by separation of the organ should be re‐evaluated.
Calcium Ions Protect Beet Root Cell Membranes against Thermally Induced Changes
Authors: TOPROVER YOCHEVED , GLINKA Z. 
Published: April 2006

AbstractThe initial heat induced increase in permeability of beet (Beta vulgaris L.) root cell membranes, as measured by betacyanin efflux, is reversible. The leakage of betacyanin stopped when tissue held for 90 min at 45°C was transferred to 27°C.Stronger heat treatments, 10 min at 60°C or 150 min at 45°C, resulted in a continuous release of betacyanin indicating an irreversible change in membrane structure.Calcium ions inhibited the heat induced betacyanin efflux only if this was due to a reversible increase in permeability.
Hormonal Control of Germination under Saline Conditions of Three Halophytic Taxa in the Genus Suaeda
Authors: BOUCAUD JEAN , UNGAR IRWIN A. 
Published: April 2006

AbstractThe interaction between hormones and salinity on seed germination of three halophytic taxa in the genus Suaeda: S. maritima (L.) Dum. var. flexilis Focke and var. macrocarpa Moq., and S. depressa (Pursh) Wats, was studied. Exogenous applications of kinetin and gibberellic acid (GA3) were applied in order to determine if either of these growth‐promoting hormones would promote germination in the two dormant taxa, Suaeda depressa and S. maritima var. flexilis and to see if osmotically induced dormancy by NaCl could be alleviated. Our results indicate that gibberellic acid is capable of breaking dormancy in these species with dormant seeds, but kinetin proved to be ineffective. A seed dormancy that was induced by osmotic stress could also be alleviated by treatments with gibberellic acid. Endogenous concentrations of both cytokinins and gibberellins were measured in seeds exposed to osmotic stress (0.85 M NaCl), and we found a reduction in cytokinin activity in these three taxa. Gibberellin‐like activity was reduced in S. depressa when seeds were soaked in 0.85 M NaCl.
Water Flow in Wheat Seedlings after Small Water Deficits
Authors: NORDIN ÅSA 
Published: April 2006

AbstractTranspiration and water uptake were measured simultaneously using a micro‐wave hygrometer and a recording potometer. Wheat seedlings (Triticum aestivum L. cv. Weibulls Starke) were kept with the roots at +1°C in nutrient solution and with the shoots in air at 20°C for 24 h, a treatment which induced a decrease of about 2% in relative water content of the leaves. The induced deficit rapidly disappeared after returning to normal root temperatures (20°C).The treatment produced after‐effects on steady rates of water absorption and transpiration in light, whereas the times taken for transient changes in transpiration brought about by changes in light conditions were not affected. The after‐effects were not completely eliminated 24 h after removal of stress. The magnitude of the after‐effects varied with the leaf water content, though some contribution of root cooling to the after‐effects cannot be excluded. The decreased water flow through the plant after removal of stress can be attributed mainly to increased stomatal resistance and not to effects on root conductivity. The increased stomatal resistance appears linked to increased membrane permeability rather than to a decrease in the active mechanism for ion uptake.
Modifications du rythme de fructification de Coprinus congregatus par le dépôt de carpophores mûrs exogènes à la surface des cultures
Authors: MANACHERE G. 
Published: April 2006

Abstract Changes in Fruiting Rhythm of Coprinus congregatus by Addition of Exogenous Mature Sporophores on the Surface of Cultures.Researches were performed over the regulating effect of mature sporophores on the fruiting rhythm of Coprinus congregatus Bull. ex Fr. Placing exogenous mature fruit‐bodies on the vegetative mycelium before the accomplishment of the first flush gives an abundant and perfectly synchronized fructification for this flush. But the fruiting rhythm is then disturbed: compared to control cultures, less sporophores are produced in the following flushes, and, in most cases, the cultures are finally characterized by fewer flushes than the controls. The nature of the substance(s) hypothetically produced by mature sporophores, which may regulate the production of other fruit‐bodies, and, correlatively, the fruiting rhythm, is as yet unknown.
Uptake and Transport of Calcium and Phosphorus in Lolium perenne in Response to N Supplied to Halves of a Divided Root System
Authors: BARTA A. L. 
Published: April 2006

AbstractThe uptake and transport of Ca2+ and HPO42− from roots of Lolium perenne L. was studied using variable N nutrition supplied to halves of a divided root system. Plants were grown for 4 weeks in solution containing 0.11 mM NO3−–N; then one‐half of the root system was supplied with either 4.0 mM NO3−–N or 0.28 mM NH4+–N while the other half of the root system remained in low‐N solution.Uptake and transport of Ca2+ increased and uptake of HPO42− declined in root halves supplied with high NO3−–N for 16 h. After supply of high NO3−–N or NH4+–N to half the root system for 6 days, the roots supplied with high‐N exhibited significantly higher rates of uptake and percentage transport to shoots of both Ca2+ and HPO42−–. However, in neither the 16‐h nor 6‐day treatment did Ca2+ or HPO42− uptake of the root half supplied with low N differ significantly from the control (low N supplied to both halves of the root).Significantly higher N concentrations were found in low‐N supplied roots (compared to the control) as a result of internal translocation of N from high‐N supplied roots to low‐N supplied roots. Although N concentration in the low‐N supplied roots increased, uptake rates of Ca2+ or HPO42− did not change implying that external N concentration may be the important factor which influences or governs N mediated uptake responses. This would further suggest that the site of uptake regulation for Ca2+ and HPO42− exists on the outer plasma membrane which is in direct contact with the external solution.Transport of Ca2+ and HPO42− to the shoot was generally increased in low‐N root halves after 6 days of high‐N supply to the other half of the root. This implies that plant growth demand may be a major factor in regulating rates of Ca2+ and HPO42− transport from roots to the shoot. It also reinforces the hypothesis that uptake and transport of ions out of the root are separately controlled or regulated in the plant.
Effect of Prolonged Geo‐stimulation and Presence of 32P on the Elongation of Lateral Shoots of Decapitated Pea Seedlings
Authors: HUSAIN SYED MUSHTAQ 
Published: April 2006

AbstractThe effects of prolonged geo‐stimulation and presence of 32P on 3‐leaf decapitated pea (Pisum sativum L. cv. Alaska) seedlings were studied with regard to lateral bud elongation as well as accumulation and recovery of isotope.Prolonged geo‐stimulation favoured the dominance of basally located, upwardly directed buds and suppressed the elongation of subapical bud — a gravimorphic response similar to the one shown by intact geo‐stimulated branches of woody plants. Basal bud 2 was an exception as it dominated both in the above‐ and below‐axis position.Accumulation of 32P in buds was the result of their own growth, whereas in the other parts of the seedlings accumulation of isotope was not necessarily related to growth.Geo‐stimulation affected 32P recovery in redistribution experiments, whereas it had no effect in distribution experiments. In the former, the decrease in the isotope level in the seedling suggests a loss of 32P.Prolonged presence of 32P in the seedlings had a deleterious effect on bud elongation.
The Content of Elements of Mineral Nutrition in Leaf Parts of Different Colour in Plants of the variegata Type
Authors: SARIĆ M. R. 
Published: April 2006

AbstractThe contents of some elements in green and whitish yellow parts of the leaves of Hedera helix and Acer negundo were examined. The contents of N, P and K were considerably higher in whitish yellow parts of the leaves compared with the green ones, and contrary to Ca in both plant species. Mg behaved like N, P and K in Hedera but like Ca in Acer. The same results were obtained in the leaves which were completely green or whitish yellow. The metabolic activities in different parts of the leaves were evaluated on the basis of the content of the individual elements. Differently coloured parts of the leaves of variegata type show differences not only in morphology and structure but also in their metabolic activity.