bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Studying Photosynthetic Capacities of Unicellular Algae Based on in vivo Chlorophyll Fluorescence
Authors: SAMUELSSON GÖRAN , ÖQUIST GUNNAR 
Published: April 2006

AbstractThe correlation between photosynthesis and DCMU‐induced fluorescence increase has been studied in four species of unicellular green algae from inoculation of the cultures to the stationary growth phase. The fluorescence increase induced by DCMU was high in exponentially growing cultures but decreased when the cultures approached the stationary phase of growth. Because of the good correlation between photosynthesis and DCMU‐induced fluorescence increase, the fluorescence technique is a promising method for describing changes in photosynthetic capacities of algal populations in natural waters.
Selective Degradation of Wood Components by White‐Rot Fungi
Authors: ANDER PAUL , ERIKSSON KARL‐ERIK 
Published: April 2006

AbstractIn order to find naturally occurring white‐rot fungi which preferentially degrade lignin. 25 different species of such fungi were cultivated on pine wood blocks and on kraft lignin agar plates with and without cellulose. Due to differences in phenol oxidase reactions on the kraft lignin agar plates, the 25 fungi could be divided into two groups, 1 and 2, which also differed in other properties. The three Group I fungi Sporotrichum pulverulentum, Phanerochaete sp. L1 and Polyporus dichrous produced high levels of endo‐l,4‐β‐glucanase and cellobiose:quinone oxidoreductase in shaking cellulose flasks and a low level of phenol oxidase in standing wood meal flasks, The four fungi Merulius tremellosus, Phlebia radiata, Pycuoporus cinnabarinus and Pleurotus ostreatus from Group 2, on the other hand, produced low levels of endo‐1,4‐β‐glucanase and cellobiose:.quinone oxidoreductase in the cellulose. flasks and a high level of phenol oxidase in the wood meal flasks.Analyses of pine wood blocks degraded by the above‐mentioned fungi in the presence of either malt extract, asparagine or NH4H2PO4 revealed that malt extract gave good lignin degradation. In the presence of this nutrient source. P. cinnabarinus, at 3.4% weight loss, even degraded 12.5% lignin without loss of cellulose or mannan. No common degradation pattern was, however, obtained using mall extract, asparagine or NH4H2PO4, It is suggested that while‐rot fungi, which preferentially degrade lignin, may be found among Group 2 fungi producing large amounts of phenol oxidases.
Changes in the Protein Composition of the Shoot Apical Bud of Sinapis alba in Transition to Flowering
Authors: PIERARD D. , JACQMARD A. , BERNIER G. 
Published: April 2006

AbstractVegetative plants of Sinapis alba L. grown in short days were induced to flower by expsoure to one or continuous long days. In both inductive conditions, the first flowers were initiated about 60 h after the start of the treatment. Soluble protein extracts were prepared from apical buds and just‐expanded leaves of both vegetative and induced plants. Rabbit antisera were prepared using extracts from vegetative and reproductive buds. Immunodiffusion tests were performed. Analysis of the precipitin bands indicated that: (1) one antigenic protein was present in the vegetative buds and disappeared from the buds of induced plants between 96 and 240 h after the start of the inductive treatment; (2) the concentration of a another antigenic protein increased in buds of induced plants 30 h after the start of the inductive treatment; (3) the concentration of a third antigenic proteín increased in buds of induced plants at 96 h.
Dehydration of Onion Cells: A Comparison of Freezing vs. Desiccation and Living vs. Dead Cells
Authors: PALTA J. P. , LEVITT J. , STADELMANN E. J. , BURKE M. J. 
Published: April 2006

AbstractMeasurements were made of the amount of liquid water present in the epidermal cells of onion at various degrees of dehydration caused by slow extracellular freezing and by desiccation. This was achieved by using a pulsed NMR spectrometer during freezing stress and by weighing the epidermal pieces during desiccation. Measurements were made on the extent of cell survival by direct microscopic observation (plasmolysis and protoplasmic streaming).Onion epidermal cells (Allium cepa L. cv. Downing Yellow Globe) were found to survive freezing temperatures as low as –20°C and an equivalent desiccation stress. This equivalence opposes the reports by others on Hordeum vulgare and on Solanum sp. of greater injury by freezing than by an equivalent dehydration due to desiccation. The discrepancy ‐has been explained in terms of the limitations of the conductivity method used by those authors to evaluate the injury.The freezing and desiccation curves correspond to the equation: L
t=L0Δtm/t+Luwhere Lt and L0 are the amounts of liquid water at temperature t and O°C respectively. Δtm is the freezing point depression of the cell sap and Lu is the amount of liquid water which does not freeze.These results demonstrate that the dehydration of onion cells during both freezing and desiccation duplicates the dehydration of ordinary aqueous solutions. This was equally true for living and dead cells, and suggests that the negative turgor invoked by others is not significantly involved in the dehydration of living Allium cepa epidermis cells. An explanation is proposed for these contradictory results.
Light‐Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii
Authors: HARIRI M. , BRANGEON J. 
Published: April 2006

AbstractThe influence of different growth irradiance conditions on plant development and foliar features were assessed in a shade‐adapted fern variety, Pteris cretica var. ouvrardii. A comparison of frond morphology, anatomy, chloroplast infrastructure and chlorophyll content of plants cultivated in both greenhouse and in controlled growth chambers under moderate light, low light (control) and extreme shade revealed pronounced phenotypic modifications. Moderate light induced decreased frond surfaces, thicker leaves, lower chlorophyll content per surface unit, and a markedly reduced density of intraplastidial membranes. In contrast, morphological responses to extreme shade included the formation of larger, thinner fronds, increased chlorophyll content; and a higher membrane density in chrloplasts. A dorsi‐ventral distribution of starch‐gorged chlroplasts (lower mesophyll cell layers) and essentially starch‐free chloroplasts (upper cell layer) characterizes low‐light and moderate light fronds, while homogenous starch‐free chloroplasts are present in all cell layers of extreme shade fronds. The light‐induced modifications are discussed as adaptive responses.
Influence of Chilling on Electrolyte Permeability, Oxygen Uptake and 2,4‐Binitrophenol Stimulated Oxygen Uptake in Leaf Discs of the Thermophilic Cucumis sativus
Authors: TANCZOS OTTO GY. 
Published: April 2006

AbstractThe effect of chilling was studied in leaf discs from the chilling‐sensitive Cucumis sativus L. by measurement of the electrolyte leakage from the discs, by oxygen uptake and by uncoupling of respiration with 2,4 dinitrophenol. Short periods of chilling are characterized by minor significant increases of electrolyte permeability, of respiration and of preserved ability to be uncoupled by 2,4‐dinilrophenol. A longer period of chilling resulted in a strongly increased electrolyte permeability, in reduced oxygen uptake and in disappearance of uncoupling by 2,4 dinitrophenol. In general the induced changes in permeability and respiration were reversible within 4 days of chilling, if the discs were placed at 25°C after chilling.
Germination of Wild Rice, Zizania aquatica, Seeds and the Activity of Alcohol Dehydrogenase in Young Seedlings
Authors: CAMPIRANON SAMPUN , KOUKKARI WILLARD L. 
Published: April 2006

AbstractSeeds of wild rice (Zizania aquatka L.) which were stored at 3°C for c. 3 months after harvest did not germinate until portions of seed coat above the embryo region were removed. During the iirst few days following germination there was no apparent difference between seedlings germinated under normal, aerated and anaerobic conditions. After 14 days, plants maintained under well aerated conditions were the most fully developed. Unlike shoot growth, roots did not develop under reduced aeration.The activity of alcohol dehydrogenase (ADH) in extracts obtained from young Zizania seedlings was highly specific for ethanol as a substrate, for NAD as the coenzyme, and the optimum pH was c. 9.1. Enzyme activity changed with stage of growth and development, reaching maximum activity 8 days after germination. Aeration strongly inhibited ADH activity. Under anaerobic conditions the activity of ADH increased several fold over the activity of ADH extracted from shoots of seedlings maintained under normal conditions.
Nucleic Acid Metabolism in the Developing Primary Leaf and Senescing Coleoptile of Germinating Oats
Authors: TESTER C. F. 
Published: April 2006

AbstractNucleic acid metabolism in the coleoptile and primary leaf tissues of the germinating oat (Avena sativa L.) seedling was studied. The concentrations of the different species of nucleic acid present at various stages of development were determined and the amounts of each compared. All species of nucleic acid in the coleaptile increased as the tissue elongated; but, with the onset of senescence all species decreased, especially rRNA. Exposing dark grown coleoptiles to light did not modify their capacity to synthesize nucleic acids. In the rapidly developing leaf, all species of nucleic. acid increased throughout early germination. A general enhancement in the synthesis of all species of nucleic acids resulted when dark‐grown‐leaves were exposed to light. Furthermore, the tRNA/DNA ratio remained constant in both tissues during development, whereas the rRNA/DNA ratio changed.
Stomatal Response to Humidity and Lanthanum
Authors: HALL ANTHONY E. , THOMSON WILLIAM W. , ASBELL CHARLES W. , PLATT‐ALOIA KATHRYN , LEONARD ROBERT T. 
Published: April 2006

AbstractLanthanum fed to the base of excised leaves of Sesamum indicum L. and Helianthus annuus L. was used as a tracer to investigate by electron microscopy the path of water in the apoplast of leaves. The generally random distribution of lanthanum in cell walls provided no support for the hypothesis that cuticular transpiration may be greater for guard cells than for adjacent epidermal cells. Occasionally, accumulations of lanthanum were observed in anticlinal walls of epidermal cells and at the outer surface of the plasma membrane but lanthanum was not observed in the symplast.The influx of 86Rb to excised roots of sesame and sunflower was inhibited during incubation with 0.5 mM lanthanum or calcium for 15 or for 180 min. Stomata of sunflower partially closed when 2.5 mM lanthanum was supplied to the base of excised shoots in a potometer, whereas this treatment had little effect on stomatal conductance of sesame shoots maintained in a constant environment. Supplying 2.5 mM lanthanum to the base of sesame shoots strongly inhibited stomatal opening response to increase in ambient humidity but had little effect on stomatal opening response to light. It was concluded that stomatal opening response to increased humidity may be dependent upon some process, such as ion influx, that is inhibited by lanthanum, and that opening response to humidity may differ in mechanism from stomatal opening response to increased irradiance.
Effect of Periodic Oscillations of Artificial Light Emission on Photosynthetic Activity
Authors: GAUDILLÈRE JEAN PIERRE 
Published: April 2006

AbstractThe effects of periodic oscillation of artificial light and of the frequency of these oscillations on photosynthetic assimilation has been measured. When the frequency is sufficiently high, the gross CO2 assimilation in fluctuating light is identical to the assimilation of the leaf under a continuous illumination equal to the efficient intensity of the intermittent light. It is necessary to consider the quality of the sensor used for measuring light intensity, particularly its response velocity.
Potassium Absorption by Rice at Different Levels of Organization
Authors: ERDEI LÁSZLÓ , ZSOLDOS FERENC 
Published: April 2006

AbstractA study was made of the effects of temperature and calcium on the properties of K+ transport in rice roots (Oryza sativa L. cv. Dunghan Shali), in cell suspension culture of rice and in callus cultures. The rates of influx and efflux of K+ were measured by using 86Rb as tracer, and the net change in K+ content was determined by atomic absorption spectrophotometry. In roots of low salt status the K+ transport mechanism exhibits a positive temperature dependence and calcium exerts a stimulation. In cell and callus cultures a transport mechanism of this kind is lacking, and the K+ fluxes are inhibited by calcium and independent of temperature. Chilling‐induced K+ leakage is similar for both types of tissue, and can be characterized by a negative temperature‐coefficient and the inhibitory effect of calcium.
Photosynthetic Electron Transport in Shoots of Sitka Spruce from Different Levels in a Forest Canopy
Authors: LEWANDOWSKA M. , HART J. W. , JARVIS P. G. 
Published: April 2006

AbstractShoots from the lower levels of a Sitka forest canopy [Picea sitchensis (Bong.) Carr.] have much lower photosynthetic capacities per unit leaf area than do those from the top of the canopy. Chloroplast fragments have been isolated from the needles at three levels in the canopy and Photosystem I and Photosystem II activities measured. Measurements were made at eight photon flux densities giving light response curves for photosystem activity in the three canopy levels. Expressed per unit leaf area, light‐saturated activities of Photosystem I and II were lower at the bottom of the canopy than at the top suggesting that photosystem activity might be limiting photosynthesis in the shoots from the bottom of the canopy. Chlorophyll concentration per unit fresh weight did not vary amongst the three levels, but specific leaf area increased and dry weight fraction decreased with increasing depth in the canopy, leading to a large reduction with depth in chlorophyll content per unit leaf area.
Influence of Mechanical Stress on Auxin‐Stimulated Growth of Excised Pea Stem Sections
Authors: MITCHELL CARY A. 
Published: April 2006

AbstractThe growth rate of etiolated pea (Pisum sativum L. cv. Alaska) seedlings was reduced by a single gentle mechanical disturbance, with thigmo (contact)‐stress more effective than seismo (vibrational)‐stress, and manipulation of the hook more effective than of the epicotyl. Manual stimulation of the apical hook progressively altered the auxin‐dependent growth of excised stem sections with increasing time between treatment and cutting sections. Stress treatment initially stimulated in vitro growth of stem sections cut from the first 5 mm of tissue below the hook during the first 8 h after cutting, but inhibited growth if cut after 8 h. Growth of sections cut from the second 5 mm of tissue was progressively inhibited with time between treatment and cutting sections. Basal (minus auxin) section growth was unaffected by stress, indicating that stress response was specific for the auxin‐dependent component of growth. Hook removal or ethylene pretreatment of seedlings had the same effects with time on section growths as did thigmo‐stress of the hook, suggesting reduced movement of growth promoters from the apex. Seismo‐ or thigmo‐stress of the inact plant also inhibited polar auxin transport by stem sections. An auxin‐ethylene interaction is implicated to be involved in mechanical stress growth reduction.
Callus Formation and Embryogenesis of Endosperm Tissues of Parsley Seed Cultured on Hormone‐Free Medium
Authors: MASUDA KIYOSHI , KODA YASUNORI , OKAZAWA YOZO 
Published: April 2006

AbstractEmbryogenic callus was induced by culturing endosperm tissues of germinating parsley seeds on Murashige‐Skoog's basal medium without any exogenous supply of growth substances. No deterioration of the embryogenic potential of this callus strain was observed on this medium for more than half a year through several passages. The endosperm callus consisted of approximately triploid cells, but diploid ones predominated in the embryos originated from this callus.
The Photostability of Different Chlorophyll Forms in Dark Grown Leaves of Wheat
Authors: AXELSSON LENNART 
Published: April 2006

AbstractThe stability against high intensity irradiation (red light, 700 W m2) was investigated for the chlorophyll(ide) pigments formed after photoreduction of the protochlorophyllide in dark grown leaves of wheat. Connections were found between changes in absorption spectrum in vivo (the Shibata shift and the late red‐shift) and changes in photostability both in young (five‐day) and old (12‐day) leaves. The photostability of both the 684‐form and the 673‐form as well as the rate of the changes in photostability (the Shibata shift and the late red‐shift) decreased with the age of the dark grown plants. It was concluded that the more pronounced decrease in the chlorophyll(ide) contents found at irradiation of older dark grown leaves mostly depended on the lower rate of the changes in the photostability of the pigment in old leaves. No resynthesis of protochlorophyllide occurred before the onset of the late red‐shift. The results and their connection with the lag in chlorophyll formation are discussed. This lag is more pronounced in older dark grown wheat.
Migrations Orientées et Phytohormones — Valeur de la Feuille Détachée comme Matériel Expérimental
Authors: PENOT M. , BERAUD JACKY 
Published: April 2006

Abstract Directed Transport and Hormones — Value of Isolated Leaf as Experimental Material.Local application of aqueous phytohormonal solution (0.1 ml of various concentrations, from 50 to 0.025 mg‐l−1, of IAA, 2,4‐D, NAA, BAP, GA3) on isolated leaves influences the direction of ion transport. All tested hormones are efficient but the action depends upon the ionic species [positive action with 32P, 35S, 36Rb (K), but null with 45Ca or 46Cl]. The movement of ions occurs through the phloem tissue and is not a cell‐to‐cell transfer. Competition between different parts of the leaf is demonstrated (a) between petiole which appears to be an important attractive centre and other parts of the leaf; (b) in a depetioloted leaf, between different centres induced by different phytohormones. In this respect, GA3 appears to be the most efficient hormone in the tested material — leaves of Pelargonium zonale (L.) Aiton.The effects on directional transport are discussed in relation to other processes controlled by hormones, for instance growth, senescence, protein synthesis. A direct relation of directional transport with growth or delay of senescence may be discarded. The value of isolated leaves as simplified experimental systems is underlined by the fact that weak hormonal doses are efficient (0.025 mg.l for GA3 and 0.5 mg.1 for 2,4‐D) as compared to the higher doses used in other plant systems.
Changes in the Composition of Cell Wall Polysaccharides of Suspension‐cultured Vinca rosea Cells during Culture
Authors: TAKEUCHI YUICHI , KOMAMINE ATSUSHI 
Published: April 2006

AbstractIn a suspension culture of Vinca rosea L. three distinct growth phases were distinguished: a cell division phase, a cell expansion phase, and a stationary phase. At various stages of the growth cycle, extra‐cellular polysaccharides (ECP) and cell wall were isolated and their compositions were investigated. ECP are mainly composed of xyloglucan, 3,6‐linked arabinogalactan, and polyuronide. From the results of gas chromatographic analyses of sugars and partially methylated sugars in each fraction of cell wall polysaccharides, the following changes were observed in the composition of cell wall polysaccharides during culture: (1) a decrease in polyuronide content, (2) a decrease in non‐cellulosic glucan content, (3) an increase in xyloglucan content, and (4) an increase in a‐cellulose content. The significance of the changes is discussed in relation to the growth of cells.
Some Morphological and Biochemical Characteristics of C3 and C4 Plants Irradiated with UV‐B
Authors: BASIOUNY FOUAD M. , VAN T. K. , BIGGS R. H. 
Published: April 2006

AbstractFour C3 and two C4 plants were subjected for 350 h to an enhanced UV‐B radiation (280 to 310 nm) regime simulating a 0.18 atm. cm ozone level (solar angle 55°) in growth chamber. Different degrees of response among plant species were observed. UV‐B radiation reduced plant height, fresh and dry weight, protein content, total chlorophyll, inhibited net CO2 uptake and the Hill reaction activity. Some broad‐leaved species with C3 type of carbon assimilation were more susceptible to UV‐B alterations of morphological and biochemical characteristics than the narrowleaved species with C4 type photosynthesis.
Light‐Induced Hg Volatilization and O2 Evolution in Chlorella and the Effect of DCMU and Methylamine
Authors: BEN‐BASSAT D. , MAYER A. M. 
Published: April 2006

AbstractThe rate of volatilization of Hg2+ as metallic Hg is accelerated by illumination of Chlorella cells. In the presence of the uncoupler methylamine the rate of volatilization in the light is greatly but transiently increased. DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea) prevented the light response. In the presence of Hg2+, O2 evolution by the cells was not completely inhibited by DCMU. Hg2+ appears to prevent DCMU reaching its binding site. Light seems to increase the amount of or leakage from the cells of a metabolite capable of reducing Hg2+ to Hg°.
Induction of Adventitious Buds on Undetached Leaves, Excised Leaves and Leaf Fragments of Heloniopsis orientalis
Authors: KATO YUKIO 
Published: April 2006

AbstractAdventitious buds were induced on intact, undetached leaves, isolated leaves, and both green and etiolated leaf fragments excised from young plants of Heloniopsis orientalis (Thunb.) C. Tanaka (Liliaceae) in darkness. Morphactin promoted bud initiation on undetached leaves. The regeneration loci on excised leaves were different in darkness and in light, and they were also modified by etiolation and by morphactin or benzyladenine. Experiments with pre‐incubation in darkness, with successive treatments by sorbitol and sucrose, and with DCMU‐treatment in light, led to the conclusion that bud formation on isolated leaves and leaf fragments is controlled by a photosynthetic system as well as the hormonal level.
Composition of Bleeding Sap in Vigna radiata
Authors: SINHA S. K. , KHANNA‐CHOPRA RENU , CHATTERJEE S. R. , ABROL Y. P. 
Published: April 2006

AbstractBleeding sap and nodules from Vigna radiata were analysed for their free amino nitrogen content and amino acid composition at different stages of growth and development. The bleeding sap contained mostly basic amino acids, whereas the nodules contained both acidic and basic amino acids. The amino nitrogen content of the bleeding sap increased during growth and then declined appreciably during fruit development. In contrast, nodule amino nitrogen declined from seedling stage onwards till flowering, increased during fruit development and then declined again. Nitrate reductase activity in the leaves examined at different stages of development increased from seedling stage onwards and was maximum during early fruit‐development stage. It declined during pod‐filling stage. The study suggests that the amount of nitrogen fixed from the atmosphere is insufficient, so that the plant has to draw upon soil nitrogen as well. This may be necessary due to the high demand of nitrogen during pod filling.