bluuebunny/crossref_metadata_2025 huggingface dataset:
NADH and NADPH Dependent Malate Dehydrogenases of Phaseolus vulgaris
Authors: VIDAL JEAN , GADAL PIERRE , CAVALIE GERARD , CAILLIAU‐COMMANAY LUCIENNE
Published: April 2006

French bean (Phaseolus vulgaris L. cv. Contender) leaf extracts catalyse the reduction of oxaloacetate to malate in the presence of NADH and NADPH. Under the experimental conditions used, the optimum pH values are 8 and 6 respectively. After chromatography on diethylaminoethyl cellulose, two principal forms of NADH‐MDH (L‐malate: NAD+ oxidoreductase, E.C. 1.1.1.37) upon which NADPH activities are superposed, can be characterized. This result is confirmed by electrophoresis on polyacrylamide gel. On the other hand, after filtration on Ultrogel 34, NADH‐MDH is eluted as a single peak; once again, NADPH activity is associated with it. When PtCl2−4, a powerful inhibitor of MDH, is added to the reaction medium, the degree of inhibition is the same irrespective of the cofactor employed. When root extracts are submitted to chromatography on diethylaminoethyl cellulose, activity profiles are identical to those obtained with leaves. These results suggest that the NAD dependent enzymes can also utilize NADP to reduce oxaloacetate. After addition of dithiothreitol, another NADPH‐MDH activity manifests itself in the leaf extracts; it differs from the foregoing ones in its optimum pH, its chromatographic properties and its response to PtCl2−4 action. Root extracts do not exhibit this activity thus showing a specific localization of this enzyme in the green part of the plant.
Reduction of Mercury Chloride by Chlorella: Evidence for a Reducing Factor
Authors: BEN‐BASSAT D. , MAYER A. M.
Published: April 2006

Evidence is brought for the presence of low molecular weight, heat stable, mercury reducing factors in Chlorella cells. Some of the properties of these factors, which appears to be normal metabolities, are described. These factors are also present in the medium in which the cells grow. The reduced mercury, Hg0, is volatilized from the culture medium more rapidly than Hg+2. The resultant decrease in the Hg concentration appears to be the main reason for the recovery of the cells from Hg stress. No resistance to Hg developed in cells emerging from the stress.
Hypoxic Quiescence in Alligatorweed
Authors: QUIMBY P. C. , KAY S. H.
Published: April 2006

Propagules (stem cuttings) of alligatorweed [Alternanthera philoxeroides (Mart.) Griseb.] were subjected to various treatments of submergence, emergence, light, dark, and oxygen to relate hypoxia to the suppression of alligatorweed growth by dark submergence. In the dark, submergence completely inhibited alligatorweed growth. A nitrogen atmosphere inhibited growth from emersed propagules in the dark. The suspension of growth by dark submergence was relieved by light (40 μ einsteins/m2× s photo‐synthetically active radiation), emergence (whereby air is transported to underwater nodes via the aerenchyma), or exposure to 100 mg · l‐1 of hydrogen peroxide solution renewed at 48‐h intervals. Suspension of growth by a nitrogen atmosphere was relieved by inclusion of 16% oxygen in the ambient atmosphere. Dark to light transfers showed that the suspension of growth was immediately relieved if the requisite conditions were restored; this phenomenon, as described, thus appears to be hypoxic quiescence. The suppression of growth of two other amphibious species, mild smartweed (Polygonum hydropiperoides Michx.) and creeping water‐primrose (Jussiaea repens L. var. glabrescens Ktze.), by dark submergence suggests that hypoxic quiescence may be a factor in the life history of amphibious species other than alligatorweed.
Tryptophansynthase in Phycomyces blakesleeanus Teil I: Eigenschaften des Enzyms
Authors: HILGENBERG WILLY , HOFMANN FRIEDER
Published: April 2006

Tryptophan synthase in Phycomyces blakesleeanus. Part I: Characterization of the enzyme.

Tryptophan synthase was tested in light grown 5 days old cultures of Phycomyces blakesleeanus.

The test was carried out only by reaction 3 (indole + serine → tryptophan + water) of the tryptophan synthase. The Km values for the substrates indole and serine were found to be 1.3 × 10‐4M and 1.0 × 10‐2M. Two Km values (1.5 × 10‐8M and 1.0 × 10‐6M) for pyridoxal 5′‐phosphate could be calculated from a Lineweaver‐Burk plot. The transformation of the Lineweaver‐Burk plot into the Hill plot resulted in a straight line with a rise of 0.35 for pyridoxal 5′‐phosphate. At higher concentrations the end product tryptophan and indole‐3‐acetic acid inhibit the tryptophan synthase in vitro.
Ion Uptake in Higher Plants and KCl Stimulation of Plasmalemma Adenosine Triphosphatase: Comparison of Models
Authors: NISSEN PER
Published: April 2006

Criteria for the acceptance or rejection of the dual, the cooperative, and the multiphasic model of ion uptake are given and are used to evaluate the models on the basis of previously published analyses. In addition, mathematical representations of the models are fitted to concentration‐dependence data for various ions and plant tissues by a general curve fitting program. The calculated parameters are evaluated for biological relevance, and the fit is compared by statistical analysis. The kinetics of ion uptake in higher plants are found to be consistent with the concept of multiphasic uptake mechanisms, while the dual and the cooperative model must be rejected. KCl stimulation of plasmalemma‐bound ATPases is also shown to obey multiphasic kinetics, thus strengthening the correlation between ion uptake and membrane‐bound ATPases.
Change in Molecular Size of Cellulose during Regeneration of Cell Wall on Carrot Protoplasts
Authors: ASAMIZU TETSUYA , TANAKA KEIICHI , TAKEBE ITARU , NISHI ARASUKE
Published: April 2006

Protoplasts isolated from carrot cells were cultured in a chemically defined medium. The majority of them regenerated cell wall and underwent cell division. Cellulose synthesis started without a noticeable lag but the rate of deposition was very low during the initial stage. The degree of polymerization of cellulose was determined by viscosity measurement of the nitrated product. The cellulose formed in the early stage of the wall regeneration consisted mainly of low molecular weight glucan chains. Change in the average molecular weight of cellulose was found during the growth cycle of carrot cells in normal suspension culture.
Alterations in Activity of Phosphatases during the Peridinium Bloom in Lake Kinneret
Authors: WYNNE DAVID
Published: April 2006

Acid and alkaline phosphatases have been isolated from Peridinium cinctum f. westii (Dinophyceae) during an algal bloom in Lake Kinneret. Acid phosphatase activity was fairly constant over the entire period of the bloom, although fluctuations in activity appeared to correlate with the chlorophyll content of the cells. Histochemical studies showed that the enzyme was localized inside the cell. Alkaline phosphatase activity was very low until May, a month after the peak of the bloom, when it increased sharply. Polyacrylamide gel electrophoresis revealed one or two bands of alkaline phosphatase that increased in intensity as the bloom progressed. However, the highest activity of the enzyme (in the last sample collected) corresponded to a new, very intense band on the gels. Similarly to acid phosphatase, alkaline phosphatase was also localized inside the cell. The appearance of alkaline phosphatase is probably related to the available phosphate concentration in the lake, although the influence of other factors that may contribute to the induction of the enzyme cannot be ruled out.
Abscisic Acid and Gibberellin‐in Three Ungrafted Apple (Malus sylvestris) Rootstock Clones
Authors: YADAVA U. L. , LOCKARD R. G.
Published: April 2006

ABA and gibberellin‐like substances were extracted from roots, shoots, and leaves of most dwarfing M9, semi‐dwarfing MM 106, and least dwarfing MM111 apple rootstock plants. Among tissues, the roots contained the largest and the shoots the smallest amounts of all the phytohormones studied. Plants of M9 contained the highest and MM111 the lowest ABA‐like substances in all tissues tested. Gibberellin4+7‐like compounds were at the highest levels in the roots of MM111 and lowest in the roots of M9, whereas GA3‐like substance was in the reverse order. All three gibberellin‐like compounds were highest in the shoots and leaves of MM111 and lowest in the respective tissues of M9 clone. Role of these phytohormones in the dwarfing mechanism is discussed.
Tryptophansynthase in Phycomyces blakesleeanus, Teil II: Tryptophansynthaseaktivität des Pilzes in Abhängigkeit von Lichtbedingungen und vom Zinkgehalt des Kulturmediums
Authors: HILGENBERG WILLY , HOFMANN FRIEDER
Published: April 2006

Tryptophan synthase in Phycomyces blakesleeanus. Part II: Activity of tryptophan synthase in Phycomyces blakesleeanus depending on the light and the content of zinc ions in the culture medium

Five‐day‐old cultures of Phycomyces blakesleeanus show notice‐able differences in the phenotype, depending on the culture conditions (permanent light, permanent dark, zinc deficiency, zinc sufficiency) and related to the distribution of tryptophan synthase activity between mycelium and sporangiophores. Permanent light and the presence of zinc ions in the medium during culturing have an antagonistic influence on the tryptophan synthase. The activity of the enzyme is being reduced in the sporangiophores and increased in the mycelium by the influence of light, while zinc ions in the culture medium increase the activity in the sporangiophores at simultaneous reduction in the mycelium.

The importance of tryptophan synthase and tryptophan for the development of the fungus in relation to the metabolism of indole acetic acid is discussed.
Changes in Ribonuclease Activity and Content of RNA during Dormancy and Growth of Bird‐cherry Buds
Authors: EKELUND R.
Published: April 2006

Ribonuclease has been extracted from buds of bird‐cherry (Prunus padus L.) by a three‐step method. In step 1 ribonuclease was extracted from the homogenized tissue at pH 6. In step 2 the tissue residue from (1) was extracted at pH 7. In step 3 the tissue residue from (2) was extracted with a buffer of pH 8.5 and containing 0.7 M KCl. The ribonuclease from step 1 and 2 is named soluble and that from step 3 bound ribonuclease. The activity of the soluble ribonuclease was very low in October and increased slowly until March. When the buds sprouted in April the activity of this fraction rose rapidly. The activity of the bound ribonuclease was rather high in October and increased continuously from autumn to spring. RNA accumulated slowly between autumn and spring. The change in activity of the two ribonuclease fractions is discussed in relation to development.
Genotypic Responses to Auxins in Tissue Cultures of Phaseolus
Authors: MOK MACHTELD C. , MOK DAVID W. S.
Published: April 2006

Responses of seven Phaseolus genotypes to the four auxins picloram, 2,4‐D, NAA and 1AA, in tissue cultures, were examined. Callus growth was promoted by picloram and the range of effective concentrations for most genotypes was broad. The auxin 2,4‐D also enhanced callus growth, but the range of optimal concentrations was markedly narrower than that of picloram. NAA when supplied at relatively high concentrations gave good growth. IAA was ineffective in supporting callus growth. The differences in 2,4‐D concentrations required for optimal growth and the differential responses to low concentrations (0.04–1.25 μM) of picloram between several genotypes tested were large. These genotypic variations in auxin responses were repeatable and may thus reflect genetic differences.
ADP, AMP and Pi interactions with a (Na++ K++ Mg2+)‐dependent ATPase in sugar beet roots
Authors: LINDBERG SYLVIA , BJÖRKLUND GUN
Published: April 2006

A dithiothreitol treated membrane fraction of sugar beet roots contains (Na++ K++ Mg2+)‐ATPase activity. Product inhibition of the ATPase activity was studied. This led to the following conclusions: 1) ADP is a competitive inhibitor to MgATP in presence or absence of Na+ and/or K+. 2) ADP does not interact with the Na or K site. 3) AMP has little influence on the velocity. 4) Little AMP is released, and the ratio between ADP and Pi release is approximately 1. 5) Pi is a weak noncompetitive inhibitor to MgATP. 6) Pi is probably released before ADP from the Enzyme–MgATP complex.
Photosynthesis of Conifers in Relation to Annual Growth Cycles and Dry Matter Production
Authors: FRY D. J. , PHILLIPS I. D. J.
Published: April 2006

Observations that deciduous and evergreen conifers growing in Britain show similar annual growth increments, despite marked differences in short‐term growth rates, led to a comparative study of seasonal photosynthetic capacity in established trees of four coniferous species with contrasting growth habits. The photo‐synthetic data were compared with seasonal changes in environmental parameters and chloroplast ultrastructure. The maximum net photosynthetic rates (at 20°C) recorded for Larix leptolepis were higher than those for the evergreen conifers when expressed on a leaf weight basis but not when expressed per unit leaf area. The photosynthetic efficiency of new needles in the evergreen species showed an overall decline from just after needle maturity until just before budbreak in their second season, after which photosynthetic rates recovered temporarily, approaching previous maximum levels. There was no obvious correlation between seasonal photosynthetic efficiency (at 20°C) on the one hand, and daily air, and (30 cm) ground temperatures on the other, and there was no obvious winter suppression of evergreen photosynthetic rates. Evergreen needles showed starch loss and some membrane changes with the onset of winter, but there was no evidence for wintertime chloroplast clumping or membrane disruption.
Interactions of Abscisic Acid, Cytokinin and Gibberellin in the Control of Betacyanin Synthesis in Seedlings of Amaranthus caudatus
Authors: BIDDINGTON N. L. , THOMAS T. H.
Published: April 2006

In de‐rooted seedlings of Amaranthus caudatus L., betacyanin synthesis induced by white light or cytokinin was inhibited by abscisic acid (ABA) or a mixture of gibberellins A4 and A7 (GA4/7). The GA4/7 and ABA effects were additive. Thus ABA inhibited the cytokinin action but had no effect on the gibberellin response.
A Method for Studying Photosynthetic Capacities of Unicellular Algae Based on in vivo Chlorophyll Fluorescence
Authors: SAMUELSSON GÖRAN , ÖQUIST GUNNAR
Published: April 2006

The 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

In 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

Vegetative 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

Measurements 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+Lu

where 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

The 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

The 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

Seeds 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

Nucleic 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

Lanthanum 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

The 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

A 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

Shoots 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

The 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

Embryogenic 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

The 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

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

In 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

Four 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

The 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

Adventitious 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

Bleeding 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.
Mechanism of Senescence Induction by Silicone Oil
Authors: NAIM RAFI , NEUMANN PETER M.
Published: April 2006

The physiological basis for senescence symptoms induced by spraying attached primary leaves of bean plant (Phaseolus vulgaris L. cv. Brittlewax) with silicone oil emulsions was investigated. It was found that chlorophyll levels declined significantly between 24 and 48 h after spraying, whereas neither protein levels nor respiration rates were affected over a 7‐day period. Rates of photosynthesis and reducing sugar levels in silicone‐sprayed leaves were however significantly reduced after 1 and 24 h respectively. These responses were obtained using plants grown under low stress controlled environment conditions. By contrast, leaves on greenhouse plants did not senesce in response to silicone sprays. A possible mechanism of silicone oil action based on selective leaf penetration and inhibition of photosynthesis is postulated.
The Location of Cytokinins and Gibberellins in Wheat Seeds
Authors: THOMAS T. H. , KHAN A. A. , O'TOOLE DIANE F.
Published: April 2006

Wheat seeds (Triticum aestivum L. cvs. Yorkstar and Sirius) were cut transversely into embryoless and embryo‐containing (embryonated) halves and the content of endogenous cytokinins and gibberellins in both halves determined before and after the seeds imbibed water for 12–15 h at 22°C in the light. Dry seeds contained little ethyl acetate‐extractable gibberellin activity as measured by bioassay but n‐butanol‐soluble cytokinins were detected mainly in the embryoless halves. Dry, embryonated half‐seeds contained water‐soluble gibberellins which could be extracted into acidic ethyl acetate after treatment of the aqueous extract with either alkaline phosphatase, β‐glucosidase or a crude pectolytic enzyme preparation.

When half‐seeds were allowed to imbibe water for 12 h and then extracted, cytokinin activity was largely lost from the embryoless halves and completely from the embryonated halves and water‐soluble gibberellins were also lost from the embryonated halves. However, ethyl acetate‐soluble gibberellins were present in the latter suggesting that “bound’ gibberellins were released during imbibition. The hormones present in normal and naturally embryoless dry grains of cv. Yorkstar were also determined. Both gibberellin and cytokinin activity was higher in normal grains suggesting that the presence of an embryo is essential for synthesis or accumulation of these hormones in the grain during development.
Properties of Invertases in Sugar Storage Tissues of Citrus Fruit and Changes in Their Activities during Maturation
Authors: KATO TADASHI , KUBOTA SHUJI
Published: April 2006

Both acid and alkaline invertases were present in immature juice sacs of satsuma mandarin (Citrus‘Unshu Marcovitch”) fruit, in which sugar content was low. Maturing and mature juice sacs, in which sugar content increased steadily with time, were characterized by the presence of alkaline invertase and the absence of acid invertase.

When the immature juice sacs were homogenized with 0.2 M sodium phosphate‐citrate buffer (pH 8.0), almost all of the acid invertase activity was found in the solubilized fraction, whereas almost all of the alkaline invertase activity was present in the insoluble fraction. The distribution of alkaline invertase between the solubilized and insoluble fractions changed with the development of fruit.

The acid invertase had a molecular weight of 69,000, optimum pH of 4.8–5.3, and Km value for sucrose of 7.3 mM. The alkaline invertase had a molecular weight of 200,000, pH optimum of 7.2–7.7, and Km value of 35.7 mM. The hydrolysing activities of both enzymes for raffinose were considerably less than those for sucrose. The alkaline invertase had lower activity for raffinose than the acid invertase.
Kinetic Measurements of Small Ethylene Changes in an Open System Designed for Plant Physiological Studies
Authors: DE GREEF J. A. , DE PROFT M.
Published: April 2006

Based upon the method we developed to measure ethylene in very low concentrations (as low as 0.01 ppb in the ambient atmosphere) an experimental chamber was constructed and integrated in the measuring system for plant physiological studies. Parameters influencing the accuracy of the technique are evaluated. The pressure in the plant chamber increased 0.05 atm at a flow rate of 10 1/h during ethylene trapping. At this flow rate the ethylene production per seedling is independent of the number of seedlings used. The ethylene measured per seedling is directly proportional to the length of trapping time. Under standard conditions of chamber configuration and volume very small changes in ethylene content can be detected accurately in a very short time range. Our experimental arrangement allows kinetic studies of ethylene evolution by biological objects in a qualitative and quantitative manner. All methods used heretofore are more complicated and less accurate compared to the measuring system presented here. Its versatility is demonstrated for both in vitro and in vivo studies of ethylene production by bean seedlings. The application fields of the apparatus are discussed.
Light‐Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii
Authors: HARIRI M. , PRIOUL J. L.
Published: April 2006

The photosynthetic capabilities of the fern Pteris cretica var. ouvrardii were analysed by means of the light response curves of CO2 exchange. In control growth conditions (greenhouse, low‐light: 20–32 W m−2); photosynthesis was shown to be saturated for low irradiance (20–25 W m−2); the saturating photosynthetic rate, very low as compared to higher plants, was due to an extremely high intracellular resistance. When irradiance during the photosynthesis measurement was higher than 60–80 W m−2, a constant decline of net CO2 exchange as a function of time was observed.

When irradiance during growth was enhanced, whether in greenhouse (20–250 W m−2) or controlled (62 W m−2) conditions, the first fronds that had developed in the new condition from the crosier stage exhibited decreased net maximal photosynthesis and a decreased efficiency in low light, but saturating irradiance was unmodified. However, the fronds whose entire differentiation (from meristem) occurred under these moderate irradiances (plants defoliated of all fronds and crosiers at the time of transfer), possessed more efficient photosynthetic characteristics than control plants.

Pteris is able to grow under extreme shade conditions (4–8 W m−2); light saturating photosynthesis and efficiency are higher under extreme shade than under control conditions. These adaptive characteristics indicate that Pteris is a well‐adapted shade species.
Interactions between Symbiotic Nitrogen Fixation, Combined‐N Application, and Photosynthesis in Pisum sativum
Authors: BETHLENFALVAY GABOR J. , PHILLIPS DONALD A.
Published: April 2006

The effect of photosynthetic photon flux density (PPFD) on nitrogen utilization was determined in peas (Pisum sativum L. cv. Alaska) inoculated with Rhizobium leguminosarum and treated with nutrient solutions containing no combined nitrogen, 16 mM NO3−, or 16 mM NH4+. Plants were grown under controlled conditions at three PPFD values ranging from severely limiting to nearly saturating.

Carboxylation efficiencies and CO2‐exchange rates were highest in the N2‐fixing plants and lowest in plants supplied with NH4+, and they generally increased with increasing PPFD. Photoefficiencies increased with PPFD but did not differ appreciably with the form of nitrogen applied. Nitrogen fixation, calculated from C2H2‐reduction and H2‐evolution data, was inhibited more by NH4+ than by NO3−application. Inhibition was counteracted by increasing PPFD. Percentage nitrogen decreased with increasing PPFD in plants treated with combined nitrogen and increased in the plants dependent on N2 fixation.

The data reveal that photosynthetic efficiency and the capacity to fix N2 in peas are functions of PPFD and the availability of combined nitrogen and that these two factors are interrelated.
Levels of Sorbitol in Bleeding Sap and in Xylem Sap in Relation to Leaf Mass and Assimilate Demand in Apple Trees
Authors: HANSEN POUL , GRAUSLUND JØRGEN
Published: April 2006

Removal of fruits and treatment with SADH (succinic acid 2,2‐dimethylhydrazide) were used to change the balance between sources and sinks for photosynthates in Malus domestica‘Golden Delicious’. Sorbitol and sugar content were measured in bleeding sap, in xylem sap prepared by suction, and in 80% methanol extracts of the roots. Concentration as well as total amount of sorbitol in bleeding sap sampled in July and September were lower in fruiting than in defruited trees, and so was the total amount of sorbitol in xylem sap from the trunk. SADH treatment tended to reduce the sorbitol content. Sorbitol in root extracts, expressed as percentage of methanol (80%) insoluble root dry matter, was highest in fruiting trees; but root dry matter was here less than half of that in defruited trees. Sorbitol content in xylem sap as well as sorbitol + sugar percentage of roots showed a distinct maximum in late winter followed by a heavy decrease during spring. It is suggested that sorbitol in xylem sap during the growth season represents a return transport from the roots, and that the level of sorbitol in this return transport reflects, to a certain degree, the ratio between leaf area and assimilate demand by the tree.
Anatomy of Maize Tissue Cultures
Authors: MOTT R. L. , CURE W. W.
Published: April 2006

Tissue cultures of Zea mays L. derived from four different somatic sources all appeared to grow as callus. Microscopic examination, however, showed this growth to be merely an aberrant root‐like form.

A continium in the degree of aberrant root behavior, ranging from cultures appearing very root‐like to those visibly indistinguishable from callus, was recognized. The continuum and ultimately the callus appearance resulted from increasing inhibition of root elongation coupled with strong enhancement of branch root initiation. This aberrant form of root growth was apparent in all cultures observed. Tissue source and growth regulator treatment interacted to shift the growth form within the extremes of the continuum but in no case was the root‐like mechanism of proliferation disrupted, even during extended subculture. Removal of exogenous growth regulators from the culture medium simply allowed outgrowth of existing root primordia as normal roots and this accounts for the characteristic ease of rhizogenesis from what has been called maize callus.