bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Agitated Liquid Medium on in vitro Cultures of Hevea brasiliensis
Authors: WILSON H. M. , EISA M. Z. , IRWIN S. W. B. 
Published: April 2006

AbstractThe initiation and prolonged growth of callus, from stem explants of young plants of Hevea brasilienies on solid medium yielded a heterogeneous callus, with areas which are the result of compact growth interspersed with brown necrotic tissue and soft white tissue formations. Subculturing this callus (O callus) to agitated liquid medium and returning it to solid medium resulted in the production of a homogeneous friable and rapidly growing callus (Rl callus) The two established lines O and Rl have remained stable over one year in culture and differ in gross morphology, anatomy, growth and auxin content. Both were maintained on Murashige and Skoog's medium, with 2 mg/1 2,4‐D and 0.5 mg/I kinetin. R 1 but not O showed enhanced growth at the lower 2,4‐D level of 0.2 mg/l: both lines failed to continue growing when 2,4‐D was omitted.It is suggested that the changes resulting from subculture in agitated liquid medium are related to those undergone by callus cultures which become habituated. Thus the Rl callus line is regarded as partially habituated. Subculture in agitated liquid medium also resulted in the production of large numberr of polyploid cells but these did not persist over the long periods of subsequent growth on agar medium, Enhanced auxin production by the establihed Rl callus line was thus observed in the absence of a detectable level of polyploidy.
Influence of Cotyledon Excision and Sucrose on Root Formation in Pea Cuttings
Authors: VEIERSKOV BJARKE , HANSEN JÜRGEN , ANDERSEN ARNE SKYTT 
Published: April 2006

AbstractSucrose was supplied to stock plants of Pisum sativum L. cv. Alaska grown at different levels of irradiance. There was no significant effect on the rooting of the cuttings by sucrose supply to intact plants regardless of the irradiance. However, an increase in the number of roots per cutting was obtained at increasing concentrations of sucrose when the stock plants had been grown at 4 W m−2 and their cotyledons had been removed two days before the cuttings were excised.Cotyledons were removed from stock plants at different times before the excision of cuttings with the intent to regulate the endogenous supply of carbohydrate. The number of roots per cutting was reduced by removal of the cotyledons and this reduction was correlated to the number of days the stock plants had grown without cotyledons as well as to the irradiance pre‐treatment. A greater reduction occurred in cuttings from plants grown under 4 W m−2 than from those grown under 38 W m−2.The growth of the stock plants and the subsequent stem growth of the cuttings was determined by the irradiance to the stock plants and by the time of removal of the cotyledons. Exogenous supply of sucrose had no effect on the stem growth of the cuttings.
Kinetic Studies of (Mg2+)ATPase in Oat Roots
Authors: CHRISTIANSEN J. L. , LINDBERG S. 
Published: April 2006

AbstractKinetic studies on a microsomal fraction from oat roots (Arena sativa) indicate that the MgATP complex is the primary substrate for the ATPase. Free ATP was a weak competitive inhibitor. Free Mg2+ appeared to be either a competitive or noncompetitive inhibitor.
Phase‐Locked Loop Technique to Record Resonance Frequency of Plant Tissue
Authors: AXELSSON P. , JOHNSSON A. 
Published: April 2006

AbstractAn apparatus based on the phase‐locked loop technique has been developed in order to record automatically the resonance frequency of a mechanically vibrating plant specimen. Hereby changes in the elasticity of the plant material can be continuously recorded.In order to demonstrate the use of the apparatus, elasticity changes of Avena coleoptiles due to exchange of the root medium were continuously recorded.
Carbohydrate Metabolism and Frost Hardiness in Pine and Spruce Seedlings Grown at Different Photoperiods and Thermoperiods
Authors: ARONSSON ARON , INGESTAD TORSTEN , LÖÖF LARS‐GÖRAN 
Published: April 2006

AbstractLarge changes occur in carbohydrate contents of pine (Pinus silvestris L.) and spruce (Picea abies (L.) Karst.) seedlings cold‐hardened by photoperiod or by combined photo‐ and thermo‐period. The largest change is in sucrose content, which is almost doubled after six weeks short‐day (6/18 h) treatment; and more than doubled (spruce) or more than tripled (pine), when also temperature is lowered (10/5°C). Development of frost hardiness is strongly correlated with the change in carbohydrate contents. At dehardening, the carbohydrate content decreases rapidly, especially in pine, and the raffinose formed during the rest period disappears within 2–4 weeks. Frost hardiness decreases in parallel.The content of soluble carbohydrates may thus play a role in frost hardiness, although it is not the only factor. Bud formation at cold acclimation is not directly correlated with the changes in carbohydrate content and hardiness.
The Physiology of Rooting Populus Cuttings
Authors: OKORO O. O. , GRACE J. 
Published: April 2006

AbstractThe changing levels of carbohydrates and the rates of photosynthesis in rooting Populus cuttings are described. The cuttings were planted in a sand medium, in controlled environment conditions. There was no evidence to support the view that failure to root in P. tremula was caused by insufficient carbohydrate reserves. In leafless hardwood cuttings, the carbohydrate levels were initially very high (14–19%) but fell rapidly (to 5–10%) as roots, callus or shoots developed. In leafy softwood cuttings, a steady accumulation of carbohydrate reserves was observed, rising from 5–10% on planting to 15–25% when roots had developed. One of the differences between the easy‐to‐root P. × euramericana and the hard‐to‐root P. tremula was the apparent downward transport of assimilates in P. × euramericana softwood cuttings.
Kinetic Studies of a (Na++ K++ Mg2+) ATPase in Sugar Beet Roots
Authors: LINDBERG SYLVIA 
Published: April 2006

AbstractKinetic studies of a dithiothreitol treated membrane ATPase fraction from sugar beet roots led to the following conclusions: 1) In the presence of MgATP, Na+ and K+ stimulate the ATPase activity in different ways following simple Michaelis‐Menten kinetics. Thus separate sites for Na+ and K+ are suggested. 2) In the absence of K+, Na+ acts as an uncompetitive modifier raising the apparent Km and Vmax for MgATP. 3) In the absence of Na+, K+ activates non‐competitively with respect to MgATP. Thus K+ increases Vmax but does not affect the apparent affinity constant. 4) K+ and Na+ double the rate constants. 5) In the presence of Na+ or K+, Mg2+ in excess acts as a weak inhibitor to Na+ and/or K+ activity. 6) The temperature‐activity dependence in the 5–40°C interval shows biphasic Arrhenius plots with the transition point between 15–18°C. The activation energy is lowered at temperatures > 18°C.
Changes in the Reactivity of the Photosynthetic Apparatus in Heterotrophic Ageing Cultures of Scenedesmus obliquus
Authors: KULANDAIVELU G. , SENGER H. 
Published: April 2006

AbstractCultures of Scenedesmus obliquus when grown heterotrophically for 10 or 30 days without addition of fresh medium showed 85 and 98% loss of their photosynthetic capacity respectively. This loss in photosynthetic capacity was accompanied by an increase in quantum requirement.No major changes in the pigment amounts or types were detected which would explain the decay in photosynthetic capacity.Partial reactions mediated by photosystem II or I showed a more or less constant decay over a period of 30 days. Photosystem II reactions appeared less stable than those of photosystem I, decaying by 95% as compared with 70%, over this time period.The results of comparative studies on aged cells for their potential of cytochrome f photooxidation, fluorescence kinetics, 520 nm absorbance change and the variable influence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea and 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐p‐benzoquinone on the photosynthetic capacity of such cells, suggest that it is the inherent ability of the cells to photooxidize plastohydroquinone which is affected primarily.In addition, secondary changes were noted in the activity of reactions on the water‐splitting side of photosystem II and in the P700 — plastocyanin — cytochrome f complex.
Changes in the Reactivity of the Photosynthetic Apparatus in Heterotrophic Ageing Cultures of Scenedesmus obliquus
Authors: KULANDAIVELU G. , SENGER H. 
Published: April 2006

AbstractUltrastructural changes of the chloroplast which occur parallel to the decay of photosynthetic capacity during the heterotrophic ageing of Scenedesmus cells have been studied. A gradual disappearance of the starch grains took place as the nutrients in the growth medium were depleted. Accompanying this change was a deterioration in the structure of the cytoplasm coupled with a concomitant granular appearance. At the same time thylakoid structures were not only well preserved but accumulated more material. This resulted in an increasing number of stacked thylakoids and a thickening of the membranes.
Nitrate Uptake during Recovery from Nitrogen Deficiency
Authors: JACKSON W. A. , KWIK K. D. , VOLK R. J. 
Published: April 2006

AbstractTwo‐week‐old nitrogen‐deficient wheat plants attained a high rate of nitrate uptake on the first day of exposure to nutrient solutions supplemented with KNO3. Ammonium uptake from similar solutions supplemented with NH4NO3 was also high during the first day of exposure, but nitrate uptake from this solution was lower than from the KNO3 treatment. During the next two to three days there was a progressive decrease in uptake of both nitrogen ions. A steady increase in uptake then occurred as the plants fully recovered from the nitrogen‐deficient state.The transient low nitrate uptake after three or four days of exposure to KNO3 was not due to an excessive accumulation of nitrate in the tissue, nor to a failure in nitrate reduction as indicated by the rate of nitrate accumulation relative to the uptake rate. Nitrogen supplied as 15N‐nitrite during the low uptake period was effectively incorporated into organic forms and effectively translocated to the shoots. Failure of the root tissue to increase in soluble carbohydrates during illumination was characteristic of the low uptake period. This contrasted with an increase in root soluble carbohydrates in the light during rapid uptake associated with full recovery from the nitrogen‐deficient state. It is concluded that carbohydrate translocation to the root system was insufficient during the intermediate recovery period for optimal nitrate uptake, although it was sufficient for effective reduction and translocation of nitrate and reduced nitrogen.Ammonium uptake from NH4NO3 was restricted during darkness by the third day whereas there was little difference between light and dark periods in nitrate uptake from KNO3 until about the sixth day of recovery. The extent to which ammonium restricted nitrate uptake increased progressively for two or three days following which a lessening influence seemed evident, and the effects were not directly associated with the rate of ammonium uptake.
Promotion of Flowering in the Pinaceae by Gibberellins
Authors: ROSS STEPHEN D. , PHARIS RICHARD P. 
Published: April 2006

AbstractFlowering was significantly promoted in 4‐year‐old grafts of mature coastal Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) clones by exogenous gibberellins (GAs) A4 and A7 (as a mixture) applied alone and in combination with A5 and A9. Biweekly applications of 400 μg GA4/7 per branch between late March and late June gave a 5‐fold increase in ovulate and 3‐fold increase in staminate strobilus production over untreated controls. 6N‐benzyladenine and 2,3,5‐triiodobenzoic acid applied in combination with GAs had no consistent effect on strobilus production. Non‐destructive branch girdling, ineffective by itself as a cultural treatment, enhanced the GA benefit to flowering. Exogenous application of GA4/7 is effective and appears to be a practical method for promotion of early and enhanced flowering in grafted Douglas‐fir seed orchards.
Factors Influencing the Growth and Division of Pea Mesophyll Protoplasts
Authors: von ARNOLD SARA , ERIKSSON TAGE 
Published: April 2006

AbstractHigh yields of viable protoplasts were produced from pea leaves provided that only leaves of the same age were used in each preparation. The conditions under which the pea plants were grown and the age of the plants were also important. The protoplasts were cultured in a medium supplemented with 1 mg/1 2iP and 1 mg/1 2,4‐D. They were able to regenerate cell walls within two days. After 5 days cell divisions were apparent and sustained divisions led to callus formation. Special emphasis has been given in this paper to the choice of leaf material for protoplast isolation.
Effects of Salt Stress on Growth, Nodulation and Nitrogen Fixation in Cowpea and Mung Beans
Authors: BALASUBRAMANIAN V. , SINHA S. K. 
Published: April 2006

AbstractThe effects of salt stress on growth, nodulation, and nitrogen accumulation in cowpea (Vigna sinensis) and mung beans (Vigna aureus) were studied in sand culture.Salinity (NaCl) retarded the growth of leaves, stem and roots of both the crops. Root growth of mung beans was more sensitive to the increase in salt stress than that of cowpea. The relative growth rates of stressed plant parts declined initially but were subsequently higher than those of control for a period, suggesting that the plants tended to adapt to unfavourable environment even while being stressed. The total nodule number, weight and nitrogen content per plant decreased due to salt treatment, which interfered with the initiation of nodules but not with their further development. There was a considerable fall in the nitrogen fixation efficiency of mung beans under saline environment; it was not so in cowpea.
Incorporation of 5‐Aminolevulinic Acid in the Chlorophyll‐Protein Complexes of the Moss Ceratodon purpureus
Authors: VALANNE NIINA , ARO EVA‐MARI 
Published: April 2006

AbstractAfter one month of cultivation in the dark in inorganic medium the chloroplasts of protonemata of Ceratodon purpureus have larger grana than chloroplasts from light‐grown cultures. Incubation of dark‐grown material with ALA increases the chlorophyll content and chlorophyll a/b ratio. On polyacrylamide‐gel electrophoresis, a préferential labelling of chlorophyll‐protein complex I is obtained after treatment with (3H) ALA in darkness. In contrast, in light, much higher activity is found in chlorophyll‐protein complex II. The free pigment zone is highly labelled in both environments.
Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors
Authors: VAN HASSELT Ph. R. , STRIKWERDA J. T. 
Published: April 2006

AbstractChlorophyll degradation in Cucumis leaf discs was measured at different temperatures between 1 and 25°C in the light and in darkness, and in the presence or absence of sucrose. Two different processes of chlorophyll degradation could be distinguished, a light‐requiring process operating at 1 and 5°C and another, light and sucrose enhanced degradation process which was evident at 25°C. Degradation of leaf pigments at low temperatures was of a photo‐oxidative nature since there was no degradation in the dark. The chlorophyll a/b ratio was decreased, carotene was degraded at a faster rate than chlorophyll, and 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) and triphenyltetrazolium chloride (TTC) which prevent photo‐oxidation, protected against chlorophyll degradation. The light and sucrose enhanced chlorophyll degradation at 25°C was of an enzymatic nature since it occurred in the dark as well as in the light. The chlorophyll a/b ratio was not affected, and carotene and chlorophyll degradation occurred at the same rate. Since DCMU completely inhibited the light enhancement at 25°C and experimentation in a low oxygen atmosphere also protected chlorophyll against the effect of light and sugar application, it is suggested that the enhancement of chlorophyll degradation by light and sucrose at 25°C may be due to increased sugar uptake of the chloroplasts and consequently excessive starch formation in the organelles.
Auxin Transport in Tendril Segments of Passiflora caerulea
Authors: JUNKER STEFFEN 
Published: April 2006

AbstractThe movement of auxin through tendril segments of Passiflora caerulca L. has been investigated using IAA‐2‐14C. It has been shown that (1) flux of IAA through the segments is strongly polarized basipetally: (2) the amount of 14C recovered in the basal receiver blocks increases linearly within a transport period of 6 h; (3) velocity of basipetal transport is 14.5 mm h−1; (4) at least 70% of the radioactivity in the receiver blocks is confined to the IAA molecule: approximately 55% of 14C from methanolic extracts of the segments is IAA: (5) at low temperatures (2–4°C) the basipetal transport is abolished; (6) white light promotes basipetal transport, and this effect is abolished in a CO2‐free atmosphere; (7) no difference could be detected in 14C content between dorsal and ventral halves of tendril segments nor among individual dorsal and ventral receiver blocks.
Regeneration of Plants from Cell Suspensions Frozen at −20, −70 and −196°C
Authors: BAJAJ Y. P. S. 
Published: April 2006

AbstractCell suspensions of carrot, Datura, tobacco and soybean subjected to −20°C, −70°C and −196°C in the presence of a suitable cryoprotective agent, and stored for various lengths of time have been revived. After revival these cells divided to form callus masses. Direct immersion in liquid nitrogen invariably killed the cells, whereas cooling at the rate of 1 or 2°C/min, or pre‐freezing briefly at −20 and −70°C, followed by freezing at −196°C retained the viability. Depending on the plant species up to 70% of the cell clumps could withstand ultra‐cooling. Tobacco and Datura cell suspensions were more sensitive to cold treatment than were those of carrot. Actively growing cell suspensions containing small cell‐clumps revived rapidly, while filtered cell‐suspensions of free cells only occasionally survived. Calli of tobacco and carrot obtained from frozen suspensions have been regenerated into plants.
Effect of Spruce Root Constituents on Extracellular Enzymes of Fomes annosus
Authors: JOHANSSON MARTIN , POPOFF THOMAS , THEANDER OLOF 
Published: April 2006

AbstractFractions of acetone extracts from heartwood, sapwood and wood from the reaction zone in roots of Norway spruce, attacked by Fomes annosus, were tested concerning their effect on the activity of cellulase, polygalacturonase, aryl‐β‐glucosidase and laccase, obtained from culture filtrates of the same fungus. A specific inhibition of polygalacturonase was recorded with the resinous fractions. The hydrolysing enzymes were more inhibited by the lignans of the reaction zone in the presence of fungal laccase than in the absence of laccase. The pH dependence of the inhibiting effect of phenols varied among the enzymes. The four enzymes were inhibited by partly different lignan fractions, and synergistic effects between minor compounds were indicated. The phenolic fractions inhibited weakly the biosynthesis of the enzymes. It was obvious that results from enzyme inhibition studies in vitro do not reflect the complicated mutual interrelationships between production and activity of the extracellular fungal enzymes and the chemical constituents of the host in vivo.
Similarities between l‐Phenylalanine and m‐Fluorophenylalanine as Substrates for l‐Phenylalanine Ammonia‐Lyase
Authors: ORKWISZEWSKI JOSEPH A. J. , KOROLY MARY J. , DIMICHELE LEONARD , WEBER DANA M. 
Published: April 2006

AbstractThe ability of l‐phenylalanine ammonia‐lyase (E.C. 4.3.1.5) to metabolize dl‐m‐, dl‐o‐ and dl‐p‐fluorophenylalanine in Avena sativa has been examined. Although all three amino acid analogues served as substrates for this enzyme, there was a marked difference in the behavior of the meta isomer from that of the para and ortho species. The Michaelis constant for the meta analogue was similar to that obtained for the natural substrate, l‐phenylalanine, but distinct from the kinetic data for the para and ortho isomers. In addition, in vivo analyses demonstrated that both l‐phenylalanine and the meta‐fluoro‐derivative served to protect against chlorogenic acid loss, whereas previous studies have shown that the para and ortho species depressed levels of this phenolic derivative. Finally, treatment of coleoptile apices with either the meta isomer or l‐phenylalanine reversed dl‐p‐fluorophenylalanine stimulated growth and attendant reduction in chlorogenic acid content. These findings provide further clarification of the effects of fluorophenylalanines upon l‐phenylalanine ammonia‐lyase mediated biosynthesis of low molecular weight phenols in Avena.
Water Potential and Leaf Elongation in Radiata Pine and Wheat
Authors: SANDS R. , CORRELL R. L. 
Published: April 2006

AbstractThe rate of leaf elongation in radiata pine (Pinus radiata) and wheat seedlings was closely related to the osmotic potential of the rooting solution. Sudden stress application and removal treatments caused immediate changes in the leaf elongation rate and a new steady‐state rate independent of the old was quickly established. The osmotic potential in the active elongation zones of a leaf differed from that of the remainder of the leaf and was considered more appropriate for deriving turgor pressure to be related to leaf elongation. Shifts in elongation rate were associated with corresponding shifts in total leaf water potential in both species and with corresponding shifts in turgor pressure in wheat.There was a linear correlation between the pitch of the helical thickenings in the protoxylem of radiata pine needles and their elongation rate. A record of elongation rate is, therefore, preserved in the needle. Developmental aspects of the deposition of the helix are discussed.
Galactose‐induced Ethylene Evolution in Mung Bean Hypocotyls: A Possible Mechanism for Galactose Retardation of Plant Growth
Authors: COLCLASURE G. CRAIG , YOPP JOHN H. 
Published: April 2006

AbstractGalactose has long been known to inhibit growth in certain plant systems and more recently to promote abscission. These same systems are similarly affected by ethylene. The mung bean (Phaseolus aureus Roxb.) hypocotyl system was employed to ascertain whether the inhibitory effects of galactose might be regulated through ethylene. Galactose alone (at 10 and 100 mM) of the many carbohydrates tested elicited high rates of ethylene evolution (1.5–4.0 nl/g fresh weight x h) as determined by gas chroma‐tography. Hook opening, pigment formation, and hypocotyl elongation were inhibited by this resultant ethylene. Galactose and auxin were found to act synergistically with respect to ethylene induction. Use of an auxin antagonist and auxin transport inhibitor revealed that galactose‐induced ethylene formation is auxin dependent. Time course studies indicate that this effect may be auxin‐sparing. Methionine appears to be the substrate of galactose‐induced ethylene. since a methionine antagonist [L‐2‐amino‐4‐(2′‐amino ethoxy)‐trans‐3‐butenoic acid] abolished the induction. Potential interrelationships between galactose and ethylene synthesis are discussed.
Regulation of Apical Dominance by Ethephon, Irradiance and CO2
Authors: ANDERSEN A. SKYTT 
Published: April 2006

AbstractApical dominance of intact pea plants (Pisum sativum L. cv. Alaska) was found to be diminished by high irradiance and by increasing the CO2 content of the air. Ethephon treatment of young plants resulted in an outgrowth of laterals, but this was significant only when the apical dominance already was weakened by high irradiance and/or CO2.