bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phloem Unloading in Stem Parts Parasitized by Cuscuta: The Release of 14C and K+ to the Free Space at 0°C and 25°C
Authors: WOLSWINKEL PIETER 
Published: April 2006

AbstractBy washing out 14C‐solutes or K+ from the free space of stem segments of Vicia faba L. and Urtica dioica L., efflux from stem tissues was measured. At 25°C the efflux of 14C or K+ from non‐parasitized stem parts was found to be comparable with the pattern known for parenchyma cells. The efflux pattern from parasitized stem parts kept at 0°C was also a normal one, but at 25°C a more complicated pattern was found. After addition of metabolic inhibitors, however, the efflux pattern appeared to be comparable with the pattern found in 0°C experiments. Also, after washing stem segments for several hours in water at 0°C, Phloem unloading was shown to start unimpeded after transfer to 25°C. Stem parts parasitized by Cuscuta can be regarded as a model system for studying the fundamental processes underlying movement out of sieve tubes in strong sink regions.
Effects of Organic Nutrients and Hormones on Growth and Development of Tissue Explants from Coconut (Cocos nucifera) and Date (Phoenix dactylifera) Palms Cultured in vitro
Authors: EEUWENS C. J. 
Published: April 2006

AbstractThe growth response (increase in weight) of cultured explants from seedling date (Phoenix dactylifera L.) and mature coconut (Cocos nucifera L. cv. Malayan Dwarf) palms to source and concentration of organic nitrogen. carbohydrate, auxins, cytokinins and gibberellins was examined. Growth was strongly stimulated by the presence of auxins (10−7 to 10−6M), cytokinins (10−6 to 10−5M), high concentrations of sucrose (0.2 M), and in the absence of NH4Cl, by organic sources of reduced nitrogen. Higher concentrations of auxin (2,4‐D or NAA at 10−6 to 10−5M) which still stimulated growth of Phoenix tissue, proved inhibitory to growth of freshly excised Cocos tissues.Explants from both palms initiated roots when subcultured on a medium with increased levels of auxin (NAA, 2.5 × 10−6 to 2.5 × 10−5M) and reduced levels of cytokinin (6‐BAP, 5 × 10−8M). Isolated roots excised from these explants continued growth and produced new laterals when subcultured on media with GA3 (5 × 10−7M) and reduced levels of auxin, cytokinin, and either minerals or sucrose.
Cytokinins and Morphological Aspects of French‐bean Roots in the Presence of Rhizobium
Authors: PUPPO ALAIN , RIGAUD JEAN 
Published: April 2006

AbstractTypical abnormalities were observed on French‐bean roots when the plants were cultivated in the presence of Rhizobium phaseoli, under hydroponic conditions. Substantial quantities of cytokinins were detected in the plant culture medium and their concentration remained high until the 9th day after inoculation, when the first nodules appeared. The presence of both partners, plant and bacteria, was required for this synthesis. Exogenous cytokinin production was responsible for morphological alterations of the roots observed before nodulation.
Allosteric Regulation of Potassium Uptake in Plant Roots
Authors: JENSÉN PAUL , PETTERSSON SUNE 
Published: April 2006

AbstractIn uptake experiments from nutrient solutions containing 2.0 mMK+labelled with86Rb+, the relationship between potassium uptake efficiency and internal potassium concentration of the roots, [K+]iwas found to be partly sigmoidal for intact plants of spring wheat (Triticum aestivumL.), glasshouse cucumber (Cucumis sativusL.), birch (Betula verrucosaEhrh.), lingonberry (Vaccinium vitis‐idaeaL.), Scots pine (Pinus silvestrisL.) and Norway spruce (Picea abies(L.) Karst.), The results were interpreted in terms of sigmoidal enzyme kinetics for allosteric regulation. Hill plots of the data gave straight lines at specific [K+]iintervals for the species. The slopes of the lines are the Hill coefficient, which could be regarded as a measure of the minimal number of allosteric sites. The Hill coefficient varied between ‐ 14.4 and ‐ 15.9. When divided by four, these values are fairly consistent with those in the literature. It is suggested that four active uptake sites interact with four groups of allosteric sites, each group containing four such sites, or that one active uptake site interacts with all the allosteric sites. Thus the results are evidence that the mechanism regulating K+uptake is basically similar for the investigated plants. It is the interval of [K+]imediating highly negatively cooperative allosteric regulation that differs among species.For some of the species,ndecreased from about 15 and approached unity at high [K+]ivalues. This may indicate that only few sites are still available, making cooperativity unimportant. Alternatively high vacuolar [K+]iconcentrations may give rise to an incorrect evaluation of data from Hill plots, since the cytoplasmic K+content likely regulates the allosteric mechanism. Moreover, it is suggested that gene‐controlled carrier synthesis is responsible for the varying maximum K+uptake efficiency among species.
Thermolability of the Alternative Electron Transport Pathway in Higher Plant Mitochondria
Authors: CHAUVEAU M. , DIZENGREMEL P. , LANCE C. 
Published: April 2006

AbstractMitochondria from four plant species showing normal (Arum maculatum L., Arum italicum Mill., Sauromatum guttatum Schott) or induced (Solanum tuberosum L.) resistance to cyanide were submitted to temperature treatments up to 90 min at 45°C. The activity of the alternative, cyanide‐resistant electron transport pathway was specifically and deeply altered by temperature treatments. Hydrogen sulfide was released in direct proportion to the reduction of activity of the alternative pathway. Only a small fraction (≃ 20%) of the total labile sulfide content of the mitochondria was associated with the operation of this pathway. In cyanide‐resistant mitochondria, the cytochrome pathway was much more resistant to thermal inactivation than the alternative pathway. On the contrary, in cyanide‐sensitive mitochondria (with no alternative pathway) the cytochrome pathway was highly sensitive to temperature treatments.These results indicate that the presence of a cyanide‐resistant alternative pathway is correlated with a higher degree of resistance to thermal denaturation of the cytochrome pathway. They also strongly suggest that iron‐sulfur proteins are regular components of the alternative pathway.
The Connection between High Energy and Low Energy Responses to Red and Far‐Red Light of Hypocotyl Elongation in Red Cabbage Seedlings (Brassica oleracea var. capitata‘Marner Septemberrot’)
Authors: OTTO KARL‐RONALD 
Published: April 2006

AbstractGrowth responses of hypocotyls of Brassica oleracea L. var. capitata caused by diurnal irradiation of various duration (0.5 h/d up to continuous irradiation) and various irradiance (0.3–1.5 W m−2) with red and far‐red light from sources characterized below can be described by the equation:
image

(W= relative effect, I= irradiance, t1= irradiation time per day, Ws= constant dependent on material and wavelength, α, B and ts, = constants dependent on wavelength.)On the basis of that equation a possible connection between longtime and short‐time irradiation responses is discussed.
Action Spectra for Conversions of Phycochrome c from Nostoc muscorum
Authors: BJÖRN G. S. , BJÖRN L. O. 
Published: April 2006

AbstractThe reversibly photochromic pigment, phycochrome c, was extracted from the blue‐green alga Nostoc muscorum strain A. Action spectra were determined for in vitro conversions of the pigment from the short wavelength to the long wavelength form and vice versa. The action peak for the absorbance decrease at 650 nm is at 630 nm. During this decrease there is only a slight increase of the absorbance in the green region. Green and yellow light (maximum efficiency at 580 nm) completely restores absorbance at 650 nm. The observations are explained by the existence of three spectrally different forms of phycochrome c: Pc630 and Pc650 which equilibrate in darkness and Pc580 which is reversibly photoconvertible to Pc630. We have also measured the absorbance changes brought about by saturating irradiations with light of various wavelengths (“photostationary state spectrum”). Extreme photostationary states were obtained with about 650 nm and 500 nm light.
The After‐Effect of Water Stress on Chlorophyll Formation during Greening and the Levels of Abscisic Acid and Proline in Dark Grown Wheat Seedlings
Authors: BENGTSON CURT , KLOCKARE BIRGITTA , KLOCKARE RUNE , LARSSON STIG , SUNDQVIST CHRISTER 
Published: April 2006

AbstractCut seedlings of wheat plants (Triticum aestivum L. cv. Starke II Weibull) between 6 and 7 days old were water stressed in darkness by exposing them to air of 35% relative humidity 2.5 to 20 h. This treatment resulted in a water potential of ‐11 bars in the leaves after 20 h. The leaves were then rewatered and irradiated. The chlorophyll formation that took place in fully turgid leaves during the greening was markedly decreased in the case of the water‐stress pretreatmet. and especially the lag phase was prolonged. The longer the stress pretreatment the more evident was the subsequent effect on chlorophyll formation. However, no linear relationship was found between the amount of stress and the chlorophyll content. Protochlorophyllide regeneration from endogenously formed δ‐aminolevulinic acid was markedly decreased even after the shortest water‐stress period. However, protochlorophyllide accumulation from exogenously supplied δ‐aminolevulinic acid was only slightly decreased following the water‐stress pretreatment. Further more, the ratio of protochlorophyllide650 to protochlorophyllide628 was slightly reduced by the same conditions.During the stress period both abscisic acid and proline were accumulated in the leaves. The content of abscisic acid increased up to six times the normal level during water stress lasting for 20 h. The increase of proline was about three‐fold for similar treatment. After rewatering the leaves the levels of both abscisic acid and proline rapidly declined and reached. 10 h later, the levels found in unstressed seedlings.The increase in abscisic acid during water stress associated with impaired chlorophyll metabolism suggested that the after‐effect of water stress might be linked to chlorophyll metabolism through abscisic acid or some of its metabolites. The changes in proline content open the possibility that this substance could function as a reserve substance for the formation of chlorophyll after the discon tinuation of the stress.
Chasmogamous and Cleistogamous Pollination in Salpiglossis sinuata
Authors: LEE CHI WON , ERICKSON HOMER T. , JANICK JULES 
Published: April 2006

AbstractPollen from chasmogamous flowers of Salpiglossis sinuata L. could not be induced to germinate in vitro unless stigmatal extract was applied to the culture medium. The substance that induces pollen germination in the stigmatal extract is water‐soluble and heat‐stable. Crosses could not be achieved between chasmogamous and cleistogamous flowers because of structural incompatibility. Pollinated pistils of chasmogamous flowers release a large amount of ethylene. The burst of ethylene release is due to an interaction between pollen tubes and stylar tissue and is directly proportional to the quantity of pollen placed on the stigma. Cleistogamous flower buds also produce a burst of ethylene at the time of pollination within the closed flower. The ethylene release may be a cause of reduced corolla development associated with cleistogamous flowers.
Accumulation of Free Proline at Low Temperatures
Authors: CHU T. M. , JUSAITIS M. , ASPINALL D. , PALEG L. G. 
Published: April 2006

AbstractThe accumulation of free proline in the first leaves of barley, Hordeum distichum L., and wheat, Triticum aestivum L., in response to a range of low temperatures was examined with 10‐day‐old plants. In barley (cv. Prior) no proline accumulated at 8°C or above, but in wheat (cv. Gabo) proline accumulated at 12°C and lower temperatures. In barley, the first leaf survived for 29 days following transfer to 5°C and continued to accumulate proline throughout this period. In contrast, the first leaves of plants maintained at 20°C survived for 13 days only and accumulated no proline. Proline accumulation at low temperature was shown to be light‐dependent, both in intact plants and excised leaf sections, and the light requirement could not be replaced by supplying leaf segments with precursors of proline. Proline accumulation in response to water stress was not light‐dependent at 20°C but was at 5°C.Inter‐specific and intra‐specific variation in the extent of accumulation in response to low temperature was also examined. Considerable variation was encountered but there was no clear relationship with geographical distribution or chilling sensitivity for the species and no correlation with accumulation in response to water stress in the cultivars of barley examined.
Effect of Magnesium on Chlorophyll‐Protein Complexes
Authors: ARO EVA‐MARI , VALANNE NIINA 
Published: April 2006

AbstractThe effect of Mg2+ during the isolation of chlorophyll‐protein complexes was studied in two moss species (Pleurozium schreberi and Ceratodon purpureus) and New Zealand spinach (Tetragonia expansa). When 2 mM MgCl2 was included in all the extraction and separation phases, the proportions of chlorophyll‐protein complex I. were very small in all plants studied. The withdrawal of Mg2+ considerably increased the proportions of CP I. The most pronounced increase in the chlorophyll present as CP I was found when Mg2+ was withdrawn from the gel, and this also increased the mobility of the CP II complex and free pigment zone. Exclusion of Mg2+ from the running buffer had very little effect. Although Mg2+ had little effect on the relative amount of chlorophyll in CP II, the withdrawal of Mg2+ from all the extraction and separation phases caused formation of polymers of CP II. In the mosses, the formation of polymers of CP II seemed to be more obvious in the species with large grana. Absence of Mg2+ from all the extraction and separation phases sometimes also produced a polymer of CP I.
Circadian Rhythmicity in Photoperiodic Regulation of Regeneration in Begonia Leaves
Authors: HEIDE OLA M. 
Published: April 2006

AbstractThe mechanism of photoperiodic regulation of regeneration in Begonia leaves has been studied by the night interruption technique in 24, 48, and 72‐h cycles. The response to 30 min red light interruptions in 48 and 72‐h cycles indicated a circadian rhythm in red light sensitivity with typical photophile and scotophile phases. In 24‐h cycles two types of response patterns were observed. With a main photoperiod of 3 h the usual response pattern with only one light‐sensitive phase near the middle of the dark period was found, whereas with 8‐h photoperiods two light‐sensitive phases were observed as previously reported by Zimmer in Begonia flowering studies (Gartenbauwissenschaft 38: 57, 1973). Reversion studies with FR indicate that the reactions are mediated by phytochrome. The results are discussed in relation to alternative hypotheses for photoperiodic timing.
The Significance of Oxygen Transport and of Metabolic Adaptation in Flood‐Tolerance of Senecio Species
Authors: LAMBERS HANS , STEINGRÖVER EVELIENE , SMAKMAN GERARD 
Published: April 2006

AbstractExperiments were designed to provide information about the physiological basis of flood‐tolerance in Senecio species. The oxygen concentration in roots of S. jacobaea L., S. viscosus L. and S. vulgaris L. became almost zero after transplantation to a solution of low oxygen concentration, and it was concluded that the flood‐sensitivity of these Senecio species could be due to insufficient oxygen transport from the shoots to the roots.The oxygen concentration in the roots of the flood‐tolerant S. congestus (R.Br.) DC., growing in a solution of low oxygen tension, was almost sufficient to maintain oxygen utilization at the rate observed in roots of plants, grown in an air‐saturated solution.Oxygen utilization by roots of the flood‐tolerant S. aquaticus Hill, growing in a solution of low oxygen tension, was inhibited 50%. However, the oxygen concentration in the roots of this species remained high enough to maintain cytochrome oxidase activity and oxidative phosphorylation at the rate observed in roots from an air‐saturated environment. The activity of a second (“alternative”) oxidase must have been drastically reduced. Alternative NADH‐oxidizing enzymes, like nitrate reductase which was induced by anaerobiosis in roots of S. aquaticus, might replace the regulatory function of the alternative oxidase. — Thus, in S. aquaticus root porosity and root length contributed to the maintenance of an oxygen concentration which was sufficient for uninhibited cytochrome oxidase activity and oxidative phosphorylation rate in roots growing in a solution of low oxygen tension.
The Effect of Inorganic Salts on the Senescence of Dianthus caryophyllus Flowers
Authors: MAYAK SHIMON , KOFRANEK A. M. , TIROSH TSIPORA 
Published: April 2006

AbstractCertain inorganic salts like KNO3, KCl, K2SO4, Ca(NO3)2 and NH4NO3 extend longevity of cut carnation flowers. The effect of KNO3 was studied in some detail. There is an osmotic adjustment in response to KNO3 treatment. The osmotic concentration change occurred in the external as well as in the internal compartments. The osmotic concentration change in the external compartment is well correlated with extension of longevity. The effect of KNO3 on the sensitivity to ethylene, and its significance in delaying senescence is discussed.
Zn2+‐Dependent Acid Inorganic Pyrophosphatase Activity as Related to Other Pyrophosphatases in Oryza sativa
Authors: KAR M. , PATRA H. K. , MISHRA D. 
Published: April 2006

AbstractAcid inorganic pyrophosphatase on the one hand, and Mg2+‐dependent alkaline inorganic pyrophosphatase and Zn2+‐dependent acid inorganic pyrophosphatase on the other hand showed opposite trends in their activities in rice (Oryza sativa L. cv. Ratna) seedlings grown in dark and sun. The opposite trends in their activities were also noted in rice seedlings grown from gamma‐irradiated seeds and in detached rice leaves floated on water in dark. The ratios of Mg2+ dependent alkaline inorganic pyrophosphatase/acid inorganic pyrophosphatase and Zn2+‐dependent acid inorganic pyrophosphatase/acid inorganic pyrophosphatase changed significantly in response to the above physical treatments, but the ratio of Mg2+ dependent alkaline inorganic pyrophosphatase/Zn2+ dependent acid inorganic pyrophosphatase remained relatively stable. The conclusion is that Zn2+‐dependent acid inorganic pyrophosphatase activity is the same as that of Mg2+‐dependent alkaline inorganic pyrophosphatase and is different from that of acid inorganic pyrophosphatase, which requires no metal ion for activity. The acid and alkaline inorganic pyrophosphatase activities are due to separate enzyme proteins.
Protein Synthesis Related to Cold Temperature Stress in the Desiccation‐Tolerant Moss Tortula ruralis
Authors: MALEK LADA , BEWLEY J. DEREK 
Published: April 2006

AbstractIncubation of hydrated Tortula ruralis (Hedw.) Gaertn., Meyer. Scherb. at temperatures down to 2°C resulted in an accumulation of polyribosomes and a decrease in single ribosomes. No changes in the levels of ribosomal subunits were detected. On rehydration of slowly dried moss, which contains no polyribosomes, these were reormed at 2, 8 and 20°C. Rapid incorporation of labelled leucine into protein was observed on reintroduction of the desiccated plant o water at 20°C and there was significant, but much reduced, ncorporation at 2°C. Previously undesiccated moss was also able o take up radioactive leucine and to synthesize protein at 2 and ‐2.5°C. Changes in the rate of protein synthesis at low temperature were not detected in cold hardened (winter collected or incubated at 2°C) T. ruralis. The moss appears to be adapted to survive freezing wear round and even summer‐collected moss can conduct protein synthesis at low temperatures: seasonal cold hardiness changes do lot appear to take place.
Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels
Authors: GROVER H. L. , NAIR T. V. R. , ABROL Y. P. 
Published: April 2006

AbstractSome aspects of nitrogen metabolism, during grain development, of the upper three leaf blades on the mainshoot of wheat (Triticum aestivum L.) cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were investigated. It was observed that these leaf blades were active in NO‐3 assimilation. Of the leaf blades, the flag lead blade had significantly higher nitrate reductase activity, higher amount of free amino acid and soluble protein content, whereas the content of NO‐3 was significantly lower than in the other two leaf blades. Application of soil nitrogen significantly enhanced the nitrate reductase activity (N30 over N0 and N120 over N30), free amino acid (N30 over N0 and N120 over N30), soluble protein (N120 over N0) and NO‐3 content (N30 and N120 over N0) in all three leaf blades. During the 35‐day period, viz. from 7 days prior to anthesis to 28 days after anthesis, the three leaf blades together reduced 280, 608 and 1397 NO‐3μmol under N0, N30 and N120, respectively.
Influence of Protein Factors on the Activation of NADP–malate Dehydrogenase by Dithiothreitol
Authors: VIDAL JEAN , JACQUOT JEAN PIERRE , GADAL PIERRE , VIDAL DIDIER 
Published: April 2006

AbstractLeaves of Phaseolus vulgaris L. contained malate dehydrogenase activity dependent on NADP (E. C. 1.1.1.82); it could be detected in extracts only when a dithiol such as dithiothreitol was present. After the addition of dithiothreitol, the activity increased with time, passed through a maximum and then diminished. The activation rate and/or the maximum level of activity were essentially dependent on dithiothreitol concentration, pH, and temperature. The presence of bovine serum albumine or glycerol in the medium decreased the inactivation rate; equivalent results were obtained at low temperatures. A mathematical model was established showing an apparent first‐order rate for activation and inactivation only under conditions of alkaline pH near 8.3. These data allowed us to demonstrate that compounds other than dithiothreitol were necessary for the activation process. Evidence suggested that these compounds were protein factors of low molecular weights which increased the activation rate and the maximum level of activity when added to the incubation medium at pH 7.3. Their efficiency in the enzyme activation was higher at alkaline pH than at acid or neutral pH.
Electrochemical State of Potassium and Sodium in Free Cells of Acer pseudoplatanus
Authors: PENNARUN ANNE‐MARIE , VAN DE SYPE GHISLAINE , GRIGNON CLAUDE , HELLER RENÉ 
Published: April 2006

AbstractThe intracellular distribution of K+ and Na+ ions has been determined by compartmental analysis of isotope exchange. The simultaneous measurement of electrical potentials allowed us to show that the distribution of K+ was close to thermodynamic equilibrium while the internal concentration of Na+ was well below the value predicted for the equilibrium. The efflux of Na+ was more sensitive to temperature than its influx. Both ouabain and variations in the external levels of KCl produced weak and inconsistent effects, observations which would emphasize the difference between the Na+ extrusion mechanism of plants and animals. The Na+ extrusion system of Acer cells ceased to be functional in Na+‐depleted cells but recovered its function if the cells were placed in 10 mM NaCl, which suggests that the extrusion system was induced by the level of internal Na+ ions.