bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compartmentation and transport of 1‐aminocyclopropane‐1‐carboxylic acid and N‐malonyl‐1‐aminocyclopropane‐1‐carboxylic acid in barley and wheat mesophyll cells and protoplasts
Authors: Tophof Susanne , Martinoia Enrico , Kaiser Georg , Hartung Wolfram , Amrhein Nikolaus 
Published: May 2006

Intracellular compartmentation of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and N‐malonyl‐1‐aminocyclopropane‐1‐carboxylic acid (MACC) in wheat (Triticum aestivum L. cv. Kanzler) and barley (Hordeum vulgare L. cv. Gerbel) leaves was studied using different methods: first, the isolation of intact vacuoles from protoplasts and, second, a non‐aqueous fractionation procedure. The two methods gave similar results. ACC concentrations were similar in the extravacuolar space and in the vacuole, whereas MACC was accumulated in the vacuolar space. Transport studies revealed that no specific carrier for ACC exists at the tonoplast. MACC transfer across the tonoplast was enhanced by 120% in the presence of ATP. MACC competitively inhibited malate transport into the vacuole indicating that the same transfer system catalyzes the transfer of the two dicarboxylates.It is concluded that malonylation of ACC is not a prerequisite for the transport of ACC through the tonoplast.
Picomolar concentrations of tentoxin affect Mg2+‐ and Ca2+‐ATPase activities of plasma membrane vesicles from roots of winter wheat seedlings
Authors: Klotz Martin G. , Bérczi Alajos , Erdei László , Liebermann Bernd 
Published: May 2006

Purified plasmalemma vesicles were isolated in the presence of 250 mM sucrose from roots of 14‐day‐old seedlings of winter wheat (Triticum aestivum L. Martonvásári‐8) by phase partitioning of salt‐washed microsomal fractions in a Dextran‐polyethylene glycol two‐phase system, and both Mg2+‐ and Ca2+‐ATPase activities were detected. Orthovanadate‐sensitive Mg2+‐ATPase activity associated with the inside of right side‐out plasmalemma (PM) vesicles (latency 98%) was inhibited 76% by 0.3 mM Ca2+, Ca2+‐dependent ATPase activity located partly on the inside and partly on the outside of plasmalemma vesicles (latency 47%) was not affected by Mg2+.Mg2+‐ATPase activity was inhibited by 68% and inhibition of Mg2+ activation by 0.3 mM Ca2+ partly disappeared in the presence of 10 pM tentoxin, a fungal phytotoxin. Mg2+‐ATPase activity remained inhibited up to 10 nM tentoxin while at 1 μM tentoxin Mg2+ activation was as high as without tentoxin. K+‐stimulation and vanadate inhibition was increased and decreased, respectively, by 100 pM‐10 nM tentoxin. Ca2+‐dependent ATPase activity was continuously increased by 1 pM‐10 nM tentoxin, but at 1 μM tentoxin the stimulation disappeared. The effects of pM tentoxin on plasma‐lemma Mg2+‐ATPase are discussed in relation to its influence on K+ transport in wheat seedlings.
Proteolysis of the main storage protein of buckwheat seeds at the early stage of germination
Authors: Dunaevsky Yakov E. , Belozersky Mikhail A. 
Published: May 2006

The changes in the main storage protein of seeds of buckwheat (Fagopyrum esculentum Moench cv. Shatilovskaya 5), 13S globulin, were studied during seed germination. During the first three days of germination the 13S globulin is subjected to a limited proteolysis, which consists in the splitting of some of its subunits into large polypeptide fragments. Insignificant changes in the sedimentation coefficient of the 13S globulin during the first days of germination as well as immunochemical data, indicate that the limited proteolysis of the 13S globulin does not cause any major changes in its structure.Dormant buckwheat seeds contain a proteolytic enzyme (a metalloproteinase), which can cause limited proteolysis of 13S globulin. The proteinase hydrolyzed some subunits of the 13S globulin to high molecular weight fragments. In the presence of sodium dodecylsulphate the electrophoretic pattern of 13S globulin, isolated from 3‐day‐old buckwheat seedlings, was almost identical to that of 13S globulin from dormant seeds hydrolyzed with metalloproteinase. It is suggested that the proteolysis of 13S globulin observed in vitro may also take place in vivo in the course of seed germination.
Density‐dependent interactions between seedlings of Dactylorhiza majalis (Orchidaceae) in symbiotic in vitro culture
Authors: Rasmussen H. , Johansen B. , Andersen. T. F. 
Published: May 2006

Growth of the heterotrophic seedlings of Dactylorhiza majalis (Rchb.f.) Hunt & Summerh. (Orchidaceae) in vitro with a symbiotic fungus (Rhizoctonia sp.) is density‐dependent, even at densities that are not high enough to exploit the growth medium fully. Competition was two‐sided; increasing density among seedlings did not increase size inequality between them. The slowly growing and smaller seedlings are normally more likely to die than the bigger ones, but mortality was not increased by higher density within the studied range. Growth depression by neighbouring seedlings is independent of their physical distance but varies with the total number of seedlings sharing the same culture dish and the same mycelium.Therefore, if the growth‐promoting effects of different fungi or treatments are to be compared in future work, the density of planting in the culture dishes should be comparable.
Changes in ribosome population and in nucleic acids during breaking of dormancy and development of apple flower buds
Authors: Li Qin‐Bao , Liu Liang‐Huan , Liang Hou‐Guo 
Published: May 2006

Changes in ribosome population, RNA species and DNA composition in flower buds of apples (Malus pumila Mill. cvs Ralls and White winter pearmain) were investigated during breaking of dormancy and development. After bursting of flower buds, total ribosomes increased approximately 4‐fold, and the polyribosomal fraction increased from 66% to 94% of total ribosomes. The newly synthesized ribosomes were identified by incorporation of radioactive precursor. The observed decrease in specific radioactivity of the monoribosomes is caused by the recruitment of monoribo‐somes into polyribosomes after breaking of dormancy.In both cultivars, the 25S and 18S rRNA peaks increased to a high level on April 8. The peaks of low molecular weight RNA were apparently increased after initial swelling of the flower buds. The DNA of flower buds was separated into three bands by electrophoresis. The median band is the main band of nuclear DNAs. The ahead band and the slow‐moving band are satellite components of nuclear DNAs, and they obviously rose after initial swelling of the flower buds. On April 8, when the flower buds had opened, two other small DNA bands could be detected. These results suggest that the changes in level of different ribosome populations, RNA species and DNA composition are related to dormancy breaking development of apple flower buds.
Ammonium toxicity: description of the syndrome in Sinapis alba and the search for its causation
Authors: Mehrer Ingrid , Mohr Hans 
Published: May 2006

In many plant species, prolonged application of ammonium (NH4+) as a source of nitrogen results in physiological and morphological disorders (‘ammonium toxicity’). In the mustard (Sinapis alba L.) seedling we have previously observed particularly severe symptoms of ammonium toxicity in the absence of external nitrate (NO3‐) or with increasing NH4+/NO3‐ ratios. In the present investigation we have studied the symptoms of this ‘toxicity’in more depth, i.e. at the morphological, plastidic, enzyme and mRNA levels, in an effort to elucidate the causation of the syndrome.It could be confirmed that the syndrome is specific for ammonium and is not caused by a surplus of nitrogen. The syndrome is caused neither by pH changes in the medium nor by non‐specific osmotic effects. Furthermore, the syndrome is not causally related to the fact that nitrate reductase (NR; EC 1.6.6.1.) is induced by ammonium. Development of the syndrome requires neither photosynthesis nor intact plastids. Nevertheless, the plastids are severely affected by ammonium application as is anthocyanin synthesis.Enzymes are differently affected. Among the plastidic enzymes, levels of ribulose‐1,5‐bisphosphate carboxylase (RuBPCase; EC 4.1.1.39) and NADP‐dependent glyceraldehyde‐3‐phosphate dehydrogenase (NADP‐GPD; EC 1.2.1.13) are strongly reduced and abundance of translatable mRNA of the small subunit of RuBPCase is decreased, whereas nitrite reductase (NIR; EC 1.7.7.1) is not affected. Among extraplastidic enzymes, the level of chalcone synthase (CHS; EC 2.3.1.74) is strongly reduced, the NAD‐dependent glyceraldehyde‐3‐phosphate dehydrogenase (NADGPD; EC 1.2.1.12) level is unaffected, whereas the isocitrate lyase (ICL; EC 4.1.3.1) level is strongly promoted.The fat → carbohydrate transformation seems to be impaired by ammonium: fat degradation is reduced, starch accumulation is strongly inhibited and the levels of glucose and fructose are decreased.It appears from the present data and from results obtained in a companion study (U. Hecht and H. Mohr, in preparation) that the ammonium toxicity syndrome is detectable as soon as ammonium accumulation occurs in the plant. However, the actual mechanism through which the excess ammonium affects metabolism remains unclear at present.
Chemical nature of P efflux from P‐adequate Spirodela and Lemna plants
Authors: McPharlin I. R. , Bieleski R. L. 
Published: May 2006

The chemical nature of P released (efflux) from healthy (P‐adequate) Spirodela oligorrhiza (Kurz) Hegelm, and Lemna major L. plants growing in sterile solution culture was investigated using thin‐layer chromatography and autoradiography. Ester patterns of P efflux material from [32 Pi] labelled plants was compared with P ester patterns in the tissue of the same plants.Nearly all of the released P was Pi (99.8% in Spirodela, 99.6% in Lemna) there being little consistent evidence for the release of significant amounts of organic P (0.2% and 0.4% of released P –Spirodela and Lemna respectively). Efflux of P predominantly as organic P (hexose or nucleotide P) would have resulted in an important loss of energy for the plant. The corresponding proportion of organic P in the tissue of the labelled plants from which the P efflux material arose was 15% (Spirodela) and 8% (Lemna). Consequently there was no evidence for the preferential release of phosphorylcholine, a compound implicated in P efflux because of its high membrane permeability. Autoradiographic resolution of the chromatogram was improved by labelling plants at high 32P specific activity [185 GBq (mol Pi)−1] compared with levels considered safe [37 GBq (mol Pi)‐1] without any detrimental effects. Spirodela and Lemna plants appear to exert a close control over both the quantity (rates of P efflux) and quality (proportion of Pi to organic P) of their P efflux. The possible role of externally located phosphatases in minimising the release of organic P is also discussed.
Regulation of cytosol acidity in plants under conditions of drought
Authors: Venekamp J. H. 
Published: May 2006

In plants under water stress, the activity of photosynthesis declines most. Stimulation of the oxidative respiration and fermentation results in an increase in the amount of related organic acids: citrate, malate and lactate. In spite of some decline in photo‐respiratory activity, dehydration may enhance the concentration of related organic acids, glycerate and glycolate. The resulting amount of H+ should stimulate NAD(P)H reduction of organic acids by dehydrogenases. Accumulation of proline could be the consequence of such reactions. In the oxidation of glycine, regeneration of NAD(P)H does not liberate H+ but NH4+.Assimilation of NH4+ by cytosolic glutamine synthetase (EC 6.3.1.2) results in positively charged glutamine. It is also conceivable that the charge is essential in the final asparagine synthesis by cytosolic asparagine synthetase (EC 6.3.1.1).At low pH the activity of the oxidative respiration declines. In water‐stressed plants, maintenance of oxidative respiration will depend on the availability of sufficient amounts of carbohydrates and on adequate removal of excess H+ by accumulation of proline and asparagine.
Dominance among fruits/sinks and the search for a correlative signal
Authors: Bangerth Fritz 
Published: May 2006

The present problems with hormonal signals transferring dominance effects are reviewed and, as a new hypothesis, it is stated that the sequence of sink development may establish the dominance effect. ‘Primigenic dominance’ (PD) is suggested to describe this kind of correlative inhibition, in which the earlier developed sink inhibits later developed organs.New results show that the polar IAA export of the earlier developed sink inhibits the IAA export of later developed sinks. This ‘autoinhibition’ occurs at ‘junctions’, where auxin streams from various sinks meet. It is suggested that this depressed IAA‐export of the subordinated fruit/sink acts as the signal that leads to inhibited development.This hypothesis avoids some of the problems related with other hypotheses, such as the requirement of a multidirectional signal. Primigenic dominance is a unifying hypothesis, which can be applied to most correlative dominance phenomena in the plant. Primigenic dominance is less complicated than the traditional ‘apical dominance’ (AD) hypothesis, because it does not require secondary messengers.
Partial purification of cell wall β‐galactosidases from Cicer arietinum epicotyls. Relationship with cell wall autolytic processes
Authors: Dopico Berta , Nicolás Gregorio , Labrador Emilia 
Published: May 2006

The protein extracted from the cell wall of the epicotyls of Cicer arietinum L. cv. Castellana was separated by ion exchange chromatography in four different fractions with β‐D‐galactosidase (EC 3.2.1.23) activity. These were called βI, βII, βIII and βIV, according to their order of elution. βII was associated with a particularly high β‐D‐glucosidase (EC 3.2.1.21) activity. Gel filtration chromatography of each of the fractions gave further subdivision of fractions βI and βIII. Subfractions 1 βI, 1 βII and 1 βIV have glucosidase activity and subfractions 2 βI and 2 βIII have galactosidase activity.The studies on the hydrolytic capacity of these fractions and its relationship with the autolytic process seem to show that subfraction 2 βIII is responsible for autolysis. The release of total and reducing sugars is very similar for autolysis and hydrolysis by 2 βIII. The sugars released are mainly galactose and, to a lesser extent arabinose and glucose. Galactose is released as a monosaccharide, while arabinose remains associated to a polysaccharide component together with glucose and small amounts of galactose.
On the aggregational states of protochlorophyllide and its protein complexes in wheat etioplasts
Authors: Böddi Béla , Lindsten Agneta , Ryberg Margareta , Sundqvist Christer 
Published: May 2006

The inner membranes from wheat (Triticum aestivumL. cv. Walde) etioplasts were separated into membrane fractions representative of prolamellar bodies and prothylakoids by differential and gradient centrifugations. The isolated fractions were characterized by absorption‐, low‐temperature fluorescence‐, and circular dichroism (CD) spectroscopy, by high performancy liquid chromatography and by sodium dodecyl sulphate polyacrylamide gel electrophoresis.The prolamellar body fraction was enriched in NADPH‐protochlorophyllide oxidoreductase (E.C. 1.6.99.1), and in protochlorophyllide showing an absorption maximum at 650 nm and a fluorescence emission maximum at 657 nm. Esterified protochlorophyllide was mainly found in the prothylakoid fraction. The carotenoid content was qualitatively the same in the two fractions. On a protein basis the carotenoid content was about three times higher in the prolamellar body fraction than in the prothylakoid fraction. The CD spectra of the membrane fractions showed a CD couplet with a positive band at 655 nm, a zero crossing at 643–644 nm and a negative band at 623–636 nm. These results differ from earlier CD measurements on protochlorophyllide holochrome preparations. The results support the interpretation that protochlorophyllide is present as large aggregates in combination with NADPH and NADPH‐protochlorophyllide oxidoreductase in the prolamellar bodies.
Internode length in Pisum. Estimation of GA1 levels in genotypes Le, le and led
Authors: Ross John J. , Reid James B. , Gaskin Paul , MacMillan Jake 
Published: May 2006

The levels of GA1, 3‐epiGA1 and GA8 in genotypes Le, le and led of Pisum sativum L. were determined by gas chromatography‐selected ion monitoring (GC‐SIM) after feeds of [3H, 13C]‐GA20 to each genotype. The levels of endogenous and [13C]‐labelled metabolites were determined by reverse isotope dilution with unlabelled GA1, 3‐epiGA1 and GA8. The results demonstrate a quantitative relationship between the level of GA1 and the extent of elongation both on a per plant and a per g fresh weight basis. These results are consistent with previous findings in peas and other species possessing a predominant early 13‐hydroxylation pathway for GA biosynthesis.The levels of 3‐epiGA1 also decreased in the genotypic sequence Le, le, led although not as rapidly as for the level of GA1. This may suggest that the alleles at the le locus also influence the formation of 3‐epiGA1.
Phototropism in hypocotyls of radish. VI. No exchange of endogenous indole‐3‐acetic acid between peripheral and central cell layers during first and second positive phototropic curvatures
Authors: Sakoda Masako , Hasegawa Koji 
Published: May 2006

ABSTRACTUsing a physicochemical method, the distribution of endogenous indole‐3‐acetic acid (IAA) was measured in the peripheral and central cell layers, as well as in the illuminated and shaded sides of phototropically stimulated radish hypocotyls (Raphanus sativus var. hortensis f. gigantissimus Makino). The IAA was evenly distributed over the illuminated and shaded sides in the first and second positive phototropic curvatures induced by a pulse or a continuous unilateral illumination with blue light. Also, no net exchange of the IAA between the peripheral and central cell layers was observed during these curvatures. These results suggest that phototropism of radish hypocotyls cannot be described by the Cholodny‐Went theory.
The nectar of the Strelitzia reginae flower
Authors: Kronestedt‐Robards Eva C. , Greger Maria , Robards Anthony W. 
Published: May 2006

The nectar of Strelitzia reginae Ait. was analysed using enzymatic methods and found to contain glucose, fructose and sucrose. Sugar composition changed considerably over the nectar producing period: there was an increase in the amount of glucose (41%) and fructose (32%) between the early and middle stage of secretion and thereafter a decrease of 13 and 24%, respectively, towards the end of secretion. Although the amount of sucrose secreted was initially as much as the glucose and fructose combined, it subsequently decreased, first by 14% and then by 70% at the end of the secretory period so that, whereas in the initial stages of secretion sucrose was quantitatively the dominant sugar, glucose and fructose made up the major part of the nectar as secretion reached its conclusion.The amounts of potassium and sodium remained at the same low level (around 150 and 30 μg g‐1 [w/v) respectively) throughout secretion, while calcium (initially 18 μg g‐1) and magnesium (initially 8.0 μg g‐1) increased by 47 and 56% respectively, between the early and late stages of secretion. No free amino acids, inorganic phosphate or iron could be detected. Enzymatic analysis revealed only a trace amount of starch. Transmission electron micrographs from both immature and mature plants, however, showed starch grains among other cytoplasmic remnants in the nectary lumen. Mitochondria, vesicles, lipid droplets and ribosomes could also be identified among the luminal cytoplasmic remnants.
Effects of applied nitrogen upon aspects of nitrogen metabolism and transport in developing nodulated winged bean plants
Authors: Chapleo S. , Hall J. L. 
Published: May 2006

Nodulated winged bean [Psophocarpus tetragonolobus (L.) DC., cv. UPS 122] were grown under constant environmental conditions and supplied with mineral nutrient solution in which nitrogen was absent or was present as nitrate (12 mg N week‐1 plant‐1).Nitrate treatment dramatically promoted plant growth, increased fruit weight 1.6 fold, was necessary for tuberisation and enhanced nodulation. The in vitro accumulation of 14C into asparagine and aspartate components of excised nodules supplied with exogenous 14CO2 and [14C]‐D‐glucose was greater for nitrate‐treated plants, whilst accumulation into ureides was reduced by nitrate treatment. Levels of amino acids in xylem sap were greater for plants supplied with a complete nutrient solution, than those grown without applied nitrate, particularly for asparagine, glutamine and proline. Xylem ureide levels were greater for plants grown in the absence of supplementary nitrate.Nitrogen accumulated in leaf, stem and petiole, and root nodule tissues for utilisation during fruit development; peak nitrogen levels and time of anthesis were retarded for plants grown without applied nitrate. The shoot ureide content increased during fruiting, coincident with decreases in the total nitrogen content, indicating that ureide pools are not utilised during the early reproductive phase. However ureide reserves, particularly allantoin, were utilised during the later stages of pod fill.Enzyme activity which metabolised asparagine was found throughout the plant and was identified as K+‐dependent asparaginase (EC 3.5.1.1) and an aminotransferase. Apart from temporal differences in developmental profiles of enzyme activity, the activity of these enzymes and of allantoinase (EC 3.5.2.5) in developing tissues were similar for both treatments. The main differences were greater asparaginase and asparagine:pyruvate aminotransferase activities in root tissues and fruit of nitrate‐supplied plants; allantoinase activity in the primary roots of plants grown without nitrate decreased during development, whilst activity in developing tubers (nitrate‐supplied plants) increased.
Regulation of abscisic acid translocation during embryo maturation of Phaseolus vulgaris
Authors: Le Page‐Degivry Marie Thérèse , Barthe Philippe , Prévost Isabelle , Boulon Brigitte 
Published: May 2006

When R, S [2‐14C] abscisic acid (ABA) was applied to the leaf of Phaseolus vulgaris, a part of the radioactivity was always found 24 h later in the only pod left on the plant. In early podfill, a large part of the labeled material was found in the maternal tissues while in late podfill, most had migrated to the embryos. During embryogenesis, embryo cells became more and more alkaline with respect to the seed coat cells. These results suggest that the distribution of ABA within the tissue is regulated by the pH differential between the two compartments.The decrease of endogenous ABA level observed in situ during the second part of the embryo development therefore cannot be explained only in terms of the passive diffusion of the undissociated species (ABA‐H). The empty‐ovules technique revealed that ABA was only partly affected by an inversion of the pH gradient and that metabolic inhibitors influenced the release of ABA. These results indicate that in addition to a diffusive path, an energy‐dependent component was involved.