bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of ethanol on alternative oxidase in mitochondria from callus‐forming potato tuber discs
Authors: VAN DER PLAS LINUS H. W. , WAGNER MARIJKE J. 
Published: April 2006

AbstractEthanol, when added to the incubation medium of callus‐forming potato tuber discs, inhibits callus growth and causes an increase of the mitochondrial antimycin‐A resistant respiration, expressed as a percentage of state III‐respiration. This increase in resistance to antimycin‐A is the result of a poor development of the cytochrome pathway in tissue discs treated with ethanol. The development of the antimycin‐A resistant alternative oxidase sensitive to chelator is about the same for treated and untreated discs.The respiratory control (RC) ratio of the mitochondrial respiration increases after addition of a chelator, which inhibits the alternative pathway. The RC ratio of the uninhibited mitochondrial respiration appears to be inversely related to the capacity of the alternative pathway, when mitochondrial preparations with different capacities to transfer electrons via the alternative path are compared. From the experimentally observed relation between RC‐ratio and alternative oxidase capacity, it was concluded that at least half of the capacity of the alternative path is used in uninhibited state IV respiration.
Auxin biosynthesis and metabolism in isolated roots of Zea mays
Authors: FELDMAN LEWIS J. 
Published: April 2006

AbstractThe synthesis and metabolism of indole‐3‐acetic acid (IAA) was investigated in isolated roots of corn, Zea mays L. Roots were cultured aseptically in media supplemented with either 14C‐tryptophan or 14C‐IAA. Exogenously supplied IAA is rapidly and completely metabolized by root tissues. The main site in the root for the synthesis of IAA is in the apex. Removal of either the root cap or the quiescent center, or the root cap and the quiescent center from the apex has no effect on the IAA‐synthesizing ability of the apex. Subdividing the terminal 2.1 cm of the root into various segments and culturing them separately stimulates IAA synthesis in these isolated root tissues. Roots in culture maintain relatively constant IAA levels, reflecting the precise controls of the level of this hormone.
The effect of adenine nucleotides and inhibitors of ADP translocation on uncoupled electron flux in bean mitochondria
Authors: LIMA M. SILVA , DE MELO D. FERNANDES 
Published: April 2006

AbstractThe uncoupled electron flux and the influence of adenine nucleotides on this flux in mitochondria isolated from hypocotyls of Vigna sinensis (L.) Savi cv. Seridó were examined. In order to avoid the functioning of other enzymes capable of utilizing adenine nucleotides the reaction medium was free of Mg2+. When an oxidizable NADH ‐linked substrate such as L‐malate was used, a stimulatory of adenosine‐5′‐monophosphate (AMP) and adenosine‐5′‐diphosphate (ADP) on uncoupled respiration was manifested. The stimulatory effect of AMP and ADP could not be shown when succinate was the substrate. Atractyloside and carboxyatractyloside had no effect on the stimulatory role played respectively by AMP and ADP in the presence of carbonyl cyanide p‐trifluoromethoxy‐phenylhydrazone (FCCP).
Factors affecting shoot initiation from tuber discs of potato (Solanum tuberosum)
Authors: JARRET ROBERT L. , HASEGAWA PAUL M. , ERICKSON HOMER T. 
Published: April 2006

AbstractDiscs of cortical and perimedullary tissue from tubers of potato (Solanum tuberosum L. cv. Superior) formed adventitious shoots when cultured on a medium containing Murashige and Skoog's salts, myo‐inositol, 100 mg/l; folic acid, 0.5 mg/l; D‐biotin, 0.05 mg/l; gibberellic acid (GA3), 0.5 mg/l; thiamine ˙ HCl, 0.1 mg/l; glycine, 2.0 mg/l; pyridoxine ˙ HCl, 0.5 mg/l; nicotinic acid, 0.5 mg/l; sucrose, 25 g/l; casein hydrolysate, 1 g/l; Bacto agar, 9.0 g/l; and a cytokinin [N6‐benzylaminopurine (BAP), N6‐γ,γ‐dimethylallylaminopurine (2iP), or N6‐furfurylaminopurine (kinetin)]. Discs of pith tissue either failed to survive or produced callus but did not undergo morphogenesis. Cytokinin was essential for explant survival, while BAP at 3.0 mg/l was most efficacious in promoting shoot initiation. Auxin was not essential for shoot initiation or development; however, a low concentration (0.03 mg/l) of α‐naphthaleneacetic acid (NAA) stimulated both explant survival and the number of shoots produced per disc. Indole‐3‐butyric acid (IBA) and indole‐3‐acetic acid (IAA) did not stimulate shoot initiation. GA3 was essential for both shoot initiation and subsequent shoot development. The highest incidence of morphogenesis (over 100 shoots in 12 weeks) occurred from tuber discs cultured at 18°C constant and under a photon flux density of 60 μE m‐2s‐1. No difference in regenerative ability was found in explants taken from source tubers stored for 0 to 20 weeks at 4°C. A histological examination indicated that shoots developed from small clusters of meristematic cells which were initiated from within small protuberances on the surface of the tuber disc 3 weeks after transfer.
The relevance of seed membrane lipids to imbibitional chilling effects
Authors: PRIESTLEY DAVID A. , LEOPOLD A. CARL 
Published: April 2006

AbstractImbibitional chilling injury during rehydration of seeds is particularly marked in soybean but not in pea. Following the previous reports that the deleterious effects of chilling on soybean germination are probably mediated at least in part through a loss of membrane integrity, differences in composition of membrane lipid components extracted from pea (chilling‐insensitive) and soybean (chilling‐sensitive) were examined. Comparative compositional analysis of phospholipids, fatty acids and free sterols revealed few disparities between the two species. When the membrane lipids were re‐formed into liposomes, little difference in permeability was found with respect to KCl, glucose or glycerol, even at chilling temperatures. It is suggested that the difference in chilling sensitivity between pea and soybean is not related to compositional differences in the major lipid components of the seed membranes.
Lipid composition and molecular organization in plasma membrane‐enriched fractions from senescing cotyledons
Authors: LEES G. L. , THOMPSON J. E. 
Published: April 2006

AbstractPlasma membrane fractions isolated from cotyledons of Phaseolus vulgaris L. cv. Kinghorn at various stages of senescence showed no significant change in fatty acid saturation with advancing senescence. However, the steroliphospholipid ratio increased by about 400% as senescence intensified. The lipid phase transition temperature of the membranes, which was measured by wide‐angle x‐ray diffraction, also rose from a point well below the growing temperature for young tissue to about 50°C for membrane from extensively senescent 9‐day‐old tissue. This means that by day 4 of germination there was a mixture of liquid‐crystalline and gel phase phospholipid in the membrane matrices. Crystallinity attributable to sterol‐sterol interaction was also apparent in the diffraction patterns for senescent membranes. The co‐existence of gel and liquid‐crystalline phase phospholipid in the aging membranes as well as the crystalline sterol aggregates presumably render the storage cells of cotyledons leaky and may thus facilitate the translocation of hydrolyzed food reserves into the vascular network.
Multiphasic accumulation of nutrients by plants
Authors: NISSEN PER , FAGERIA NAND K. , RAYAR ANTONI J. , HASSAN MOKHTAR M. , HAI TANG VAN 
Published: April 2006

AbstractSeedlings of rice (Oryza sativa), soybean (Glycine max) and sour orange (Citrus aurantium) were grown for 20 to 125 days under controlled conditions in nutrient solutions wiht up to 16 different concentrations of NH4+, H2PO4‐, K+, Ca2+, Mg2+ or Zn2+. Nutrient concentrations differed by up to 4 orders of magnitude (H2PO4‐ and Zn2+) and were kept constant or within certain limits by changing solutions daily. Dry weights and concentrations of N, P, K, Ca, Mg or Zn were determined for roots and tops (or roots, stems and leaves). The relationship between tissue concentration of an element and external concentration of the corresponding nutient ion was invariably multiphasic, with phases separated by sharp breaks or jumps. The kinetics of accumulation were similar to those of short‐term uptake of the same ions. Reanalysis of previously published data (including data for Mn2+) for other plants yielded, similarly, bi‐ or multiphasic isotherms for accumulation. Accumulation patterns and growth were in several instances correlated, with separate phases coinciding with regions of poverty adjustment, luxury consumption and toxicity.Implications of multiphasic kinetics of long‐term nutrient accumulation for membrane properties, fluxes and regulation include: (i) Membranes and uptake mechanisms must remain relatively constant throughout the life of the plant with respect to affinities for ions and concentrations at which transitions occur. (ii) Rate‐limitation occurs at the plasmalemma of the root cortical cells. (iii) Uptake is at all times under multiphasic control by the external solution.
Metabolism of free sugars in relation to starch synthesis in the developing Sorghum vulgare grain
Authors: BHATIA I. S. , GUMBER S. C. , SINGH RANGIL 
Published: April 2006

AbstractAccumulation of starch at expense of its free‐sugar precursors was studied in the developing grains of the ‘SL‐44’variety of Sorghum vulgare Pers. The content of starch gradually increased with the maturation of the grain and this increase was relatively fast until 18 days after anthesis. The daily rate of starch accumulation was at a maximum 15 days after anthesis. The content of total free sugars, reducing sugars, non‐reducing sugars other than sucrose, total and non‐sucrosyl fructose, and glucose also increased, reaching maximum values at 18 days after anthesis. Sucrose content gradually increased with a concomitant decrease in the activity of invertase, and sucrose was the major non‐reducing sugar in the matured grains. Detached heads incubated in labelled sugars indicated that, compared to sucrose and fructose. 14C was more efficiently incorporated from glucose into grain starch, which was maximally synthesized at the mid‐milky stage of grain development. Exogenous supply of NAD+ plus ATP stimulated the in vivo incorporation of 14C from sucrose to starch. The decline in the rate of starch accumulation did not synchronise with that of protein synthesis.
Properties of glutamate dehydrogenase from Beta vulgaris
Authors: NESSELHUT TH. , HARNISCHFEGER G. 
Published: April 2006

AbstractGlutamate‐NAD oxidoreductase, E.C. 1.4.1.3 (GDH), from seedlings of Beta vulgaris cv. Rota, Jahnsch Peragis Comp., was enzymatically characterized. This enzyme with molecular weight of 2.6 × 105 has a pH optimum of around 8 for animation of α‐KGA and around 9.5 for the desamination of glutamate. The apparent Km for α‐KGA is 6.7 × 10−4M, for NH3 2.5 × 10−3M, for NADH 3.2 × 10−5M and for NAADPH 5.5 × 10−4M. NAD1 inhibits the reaction non‐competitively when NADPH serves as substrate. The apparent K1 is 4.5 × 10−4M. The data are discussed on relation to the properties of GDH from other plant sources.
Extracellular invertase from Aspergillus flavus
Authors: OLUTIOLA P. O. , COLE O. O. 
Published: April 2006

AbstractAn extracellular invertase was induced in cultures of Aspergillus flavus Link during growth in liquid medium that contained sucrose as the sole carbon source. Synthesis of this enzyme was repressed by the addition of glucose or fructose to sucrose‐metabolizing cells, and was induced in a glucose or fructose‐metabolizing culture by the addition of sucrose. A. flavus invertase had a pH optimum of 6.0 and an apparent Km of approximately 133 mM for sucrose. The enzyme required potassium phosphate for maximum activity, optimum concentration being 250 mM. The enzyme was partially purified by ammonium sulphate precipitation followed by dialysis and separated by molecular exclusion into three components with molecular weights ranging from approximately 40,000 to 55,000.
Proline catabolism, relaxation of osmotic strain and membrane permeability in the diatom Phaeodactylum tricornutum
Authors: SCHOBERT BRIGITTE 
Published: April 2006

AbstractThe influence of osmotic stress on proline catabolism in the diatom Phaeodactylum tricornutum and the fate of proline after relaxation of osmotic stress are described. The conversion of 14C‐proline into metabolic products is greatly inhibited during water stress conditions. A sudden reversal of osmotic stress from 1.9 to 0.77 osmolar in the algal medium leads to a rapid decrease of the cellular proline concentration. This is mainly due to a release of proline into the outside medium of the algal cells, caused by a temporary breakdown of selective permeability in the plasmamembrane. The magnitude of membrane leakage depends on the concentration differences applied. It is supposed that the altered barrier properties reflect an increase in membrane fluidity, as a consequence of osmotic downshock. A replacement of NaCl by KCl, during continued osmotic stress, leads to a rapid and irreversible breakdown of selective permeability in the plasmamembrane. This effect might be due to a special lipid composition of the plasmamembrane or caused by an influence on the membrane potential.
A comparison of the influence of iron on the growth and nitrate metabolism of Anabaena and Scenedesmus
Authors: VERSTREATE DAVID R. , STORCH THOMAS A. , DUNHAM VALGENE L. 
Published: April 2006

AbstractA comparative study of growth and nitrate metabolism of Anabaena flos‐aquae (Lyng.) Bréb. and Scenedesmus bijugatus var. seriatus Chodat investigated possible mechanisms for the iron‐stimulated increases in growth specific for blue‐green algae in mixed algal communities. Algae were separately grown in an morganic medium with varying concentrations of iron and nitrate to determine the effects on each organism.Iron was found to be a limiting nutrient for cultures of both Anabaena and Scenedesmus as determined by chlorophyll a concentrations and cell enumeration. Both iron and nitrate stimulated the specific activity of nitrate reductase, nitrite reductase, and glutamine synthetase in Anabaena. Iron enrichment did not increase the activity of the enzymes in Scenedesmus, but inhibited the activity of nitrate reductase and glutamine synthetase. The stimulation of growth by iron in cells grown under iron limiting conditions was associated with increased nitrate metabolism in Anabaena but not in Scenedesmus.
Photooxidative damage to the photosynthetic apparatus during chilling
Authors: VAN HASSELT PHILIP R. , VAN BERLO HAN A. C. 
Published: April 2006

AbstractShort periods of chilling in the presence of light (up to 6 h: 1°C; 270 W/m2) decreased the subsequent apparent photosynthesis and chlorophyll fluorescence of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe. The extent of the injury depended on the duration of the chilling pretreatment. After 6 h the subsequent apparent photosynthesis even reached a negative value, and it increased only slightly during the next 2 1/2 h. The decrease of apparent photosynthesis was not a consequence of increased dark respiration but was of photooxidative origin since the presence of both light and oxygen was required. Preincubation in the light for 2 h at 20°C sensitized leaf discs to subsequent photooxidation during chilling. Prompt and delayed chlorophyll fluorescence decreased simultaneously after chilling and light treatment. The corresponding decrease of photosynthesis and chlorophyll fluorescence is discussed in relation to primary photooxidative damage to the photosystems in the chloroplast membrane.
Nitrogen fixation, stomatal response and transpiration in Medicago sativa, Trifolium repens and T. subterraneum under water stress and recovery
Authors: APARICIO‐TEJO PEDRO M. , SÁNCHEZ‐DÍAZ MANUEL F. , PEÑA JOSÉ I. 
Published: April 2006

AbstractStomatal behaviour, transpiration and nitrogen fixation were investigated in Medicago sativa L. (cvs. Tierra de Campos and Aragon, Hidalgo‐Maynar 1966), Trifolium repens L. (cv. Aberystwyth S‐184) and Trifolium subterraneum L. (cv. Clare) subjected to drought by withholding water and then to three days’ recovery after rewatering. Dawn leaf water potential was measured with pressure chamber, stomatal response with a diffusion porometer and nitrogen fixation by using acetylene reduction technique.At low water potentials, the leaf resistance was higher in Medicago than in Trifolium. As water stress developed all species decreased their transpiration, T. subterraneum being the one most affected by moderate deficits. During water stress ‘Tierra de Campos’ always maintained higher acetylene reduction levels than ‘Aragon’ and the Trifolium species, except for the lowest water potentials.During recovery from water stress only ‘Tierra de Campos’ reached predeficit transpiration rates. In ‘Tierra de Campos’ acetylene reduction recovery after rewatering was more rapid and intense than in ‘Aragon’. It is concluded that, of the plants investigated, ‘Tierra de Campos’ was best adapted to water deficits.
Callus formation from protoplasts of cell suspension cultures of Rosa ‘Paul's Scarlet’
Authors: STRAUSS ANDRÉ , POTRYKUS INGO 
Published: April 2006

AbstractSustained divisions of protoplast‐derived cells obtained from cell suspension cultures of Rosa‘Paul's Scarlet’ leading to colony and callus formation was achieved. The rather low plating efficiencies observed for agar‐plated protoplasts were partly due to early arrests in further development of dividing protoplast‐derived cells and cell clusters. Successful cultivation of dividing protoplast‐derived cells was particularly dependent upon frequent subculturing of the precultures and on an efficient procedure for viable protoplast isolation. Colony formation was largely independent of medium composition.
Cytokinin activity in oak (Quercus robur) with particular reference to transplanting
Authors: SMITH DAVID J. , SCHWABE W. W. 
Published: April 2006

AbstractCytokinin activity in sap collected under vacuum from field grown oaks (Quercus robur L.) was determined at monthly intervals throughout the year. A very low level in January was followed by an increase in February and March which reached its maximum 20–25 days before bud‐break. Levels decreased through April and May during leaf expansion, rising once more in June, 10–15 days before a second shoot growth flush. The levels then progressively decreased to reach a minimum in November and December.Cytokinin activity in roots, 24 h and one week after root‐tip removal did not differ significantly from that in intact control plants. Cytokinin activity in roots and shoots determined in relation to shoot growth flushes revealed no differences in the shoot while the activity in root extracts was lowered after a single flush of shoot growth.The effects of applying growth regulators at the time of transplanting were investigated by soaking entire transplants in hormone solution. Gibberellin promoted shoot growth at the expense of root growth, but root growth could be restored to normal levels by a simultaneous application of auxin. Cytokinin treatment increased leaf number, but resulted in small bushy plants.The seasonal changes in cytokinin activity are discussed with regard to successful transplanting.
Localization of divalent cations in phosphate‐rich cytoplasmic granules in yeast
Authors: ROOMANS GODFRIED M. 
Published: April 2006

AbstractPhosphate‐rich yeast cells (Saccharomyces cerevisiae) take up more calcium and strontium than phosphate‐deficient cells. The divalent cations appear to be tightly bound in phosphate‐rich cells. Electron microscopical investigations, combined with energy‐dispersive X‐ray microanalysis, showed that divalent cations were sequestered in cytoplasmic granules, together with a large amount of phosphorus. The major part of the divalent cations is retrieved in the polyphosphate fraction, a minor part is bound to lipids. The results suggest that polyphosphate granules may serve as an important store for divalent cations.
Variation in cell composition and utilization of N and P for growth of Selenastrum capricornutum
Authors: CLAESSON ANDERS 
Published: April 2006

AbstractCell material from different phases of growth for the green alga Selenastrum capricornutum Printz was analysed for major elements and chlorophyll a content. The ranges in percentage of the dry weight were 50–80%, 4.4–8.8%, 0.24–3.0%, and 0.20–3.23% for C, N, P and chlorophyll a, respectively. The dry weight per cell varied 2.3 times between different growth phases. A N/P‐quotient of about 10 (by weight) was found to be a critical level for Selenastrum when these elements were the most limiting nutrients for growth. 31 different organic N‐compounds were tested as single N sources in growth experiments with Selenastrum. At least 19 of them could be utilized to varying extent for algal growth. Three organic P‐compounds of six tested, were utilized for algal growth.Yield coefficients (mm3 cell volume/mg limiting nutrient element) for Selenastrum were determined with NO3, ‐N (yN= 134). NH4‐N (YN= 111) and PO4‐P (YP= 2580).
Control of respiration of binucleate and trinucleate pollen under humid conditions
Authors: HOEKSTRA FOLKERT A. , BRUINSMA JOHAN 
Published: April 2006

AbstractThe equal rates of water vapour absorption by both bi‐ and trinucleate pollen indicate that their widely‐differing rates of respiration have an intrinsic, biochemical basis. This was investigated with various metabolic inhibitors that were previously introduced into dry pollen via anhydrous acetone.The uncoupler, carbonyl cyanide m‐chlorophenyl hydrazone, inhibited the O2 uptake of rapidly respiring pollen and stimulated that of slowly respiring types to similar absolute values, that probably reflect the rates of substrate transport across the mitochondrial membranes.The extent of inhibition of the O2 uptake by oligomycin, dicyclohexyl carbodiimide, antimycin A, and salicyl hydroxamic acid, alone and in combinations, indicates that hardly any oxidative phosphorylation and anabolic activities occur in slowly respiring, binucleate pollen species, having low‐developed mitochondria and high energy charge values. The presence of the alternative pathway was insignificant.In other binucleate pollen species, characterized by recognizable mitochondria and low energy charge values, a limited ATP synthesis was established. The low energy charge values point to imbalance between phosphorylative and anabolic activities.In rapidly respiring, trinucleate pollen, containing well‐developed mitochondria, a significant activity of the alternative oxidase was found. The energy charge values were high notwithstanding the large demand for ATP, mounting to 1.7 μmol h−1 (mg pollen)−1.In some pollen species, oligomycin highly stimulated the flow of electrons through the cytochrome pathway, which made an estimation of the ATP synthesis impossible.
Analysis of newly synthesized proteins during differentiation of cultured Douglas fir cotyledons
Authors: YASUDA TAKESHI , HASEGAWA PAUL M. , CHENG TSAI‐YING 
Published: April 2006

AbstractAddition of plant growth regulators (5 nM NAA and 5μM BAP) to a defined basal medium stimulated adventitious bud formation of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) cotyledon explants in culture. Cytoplasmic soluble proteins synthesized during early stages of adventitious bud formation were analyzed by electrophoresis of 3H‐ and 14C‐leucine labeled proteins on SDS polyacrylamide gels. Increased synthesis of low molecular weight proteins (16,000 to 20,000 daltons) was detected after 2 days in culture and reached a maximal level at day 4. When cotyledon explants cultured on bud medium for 2 days were transferred to callus medium (which suppressed adventitious bud formation), suppression of the synthesis of low molecular weight proteins was also observed, suggesting that these proteins may be associated with early stages of adventitious bud formation.