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Abstract. Exudation of sugars (glucose, fructose and sucrose) and that of cations and anions from intact roots of kallar grass [Leptochloa fusca (L.) Kunth] grown hydroponically with ammonium or nitrate (3mM) as N source was investigated. In different experiments, plants grown on ammonium had slightly higher sugar contents than nitrate-grown plants, but their total sugar exudation during a 2-h period...
Abstract. In mesophyll cells of the aquatic angiosperm Vallisneria gigantea Graebner, red, blue, or blue plus far-red light induced a typical membrane hyperpolarization, whereas far-red light alone had little effect. Both N,N-dicyclohexylcarbodiimide, a potent inhibitor of H+-ATPase, and carbonylcyanide m-chlorophenylhydrazone, an uncoupler, produced a considerable membrane depolarization in the dark-adapted...
Abstract. In shoot tip-derived tissue cultures of Scots pine (Pinus sylvestris L.), browning and subsequent degeneration of the culture is accompanied by lipid peroxidation and lignification of cells, which are characteristic features of a plant defense reaction. Since chitinases are enzymes acting primarily in plant defense, their expression was studied in pine callus in order to elucidate the defense...
Abstract. The conversion of nicotine to nornicotine by Nicotiana plumbaginifolia Viv. cells was investigated by analysing the redistribution of label during feeding experiments with (R,S)-[2H-methyl]nicotine, (R,S)-[13C-methyl]nicotine and (R,S)-[14C-methyl]nicotine, and the results show that the N-methyl group of nicotine can be recycled into primary metabolism. Nuclear magnetic resonance (NMR) analysis...
Abstract. Physiologically active gibberellins (GAs) are key regulators of shoot growth in trees. To investigate this mechanism of GA-controlled growth in hybrid aspen, we cloned cDNAs encoding gibberellin 20-oxidase (GA20-oxidase), a key, highly regulated enzyme in the biosynthesis of GAs. Clones were isolated from leaf and cambium cDNA libraries using probes generated by polymerase chain reaction,...
Abstract. In plants of Sinapis alba L. induced to flower by one long day (LD), previous work showed that the phloem sap feeding the shoot apex is enriched in cytokinins of the isopentenyladenine (iP)-type between 9 and 25h after start of the LD [P. Lejeune et al. (1994) Physiol Plant 90:522528]. We have checked the hypothesis that the cytokinin content of the shoot apical meristem (SAM) should increase...
Abstract. Reactive oxygen intermediates, i.e. the superoxide radical ( ), hydrogen peroxide (H2O2) and the hydroxyl radical ( ), are generally regarded as harmful products of oxygenic metabolism causing cell damage in plants, animals and microorganisms. However, oxygen radical chemistry may also play a useful role in polymer breakdown leading to wall loosening...
Abstract. CO2 fluxes in the marine microalga Nannochloris atomus were studied by mass spectrometry using inhibitors and artificial acceptors of photosynthetic electron transport to investigate the energy source for CO2 uptake. This algal species is capable of taking up CO2 from the external medium by active transport but lacks active HCO3 transport and extracellular carbonic anhydrase. The capacity...
Abstract. The role of S-assimilation and the biosynthesis of cysteine and glutathione were studied during the response to salt stress of wild-type and salt-tolerant transgenic Brassica napus L. (canola) plants overexpressing a vacuolar Na+/H+ antiporter. A 3-fold increase in cysteine and glutathione content was observed in wild-type plants exposed to salt stress, but not in the transgenic plants....
Abstract. Zygotic embryos of three Arabidopsis thaliana (L.) Heynh. mutants lacking an embryonic shoot apical meristem (SAM), shoot meristemless (stm), wuschel (wus) and zwille/pinhead (zll/pnh) were used as explants to establish embryogenic cell cultures. Somatic embryos of all three mutants showed the same mutant phenotypes as their zygotic equivalents. These results provide genetic evidence that...
Abstract. Thaumatin-like proteins (TLPs) were isolated and characterized from fruits and leaves of elderberry (Sambucus nigra) and their corresponding genes cloned. In addition, the developmental regulation and induction of the different TLPs was followed in some detail. Ripening berries accumulated a fruit-specific TLP during the final stages of maturation. This fruit-specific TLP had no antifungal...
Abstract. Treatment of tomato (Lycopersicon esculentum L. cv. Beefstake) fruit with low concentrations of (0.01mM) methyl jasmonate (MeJA) or methyl salicylate (MeSA) substantially enhanced their resistance to chilling temperature and decreased the incidence of decay during low-temperature storage. While studying the expression of pathogenesis-related (PR) protein genes, different accumulation patterns...
Abstract. The effect of the anti-microtubular drug oryzalin on growth and morphology of cultured rice (Oryza sativa L., cv. Roncarolo) cells was evaluated with specific reference to mechanisms that control intracellular tubulin levels. The addition of oryzalin caused a great reduction in the level of both - and -tubulin polypeptides, as detected by Western blot analysis. However, no appreciable decrease...
Abstract. Cell-suspension cultures were produced from transgenic tobacco (Nicotiana tabacum L. ) plants harboring a constitutively expressed alfalfa cinnamate 4-hydroxylase (C4H) transgene. Increased levels of C4H enzyme activity in the transgenic cultures were observed only following exposure of the cells to yeast elicitor, although alfalfa C4H transcripts were expressed at a high level from the...
Abstract. Sporangiophores of Phycomyces blakesleeanus that are gravitropically stimulated by inclining them relative to the earth's gravitational vector obey the sine law for inclination angles between 0 and 150. The quantitative relation between gravitropism and phototropism was analyzed for sporangiophores that were kept in balance between opposing gravitational and phototropic stimuli. The gravitropism...
Abstract. The metabolic cross-talk associated with re-assimilation of photorespiratory NH4+ was analysed in transformed tobacco (Nicotiana tabacum L.) plants with low activities of ferredoxin-dependent glutamine-ketoglutarate aminotransferase (Fd-GOGAT; EC 1.4.7.1). Amounts of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) protein and Rubisco transcripts were similar in all...
Abstract. In vitro treatment with trypsin of plasma membrane (PM) vesicles isolated from the leaves of Vallisneria gigantea Graebner, an aquatic monocot, produced a marked decrease in the Km for ATP and an increase in the Vmax of H+-transporting activity. Concomitantly, the removal of 8kDa of the C-terminal domain from the 94-kDa PM H+-ATPase was confirmed by immunoblotting using different kinds of...
Abstract. Emerging data suggest that the mechanisms regulating plant copper homeostasis could be implicated in stress and senescence signal transduction pathways. To gain insight into copper-modulated patterns of gene expression, copper-treated Arabidopsis thaliana (L.) Heynh. plants were analysed by mRNA differential display. The experimental conditions were selected using aggregation of ribulose-1,5-bisphosphate...
Abstract. We previously reported on Vicia narbonensis seeds with largely decreased -D-glucose-1-phosphate adenyltransferase (AGP; EC 2.7.7.27) due to antisense inhibition [H. Weber et al. (2000) Plant J 24:3343]. In an extended biochemical analysis we show here that in transgenic seeds both AGP activity and ADP-glucose levels were strongly decreased but starch was only moderately reduced and contained...
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