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Abstract. Castor bean (Ricinus communis L.) plants were grown for 57 weeks in a controlled environment at 350ll1 or 700ll1 CO2. Carbon assimilation, assimilate deposition, dark respiration and assimilate mobilization were measured in leaves 2, 3 and 4 (counted from the base of the plant), and a balance sheet of carbon input and export was elaborated for both CO2 concentrations. Carbon dioxide assimilation...
Abstract. During senescence of flowering plants, only breakdown products derived from chlorophyll a were detected although b disappears, too (Matile etal., 1996, Plant Physiol 112: 14031409). We investigated the possibility of chlorophyllb reduction during dark-induced senescence of barley (Hordeum vulgare L.) leaves. Plastids isolated from senescing leaves were lysed and incubated with NADPH. We...
Abstract. Mutations that reduced the rate of starch synthesis in pea (Pisum sativum L.) embryos through effects on enzymes on the pathway from sucrose to adenosine 5-diphosphoglucose (ADPglucose) also led to a reduction in the amylose content of the starch of developing embryos. Evidence is presented that this relationship between rate of synthesis and the composition of starch is due to the fact...
Abstract. Many bulbous plants need a low-temperature treatment for flowering. Cold, for example, affects the elongation of the stalk, thereby influencing the quality of the cut flower. How the elongation of the stalk is promoted by cold and which physiological and biochemical mechanisms are involved have remained obscure. As invertase has been shown to be involved in the cold-induced elongation of...
Abstract. The aim of this work was to investigate the extent to which starch synthesis in potato (Solanum tuberosum L.) tubers is controlled by the activity of ADPglucose pyrophosphorylase (EC 2.7.7.27; AGPase). In order to do this, fluxes of carbohydrate metabolism were measured in tubers that had reduced AGPase activity as a result of the expression of a cDNA encoding the B subunit in the antisense...
Abstract. During the glyoxysomal -oxidation of long-chain acyl-CoAs, short-chain intermediates accumulate transiently (Kleiter and Gerhardt 1998, Planta 206: 125130). The studies reported here address the underlying factors. The studies concentrated upon the aspects of (i) chain length specificity and (ii) metabolic regulation of the glyoxysomal -oxidation of sunflower (Helianthus annuus L.) cotyledons...
Abstract. The composition of seed storage proteins is regulated by sulfur and nitrogen supplies. Under conditions of a low sulfur-to-nitrogen ratio, accumulation of the -subunit of -conglycinin, a sulfur-poor seed storage protein of soybean (Glycine max [L.] Merr.), is elevated, whereas that of glycinin, a sulfur-rich storage protein, is reduced. Using transgenic Arabidopsis thaliana [L.] Heynh.,...
Abstract. The degradation of peroxisomal and nonperoxisomal proteins by endoproteases of purified peroxisomes from senescent pea (Pisum sativum L.) leaves has been investigated. In our experimental conditions, most peroxisomal proteins were endoproteolytically degraded. This cleavage was prevented, to some extent, by incubation with 2mM phenylmethylsulfonylfluoride, an inhibitor of serine proteinases...
Abstract. Phototropism and polarotropism in protonemata of the moss Ceratodon purpureus are controlled by the photoreceptor phytochrome. One class of phototropism mutants is characterised by growing randomly when kept for a prolonged time (5d or longer) in unilateral red light. It was found that a subclass of these mutants grows faster than the wild type, the rate of cell division and the length of...
Abstract. Water stress stimulates sucrose synthesis and inhibits starch and cell-wall synthesis in tissue slices of growing potato (Solanum tuberosum L. cv. Desire) tubers. Based on the analysis of fluxes and metabolites, Geigenberger etal. (1997, Planta 201: 502518) proposed that water deficits up to 0.72MPa stimulate sucrose synthesis, leading to decreased starch synthesis as a result of the resulting...
Abstract. Freshly cut discs from growing potato tubers were incubated for 3h with 10mM orotate or 10mM uridine. Control discs incubated without precursors showed a 3040% decrease of uridine nucleotides, but not of adenine nucleotides. Orotate- and uridine-feeding led to a 1.5- to 2-fold increase in the levels of uridine nucleotides compared with control discs, and a 1530% increase compared with the...
Abstract. Apical cells of protonemata of the moss Ceratodon purpureus (Hedw.) Brid. are negatively gravitropic in the dark and positively phototropic in red light. Various fluence rates of unilateral red light were tested to determine whether bothtropismsoperate simultaneously. At irradiances 140nmolm2s1 no gravitropism could be detected and phototropism predominated, despite the presence of amyloplast...
Abstract. In order to obtain a three-dimensional view of the plastid-dividing ring (PD ring) and promote the biochemical study of plastid division, we developed a procedure to isolate structurally intact dividing chloroplasts (rhodoplasts) possessing PD rings from a highly synchronized culture of the unicellular red alga Cyanidioschyzon merolae. The procedure consists of five steps. (1) The chloroplast...
Abstract. The import and assembly of mitochondrial proteins synthesized in the cytosol is mediated by the protein-import apparatus which plays a central role in mitochondrial biogenesis. Ten years ago only some components of the protein-import apparatus from fungi and mammals were characterized, but today its major components have been analyzed at the molecular level also in plants. Interestingly...
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