Showing papers by "University of Hohenheim published in 1978"

Effect of silicon on manganese tolerance of bean plants ( Phaseolus vulgaris L.)

Abstract: The effect of silicon on manganese tolerance of bean plants (Phaseolus vulgaris L var ‘Red Kidney’) grown in water culture was studied at different levels of manganese supply Without silicon, growth depression and toxicity symptoms occurred already at 5 × 10−4 mM Mn in the nutrient solution After addition of Aerosil (075 ppm Si), the plants tolerated 5 × 10−3 mM Mn and, at a higher silicon supply of 40 ppm, as much as 10−2 mM Mn in the nutrient solution without any growth depression This increase in manganese tolerance was not caused by a depressing effect of silicon on uptake or translocation of manganese but rather by an increase in the manganese tolerance of the leaf tissue In absence of silicon, 100 ppm Mn was already toxic for the leaf tissue, whereas with a supply of 40 ppm Si, this ‘critical level’ in the leaves was increased to more than 1000 ppm Mn At lower manganese levels in the leaf tissue, a molar ratio Si/Mn of 6 within the tissue was sufficient to prevent manganese toxicity Above 1000 ppm Mn, however, even a much wider Si/Mn ratio (> 20) could not prevent growth depression by manganese toxicity With54Mn and autoradiographic studies, it could be demonstrated that, in absence of silicon, even at optimal manganese supply (10−4 mM), the distribution of manganese within the leaf blades was inhomogeneous and characterized by spot-like accumulations In presence of silicon, however, the manganese distribution was homogeneous in the lower concentration range of manganese and still fairly homogeneous in the high concentration range This effect of silicon on manganese distribution on the tissue level was also reflected on the cellular level In the presence of silicon, a higher proportion of the leaf manganese could be found in the press sap,ie, had been transported into the vacuoles, than in the absence of silicon The increase in manganese tolerance of bean leaves by silicon therefore seems to be primarily caused by the prevention of local manganese accumulation within the leaf tissue which leads to local disorders of the metabolism and, correspondingly, growth depression

Metabolism of hydrogenated palatinose, an equimolar mixture ofα-D-glucopyranosido-1,6-sorbitol andα-D-glucopyranosido-1,6-mannitol

Abstract: Hydrogenated palatinose, an equimolar mixture ofα-D-glucopyranosido-1,6-sorbitol andα-D-glucopyranosido-1,6-mannitol, was investigated as a potential oral sugar substitute in the following experiments in man and rat. 1. Enzymatic cleavage occured at slow rates by maltase (α-glucosidase) of jejunal mucosa, liver lysosomes and yeast. 2. Part of ingested hydrogenated palatinose arrived unsplit at the caecum of the rat and underwent fermentation there; excretions in feces and urine are neglegible in man and rat. 3. Growth and maintenance of rats demonstrated 20–40% diminished caloric utilisation of diets containing 34.5% hydrogenated palatinose whereas indirect calorimetry in man showed about 50% caloric deficit. 4. Blood sugar did not increase in man after oral doses up to 100g. 5. The capacity of the rat kidneys for excretion of hydrogenated palatinose and its constituents was high, symptoms of incompatibility were not observed.

Inhibition of ergosterol biosynthesis by triadimenol in Ustilago avenae

Abstract: In Ustilago avenae sporidia, following the first doubling period of about 4 h, triadimenol (2 μg ml−1) affected sporidial multiplication more severely than other growth processes; daughter cells failed to separate from the parent sporidia resulting in chains of interconnected cells. Triadimenol incubated with the fungus for 8 h interfered neither with respiration nor with protein and nucleic acid synthesis but after 6 h the toxicant had induced a higher content of free fatty acids. Triadimenol markedly altered, both quantitatively and qualitatively, the sterols in sporidia of U. avenae. Incorporation of [14C]acetate (in the form of sodium acetate) into lipid fractions for a period of 2 h revealed that the toxicant powerfully inhibited the synthesis of the 4-demethyl sterol fraction (predominantly ergosterol), whilst the 4,4-dimethyl sterol fraction rapidly accumulated. This was confirmed by g.1.c. analysis of the sterols after 6 and 8 h incubation which showed that the amount of ergosterol, the major sterol in untreated sporidia, was diminished while simultaneously 4,4-dimethyl, 4-methyl and 14-methyl sterols increased. The accumulation of 14-methyl sterols suggests that triadimenol acts as a potent inhibitor of one of the metabolic steps involved in the demethylation at the 14-position during ergosterol biosynthesis.

Characterization of a new methylotrophic strain, Methylomonas clara

Abstract: The organism examined was identified as an obligate methylotroph and as an organism of type I, because it has some characteristics of this group: methanol is utilized via the hexulose phosphate pathway, the enzymes glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malate dehydrogenase, and isocitrate dehydrogenase (both NAD- and NADP-specific) could be detected, whereas the citric acid cycle is incomplete (in particular α-ketoglutarate dehydrogenase could not be found). Furthermore, the organism is able to fix nitrogen. In contrast, there are some different characteristics: carbon dioxide can be fixed in connection with methanol. There is no formate dehydrogenase, and formaldehyde dehydrogenase can be induced by different culture conditions. Moreover, the GC content (49.2%) is distinctly lower than normal, and the hexulose phosphate synthase shows a higher activity with NAD as cosubstrate than with NADP. Carbon is not metabolized via the Embden-Meyerhoff-Parnas pathway, but via the Entner-Doudoroff pathway. In the disk test, the organism is resistant to some antibiotics: chloramphenicol, fusidic acid, methicillin and lincomycin. A partial resistance can be observed with penicillin, neomycin, novobiocin, and cloxacillin.

Gibberellin like Substances in Parts of Developing Barley Grain

Abstract: In husks, the activity of gibberellin-like substances extracted with aqueous methanol (M-“free” GAs) showed a maximum on the 9th day after pollination. In developing embryos, M-“free” GAs showed no biological activity, whereas biological active component(s) were obtained when the embryos were extracted with Tris buffer. The “free” GAs found in the buffer homogenates (B-“free” GAs) of developing embryos showed a maximum of activity on the 33rd day after pollination. Bound GAs recovered from the precipitated protein of the buffer homogenate (“Protein-bound” GAs) were found in embryo and endosperm. Developing endosperm generally contains the major amount of the extractable gibberellin-like substances. In this tissue, the amount of all examined fractions (M-“free” GAs, B-“free” GAs and “protein-bound” GAs) increased after pollination to reach a maximum on the 21st day, before decreasing to a minimum at grain maturity. Moreover, the curves for dry weight increase and gibberellin like substances follow a remarkably similar course, with the latter reaching its maximim slightly earlier than the former one. This result indicates that gibberellines may participate in the regulation of the accumulation process in the endosperm of barley grain.

The limited contribution of the nuclear envelope to metabolic compartmentation.

Abstract: If compartmentation is understood as the structural organization of cells, which in consequences permits the spatial separation of temporal events such as metabolic chain reactions and/or their single steps, then the nuclear envelope is indeed no prominent representative of strictly efficient separation phenomena as indicated in the title of this paper. Yet various experimental designs, requiring careful individual scrutiny for the admissibility of the methods used, yield data suggestive of compartmentation phenomena at the site of the cell nucleus.

Isolierung und Charakterisierung Antipyrin-abbauender Bakterien / Isolation and Characterization of Antipyrine-degrading Bacteria

Abstract: Abstract Five different strains of bacteria ultilizing antipyrine as sole source of carbon were isolated from soil. It was shown by morphological and physiological examinations, that the new isolates are closely related to strains selected with the herbicide chloridazon. A ll of these bacteria are charac terized by special features and cannot be classified according to Bergey’s Manual of Determinative Bacteriology. Part of the strains which were selected with antipyrine not only grow with antipyrine but also with chloridazon. The others cannot be grown on chloridazon. However, resting cells of the latter group convert chloridazon to its catechol derivative (5-amino-4-chloro-2 (2,3-dihydroxyphenyl) -3 (2H)-pyridazinone). In these bacteria a catechol-2,3-dioxygenase (catechol: oxygen 2,3-oxido-reductase, EC 1.13.11.2) was found which readily catalyzes the cleavage of the catechol derivative of antipyrine (2,3-dimethyl-l-(2,3-dihydroxyphenyl)-pyrazolone (5)). The enzyme shows only slight activity with the corresponding derivative of chloridazon.

Partial Diallel Cross in Multi‐environment

Abstract: Analysis of partial diallel cross repeated over environments is discussed. Formulae are given to estimate the general combining ability effects and their interaction effects with environments. Analysis of variance table along with expected mean squares is given.