6533b862fe1ef96bd12c6ae8

RESEARCH PRODUCT

Die Wirkung unterschiedlicher Lichtintensitäten auf die Nitratreduktase-Aktivität, den Gehalt an löslichen Proteinen und löslichen reduzierenden Zuckern von Sinapis alba im Verlauf der Entwicklung von der Keimung bis zum Blühen

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Summary Plants of Sinapis alba (white mustard) grown under strong light conditions have a higher content of soluble reducing sugars, of soluble proteins and a higher dry wight during growth from germination to flowering. Furthermore, in these plants the nitrate reductase activity is essentially higher during the vegetative development, but before the beginning of the flowering phase the activity is less than the level of plants grown under low light intensities. The results obtained indicate a direct correlation between nitrate reductase activity and the content of soluble proteins. In the high-light plants both components show distinct maxima 13—14 days after sowing the seeds. The enhancement of the nitrate reductase activity is quickly followed by a higher concentration of soluble proteins. In low-light plants the nitrate reductase activity requires about 46 days to attain the maximum rate. The maximum rate of nitrate reductase activity and of protein content is accompanied by a minimum in the content of reducing sugars. Two hypotheses are proposed to explain these results: During the time of high nitrogen assimilation the products of photosynthesis are needed to establish the reductant required in the conversion of nitrate to ammonia and the carbon skeletons for amino acid biosynthesis. Another explanation is that the concentration of reducing sugars exerts a regulatory influence on metabolic processes of nitrogen assimilation. The latter hypothesis is favoured by other results which show that the primary effect of sublethal dosis of photosynthesis inhibiting herbicides is a lowering of the concentration of reducing sugars followed by an increased level of nitrogen and the stimulation of both nitrogen reductase activity and protein synthesis.