Einfluß der Schwefelversorgung auf das lösliche Blattprotein sowie die Ausbildung und die spezifische Aktivität einiger Enzyme junger Sonnenblumen

Influence of the amount of sulfur supplied on the soluble leaf protein, the synthesis and the specific activity of some enzymes of young sunflower plants The influence of a sulfur supplement on the pattern of leaf proteins, soluble in 0.1 M phosphate buffer, pH 7.5, was studied in experiments with young sunflower plants. The leaves were harvested after growing periods of 14 and 21 days, respectively. In addition, the electrophoretic distribution of isoenzymes of some enzyme systems and their specific activities have been analyzed. 1. Plant fresh weight was not affected by the level of sulfur supply, although symptoms of S-deficiency were observed in the low S-treatment. 2. In contrast to this finding, a clear effect of S-deficiency on the electrophoretic patterns of the leaf proteins was detected. This was specially the case in plants. grown for three weeks at a low sulfur level. Increased contents of low molecular protein fractions were found, whereas the relative amounts of high molecular proteins were reduced. 3. In plants, which were kept S-deficient, the number of isoenzyme components was lower in comparison to plants, which were adequately supplied with sulfur. The isoenzymes of malate dehydrogenase and acid phosphatase, however, were synthesized to about the same degree in both S-treatments. 4. The specific activities of most of the enzymes studied in these investigations were lower in the plants, grown at S-deficiency in comparison with the control. These findings were particularly evident after a growth period of 3 weeks. The specific activities of glutaminate dehydrogenase, succinate dehydrogenase and a-ketoglutarate dehydrogenase were not significantly influenced by the level of S-supply. The specific activities of acid phosphatase and malate dehydrogenase were relatively high even in those plants, which were treated with low amounts of sulfur.