Studies on the Nitrogen Metabolism in Crop Plants : IV. Effects of several chemical substances and root extracts of rice plant on chlorophyll retention in rice leaf sections

[摘要] Effects of kinetin and other natural substances on chlorophyll retention in rice leaf sections were studied. A leaf section was floated in a petri dish containing a solution of test substance (s) and allowed to stand for 72 hours at 30°C in the dark. It was found that the effect of kinetin on chlorophyll retention in rice leaf sections was more marked in the mature leaf than the young. In this assay, kinetin gave a linear response at concentrations ranging from 0.001 to 0.1 ppm if plotted on a logarithmic scale. Several substances, which were found ordinarily in plant, were tested for their activity of chlorophyll retention in leaf sections. Among those substances tested, a mixture of adenine (100 mg/l) and casein hydrolyzate (1000 mg/l) showed a comparable effect as that of kinetin. Combined effects of kinetin and gibberellic acid (GA3), and kinetin and indole-3-acetic acid (IAA) were tested. High concentration. of GA3 stimulated a degradation of chlorophyll. In the presence of GA3, level of kinetin required for chlorophyll retention increased. Similar results have also been obtained with IAA. It may be assumed that there were antagonistic interaction between kinetin and GA3, and kinetin and IAA. It was also attempted to isolate kinetin-like substances from roots of rice plant (Oryza sativa. var, Honenwase). Kinetin-like activity was determined by two ways; chlorophyll retention of rice leaf sections and carrot callus growth. The roots extract was held on Dowex 50W H+ form at pH 2.5 and eluted with 5N ammonium hydroxide. The eluate was further developed on a filter paper (Toyo, No. 51) using a solvent system of n-butanol-acetic acid-water (12:3:5 v/v). The kinetin-like activity was found at Rf 0.20-0.30, 0.50-0.55, and 0.75-0.80. Substance of Rf 0.50-0.55 was found to be highly active in the chlorophyll retention assay, while substance of Rf 0.75-0.80 was very active in the carrot callus-growth assay. These substances were further fractionated by a column chromatography with Dowex 50W-X8, H+ form. When eluted with 2.0N hydrochloric acid, kinetin-like activity was found in fraction Nos. 110∼200. Chromatographic behavior of the fraction 110∼200 seems to be similar to that of factors reported by Rogozinska et al. (1965) and Matubara et al. (1966).

[学科分类] 农业科学（综合）