Studies on Nitrogen Metabolism of Soybean Leaves : 2. Protein metabolism of petiole-girdled leaves with special reference to the behaviour of nitrogen liberated by protein breakdown

Abstract

The petiole-girdled leaves of soybean plants, which have been placed for a short period of time in the nitrogen deficient solution, exhibited continual decrease in protein with corresponding increase in soluble nitrogenous compounds. Translocation of these soluble nitrogenous compounds through the girdle was found to be almost entirely disturbed, as total nitrogen content (expressed as leaf area basis) in the leaves plus petioles (portions above the girdle) were little changed throughout the experimental period. About half the nitrogen liberated by protein degradation in the petiole-girdled leaves appearred in the petiole portions above the girdle, and there, fair amount of the migrated nitrogen was elaborated into petiole proteins. Pteiole-girdled leaves, which have been deprived of exogenous nitrogen sources, recovered the ability of synthesizing and maintaining protein only when nitrogen was added exogenously to the plants. The results of chemical analysis as well as the facts mentioned above suggested that newly added nitrogen may have been better available for new protein synthesis than soluble nitrogen that had been retained in the petiole-girdled leaves.