Respiration of soybean plants in relation to their physiological conditions. IV. Time course changes in nitrogen metabolism in a leaf.

Abstract

Time course changes in nitrogen transformation among nitrogenous compounds in a detached leaf of soybean was examined in relation to respiration rate. Nitrogen content in protein continued to increase for 12 hours from the onset of dark period. This apparent protein synthesis showed a high peak betwreen 0:00 and 3:00 in an expanding leaf, and a low peak in an expanded leaf, followed by a steep decrease in both leaves. This trend of protein synthesis fitted to the time course change of respiration rate. The time of maximum protein synthesis rate corresponded to that of midnight rise of respiration appearance. It was, therefore, supposed that the time course changes in respiration which has been examined in the previous papers, is the reflection of diurnal changes in protein synthesis rate in a leaf.