Effect of nitrogen source and light conditions on 14C-behavior of 14C-[U]-sucrose, 14C-[U]-asparagine, and 14C-[U]-serine introduced to leaf of rice and sorghum plants

Abstract

For the study of the 14C-behavior of introduced 14C-compounds, 14C-[U]-sucrose, 14C-[U]-asparagine, and 14C-[U]-serine were introduced from the tip of the leaf at the vegetative growth stage of rice and sorghum plants, which were grown with NH4-N or NO3-N, and under light or dark conditions. The results obtained were as follows. 1. Pattern of 14CO2release rate was similar between light-light (indicating light conditions before and after 14C-compounds were introduced) and dark-light conditions, and between light-dark and dark-dark conditions, but different between light-light and light-dark conditions and between dark-light and dark-dark conditions, irrespective of crop species. Thus, 14CO2release rate was strongly affected by the light conditions after introduction of the 14C-compounds. 2. Since the 14CO2release rate of rice was higher than that of sorghum under the light condition, it was assumed that sorghum was able to reassimilate CO2which was released by respiration in the cells. 3. 14CO2release from introduced 14C-sucrose and introduced 14C-asparagine was not affected by the nitrogen source, but 14CO2release from 14C-serine was larger to some extent when NO3-N was applied than when NH4-N was applied. © 1995 Taylor & Francis Group, LLC.