Compartment analysis of nitrogen flows through mature leaves

Abstract

Nitrogen flows in mature leaves of rice, sunflower and corn were analyzed by multicompartment analyses of data from 15N tracer experiments. The fourcompartment model fit the measured data better than the two- or three-compartment models. Rate constants of the nitrogen flows, transfers with or without protein turnover and flow through a storage pool of soluble-N, were derived from a least-squares fit between the mathematical expressions and the corresponding measured data.Results of computations indicated the following: The flow of nitrogen through the protein pool was larger than the direct flow in recently matured leaves, whereas the reverse was true in senescent leaves. The presence of a temporary storage pool of soluble N was suggested, and the half-life of the N exchange in that pool was estimated to be roughly the amount of the insoluble N present in three of the four cases examined. The half-lives of insoluble N (protein) pools were 35 to 150 h. The pool for the N efflux from the leaves was small with the shortest half-lives (most less than 2 h) of N turnover. Some recycling of N during protein turnover was suggested in sunflower leaves, but the extent in the leaves of rice seedlings was estimated to be little. Copyright © 1984. The Japanese Society of Plant Physiologists.