Effect of Nitrogen Application on Ultrastructure of the Chloroplasts in Rice Plants

Abstract

Rice plants were grown in 1/5000 are Wagner pots with different levels of nitrogen basal dressing (non-application, 0.6 g nitrogen per pot, 3.0 g nitrogen per pot), and changes in chloroplasts ultrastructure were observed immediately after the leaves had fully expanded (Table 1, Figs. 1-3). The size of chloroplasts and the number of grana increased by nitrogen application, but the effect was not so marked when the amount of applied nitrogen was increased from 0.6 g to 3.0 g. The starch grains in the chloroplasts were markedly reduced by application of 3.0 g nitrogen. Effect of nitrogen top-dressing was observed on ultrastructure of the chloroplasts in fully expanded leaves of nitrogen-deficient plants (Table 1). In the chloroplasts of nitrogen-deficient plants, the separation of thylakoid membranes, which is the first sign of senescence, was observed at 11 days after leaf expansion (Fig. 4). However, by nitrogen top-dressing the senescence was depressed and the formations of grana and stroma were accerelated (Fig. 5). The size of chloroplasts also increased by nitrogen top-dressing (Table 2), therefore the chloroplasts increased the surface area which contact with inner surface of the cell wall. In the leaves top-dressed by nitrogen, the starch grains were disappeared, but the amount of plastoglobuli was not reduced.