Studies on Protein Content in Rice Grain : III. Effect of nitrogen top-dressing at full heading time on the translocation of nitrogen to the ear

Abstract

Using the rice varieties grown under pot cultivation, we investigated the effect of nitrogen top-dressing at full heading time on the distribution of nitrogen among the different organs and discussed about the translocation of nitrogen from other organs to the ear. The results are summarized as follows: 1. The nitrogen content of the leaf blade on the control (non top-dressed) plot decreased rapidly with time throughout ripening period. The nitrogen content of the leaf blade on the treatment (top-dressed) plot increased temporarily after top-dressing. Although it decreased thereafter continuously till maturing stage, the nitrogen content of the leaf blade at maturing stage showed more than double of that on the control plot. 2. The nitrogen content of the leaf sheath and the culm gradually decreased after full heading time on both plots. The nitrogen content of the leaf sheath and the culm at maturing stage on the top-dressing plot was nearly equal or rather superior to that at full heading time, because their nitrogen content as well as that of the leaf blade increased temporarily after top-dressing. 3. The nitrogen content of the ear on the top-dressing plot increased rapidly compared with that of the control plot and the nitrogen content of the ear at maturing stage was 1.4∼1.8 times more than that on the control plot. It seemed that this fact did not depend on the difference of ear weight but was caused by the difference of nitrogen percentage of the ear on both plots. 4. Most of the nitrogen contained in the ear at maturing stage on the control plot seemed to be translocated from the other organs, especially the leaf blade. The nitrogen absorbed from soil seemed to be only a very small amount in the nitrogen of the ear on the control plot. The nitrogen absorbed after top-dressing on the treatment plot seemed to be a large amount of the nitrogen contained in the ear and it corresponded to 58∼74 percent of the nitrogen content of the ear at maturing stage. The nitrogen content translocated from the leaf blade to the ear on the treatment plot was about 14∼26 percent in the nitrogen of the ear at maturing stage and the nitrogen translocated to the ear from the leaf sheath and culm seemed to be negligible or nothing.