Effects of shading and nitrogen fertilizer rates on the leaf emergence rate and tillering of rice plants, with special reference to the turning point of the leaf emergence rate.

摘要

In pot experiments, rice plants were grown with 0, 50 or 95% shading and given 25, 100 or 300 mg N/pot (1/5000 a pots) supplied every 10 days after sowing. The number of leaves on the main stem in the 0 and 50% shading treatments increased linearlyup to the turning point of the leaf emergence rate (TPLER), then showed a lower linear increase, while in the 95% shading treatment the increase was shown by a single straight line because there was no TPLER. The leaf emergence rate before TPLER was affected strongly by light intensity, but not by the level of N, and was fastest in the plot with the highest light intensity. The effect of light intensity on the leaf emergence rate decreased markedly after TPLER. The leaf emergence rate in the plot with no shading was faster with higher N levels both before and after TPLER, but this was not true for the shaded plots. Tillering was influenced by light intensity and the largest number of tillers was obtained in the plot with no shading both before and after TPLER. Moreover, the number of tillers in this plot increased as the N level increased, but the tillers in the shaded plots were not affected as strongly by the N level. A highly positive correlation between the leaf emergence rate and number of emerged tillers in the unshaded and 50% shaded plots was observed before TPLER, but not after TPLER.