Abstract
Gibberellic acid (GA) was continuously sprayed to the plant for a month at the concentration of 0, 1, 5, 10, 50, 100, 500 and 1000ppm (treatments (1)-(8)) during vegetative (Exp. I) or reproductive (Exp. II) stage. In Exp. I, the kernel yields dropped in all treatments due to the decrease of both the number of panicles and the number of spikelets per panicle. The results of Exp. II were summarized in Fig. 8. The number of leaves, leaf area and dry weight per stem and the dry weight percentage of leaf to total top increased with the higher level of GA application. The number of spikelets per panicle also increased, but with higher percentages of degenerated flowers and unripened grains at the concentrations more than 50 ppm. However, the number of stems and leaves per plant decreased gradually with the increase of the concentrations. As a result of these changes, the kernel yields increased with the application of 10 ppm of GA.
