Abstract

In the present study, GA₃ and NAA were used to inhibit the growth of unproductive tillers of rice plants, and we measured the tiller occur and the grain yield of different treatments, the object of this study was to determine the effect of external hormones on the tiller growth and grain yield, and whether we can regulate the tiller growth by some manipulations of the hormone levels. The results indicated that external 10 mg L^-1 GA₃ and 1000 mg L^-1 NAA significantly inhibit the growth of unproductive tillers, and the elimination of unproductive tillers promoted the growth of productive tillers at the middle and late growth stages, and promoted the development of heavy panicles, and finally increased the grain yield. However, the external 100 mg L^-1 GA₃ (G100) significantly decreased the grain yield of Yangdao 6. The reason was that the most of the plants of G100 treatment of Yangdao 6 were lodging at filling stage, and the lodging significantly decreased the spikelet filling and grain weight, and finally decreased the grain yield. These results suggested that the application of GA₃ in field production may lead to lodging, especially for the indica cultivars. So in field production, GA₃ should be used carefully.

Key words: Rice (Oryza sativa L.), gibberellic acid (GA₃), α-naphthalene acetic acid (NAA), tiller, yield.