Study On Regulation Of Spikelet And Floret Development With Exogenous ABA And ZT In Wheat

This study was carried out in Agricultural University of Hebei, Baoding during 2000-2001 with zhongmai No.9. Its aim was to systematicly research the effect of exogenous hormones on the condition of nutrition, the metabolism of carbon and nitrogen, and endogenous plant hormones in the process of spike and floret development, which further probed into the regulation mechanism of grain number of wheat spike. The results showed as follows:The exogenous ABA and ZT did not remarkably affect spikelet number and spikelet length. But the peak of floret numbers appeared in advance of that on the control plant under the treatment condition of exogenous ABA and ZT of the differentiation stage ( Dif-stage ) of anther chamber, which decreased the total numbers of floret. Moreover, the treatment of ABA and ZT also remarkably decreased the fertile spikelet and floret, but increased them at the period of tasselling and anthesis.The treatment of ABA and ZT inhibited the growth of root and decreased the leaf area and the dry weight after flag stage, which resulted in the lack of nutrition. The result also indicated that the grain number of spike was significantly positively correlated to dry weight. So the dry weight of the plant was very important to the grain number.The effects of exogenous hormones on soluble sugar, soluble protein and the C/N ratio were various in different periods of spike differentiation, especially at the Dif-stage of anther chamber and the formating stage of tetrad. The results indicated that the soluble sugar and the ratio of C/N remarkably were decreased under the condition of the treatment of ABA and ZT, but the soluble protein was increased at the Dif-stage38of anther chamber. However, the exogenous ABA made the content of soluble protein decrease at the formating stage of tetrad, but the content of soluble sugar and the ratio of C/N varied with the accumulative intension of ABA at the anthesis. Furthermore, the former treatment of ZT increased the content of soluble protein and decreased the content of the soluble sugar of young spike.The contents of endogenous plant hormones varied with the stages of the young spike differentiation and development. The contents of endogenous IAA, GA3 and ZR were much lower by treated with ABA and ZT than those of the control plant at the stage of differentiation of anther chamber and formating stage of tetrad, but those of endogenous ABA were higher. To the hormonal balance, IAA/ABA and ZR/ABA ratios were higher than the control plant at the period of floret differentiation. But with the floret development, IAA/ABA, GA3/ABA and ZR/ABA ratios obviously reduced, respectively. The results indicated that the higher ratio of IAA/ABA, GA3/ABA and ZR/ABA benefited to the formation of fertile floret.With the accumulative intension of ABA increase, the grain set rate of the 1 st and 2nd florets decreased and the 3rd florets were mostly infertile. But ABA affected more remarkably the upper floret than the lower. The treatment of ZT at earlier stage accorded with the treatment of ABA. However, the treatment of ZT increased the grain set rate at upper floret position of a spikelet.The treatment that ABA and ZT prior to tasselling obviously decreased the grain weight of the different grain positions. But the later treatment of ABA remarkably increased the 1st grain weight of every spikelet, while decreased the grain weight of the 2nd and 3rd grain positions. However, the later treatment of ZT increased the weight of spike by affecting the grain weight of the 2nd and 3rd floret positions.