Changes of endogenous hormone contents during grain development in different types of rice

The difference of grain filling on sink basis and the related endogenous plant hormones contents of rice are studied with different types of rice．The results show that the superior grains of rice in each entry have higher grain-filling rates than the inferior grains and it is contrary in the late grain-filling stage．Among the three rice cuhivars concerned，the superior-inferior grains of“IR_65600.85”are an asynchronous grain—filling type，in turn leading to much lower grain filling in the inferior grains．Analyzing from the hormones of grains，the superior gr ains perform higher contents of IAA and ABA ，higher ratios of ABA／IAA，ABA／GA_l+3 and ABA／(IAA+GA1+3+ZR_s+ABA)than the inferior grains in each entry during the early stage of grain-filling．The situations in the inferior grains are contrary，especially those in “IR_65600.85”，therefore they show lower grain filling and percentage of filled grains．