【Objective】 The purpose of this study is to analyze the differences of grain yield in different parts of panicle given the levels of endogenous hormones in rice at grain filling stage. 【Method】 Six conventional japonica rice varieties from Zhejiang Province, including Jia 58, Jia 67, Zhejing 99, Xiushui 121, Xiushui 134 and Zhongjia 8, were used as materials. All the rice materials were grown in the same conditions. According to the internodes of the primary rachis branch on the main panicle, the rice panicle was divided into the top, middle and bottom parts. The dynamic changes of grain salicylic acid (SA), abscisic acid (ABA), indole-3-acetic acid (IAA), fresh biomass, thousand-grain weight, head rice yield, length-width ratio, gel consistency, alkali spreading value during six rice development stages were measured. 【Result】 The thousand-grain weight of grains from different panicle parts increased steadily during the filling stages(0-35 days) with the top parts being the heaviest and the bottom part being the lightest. The variation coefficient of grain biomass in different panicle parts ranged from 1.66% to 10.26% on the 35th day. Then the gaps between different panicle parts were narrowed, but the differences could be still observed. After maturity, the thousand-grain weight still followed the trend of the top (25.08-33.88 g) > the middle (24.04-32.49 g) > the bottom (23.46-31.78 g). There was a slight difference in head rice yield and length-width ratio among different panicle parts. The correlation analysis among all the parameters showed that thousand-grain weight was positively correlated with length-width ratio (r = 0.89, P< 0.01), and negatively correlated with head rice yield (r = -0.68, P< 0.01). For the gel consistency and alkali spreading value, the differences among the six varieties was significantly greater than those among the three panicle parts. Significant differences were observed among the three endogenous phytohormones from different panicle parts. The variation coefficients of SA, ABA and IAA from different panicle parts were 0.59%-25.90%, 1.35%-66.25% and 0.16%-81.04%, respectively. At the early filling stage, the SA content showed a tendency top > middle > bottom, while at the late filling stage, bottom > middle > top. 【Conclusion】 It was found that the endogenous phytohormones and grain yield parameters of different panicle parts were significantly different. SA was positively correlated with ABA (r =0.54, P < 0.05), IAA (r =0.59, P< 0.01) and head rice yield (r = 0.95, P < 0.01), and was negatively correlated with thousand-grain weight (r = -0.53, P < 0.05) and length-width ratio(r = -0.66, P < 0.01).
