Abstract: The grain filling processes of late japonica hybrid and conventional rice cultivars from southern China were analyzed with the Richards’ growth equation,as well as the leaf photosynthesis and chlorophyll fluorescence characteristics at late growth stage.Hybrid rice combination Xiuyou 5 showed slightly lower initial grain filling potential,maximum grain filling rate and mean grain filling rate than the conventional rice cultivar Xiushui 110,but longer active grain filling duration,contributing to get heavier grain weight and to cut down the competition for assimilate among grains per panicle.The differences in leaf photosynthesis and chlorophyll fluorescence parameters were not significant between Xiuyou 5 and Xiushui 110 at 10 d after flowering.However,Xiuyou 5 had significantly higher leaf photosynthesis and chlorophyll fluorescence parameters than Xiushui 110 at 25 d after flowering,except for the unquenchable portion of fluorescence.It is suggested that maintaining higher leaf biomass production capacity at late grain filling stage is a very important physiological mechanism for late japonica hybrid rice,resulting in longer active grain filling duration,and finally a relative better grain filling,heavier grain weight and higher grain yield despite the larger number of spikelets per panicle.

Key words: hybrid rice, conventional rice, japonica rice, grain filling, leaf, photosynthesis characteristic, chlorophyll fluorescence characteristic

摘要： 以南方杂交晚粳秀优5号和常规晚粳秀水110为材料，应用Richards方程对两个品种的籽粒灌浆过程进行拟合，研究了两个水稻品种的灌浆特性，并测定分析了两类品种的后期叶片光合特性。 秀优5号的起始灌浆势、最大灌浆速率和平均灌浆速率均略低于秀水110，但活跃灌浆时间明显长于秀水110，说明杂交晚粳灌浆更为平缓、灌浆期长，有利于获得较高粒重，也有利于缓解其穗型较大引起的籽粒间物质的激烈竞争。齐穗后10 d，秀优5号的光合和叶绿素荧光参数与秀水110无显著差异，但齐穗后25 d，秀优5号除初始荧光值的增加幅度未达显著水平外，其他参数均显著高于秀水110。研究结果表明，南方杂交粳稻在灌浆后期仍保持较高的物质生产能力，是它具有较长籽粒灌浆持续期，大穗与较高粒重相协调，最终实现高产的重要生理基础。

关键词: 杂交水稻, 常规水稻, 粳稻, 灌浆, 叶片, 光合特性, 叶绿素荧光特性