Abstract: Grain filling characters of hybrid and conventional rice cultivars from northern China were analyzed by Logistic equation. There existed very significant difference in grain filling parameters between the conventional and hybrid rice. The difference in grain filling duration would result in the discrepancy of grain weight in different varieties, and this was one of the main factors. It would be favorable to increase grain weight by enhancing initial rate of grain filling and prolonging grain filling duration. The discrepancy of grain weight among the same cultivar might result from the difference of grain filling rate. The assimilate distribution rate to the grain in hybrid rice remained higher than that of the conventional rice, which compensated the deficiency of assimilate during the later period of grain filling. It suggested that to maintain longer duration with high rate of grain filling would be helpful to obtain heavier grain weight.

Key words: hybrid rice, conventional rice, grain filling, assimilate distribution, translocation rate

摘要： 以北方杂交稻和常规稻品种为试验材料，用Logistic方程对不同品种的籽粒灌浆过程进行了拟合。结果表明，杂交稻和常规稻的灌浆参数存在极显著差异，灌浆持续时间的不同是造成不同品种粒重差异的主要因素。灌浆阶段，渐增期短，启动灌浆速率大，灌浆快增期早，快增期和缓增期延长等特性有利于增加粒重。同一品种的粒重差异来源于灌浆速率的不同。在灌浆期杂交稻的光合同化物向籽粒运转率高，干物质由茎鞘源源不断地向籽粒输送，使杂交稻保持较长的高速灌浆期和缓增期，最终形成较大的粒重。

关键词: 杂交稻, 常规稻, 灌浆, 同化物分配