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Abstract: Shanyou 3, Siyou 2 and Shanyou 63 etc. of hybrid rice were used for the studies in 1979-1988. The results were as follows: 1. Hybrid rice Shanyou 3 had two peak periods of grain-filling. It happened respectively at the 12th and the 30th day after anthesis. 2. The duration of grain-filling in hybrid rice consisted of five stages from heading to maturation. The dry matter was accumulated slowly within 0-5 days after the anthesis of Shanyou 3. Adequate unlight and higher temperature were needed for matter production and translocation, the rate of grain-filling was positively correlated with temperature within 19-30℃ at this stage. 27. 3℃ mean daily temperature, 75% R. H. and enough sunshine per day were helpful to grain-filling in 5-10 and 11-15 days after anthesis. But 22. 2℃, 70-80% R. H. and more than 6. 53 hr. per day were optimum for it in late maturation period. If the daily highest temperature (more than 35℃) appeared in 6-10 or 16-20 days after anthesis, setting percentage would markedly decrease. 3. If adverse weather occured or the upper leave of rice withered early at late growing period, the grain-filling of hybrid rice had only on peak, which in turn let to the decreace of setting percentage, 1000-grain weight and yield. So. the anagement of field was very important before harvest.

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