Abstract: With rice varieties “Xieyou 9308” and “Xiushui 110” as test materi als, this paper analyzed the effects of non-shading, shading at whole grain-fi lling stage, and shading at part phases of grain-filling stage on the dynamics of grain- filling, and studied the grain growth and its relations with grain ch alkiness degree and amylose content under weak light stress. In shading treatmen ts, the final grain mass and the maximal grain-filling rate (GRmax) of the two varieties decreased significantly with increasing shading intensity (P<0.05). Sh ading at whole grain-filling stage had no general pattern in its effects on the average grain-filling rate, relative initial grain-filling power, and effecti ve filling time; while shading at 15 days or 30 days after flowering decreased t he average grain-filling rate but increased the relative initial grain-filling power and effective filling time with the increase of shading intensity (P< 005). In the treatment of shading at whole grain-filling stage, the Q enzyme activity, seed-setting rate, kernel mass, and amylose content of rice grain dec reased, and the chalkiness degree increased with increasing shading intensity; w hile in the treatments of shading at 15 days or 30 days after flowering, these p arameters had no general change pattern. Shading at part phases of grain-fillin g stage had less effects on the seed-setting rate, kernel mass, chalkiness deg ree, and amylose content of rice variety “Xieyou 9308”, but greater effects on those of “Xiushui 110”, suggesting that “Xieyou 9308” had higher shade-tol erance than “Xiushui 110”.

Key words: Recovery of fertilizer, Field experiment