Abstract: This paper studied the grain quality and Q-enzyme activity of three rice varieties and their combinations as affected by air temperature and sinksource volume.The results showed that at the early stage of milk filling,the grains of fully milk filling under high temperature had a higher chalkiness,lower transparency,and lower rate of white rice.Compared with the grain of early-rice,that of late rice had higher gel consistency and transparency,and higher rate of white rice.Planting rice at early-or late season had no significant effect on the amylose and protein contents of rice grain.Leaf-cutting to limit source decreased grain quality markedly,while grain-thinning to decrease sink improved grain quality significantly.

Key words: Copper, Soil, Tibet