Influences of environmental conditions on the amylose content of grain at different positions in a rice panicle

The influences of environmental conditions on the amylose content of rice grain at different positions in the panicle were studied. The amylose content of the grains on lower rachis branches (LG) was lower than that on the upper (UG) and middle rachis branches (MG) under all the environmental conditions examined. LG, UG, and MG produced in the late-season culture plot had the highest amylose content, while LG, UG, and MG produced in the early-season culture plot had the lowest. LG showed a larger variation in the amylose content (6.9%) than UG (5.9%) or MG (6.6%). Among LG, MG, and UG, there was a proportional relationship between the content and / or amount of amylose and the crude grain weight. Therefore, the low amylose content of spikelets with a low grain weight might be due to the deficiency of starch accumulation in the rice endosperm as shown by the decrease in the amount of amylose. It was concluded that the variations in the amylose content in a rice panicle were caused by the differences in the crude grain weight, which was closely related to the earliness or lateness of flowering time. Among the plants transplanted at different times, amylose content was affected by atmospheric temperature during the ripening period rather than grain weight. By contrast, among the plants transplanted at the same time, amylose content was affected by grain weight rather than atmospheric temperature.