DEVELOPMENT OF ENDOSPERM AND SYNTHESIS OF STARCH IN RICE GRAIN .3. STARCH PROPERTY AS AFFECTED BY THE TEMPERATURE DURING GRAIN DEVELOPMENT

Japonica rice plants (cultivar, Koshihikari) were treated at high and low temperatures in the early and late ripening stages. Starches prepared from the outer layer and inner portions of these rice grains were tested for their physicochemical properties. Generally, starch in the inner portion of rice grains was affected by temperature in the early ripening stage; whereas in the outer layer it was more affected in the late ripening stage. Amylose content was determined by iodine colorimetry and iodine binding capacity method. The amylose content of the outer layer and inner portion starches increased at low temperatures during grain development. Miniviscographic, parameters of both starches were affected mainly by temperature in the early ripening stage and modified by that in the late ripening stage. The differential scanning calorimetric (DSC) transition temperature and gelatinization heat increased under high temperatures for the inner portion starch in the early ripening stage and for the outer layer starch in the late ripening stage. While the lipid content of inner portion starch increased at high temperatures in the early ripening stage, the lipid content of the outer layer starch decreased under high temperature in the late ripening stage. The fatty acid composition of lipids of the outer layer starch responded to temperature in a manner different from that of the inner portion starch. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.