Developmental Changes in the Structure of Endosperm Starch of Rice ( Oryza sativa L.)

The developmental changes in the structure and properties of endosperm starches were investigated using the near-isogenic lines for wx alleles of rice. The amylose content in nonwaxy starch was increased during the development of rice grains. Because the accumulation of amylose in endosperm stopped earlier than that of amylopectin during development, the percentages of amylose reached a maximum at the 17th day after flowering in nonwaxy endosperm. Since the distributions of the unit-chain length of amylopectin in waxy and nonwaxy starches were unchanged with the development of the grains, these amylopectins would be synthesized in a similar manner through development. The structure and properties of endosperm starches were reconfirmed to be conspicuously affected by the temperature at the early developmental stages of the grain-filling period, namely, they appeared to be characterized by the temperature at which the starch was accumulated in the endosperm.