Changes in Nuclear DNA Content of Endosperm Cells During Grain Development in Rice (Oryza sativa)

Morphological, cytological and quantitative DNA changes associated with endosperm development in rice caryopsis were investigated. Following a brief free-nuclear phase, the endosperm became cellular by the 4th d after anthesis. While the mean length and breadth of grain attained maximum values at about 10, d after anthesis, f. wt of the whole grain, and of the endosperm separately, continued to increase until about 16 d after anthesis. Cell divisions in the endosperm continued until 10 d and following stabilization of the cell number, the nuclei attained irregular shapes. The size of the nuclei and nuclei and the amount of nuclear DNA varied considerably during endosperm development. The endosperm nuclei did not retain the expected 3C–6C DNA level after the first few rounds of division and nuclei having more than 30C DNA were frequent 8 d past anthesis. The highest C value recorded was 74C in a 16-d-old endosperm cell.