On the Development of the Tissue of Starch-Cell in Rice Kernels

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1. 3 days after the frowering, the endosperm cells migrate towards the walls of the embryo sac against the impoverished nucellus. (Fig. 1) 4 days after the flowering, the endosperm cells undergo rapid divisions. 5 days after the flowering, these initial endosperm cells undergo further divisions. Cell divisions proceed until the whole sac becomes completely filled up with endosperm tissue. (Fig. 2) 6 days after the flowering, the endosperm cells begin to from the aleurone layer, so cell divisions already have done. (Fig. 3) 7 days after the flowering, the center line appears clearly in the middle of young kernel. Around the center line the starchy endosperm cells are spindly shape with their longer diameters parallel to the long axis of the kernel in the longitudinal section. In this form the length of kernel is nearing completion. (Fig, 4, 5) Since then the starchy endosperm cells grow up in dorso-ventral direction and become rectangular with their long diameters parallel to the minor axis of the kernel in the longitudinal section. (Fig. 6, 7, 8) In that form dorso-ventral diameter of kernel is nearing completion about 10 days after the flowering, but few layers of starchy endosperm in the neighbourhood of aleurone layer continue to grow up until about 15 days after the flowering. The growth of lateral diameter of kernel is similarly done as that of dorso-ventral diameter, and is nearing completion about 15 days after the flowering. Rice kernels begin to become translucent from the center line, and the translucent area proceed around, and that progression in the ventral part of kernel is slowly than in the dorsal part. There is high correlation between the ventral diameter and the dorso-ventral diameter. (Table 1, 2). 2. White-belly is frequently observed in grain that has large ventral part of kernel, and this shows that nutrient locomotion is insufficient to fill the well-developed ventral part. Sometimes, white-belly is found in grain that has minor ventral part ; in this case, it is recognized that the accumulation of nutrient is too poor in spite of decrease of ventral part. (Table 1, 2). 3. In the notched-belly kernel, it is observed that the atarch-cells of the notched portion of the kernel nearly stopped their growth at early atage of development, but those of the other portion continued their growth, and in milk-white grain, the starchy endosperm cells of opaque part show poor development and insufficiency of nutrient accumulation. (Fig. 11, 12, 13, 14, 15).

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