On Varietal Differences in the Tissue of Starch-Cell of Rice Kernels

Abstract

1. Cross sections were taken from mature rice kernels which had been kept in water for 24 or 36 hours, and were heated with an alcohol-lamp untill they became translucent. 2. When the embryo-sac becomes completely filled up with endosperm cells, 5∼7 days after flowering, the disposition of starch-cells in the cross section of kernel becomes to be characterized according to the variety, and toward 10 days after flowering, this characteristic disposition connected with the variety becomes more distinct, and thereafter it does not show any remarkable change until the mature time. 3. These varietal characteristics of the disposition of starch-cell are represented by the following 3 types. (1) In the first type, starch-cells are disposed radially and concentrically from the center of the tissue, and the starch-cells develope more vigorously along the dorso-ventral diameter than those in the other two types. The disposition of starch-cell of the varieties belonging to foreign rice, upland rice, glutinous rice and koshitsu-mai show this type. (Photos. 1, 2, 3, 4, ) (2) The second type is found in the kernel of the varieties used for brewing. Several layers of endosperm tissue are compressed along the dorso-ventral diameter into slender layers, because the growth of cells in these layers is very poor. In white-core kernels, these layers are conspicuously under grown and the disposition of adjacent starch-cells are disturbed. (Photos. 7, 8, 9, 10) (3) The third type is medial between the types 1 and 2, and the varieties of nanshitsu-mai belong to this type. (Photos. 5, 6) (Fig. 1) 4. The grade of fullness of rice kernel is appropriately indicated by its specific gravity, and in general the specific gravity is low in the outer part of kernel and becomes higher toward the inner part. In the kernels of the varieties belonging to the type 1, the specific gravity becomes higher consistently toward the core. In the kernel of the varieties of type 2, however, it is highest in the middle part of kernel and lower in the central part. In the type 3, it is highest in the middle part, while it does not lower at the central part. (Fig. 2)