Studies on the Development of Endosperm in Rice 2. : Process of endosperm tissue formation with special reference to the enlargement of cells.

[摘要] In the development of the rice endosperm, the cell division period, in other words. the period of increase in cell number, ceased on the 9th day after anthesis. Hence, during the 9th day to around the 30th day, the development in size of endosperm tissue should be attained through the enlargement of individual cells. And even in the period prior to the 9th day, the cell enlargement had already been proceeded in the inner portion of the tissue. Length along the top-basal axis of the endosperm tissue reached a maximum on the 6th day, and width (or dorso-ventral diameter) and thickness (or lateral diameter) of the tissue in the middle portion reached a maximum on the 15th and about 30th days, respectively. Every cell situated at any portion of the tissue showed no increase in size in a direction along the top-basal axis. Therefore, development of the whole tissue along the top-basal axis was attained only by the increase in the number of cells through the cell division. This can be understood well from the result of our observation that the enlargement of the whole tissue along the top-basal axis has reached a maximum on the same day when the cell division in this direction ceased. Cells situated at the portion of dorso-ventral axis showed the elongation along the dorso-ventral axis and thus they became column-shape. Such elongation was found out particularly in the cells in the middle portions of the dorsal and ventral radii. Cell elongation was vigorous during the 5th to 10th day, particularly during the 5th to 7th day, and ceased on the 15th day. Because of the several cells on dorsal side elongated more vigorously than those on the ventral side, and because of the fact that the elongation of the former continued up to the 15th day against to the continuation up to the 12th day of the latter, the dorsal radius become longer than the ventral radius, and the 'central point' of the tissue moved gradually toward the ventral side. Cells that situated in the portion along the lateral diameter and those in the intermediate areas between lateral and dorso-ventral diameters grew and formed the flat-polygonal or fan-shape. Cell enlargement of these areas had proceeded rapidly until the 15th day, but thereafter, a slight growth has been continued partially until around the 30th day. Cells which around the central point showed no increase in any direction. The growth habit and the resulted arrangement and the shape of the cells became symmetrical on both sides of the dorso -ventral axis of the tissue.

[学科分类] 农业科学（综合）