Abstract
Based on the anatomical studies of the wheat grains which were sampled everyday beginning from the day of anthesis to the maturity, the stages of development of the endosperm were classified under 13 heads as follows (parenthesized figures show the days after anthesis under natural condition): Stage I, division of endosperm mother cell (∼1). Stage II, multiplication of endosperm nuclei (1-3). Stage III, cell membrane formation (4). Stage IV, the peripheral cell layer formation (5). Stage V, filling up of the embryo sac cavity (6). Stage VI, deposition of the "first type" starch grains (7). Stage VII, stop of cell division at the inner part of endosperm (11). Stage VIII, deposition of the "second type" starch grams (17). Stage IX, end of cell division in an entine endosperm (18). Stage X, enlarging of the endosperm cells (20). Stage XI, beginning of maturation from inner part of endosperm (30). Stage XII, completion of cell growth (37). Stage XIII, constriction of tissue (40). During the early stages (V-VII) of development, the cell divisions proceed not, only at outer zone of endosperm tissue but also at inner zone. The cell division of the most exterior cell layer ceases lastly and matures as the aleuron layer by about 20 days after anthesis. From the stage X onwards, the cells elongate into cylindrical form at the bridge, while they enlarge into spherical polygons at the flank. Starch grains reserved in every cell are of two types. The "first type" grams are deposited during early stages (VI∼) and all the grains becolne large and uniform in size, and lenticular in appearance. The "second type" grains appear in the same cells about 10 days later than the first type grains, and continue to increase in number extending over a long period. However, they grow only a little in size and become spherical in shape. Reserve protein particles (gluten) are deposited in the cytoplasma by 10∼13 days after anthesis, and thereafter they grow in form which are indeterminate by increasing their volume. These protein particles are more abundantly found in the hard variety than in the soft one.
