Studies on the Starch Contented in the Tissues of Rice Plant : I. Transformation of starch grains in the tissues with their development of growth

Abstract

Starch accumulated in the tissue of rice plant varied in amount according to the growth of the plant, and the size of the grain changed nearly in direct proportion to the amount of them. The process of transformation of starch grain in the tissue of the plant was studied, the results being as follows. (1) The cells newly formed by cell-division contained at first many granules but no starch grains, while a little later, the proplastids in them formed swellings in each of which a small starchgrain (single or more often completely compound) appeared. (Fig 1). Starch grains thus formed developed in size during the slow growth of the cell. But they soon disappeared when the cells grew rapidly, the former probably being consumed for the growth of the cells (Fig 3, I, II, ) Thereafter, in the photosynthetic tissues, the proplastids enlarged their volume and developed into chloroplasts, and henceforth some of them often produced minute temporay starch grains (Fig 3, A). In the majority of parenchymatous tissues except that of the root, the proplastids developed into leucoplasts or amyloplasts in which very large shaped compound grains were formed again (Fig. 3). (2) In the leucoplasts of the parenchyma of leaf sheath, starch grains of largest sizes were formed just when the largest amount of starch had been accumulated in that tissue, and similarly in the parenchyma of internode, the largest grains were seen at the beginning stage of the spike fruiting (Fig. 2). Henceforth the starch grains in leaf sheaths diminished in their sizes and disappeared when the leaf became old and died. In internodes of the culm they similarly diminished with progress of fruiting; but about a month later when the fruiting process nearly came to an end, they were again accumulated and increased in their size in the lower internodes till the crop matured completely (Fig. 3). (3) As the starch grains were found to change their size according to the growth of cells as described above, it may be said that the younger or upper internodes and younger or inner leaf generally contain smaller starch grains (Fig. 5, 6), and in the internodes of the upper portion of the culm contain the larger ones (Fig. 7). In the other tissues and parts the simlilar relations were observed. Besides, the dimensions of starch grains seemed to vary according to the species of plant and to environmental factors. (4) Starch tissues was not found in the root except that of root-cap where small starch grains were usually seen (Fig 4).