Abstract
The whole surface of rice embryo was continuously covered with a cuticular layer until 4 days after anthesis. The cuticular layer became intermittent at only the abaxial side of scutellum at 5 days and disappeared completely up at 7 days. By the extinction of this cuticular layer, it was possible to distinguish scutellar epithelial cells from epidermal cells on the other side of the embryo. Therefore, scutellar epithelial cells began to establish a peculiar nature from about 5 days. Epithelial cells, in this time, were still rich in cytoplasm and showed anticlinal divisions. At the end of the anticlinal divisions, epithelial cells gradually altered to an elongated profile in shape. Tiny ingrowths of cell walls were often observed at the surface of cell walls. The walls of epithelial cells were lengthened at a right angle to the outer surface and thickened about half the length inward from the surface, showing unique characteristic of scutellar epithelial cells. Thereafter, the number of lipid bodies and amyloplasts increased in the cells and vacuoles accumulated their contents and transformed to protein bodies. As the embryo developed into the dormant stage, lipid bodies were displaced near the cell walls. By using freeze-substitution method, it was noticed that membrane systems are smooth and the inside of mitochondria or plastids is more electron-dense in comparison with chemical fixation. The presence of tiny ingrowth and thickening of cell walls was also observed by freeze-substitution method.
