Abstract
It has been found by the authors that epidermis of crown roots is composed of two types of cells; haired short cells and hairless long cells. The present studies were conducted to find out on what developmental stage of epidermis and how these cells are differentiated. After the last anticlinal cell division in meristematic region of epidermis was completed, two types of cells, rich or poor in ribonucleic acid (RNA) were observed. But morphologically such cells were similar. The cells rich in RNA elongated slowly and developed in haired short cells. On the contrary, the cells poor in RNA elongated rapidly and developed in hairless long cells. It was also found that elongating root hairs, especially their tips, contained much RNA, as compared with other epidermal cells; hair-bearing cells and long cells. Furthermore, RNA in fully developed root hairs existed for a long time, after RNA in other epidermal cells was extinct. Recently it was reported by other workers that the process of potassium absorption in rice roots is closely related with the metabolism of RNA. From these facts it is suggested that the physiological longevity of root hairs should be studied by means of the existence of RNA in root hairs.
