Shin-ichiro Kawata

Studies on the Effects of Some Organic Acids on the Root Hair Formation in the Root of Rice Plants.

It was found by the authors that the root hair formation and their growth in rice roots are accelerated when the water percolates vertically in the paddy soils, and was thought that certain substances responsible for regulating the root hair development are derived from the compost under the irrigated condition, and they are probably eliminated from the paddy soils by water-percolation (KAWATA and ISHIHARA, 1961 a). The present experiment was carried on to find the morphogenetical effects of some organic acids (formic, acetic and butyric acid) on the development of the root hairs and epidermal cells of the roots by using the ordinary or aseptic water culture method. The following results were obtained. When the concentration of acetic acid was kept between 2.5 mmol and 5.0 mmol., which is known to be frequently found in the paddy soils, it inhibited the root hair formation and their growth to a great extent, but it did not affect the root and epidermal cell elongation so much. This morphological appearance of epidermis of the root treated with acetic acid was similar to that of the rice plants grown in the non water-percolated soils. Formic acid (2.5 mmol. and 5.0 mmol.) and butyric acid (2.5 mmol. and 0.50 mmol.) retarded not only the root hair formation and their growth, but also the root and epidermal cell elongation. From these results, especially in the case of the acetic acid, our hypothesis mentioned above seems to be true. As reported in the previous paper (KAWATA and ISHIHARA, 1961 b) the ribonucleic acid, the metabolism of which is closely related to the process of the potassium absorption in rice roots, was found to exist in the root hairs for a long time. It is suggested, on the basis of these facts, that the development of the rice plants in the paddy fields is affected because of the accumulation of these organic acids in the soils, which control the absorption of nutrients.