Studies on the Physiological Longevity of Root Hairs in the Crown Roots of Rice Plants by Means of RNA Detection.

Abstract

It was found by the authors that the elongating root hairs of rice roots contain much RNA, as compared with the epidermal cells i. e. hair-bearing short cells as well as hairless long cells, and that RNA in the mature root hairs still has existed for a long time, after RNA in the epidermal cells was extinct. On the other hand Mitsui et al reported that the process of potassium absorption in rice roots is closely related to the metabolism of RNA in them. From these findings it is assumed by the authors that the physiological longevity of the root hairs can be estimated by means of RNA detection. From this point of view the present experiments were conducted to study the physiological longevity of root hairs as well as to find the effects of vertical water percolation in paddy soils on it. The following results were obtained. Most root hairs developed in the young crown roots contained RNA, and in the mature crown roots the percentage of the root hairs containing RNA to all the root hairs per unit-root length decreased towards the base. But a small number of root hairs developed at the basal part of the crown roots as much as 18 cm in length were still found to contain RNA. In the vertically water-percolated paddy soils, the percentage of root hairs containing RNA was large, as compared with that of grown in the non-water-percolated soils. For example, in the middle part of the crown roots as much as 7 cm in length, sixty percent of root hairs formed in the former soil condition contained RNA, while in the latter one only twenty five percent of root hairs contained it. From these result it may be concluded that the root hairs of the crown roots grown in paddy soils have the physiological activity for a longer period than that suggested before, and that the physiological activity of root hairs in the non-water-percolated soils is lost at an earlier age, as compared with that in the water-percolated soils, that is to say, that the process of maturation of the epidermis of the crown roots grown in the non-water-percolated soils is accelerated.