Studies on the lateral root formation in rice plant : (I) Lateral root formation under conditions of nutritive deficiency

Abstract

This paper dealt mainly with the effects of nutritive deficiency upon the formation and physiological characteristics of lateral roots in rice plant. Thirty days old seedlings of the variety Norin No. 1 were grown in culture solutions, from which main nutritive elements such as N, P or K was remorvd respectively (Table 1). Plants were sampled 1 month later for the investigations of ecological characteristics of their primary and secondary roots. Main results were as follows: (1) Under conditions of abnormal nutrition, number of primary roots, especially of the newly emerged ones (A class root), decreased in contrast to those of more aged roots (B, C, D and E classed). The length of all roots classified was almost reversely circumstanced as compared with numbers. The root diameter increased in general (Table 2). (2) Total number of lateral roots per primary root and their density increased particularly in B and C class roots, when plants were affected by abnormal nutritions (Table 2). Lateral roots showed a tendency to appear near the tip of a primary root in those cases (Fig. 2). In addition to this experiment, the effects of nitrogen deficiency on lateral roots of the seedlings were examined. From results of this experiment, it was concluded that their lateral roots were similarly increased by the deficiency of the element (Fig. 4). Moreover, physiologically abnormal branch roots (c and t1), showing less TTC reducing activity (Fig. 3), increased in such a case (Fig. 5).