Physiological Studies on the Tolerance of Rice Plants to Salinity : 1. Mechanism of absorption of chloride ion by rice root

Abstract

Listen

Translate article

A high rate of salt accumulation in rice plants is usually observed when these plants were heavily injured by salinity. Accordingly the mechanism of salt absorption and accumulation in such rice plants injured by a high salt concentration could not be considered similarly to that of rice plants growing under normal nutritional conditions. Actually, very little is known about the absorption mechanism of sodium chloride by rice plants under the condition of presence of excess salt in the cultures. The present study was undertaken to obtain some approach to the solution of this side of the problem, using Oryza sativa L. variety Eiko as material. Rice plants were cultured in the nutrient solution for 21 days, then these young seedlings were used for the absorption test in the solution containing O. 1 Mol of sodium chloride. Amounts of chloride ion and phosphorus ion absorbed were measured for comparison, as the latter is considered to be absorbed in close conjunction with metabolic processes. The exprimental results obtained may be summarized as follows: (1) Metabolic inhibitors (DNP, KCN, NaN3) showed some tendencies to promote the absorption of chloride ion, while they suppressed the absorption of phosphorus ion. (2) The absorption of phosphorus ion was clearly depressed by subjection to low temperature (5C). but very little effect of low temperature on the absorption of chloride ion was recognized. (3) The root system of the intact rice plant which was killed previously by immersing into boiling water, showed no capacity to absorb phosphorus ion, while the amount of chloride ion absorbed was higher than that by the healthy rot system. (4) These results suggest that the absorption and accumulation of chloride ion by rice plants does not take place metabolically. (5) When the roots of rice plants were transferred from a nutrient solution containing excess sodium chloride (0.1, 0.2, 0.3, Mol) to deionized water, no exudation of chloride ion from the root cell into this water was recognized.