Abstract
The mechanisms of growth suppression of rice plants by high concentrations of NaCl were examined by means of the detachment of roots, the addition of metabolic inhibitors, and the equalization of osmotic pressure in culture solution, and by then making a comparison between Na absorption of excised roots and whole plants. The results obtained are summarized as follows : 1) The varietal differences of salt tolerance among rice plants were caused by the differences from the response of ion injury in plants rather than of high osmotic pressure in medium at least at about 160 mOsmol/kg in culture solution. 2) The varietal differences of Na accumulation in the shoot were attributed to two processes such as Na-holding ability and Na-excluding power of their roots. But both might not be independent processes, and it was suggested that they were physiologically connected with each other. 3) If the rice plants were grown in culture solution supplied with the high Na of 80 mM, the susceptible varieties that had lower Na-holding ability of their roots immediately showed decreased ATPase activity in their roots, so that Na accumulations in their shoots were accelerated more rapidly than in tolerant varieties.
