STUDIES ON SALT TOLERANCE IN KOREAN RICE CULTIVARS .2. EFFECTS OF NACL TREATMENT ON SODIUM AND POTASSIUM-IONS CONCENTRATION IN LEAF BLADE, LEAF SHEATH AND ROOT OF RICE PLANTS

The mechanism of cultivar difference in salt tolerance was investigate d with Korean rice cultivars, paying special attention to the relation ship between sodium (Na) and potassium (K) ions in various organs. Thr ee tolerant and three sensitive cultivars, with Nipponbare and IR8 as the reference cultivars, were cultured in solutions containing differe nt concentrations of NaCl. The Na ion concentration in the leaf blade, leaf sheath and root increased with increasing NaCl in the culture so lution in all cultivars. Furthermore, with increasing Na ion, the K io n concentration decreased in the root and leaf sheath. Conversely, in the leaf blade, the K ion concentration increased with increasing Na i on. No relationship between the extent of accumulation of Na and K ion in the leaf blade and salt tolerance was observed, hence, these findi ngs do not support the hypothesis that salt tolerance is related with the exclusion of K ion by absorbed Na ion in the leaf blade. However, exclusion of K ion by Na ion in the root was found in all the cultivar s tested, and extent of the K exclusion might be related to the salt t olerance in rice plants.