Salt Tolerance in the HalophyteSuaeda maritimaL. Dum.: Intracellular Compartmentation of Ions

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Abstract
The time-course of exchange of sodium and potassium ions from root and leaf material of the halophyte Suaeda maritima has been followed and the data analysed according to the phenomenology of efflux, or compartmental, analysis. Sodium ions were exchanged much more slowly (c. 4 times) from the vacuoles of leaf cells of plants grown in sodium chloride than were potassium ions from the vacuoles of leaf cells of plants grown either in similar concentrations of potassium chloride or in low concentrations of potassium. In plants grown in sodium chloride, sodium ions were exchanged 9 times more slowly from the vacuoles of leaf cells than from the vacuoles of root cells. The concentration of sodium ions in the cytoplasm of leaf cells of plants growing in 340 mol m−3 sodium chloride was estimated to be 165 mol m−3 when the average concentration in the leaf tissue was about 600 mol m−3. As measured by movement from mature to developing leaves in intact plants; there was less in vivo retranslocation of 22Na and 36CI in plants growing in sodium chloride than there was of 86Rb in plants growing either in potassium chloride or in non-saline conditions. The results are discussed in terms of the concept and energetics of compartmentation of ions in the cells of halophytes.