| Summary: | The K, Na and Cl concentrations of the chloroplast layer and the flowing cytoplasm of Nitella flexilis have been determined by applying an internal perfusion technique, which enabled us to avoid contamination of ions from the cell sap. K, Na and Cl concentrations of the chloroplast layer are 110, 26 and 136 mM and those of the flowing cytoplasm are 125, 5 and 36 mM respectively. The cell sap contains 80 mM K, 28 mM Na and 136 mM Cl. Although there are some variations in these values among samples, the flowing cytoplasm is rich in K and poor in Cl and especially in Na. The exchange of K and Na across the tonoplasl occurs fairly easily (half-time, a few hours), while that of Cl occurs extremely slowly (half-time, a few days).
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