IONIC COMPOSITION OF THE CYTOPLASM OF NITELLA FLEXILIS

The K, Na and Cl concentrations of the chloroplast layer andthe flowing cytoplasm of Nitella flexilis have been determinedby applying an internal perfusion technique, which enabled usto avoid contamination of ions from the cell sap. K, Na andCl concentrations of the chloroplast layer are 110, 26 and 136mM 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. Althoughthere are some variations in these values among samples, theflowing cytoplasm is rich in K and poor in Cl and especiallyin Na. The exchange of K and Na across the tonoplasl occursfairly easily (half-time, a few hours), while that of Cl occursextremely slowly (half-time, a few days). ¹This work was supported by Research Grants from the Ministryof Education of Japan