The Ionic Relations of Acetabularia mediterranea

The concentrations of K⁺, Na⁺, and Cl^– in the cytoplasmand the vacuole of Acetabularia mediterranea have been measured,as have the vacuolar concentrations of SO₄^–– andoxalate. The electrical potential difference between externalsolution, and vacuole and cytoplasm has been measured. The resultsindicate that Cl^– and SO₄^–– are probably transportedactively into the cell, and that active transport of Na⁺ isoutwards. The results for K⁺ are equivocal. The fluxes of K⁺,Na⁺, Cl^–, and S0₄^–– into the cell and theeffluxes of Na⁺ and Cl^– have been determined. The Cl^–fluxes are extremely large. In all cases the plasmalemma isthe rate-limiting membrane for ion movement. A technique isdescribed for the preparation of large, completely viable cellfragments containing only cytoplasm, with no vacuole.