Ion Permeability of the Plasmalemma of the Plant Cell

Abstract

WALKER¹ has suggested that for Nitella there is evidence for a layer on the outside of the cytoplasm, a plasmalemma, which offers considerable resistance to the passage of ions. In support of this suggestion he advances two pieces of evidence—the bulk of the high d.c. resistance across the cytoplasmic layer from vacuole to outside solution of chloride lies in the cytoplasm and not in the tonoplast, and secondly, that the equilibrium concentration of calcium ions in the cytoplasm calculated from the potential difference is absurdly high.