Ionic Relations of Cells of Ohara Australis R.BR. IV. Membrane Potential Differences and Resistances

Abstract

Experiments are described in which the electric potential difference and resistance between the cytoplasm and the external medium were measured in cells of Ohara australi8. The method was designed to eliminate the effect of the negatively charged Donnan system of the cell wall. Both the potential difference and the resistance are attributed to the outer cytoplasmic membrane. It is shown that they may be quantitatively explained by the passive diffusion of potassium and sodium ions across the membrane with permeabilities of the order of 10-5 and 10-8 cm sec-1 respectively. The resistance-voltage characteristic of the membrane is accurately predicted by the constant field equation of Goldman (1943). The ignificance of these findings is discussed.