Effect of Salinity upon Cell Membrane Potential in the Marine Halophyte, Salicornia bigelovii Torr

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Abstract
The electrophysiology of root cells of the marine halophyte, Salicornia bigelovii Torr., has been investigated. Cellular concentrations of K+, Cl−, and Na+ and resulting cell membrane potentials were determined as functions of time and exposure to dilutions of artificial seawater. Treatment of these data by the Nernst criterion suggests that Cl− is actively transported into these root cells, but that active transport need not be invoked to explain the accumulation of Na+ at all salinities investigated nor for K+ at moderate to high salinities. In low environmental salinity, the cell electropotential of Salicornia root cells was found to respond to inhibitors in a fashion similar to that observed in glycophytes; in high environmental salinity, root cell membrane potential appears to be insensitive to bathing salinity and m-chlorocarbonylcyanide phenylhydrazone induces membrane hyperpolarization, in contrast to the response of glycophytes to such treatments. The fact that measured membrane potentials exceed diffusion potentials for Na+, K+, and Cl− and the observation of a rapid depolarization by CO in the dark suggests an electrogenic component in Salicornia root cell membrane potentials.