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

Department of Biology, University of Houston, Houston, Texas 77004

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.