Chara buckellii, a euryhaline charophyte from an unusual saline environment. II. Membrane potential and membrane conductance at steady state

摘要

Electrophysiological experiments were performed on internodal cells ofChara buckelliicultured in saline and freshwater media to see whether the membrane potential (Evo) and membrane conductance (Gm) are dominated by passive K+conductance (K state), passive H+conductance (H state), or active proton pumping (P state). Unlike other euryhaline charophytes,C.buckelliicells cultured under saline conditions were not dominated by any one state, showing little dependence on external K+concentration and pH (pHdeg;).Chara buckelliicells cultured in freshwater share some membrane properties with other freshwater charophytes. Freshwater cells appeared to be in the P state between pHdeg; 5 and 7 as expected but never attained the H state usually observed at high pHdeg; (ensp;10). Freshwater cells also showed a temporary, threefold increase inGmat pHdeg; 5, which could not be explained by an increase in passive Clminus;or K+conductance. Evidence consistent with an electrogenic Clminus;/2H+symport in freshwater-grownC.buckelliiat pHdeg; 5 and 7 is also presented.