Significance of potassium and chloride membrane currents in mechanisms of salt tolerance in Chara corallina and Chara inflata

Abstract

In voltage clamp experiments, a two-pulse voltage procedure was used to investigate the ionic currents underlying the action potential (AP) in Chara corallina, a fresh water algae, and Chara inflata, a less salt-sensitive algae. In comparison with C. inflata, the membrane currents of C. corallina revealed two distinct characteristics: the absence of a “hump” (i.e., a transient outward K + current, and the presence of succession oscillating peaks (i.e., transient inward Cl − currents). In C. inflata the transient outward K + current or the “hump” has the important role of repolarizing the membrane potential ( V m ) which is essential for maintaining favourable electromotive force for ion transport. On the other hand, C. corallina regulates the strength of response to its environment by altering the frequency of the AP transmitted to the cell interior.