| Abstract: | The effects of pH on the resting and action potentials and onthe fluxes of potassium, sodium, and chloride across the membranesof internodal cells of Chara australis have been investigated. Experiments were carried out in an artificial pond water (A.P.W.)of standard composition: CaCl2, 01 mM; KCl, 0.1 mM; NaCl, 1.0mM. The resting potential decreased as the pH was lowered from6.5, being depolarized by about 75 mV at pH 4.5. Measurementsof the ion fluxes as a function of pH suggested that this depolarizationwas caused by an increase in the permeability to sodium anda decrease in permeability to potassium at pH 4.5. Action potentialsof constant peak value can be elicited for some time at pH 4.5,but after 20 min or so the cell becomes refractory. All theseeffects on resting and action potentials are fully reversible.We briefly speculate about the mechanism of these pH effects. |
