Chloride Electrochemical Potentials and Membrane Resistances in Nitella translucens

The chloride electrochemical potential difference between theinside of cells of Nitella translucens and the bathing mediumhas been measured by a direct electrical method employing Ag/AgClelectrodes. The membrane potential has been measured by meansof conventional salt bridge microelectrodes. These data havebeen used to calculate the internal chloride concentration ofthe cells; the mean value obtained was 39 mM. This chlorideelectrochemical potential difference has been short-circuitedthus causing an outward (depolarizing) electric current to flowthrough the cell membrane. The resulting membrane depolarizationhas been measured at two points along the length of the cellenabling the membrane resistance and space constant to be deduced;the respective values obtained were 24.8 Kcm² and 3.0 cm. Itis suggested that these experiments lend additional supportto the hypothesis that during the action potential in the Characeaethere occurs a transient increase in the chloride conductanceof the plasmalemma.