Résumé : Homble F. 1985. Effect of sodium, potassium, calcium, magnesium and tetraethylammonium on the transient voltage response to a galvanostatic step and of the temperature on the steady membrane conductance of Chara corallina: A further evidence for the involvement of potassium in the fast time variant conductance.-J. exp. Bot. 36: 1603-1611.Potassium channels of Chara corallina have an activation energy of 36±1 kJ mol-1 and 50±2 kJ mol-1 at temperatures higher and lower than 15°C respectively. The fast time variant conductance property of potassium channels is insensitive to sodium and magnesium ions and is depressed by the presence of calcium, potassium and tetraethylammonium ions. It is suggested that in Chara two different kinds of potassium channels exist, each kind being distinguished by their kinetics and their response to calcium and magnesium ions. © 1985 Oxford University Press.