[Dependence of membrane potential of Chlorella fusca on pH, temperature and light]

The dependence on external parameters of the membrane potential of Chlorella fusca (Shihira et Krauss) 211-8b, Göttingen, has been measured in media containing no salt except KCl. Near neutrality the potential is practically independent of pH. The negative potential increases with temperature from-12 mV at 5°CC to-45 mV at 20°, and remains constant thereafter, i.e., at least up to 30°. Upward temperature jumps of 5 degrees cause a fast hyperpolarisation, which is independent in magnitude of the starting temperature. The potential is influenced by illumination, and this effect increases with temperature. The light effect is reduced by 3-(3,4-dichlorophenyl)-1,1-dimethyl urea and practically abolished by carbonyl cyanide-m-chlorophenyl hydrazone.