Electrical Membrane Properties and Circadian Rhythm in Extensor Cells of the Laminar Pulvini of Phaseolus coccineus L.

Circadian changes of three parameters of electrical properties in extensor cells of the laminar pulvini of Phaseolus coccineus L. have been recorded by standard microelectrode techniques. In the low turgor state of the cells, the resting potential and the CN(-) (1 millimolar NaCN) induced depolarizations are large, while the K(+)-induced voltage changes are small, and vice versa in the high turgor state. These results demonstrate that during a circadian cycle the low turgor state of the extensor cells is correlated with the active state of an electrogenic pump. This correlation can be explained by electroosmosis.