Circadian Rhythmicity in Leaf Pulvini

Abstract
Circadian rhythmic and light-mediated leaf movements of nyctinastic plants are caused by the shuttling of ions, chiefly K+ and Cl, between opposing sides of the pulvinus. K+ uptake is probably powered by active H+ extrusion. Cellular membranes may play a key role in the pacemaker mechanism and photoreception, as well as in ion transport.