Regulatory mechanism of plant nyctinastic movement: An ion channel-related plant behavior

Leguminous plants open their leaves during the daytime and close them at night as if sleeping, a type of movement that follows circadian rhythms, and is known as nyctinasty. This movement is regulated by the drastic volume changes in two kinds of motor cell of the pulvinus, which is located at the bottom of the leaf stalk. The detailed mechanism of the ion channel-regulated volume change of the motor cells largely remains to be elucidated. In this chapter, we reviewed the mechanism of nyctinasty from two view points, electrophysiology of potassium channel and endogenous chemical substance triggering nyctinastic leaf closure. We focused on the nyctinasty of Samanea saman plant because almost all of physiological studies on nyctinasty have been carried out using this plant.