Timelapse of nyctinasty

"In nyctinasty, some plants are able to assume a position at night that is different from their position during daytime. It is a biological rhythm since this behavior recurs in each circadian day. The sleeping position of these plants are said to be associated with pulvinar movement, circadian clock, and light signal transduction through phytochrome. Pulvinar movement involves pulvinar cells at the base of a plant leaf (or leaflet) or at the apex of the petiole that facilitates nyctinastic and nastic movements in a mechanism similar to stomatal closure."

Via BoingBoing.