Nyctinasty
（重定向自Nyctinastic）
![Illustration of sleep movements in Medicago leaves, from: Charles Darwin (1880): The Power of Movement in Plants.](/Images/godic/202501/30/Fig139Movement_of_Plants5558.png")
Nyctinasty is the circadian rhythmic nastic movement of higher plants in response to the onset of darkness. Examples are the closing of the petals of a flower at dusk and the sleep movements of the leaves of many legumes.
Nyctinastic movements are associated with diurnal light and temperature changes and controlled by the circadian clock and the light receptor phytochrome. Several leaf-opening and leaf-closing factors have been characterized biochemically. The earliest observation of this behavior in plants dates back to 324 BC when Androsthenes, a companion to Alexander the Great, noted the opening and closing of tamarind tree leaves from day to night.