A circadian rhythm in oxygen uptake by samanea pulvini.

The rate of O(2) uptake by excised Samanea pulvini oscillates with a circadian rhythm during 52 hours of darkness. Rates of respiration increase during pulvinar opening and decrease prior to and during closure, consistent with the concept that opening requires a greater expenditure of energy. Externally supplied sucrose, necessary for perpetuation of the leaflet movement rhythm, has a small promotive effect on the rate of respiration.