Circadian rhythm of oxygen evolution in cell fragments of Acetabularia mediterranea

Abstract The O 2 production of Acetabularia cell fragments under constant light and temperature conditions has been measured with a Pt-electrode in a flow-through system. Apical and basal fragments, the isolated cap, and even 10 mm long pieces of the apical half of the stalk show a well pronounced O 2 production as a demonstration of their viability and express a clear circadian rhythm of this activity. In the late developmental stage when cysts are formed, the rhythm of the O 2 production disappears, whereas a reduced O 2 evolution still persists.