Circadian rhythm of the transcellular current in regenerating enucleated posterior stalk segments of Acetabularia mediterranea

The electrical current through Acetabularia posterior stalk segments (PSSs) and enucleated posterior stalk segments (EPSSs) was measured and recorded continuously. It consists of pulses superimposed to a steady state current. The intensity of the steady state current varies rhythmically along each day and night cycle. The circadian character of this variation is demonstrated in free-running conditions. The rhythm occurs in the presence as well as in the absence of the nucleus; its amplitude is light-sensitive. The facts suggest the importance of the plasma membrane in the determination of the circadian clock. The spontaneous current pulses may have some circadian character also, but this is not so obvious as for the steady-state current. © 1976.