Controlling Synchrony of Circadian Clocks by Dark-Pulse Perturbations in Plant

A plant circadian system is composed of a large number of self-sustained cellular oscillators that synchronize with each other to produce a strong output rhythm. We show that the application of pulse perturbations, i.e., short-term injections of darkness under constant light, provides a novel technique for controlling the synchronized behaviour of the plant rhythm in Arabidopsis thaliana. By destroying synchrony, the circadian singularity was experimentally induced for the first time in vivo. The present technique is based upon the theory of phase oscillators, which does not require prior knowledge of the detailed dynamics of the plant system but only knowledge of its phase and amplitude responses to the pulse perturbation. Our approach can be applied to diverse problems of controlling biological rhythms in living systems.