The physiology of circadian rhythms in plants

Circadian rhythms regulate many aspects of plant physiology including leaf, organ and stomatal movements, growth and signalling. The genetic identity of some of the components of the core circadian oscillator has recently become known. Similarly, the photoperception and phototransduction pathways that entrain the oscillator to the day and night cycle are being determined. Less clear are the pathways by which the circadian oscillator regulates cellular physiology. Circadian oscillations in cytosolic free calcium might act to transduce the temporal outputs of the circadian oscillator. This hypothesis requires rigorous testing using novel noninvasive technologies. Plants might gain advantage from the circadian clock by being able to predict changes in the environment and coordinate physiological processes, presumably increasing survival and hence, reproductive fitness. Technical advances coupled with cell-specific measurement techniques will allow the advantages of the circadian regulation of physiology to be quantified.