Biological timing in plants

Plants present unique advantages for the study of circadian rhythms. One is the variety of physiological processes that exhibit circadian rhythmicity. The use of novel luminescent reporters of gene expression and of calcium levels recently provided the first clues as to how the clock orchestrates many different activities in parallel. Signaling cascades for the transduction of light signals are the subject of intensive studies, making plants an unparalleled system for the dissection of phototransduction pathways for the entrainment of the clock to daily light–dark cycles. Finally, mutants with aberrant circadian rhythms have been isolated in the small weedArabidopsis, that may lead to the identification of molecular cogs of the circadian oscillator in plants.