Leaf veins share the time of day

Techniques for isolating and analysing leaf cell types have now been developed, leading to the discovery that circadian clocks in the plant vasculature communicate with and regulate clocks in neighbouring cells. See Letter p.419 A dual-clock system in plants Biological circadian clock systems help many organisms to adapt their physiological activities to daily and seasonal environmental changes. In mammals, circadian clock systems have a dual nature, whereby a group of brain neurons in the suprachiasmatic nucleus acts as the central dominant clock, regulating local clocks in peripheral tissues. In contrast, it has long been thought that plant circadian rhythms are equivalent in all cells. Motomu Endo et al . now provide evidence that plants also have a dual-clock system. Through a detailed analysis of Arabidopsis thaliana leaf tissues using two new versatile techniques, the authors find that within the vasculature tissue the clocks have characteristics distinct from those in other tissues, and that the vasculature clocks affect circadian clock regulation in other tissues.