Time for plants. Progress in plant chronobiology.

More than 270 years ago plants played the pivotal role in a remarkable discovery: Organisms possess within themselves a surprisingly accurate timing device that synchronizes physiology with the daily environmental cycle. The field of circadian biology arose from the curious observation of de Mairan in 1729 that the daily leaf movements of plants (Mimosa pudica) persisted for several days after he placed them in his basement in constant darkness (24). Plant circadian rhythms continued to intrigue scientists from Linnaeus to Darwin, but little progress ensued until 2 centuries later, contemporaneous with the first years of Plant Physiology, when Erwin Bünning revived the field, again using plants as the subject of study (24). Plant studies are now poised to deliver novel insights of the inner workings of a unique 24-h biological clock, largely through the development of molecular genetic tools that allow the automation of rhythm analysis.