Genetic basis of the “sleeping leaves” revealed

Abstract

Like most animals, plants also sleep at night, or at least some of them. For instance, the flowers of many species, such as crocus, tulip, and morning glory, are open during the day or part of the day and close at night. Based on such observations, in 1751, the Swedish botanist Carl von Linne suggested combining several plant species in which the flowers open or close at specific and different times of the day to build a “Horologium Florae” (flower clock) that would accurately and colorfully predict time. Such daily movements of plants are not limited to flowers. In his book entitled The Power of Movement in Plants, Darwin (1880) described many examples of “sleep movements of leaves” and provided a “List of Genera, including species the leaves of which sleep” (1). Among these, he noted that the legume family “includes many more genera with sleeping species than all the other families put together.” He also described a specialized organ, called a joint, cushion, or pulvinus responsible for such movement (1). In PNAS, Chen et al. (2) identify the genetic determinant for the formation of these pulvini in three legumes: Pisum sativum (pea), Medicago truncatula (barrel medic), and Lotus japonicus.