Beyond floral initiation: the role of flower bud dormancy in flowering time control of annual plants.

The phenology of temperate perennials, including the timing of vegetative growth and flowering, is well known to be controlled by seasonal dormancy cycles. Dormant structures are known as buds and have specialised covering structures, symplastic isolation from the plant and often autonomous stores of carbon and nitrogen reserves. In contrast, in annual plants our current understanding of the control of the timing of flowering focuses on the mechanisms affecting floral initiation, the transition from a vegetative apical meristem to a inflorescence meristem producing flower primordia in place of leaves. Recently we revealed that annual crops in Brassicaceae exhibit chilling-responsive growth control in a manner closely resembling bud dormancy breakage in perennial species. Here I discuss evidence that vernalisation in autumn is widespread and discuss its role in inducing flower bud set prior to winter, and review evidence that flower bud dormancy has a more wide-spread role in annual plant flowering time control than previously appreciated.