Phase Change and Phenology in Trees

A long life span and large size are central characteristics of the tree growth habit. This growth habit requires a prolonged management of meristems as well as the long-term maintenance of above-ground tissues that are exposed to a variety of abiotic and biotic conditions, both seasonally recurring as well as episodic. Phase change and phenology, the timing of life cycle events, are key adaptive traits that alter meristem activity and identity as well as other aspects of growth and physiology. We review these processes and illustrate some of the diversity among taxa. The increasing genomic resources for trees and technological innovations are enabling the elucidation of the complex regulatory networks underpinning these processes as well as the variation within and between tree taxa. We address the current state of knowledge of environmental signals, genes and pathways regulating the multiple component processes of vegetative and reproductive phase change and phenology in trees.