Activity of the shoot apical and cambial meristems: Coordination and responses to environmental signals

A tree shoot includes multiple developmental gradients that reflect the relationships of the shoot apical meristem, the cambial meristem and the tissues and organs they produce. The adaptation of trees to temperate and boreal climates depends on the ability of these two meristems to appropriately respond to environmental signals that are markers of seasonal changes. The aim of this review is to present a more holistic view of the tree shoot, including the developmental changes associated with seasonally regulated growth transitions. We consider the role of long-distance communication in coordinating leaf development, the transition to secondary growth and meristem activity. Using Populus as the model, we discuss the roles of signalling mediated by hormones, sugar and FLOWERING LOCUS T2 (FT2) in coordinating tree shoot developmental processes.