Hormones and Endodormancy Induction in Woody Plants

Abstract

Summary The scope of this review is limited to hormonal involvement in the induction of woody bud endodormancy and does not address dormancy maintenance or release. Knowledge of hormonal regulation of processes has become increasingly more complex, particularly with recent findings of auxin- and ethylene-triggered abscisic acid induction revealing many more responses mediated by ABA than originally considered. The intent of this review is to provide an account of the current state of knowledge of hormones in bud dormancy research within an historical context with a focus on promising avenues of research. While hormones are undoubtedly involved at some point during dormancy induction, meaningful progress in unraveling the mechanism of endo-dormancy-induction is difficult through this hormone-centered approach. The path to dormancy acquisition is a continuum. In many plants, this path begins far earlier than the traditionally-examined autumn period. Aside from more useful hormonal localization studies within the bud and utilization of mutants, continued gross analysis of hormone presence/absence during dormancy induction may not be fruitful. Examining the regulation of the early molecular switch within key cells of the apical meristem or subtending tissues may provide greater insight into dormancy induction. Turgor pressure-dependent cellular differentiation within the apical meristem and the extrinsic and intrinsic factors regulating turgor may be central to that molecular switch. Simpler model systems may need to be utilized to test these hypotheses. Only then can the potential role of hormones in endodormancy induction be more clearly articulated.