Molecular mediation of photoperiodic control in activity-dormancy tree growth cycles

Plants residing in temperate and boreal regions undergo annual activity-dormancy cycles in order to cope with the extreme variations in climate that accompany changes in seasons. Photoperiod and temperature signals act as the key environmental cues controlling growth cessation and dormancy.

Seasonal changes that occur in the apex of hybrid aspen during the activity–dormancy cycle. Under long-day (LD) and warm temperature (WT) conditions, such as those experienced during the summer, trees grow actively. They stop their growth upon sensing short days (SDs) during early autumn. Initially, growth cessation is reversible by exposure to the growth-promoting LDs, as the buds are in an ecodormant state. SDs induce dormancy in the buds during late autumn. Once dormancy is established, growth becomes insensitive to any growth-promotive signals and the buds are endodormant. Chilling temperatures during the winter periods promote the release of dormancy and buds become ecodormant again. Relatively warmer temperatures in the spring promote bud burst, which is followed by active growth in the summer.

Maurya and Bhalerao highlight data indicating that symplastic communication may mediate certain aspects of seasonal growth; the results point to a high level of conservation in the signalling pathways that mediate photoperiodic control of seasonal growth in trees and flowering in annual plants such as Arabidopsis. This review article suggests that the future challenge is extending these insights into the control of phenology in model plants such as poplar and spruce by applying a similar framework to other, non-model trees.