Sustained energy dissipation in winter evergreens

Abstract

Summary: Evergreens are faced with the challenge, during winter, of low temperatures in combination with light exposure, resulting in an imbalance between light absorption and its utilization via photosynthetic carbon reduction. To cope with excess light, evergreens increase their use of thermal energy dissipation, which occurs in a sustained form during winter. There are two forms of sustained thermal dissipation that occur in winter-stressed evergreens, characterized by their rate of reversal upon warming. A rapid form reverses within minutes to hours upon warming, while a slower form reverses over the course of days. The light environment and the severity of winter conditions both play a role in determining the relative amount of each type of sustained energy dissipation throughout the winter. It is suggested that the two forms of sustained dissipation observed in winter-stressed evergreens correspond to sustained forms of the two mechanisms of thermal energy dissipation proposed by Holzwarth and colleagues, with the rapidly reversible component corresponding to a sustained form of the energy-dependent form of thermal energy dissipation (qE) and the slowly reversible component corresponding to a sustained form of the zeaxanthin-dependent mechanism (qZ). Additional outstanding questions and future directions are discussed. © 2013 New Phytologist Trust.