Sustained energy dissipation in winter evergreens

Abstract

SummaryEvergreens 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.

Seasonal Photoprotective Responses in Needles of Korean Fir (Abies koreana) Over an Altitudinal Gradient on Mount Halla, Jeju Island, Korea

“…Xanthophyll cycle pool sizes similar and/or greater than what we report here for S. pulchra have been reported for evergreen species from more temperate climates; however, only when examined during the winter, when cold temperatures inhibit primary metabolism (Verhoeven et al, 1999(Verhoeven et al, , 2009Adams et al, 2002Adams et al, , 2004Verhoeven, 2014). For example, in many overwintering evergreens, large xanthophyll cycle pool sizes and high levels of nocturnal Z+A retention are accompanied by a substantial downregulation in photosynthetic capac- ity during winter, a season when photosynthetic activity would otherwise be greatly inhibited by low temperatures (Adams et al, 2002(Adams et al, , 2004Verhoeven 2014).…”

“…For example, in many overwintering evergreens, large xanthophyll cycle pool sizes and high levels of nocturnal Z+A retention are accompanied by a substantial downregulation in photosynthetic capac- ity during winter, a season when photosynthetic activity would otherwise be greatly inhibited by low temperatures (Adams et al, 2002(Adams et al, , 2004Verhoeven 2014). Thus, so-called "chronic photoinhibition," which is commonly observed in overwintering evergreens, may represent the manifestations of acclimation to winter conditions and not the result of light-mediated damage to the photosynthetic apparatus, per se (Adams et al, 2004).…”

Nonphotochemical Chlorophyll Fluorescence Quenching: Mechanism and Effectiveness in Protecting Plants from Photodamage

“…It was later discovered that the formation of zeaxanthin is closely related to the NPQ mechanism (Demmig-Adams et al, 1989Demmig-Adams and Adams III, 1992; for review see Demmig-Adams et al, 2014) and as such, a portion of qI is often termed qZ to reflect the long-term quenching effect that is correlated with the presence of this pigment (Nilkens et al, 2010). In addition, other sustained components of NPQ are triggered by low temperature acclimation (Verhoeven, 2013), prolonged illumination in the presence of zeaxanthin (Ruban and Horton, 1995), slow proton equilibration between different membrane compartments (Ruban and Horton, 1995;Joliot and Finazzi, 2010), or simply the formation of high levels of NPQ in some types of photosynthetic materials Ware et al, 2015b). Hence, qI appears to be a highly complex component of NPQ that remains difficult to interpret, and the temporal criterion for quantification of qE is rather ambiguous.…”

Foliar photochemical processes and carbon metabolism under favourable and adverse winter conditions in a Mediterranean mixed forest, Catalonia (Spain)

“…The F v /F m ratio provides information about the maximum or optimum quantum yield and serves as an indicator of stress in the photosystems (Buschmann, 2007). Ratios below 0.80 are indicative of induced photoprotection and sustained energy dissipation (Maxwell and Johnson, 2000;Verhoeven, 2014), whereas leaves with ratios below 0.74 are considered to be below the recovery threshold (Björkman and Demmig, 1987). The effective quantum yield of PSII was estimated by…”