Differences in photoprotective strategy during winter in Eastern white pine and white spruce.

This article investigates the photoprotective mechanisms employed by two temperate conifers, Eastern white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss), during winter and spring recovery from low temperature stress. Both species utilize sustained thermal dissipation involving retention of the xanthophyll cycle pigments antheraxanthin and zeaxanthin (A + Z), with a dynamic form activated by subzero temperatures in spring. White spruce, unlike pine, maintains higher levels of cytochrome b6f complex and photosystem I (PSI) proteins and exhibits pronounced sustained phosphorylation of light-harvesting complex II (LHCII) and photosystem II (PSII) core proteins, suggesting upregulation of cyclic or alternative electron transport and a possible mechanism of direct energy transfer from PSII to PSI for photoprotection. The study highlights species-specific strategies in coping with winter stress and the importance of flexible, temperature-dependent photoprotective responses during transitional periods.