Winter acclimation of PsbS and related proteins in the evergreen Arctostaphylos uva-ursi as influenced by altitude and light environment.

The evergreen groundcover bearberry (Arctostaphylos uva-ursi [L.] Sprengel) was characterized over two successive years (2002-2004) from both sun-exposed and shaded sites at a montane ponderosa pine and subalpine forest community of 1900- and 2800-m-high altitudes, respectively. During summer, photosynthetic capacities and pre-dawn photosystem II (PSII) efficiency were similarly high in all four populations, and in winter, only the sun-exposed and shaded populations at 2800 m exhibited complete down-regulation of photosynthetic oxygen evolution capacity and consistent sustained down-regulation of PSII efficiency.

Photosynthetic capacity and light harvesting efficiency during the winter-to-spring transition in subalpine conifers.

Some coniferous forest ecosystems undergo complete photosynthetic down-regulation in winter. The present study examined the influence of several environmental parameters on intrinsic, needle-level photosynthesis and photoprotection during the spring reactivation of photosynthesis in subalpine conifers. Maximal photosystem II (PSII) efficiency, photosynthetic capacity, and amounts of zeaxanthin and early light-inducible protein (Elip) family members were assessed in three subalpine conifer species over 3 years, and intensively during the 2003 winter-to-spring transition.

Winter down-regulation of intrinsic photosynthetic capacity coupled with up-regulation of Elip-like proteins and persistent energy dissipation in a subalpine forest.

Overwintering, sun-exposed and photosynthetically inactive evergreens require powerful photoprotection. The goal of this study was to seasonally characterize photosynthesis and key proteins/components involved in electron transport and photoprotection. Maximal photosystem II (PSII) efficiency and photosynthetic capacity, amounts of zeaxanthin (Z), antheraxanthin (A), pheophytin and proteins (oxygen-evolving 33 kDa protein (OEC), PSII core protein D1 and subunit S (PsbS) protein, and members of the early light-inducible protein (Elip) family) were assessed in five conifer species at high altitude and in ponderosa pine (Pinus ponderosa) at moderate altitude during summer and winter.