Photosynthesis of Overwintering Evergreen Plants

Abstract

In this review we focus on photosynthetic behavior of overwintering evergreens with an emphasis on both the acclimative responses of photosynthesis to cold and the winter behavior of photosynthesis in conifers. Photosynthetic acclimation is discussed in terms of the requirement for a balance between the energy absorbed through largely temperature-insensitive photochemical processes and the energy used for temperature-sensitive biochemical processes and growth. Cold acclimation transforms the xanthophyll-mediated nonphotochemical antenna quenching of absorbed light from a short-term dynamic response to a long-term sustained quenching for the whole winter period. This acclimative response helps protect the evergreen foliage from photooxidative damage during the winter when photosynthesis is restricted or prevented by low temperatures. Although the molecular mechanisms behind the sustained winter excitation quenching are largely unknown, it does involve major alterations in the organization and composition of the photosystem II antenna. In addition, photosystem I may play an important role in overwintering evergreens not only by quenching absorbed light photochemically via its support of cyclic electron transport at low temperatures, but also by nonphotochemical quenching of absorbed light irrespective of temperature. The possible role of photosystem II reaction centers in nonphotochemical quenching of absorbed energy in overwintering evergreens is also discussed. Processes like chlororespiration and cyclic electron transport may also be important for maintaining the functional integrity of the photosynthetic apparatus of overwintering evergreens both during periods of thawing in winter and during recovery from winter stress in spring. We suggest that the photosynthetic acclimation responses of overwintering evergreens represent specific evolutionary adaptations for plant species that invest in the long-term maintenance of leaf structure in cold climatic zones as exemplified by the boreal forests of the Northern Hemisphere.

Photosynthetic ecophysiology of evergreen leaves in the woody angiosperms – a review

“…This regulated acclimation process occurs in response to the onset of low temperatures and is followed by springtime de-acclimation and photosynthetic recovery (Oberhuber and Bauer 1991;Verhoeven et al 1998;Neuner et al 1999;Öquist and Huner 2003). Winter decline of photosynthesis thus results from both environmental and endogenous controls.…”

Regulation of the photosynthetic apparatus under fluctuating growth light

“…During these seasons, their needles continue to absorb light, even though it cannot be used for CO 2 assimilation because the enzyme systems are largely inhibited at low temperatures. Survival of evergreens in these conditions involves reduction of the light-harvesting antenna size [16], as well as a marked reduction in the amount of PSII complexes, while the amount of PSI remains unchanged [17][18][19]. More generally, it is highly possible that slowing down PSII photochemistry and the accompanying redox chemistry can function as a protection system for the entire photosynthetic machinery against photodamage.…”

Populations of photoinactivated photosystem II reaction centers characterized by chlorophyllafluorescence lifetimein vivo

“…Fluctuations of solar energy input can be accommodated by a tradeoff between energy utilization in photosynthetic carbon assimilation and energy dissipation by various photoprotective mechanisms that modulate absorption and dissipation of excess light energy (1)(2)(3). Despite the complex suite of strategies for photoprotection, however, photooxidative damage inevitably occurs to photosystem (PS) II, in which P680 ϩ (a special Chl in the PSII reaction center), the strongest biological oxidant, is generated to split water to molecular oxygen, protons, and electrons (4).…”