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.

中文翻译：

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越冬常绿植物的光合作用

在这篇综述中，我们关注越冬常绿植物的光合行为，重点是光合作用对寒冷的适应反应和针叶树光合作用的冬季行为。光合驯化是根据在很大程度上对温度不敏感的光化学过程吸收的能量与用于温度敏感的生化过程和生长的能量之间保持平衡的要求来讨论的。冷驯化将吸收光的叶黄素介导的非光化学天线猝灭从短期动态响应转变为整个冬季的长期持续猝灭。这种适应反应有助于保护常绿树叶在冬季光合作用受到低温限制或阻止时免受光氧化损伤。尽管持续冬季激发猝灭背后的分子机制在很大程度上是未知的，但它确实涉及光系统 II 天线的组织和组成的重大改变。此外，光系统 I 可能在常绿越冬中发挥重要作用，不仅通过其在低温下支持循环电子传输以光化学方式淬灭吸收的光，而且还通过与温度无关的吸收光的非光化学淬灭。还讨论了光系统 II 反应中心在越冬常绿植物吸收能量的非光化学猝灭中的可能作用。氯呼吸和循环电子传递等过程对于在冬季解冻期间和春季从冬季压力恢复期间维持越冬常绿植物光合装置的功能完整性也很重要。我们认为，越冬常绿植物的光合适应反应代表了植物物种的特定进化适应，这些植物物种在寒冷气候区长期维持叶片结构，例如北半球的北方森林。