Department of Plant Sciences, University of Western Ontario, N6A 5B7, London, Canada.
Photosynth Res. 1993 Jul;37(1):19-39. doi: 10.1007/BF02185436.
Cold acclimation requires adjustment to a combination of light and low temperature, conditions which are potentially photoinhibitory. The photosynthetic response of plants to low temperature is dependent upon time of exposure and the developmental history of the leaves. Exposure of fully expanded leaves of winter cereals to short-term, low temperature shiftsinhibits whereas low temperature growthstimulates electron transport capacity and carbon assimilation. However, the photosynthetic response to low temperature is clearly species and cultivar dependent. Winter annuals and algae which actively grow and develop at low temperature and moderate irradiance acquire a resistance to irradiance 5- to 6-fold higher than their growth irradiance. Resistance to short-term photoinhibition (hours) in winter cereals is a reflection of the increased capacity to keep QA oxidized under high light conditions and low temperature. This is due to an increased capacity for photosynthesis. These characteristics reflect photosynthetic acclimation to low growth temperature and can be used to predict the freezing tolerance of cereals. It is proposed that the enhanced photosynthetic capacity reflects an increased flux of fixed carbon through to sucrose in source tissue as a consequence of the combined effects of increased storage of carbohydrate as fructans in the vacuole of leaf mesophyll cells and an enhanced export to the crown due to its increased sink activity. Long-term exposure (months) of cereals to low temperature photoinhibition indicates that this reduction of photochemical efficiency of PS II represents a stable, long-term down regulation of PS II to match the energy requirements for CO2 fixation. Thus, photoinhibition in vivo should be viewed as the capacity of plants to adjust photosynthetically to the prevailing environmental conditions rather than a process which necessarily results in damage or injury to plants. Not all cold tolerant, herbaceous annuals use the same mechanism to acquire resistance to photoinhibition. In contrast to annuals and algae, overwintering evergreens become dormant during the cold hardening period and generally remain susceptible to photoinhibition. It is concluded that the photosynthetic response to low temperatures and susceptibility to photoinhibition are consequences of the overwintering strategy of the plant species.
冷驯化需要适应光照和低温的组合，这些条件可能具有光抑制性。植物对低温的光合响应取决于暴露时间和叶片的发育历史。将冬小麦的完全展开叶片暴露于短期低温下会抑制，而低温生长会刺激电子传递能力和碳同化。然而，低温对光合作用的响应显然取决于物种和品种。在低温和中等光照下积极生长和发育的冬一年生植物和藻类获得了对光照的抗性，比其生长光照高出 5 到 6 倍。冬小麦对短期光抑制（小时）的抗性反映了在高光条件和低温下保持 QA 氧化的能力增加。这是由于光合作用能力的增加。这些特征反映了对低温生长的光合作用适应，可用于预测谷物的耐寒性。有人提出，增强的光合作用能力反映了由于蔗糖在源组织中的通量增加，作为增加的碳水化合物作为叶肉细胞液泡中的果糖苷储存和由于其增强的向冠的出口而导致的蔗糖出口增加的结果。谷物长期（数月）暴露于低温光抑制表明，PS II 的光化学效率的这种降低代表 PS II 的稳定、长期下调以匹配 CO2 固定的能量需求。因此，体内光抑制应被视为植物根据环境条件调整光合作用的能力，而不是必然导致植物损伤或伤害的过程。并非所有耐寒的草本一年生植物都使用相同的机制来获得对光抑制的抗性。与一年生植物和藻类相反，越冬常绿植物在冷驯化期间休眠，并且通常仍然容易受到光抑制的影响。因此，可以得出结论，对低温的光合响应和对光抑制的敏感性是植物物种越冬策略的结果。
