Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD25DA, UK.
Physiol Plant. 2011 May;142(1):87-104. doi: 10.1111/j.1399-3054.2011.01465.x. Epub 2011 Mar 28.
Photoinhibition is an inevitable consequence of oxygenic photosynthesis. However, the concept of a 'photoinhibition-proof' plant in which photosystem II (PSII) is immune to photodamage is useful as a benchmark for considering the performances of plants with varying mixes of mechanisms which limit the extent of photodamage and which repair photodamage. Some photodamage is bound to occur, and the energy costs of repair are the direct costs of repair plus the photosynthesis foregone during repair. One mechanism permitting partial avoidance of photodamage is restriction of the number of photons incident on the photosynthetic apparatus per unit time, achieved by phototactic movement of motile algae to places with lower incident photosynthetically active radiation (PAR), by phototactic movement of plastids within cells to positions that minimize the incident PAR and by photonastic relative movements of parts of photolithotrophs attached to a substrate. The other means of avoiding photodamage is dissipating excitation of photosynthetic pigments including state transitions, non-photochemical quenching by one of the xanthophyll cycles or some other process and photochemical quenching by increased electron flow through PSII involving CO₂ and other acceptors, including the engagement of additional electron transport pathways. These mechanisms inevitably have the potential to decrease the rate of growth. As well as the decreased photosynthetic rates as a result of photodamage and the restrictions on photosynthesis imposed by the repair, avoidance, quenching and scavenging mechanisms, there are also additional energy, nitrogen and phosphorus costs of producing and operating repair, avoidance, quenching and scavenging mechanisms. A comparison is also made between the costs of photoinhibition and those of other plant functions impeded by the occurrence of oxygenic photosynthesis, i.e. the competitive inhibition of the carboxylase activity of ribulose bisphosphate carboxylase-oxygenase by oxygen via the oxygenase activity, and oxygen damage to nitrogenase in diazotrophic organisms.
光抑制是放氧光合作用不可避免的后果。然而，“光抑制-proof”植物的概念是有用的，它是一个基准，可以用来比较不同机制限制光破坏程度和修复光破坏的植物的性能。一些光破坏必然会发生，而修复的能量成本是直接修复成本加上修复过程中损失的光合作用。一种允许部分避免光破坏的机制是限制单位时间内作用于光合作用装置的光子数量，这可以通过游动藻类向光合作用有效辐射（PAR）较低的地方进行趋光运动、细胞内质体向最小化入射 PAR 的位置进行趋光运动以及附着在基质上的光养生物的部分相对运动来实现。另一种避免光破坏的方法是耗散光合色素的激发，包括状态转变、叶黄素循环的非光化学猝灭或其他一些过程以及通过增加电子流通过 PSII 引起的光化学猝灭，涉及 CO₂ 和其他受体，包括参与额外的电子传递途径。这些机制不可避免地具有降低生长速度的潜力。除了光破坏导致的光合速率降低以及修复、避免、猝灭和清除机制对光合作用的限制之外，还有产生和运行修复、避免、猝灭和清除机制的额外能量、氮和磷成本。还比较了光抑制的成本与放氧光合作用引起的其他植物功能的成本，即通过加氧酶活性竞争抑制核酮糖二磷酸羧化酶-加氧酶的羧化酶活性，以及固氮生物中氮酶的氧气损伤。
