Photoinhibition occurs when light energy exceeds the demand for photosynthesis. The basic feature of photoinhibition is the reduction of photosynthetic efficiency (quantum efficiency of photosynthetic carbon assimilation and photochemical efficiency of photosystem II). According to the difference in the recovery speed of photosynthetic efficiency after the removal of photoinhibitory conditions, it can be divided into two types of photoinhibition: fast recovery and slow recovery. The former is related to the enhancement of some heat dissipation processes; the latter is mainly related to the destruction of the photosynthetic apparatus. The destruction of photosynthetic machinery mainly refers to the destruction, degradation and net loss of the core component DI protein in the PSII reaction center complex.
There are three mechanisms for the heat dissipation process of the photosynthetic machinery, which are the heat dissipation fading relying on the proton gradient across the thylakoid membrane, the heat dissipation relying on the xanthophyll cycle, and the heat dissipation relying on the reversible inactivation of the PSII reaction center. In the absence of other environmental stresses, photoinhibition by saturated light is generally not accompanied by disruption of the photosynthetic machinery, i.e., a net loss of D1 protein.
However, in the case of simultaneous strong light and low temperature stress, the light-induced photoinhibition was accompanied by the loss of D1 protein. When several environmental stresses exist at the same time, since photosynthesis is severely inhibited, resulting in a large amount of light energy remaining, the protection mechanism is inhibited, and photoinhibition or even photodestruction will occur even under medium and low light intensities.
Therefore, as an adaptation to strong light, plants enhance the synthesis of antioxidants and flavonoids that can absorb ultraviolet light, thereby improving tolerance to strong light (Hodson and Bryant, 2012). Photosynthetic “lunch break” is an ecological adaptation and self-regulation of plants to hot climate conditions (Gao Chao et al., 2011).
Typical state of plant photosynthesis（二）
photoinhibition
Photoinhibition occurs when light energy exceeds the demand for photosynthesis. The basic feature of photoinhibition is the reduction of photosynthetic efficiency (quantum efficiency of photosynthetic carbon assimilation and photochemical efficiency of photosystem II). According to the difference in the recovery speed of photosynthetic efficiency after the removal of photoinhibitory conditions, it can be divided into two types of photoinhibition: fast recovery and slow recovery. The former is related to the enhancement of some heat dissipation processes; the latter is mainly related to the destruction of the photosynthetic apparatus. The destruction of photosynthetic machinery mainly refers to the destruction, degradation and net loss of the core component DI protein in the PSII reaction center complex.
There are three mechanisms for the heat dissipation process of the photosynthetic machinery, which are the heat dissipation fading relying on the proton gradient across the thylakoid membrane, the heat dissipation relying on the xanthophyll cycle, and the heat dissipation relying on the reversible inactivation of the PSII reaction center. In the absence of other environmental stresses, photoinhibition by saturated light is generally not accompanied by disruption of the photosynthetic machinery, i.e., a net loss of D1 protein.
However, in the case of simultaneous strong light and low temperature stress, the light-induced photoinhibition was accompanied by the loss of D1 protein. When several environmental stresses exist at the same time, since photosynthesis is severely inhibited, resulting in a large amount of light energy remaining, the protection mechanism is inhibited, and photoinhibition or even photodestruction will occur even under medium and low light intensities.
light adaptation
The adaptation of plant photosynthesis to strong light involves a balanced increase in the ability of photochemical reactions and biochemical reactions; while its adaptation to weak light is an increase or change in the ability of the supplementary light system, while the levels of components involved in electron transfer and carbon fixation decrease . Strong light involves two damaging factors: one is the generation of reactive oxygen species, which is a strong DNA damage agent, which can oxidize and destroy guanine and deaminate cytosine; produce.
Therefore, as an adaptation to strong light, plants enhance the synthesis of antioxidants and flavonoids that can absorb ultraviolet light, thereby improving tolerance to strong light (Hodson and Bryant, 2012). Photosynthetic “lunch break” is an ecological adaptation and self-regulation of plants to hot climate conditions (Gao Chao et al., 2011).