Han Li-Jun, Fan Da-Yong, Wang Xiang-Ping, Xu Cheng-Yang, Xia Xin-Li, Chow Wah Soon
The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University, Beijing 100083, China.
School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China.
Plant Cell Physiol. 2023 Feb 16;64(1):43-54. doi: 10.1093/pcp/pcac137.
Non-photochemical quenching (NPQ) has been regarded as a safety valve to dissipate excess absorbed light energy not used for photochemistry. However, there exists no general consensus on the photoprotective role of NPQ. In the present study, we quantified the Photosystem II (PSII) photo-susceptibilities (mpi) in the presence of lincomycin, under red light given to five shade-acclimated tree species grown in the field. Photosynthetic energy partitioning theory was applied to investigate the relationships between mpi and each of the regulatory light-induced NPQ [Y(NPQ)], the quantum yield of the constitutive nonregulatory NPQ [Y(NO)] and the PSII photochemical yield in the light-adapted state [Y(PSII)] under different red irradiances. It was found that in the low to moderate irradiance range (50-800 μmol m-2 s-1) when the fraction of open reaction centers (qP) exceeded 0.4, mpi exhibited no association with Y(NPQ), Y(NO) and Y(PSII) across species. However, when qP < 0.4 (1,500 μmol m-2 s-1), there existed positive relationships between mpi and Y(NPQ) or Y(NO) but a negative relationship between mpi and Y(PSII). It is postulated that both Y(NPQ) and Y(NO) contain protective and damage components and that using only Y(NPQ) or Y(NO) metrics to identify the photo-susceptibility of a species is a risk. It seems that qP regulates the balance of the two components for each of Y(NPQ) and Y(NO). Under strong irradiance, when both protective Y(NPQ) and Y(NO) are saturated/depressed, the forward electron flow [i.e. Y(PSII)] acts as the last defense to resist photoinhibition.
非光化学猝灭（NPQ）被视为一种安全阀，用于耗散未用于光化学的过量吸收光能。然而，关于NPQ的光保护作用尚无普遍共识。在本研究中，我们在田间种植的五种适应阴生的树种接受红光照射的情况下，在存在林可霉素的条件下对光系统II（PSII）的光敏感性（mpi）进行了量化。应用光合能量分配理论来研究在不同红光辐照度下，mpi与调节性光诱导NPQ [Y(NPQ)]、组成性非调节性NPQ的量子产率 [Y(NO)] 以及光适应状态下的PSII光化学产率 [Y(PSII)] 之间的关系。研究发现，在低至中等辐照度范围（50 - 800 μmol m-2 s-1）内，当开放反应中心的比例（qP）超过0.4时，跨物种的mpi与Y(NPQ)、Y(NO)和Y(PSII)均无关联。然而，当qP < 0.4（1500 μmol m-2 s-1）时，mpi与Y(NPQ)或Y(NO)之间存在正相关关系，而mpi与Y(PSII)之间存在负相关关系。据推测，Y(NPQ)和Y(NO)都包含保护和损伤成分，仅使用Y(NPQ)或Y(NO)指标来确定物种的光敏感性存在风险。似乎qP调节了Y(NPQ)和Y(NO)各自的两种成分之间的平衡。在强光照射下，当保护性的Y(NPQ)和Y(NO)都达到饱和/受到抑制时，正向电子流 [即Y(PSII)] 作为抵抗光抑制的最后一道防线。
