The Key Laboratory for Silviculture and Conservation of Ministry of Education, College of Forestry, Beijing Forestry University, Beijing, 100083, China.
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Ann Bot. 2023 Oct 4;132(1):163-177. doi: 10.1093/aob/mcad086.
The photoprotective role of foliar anthocyanins has long been ambiguous: exacerbating, being indifferent to or ameliorating the photoinhibition of photosynthesis. The photoinhibitory light spectrum and failure to separate photo-resistance from repair, as well as the different methods used to quantify the photo-susceptibility of the photosystems, could lead to such a discrepancy.
We selected two congeneric deciduous shrubs, Prunus cerasifera with anthocyanic leaves and Prunus triloba with green leaves, grown under identical growth conditions in an open field. The photo-susceptibilities of photosystem II (PSII) and photosystem I (PSI) to red light and blue light, in the presence of lincomycin (to block the repair), of exposed leaves were quantified by a non-intrusive P700+ signal from PSI. Leaf absorption, pigments, gas exchange and Chl a fluorescence were also measured.
The content of anthocyanins in red leaves (P. cerasifera) was >13 times greater than that in green leaves (P. triloba). With no difference in maximum quantum efficiency of PSII photochemistry (Fv/Fm) and apparent CO2 quantum yield (AQY) in red light, anthocyanic leaves (P. cerasifera) showed some shade-acclimated suites, including lower Chl a/b ratio, lower photosynthesis rate, lower stomatal conductance and lower PSII/PSI ratio (on an arbitrary scale), compared with green leaves (P. triloba). In the absence of repair of PSII, anthocyanic leaves (P. cerasifera) showed a rate coefficient of PSII photoinactivation (ki) that was 1.8 times higher than that of green leaves (P. triloba) under red light, but significantly lower (-18 %) under blue light. PSI of both types of leaves was not photoinactivated under blue or red light.
In the absence of repair, anthocyanic leaves exhibited an exacerbation of PSII photoinactivation under red light and a mitigation under blue light, which can partially reconcile the existing controversy in terms of the photoprotection by anthocyanins. Overall, the results demonstrate that appropriate methodology applied to test the photoprotection hypothesis of anthocyanins is critical.
叶片类黄酮的光保护作用一直存在争议：加剧、不影响或减轻光合作用的光抑制。这种差异可能是由于未能将光抗性与修复分开，以及用于量化光系统光敏感性的不同方法导致的。
我们选择了两种同属的落叶灌木，叶片呈花青素的樱桃李（Prunus cerasifera）和叶片呈绿色的三叶李（Prunus triloba），在野外相同的生长条件下生长。通过非侵入性的PSI 中 P700+信号，量化了在林可霉素（用于阻断修复）存在下，暴露叶片的 PSII 和 PSI 对红光和蓝光的光敏感性。还测量了叶片吸收、色素、气体交换和 Chl a 荧光。
红叶（樱桃李）中的类黄酮含量是绿叶（三叶李）的 13 倍以上。在红光下，PSII 光化学最大量子效率（Fv/Fm）和表观 CO2 量子产量（AQY）没有差异，花青素叶片（樱桃李）表现出一些荫蔽适应的特征，包括较低的 Chl a/b 比、较低的光合作用速率、较低的气孔导度和较低的 PSII/PSI 比值（在任意尺度上），与绿叶（三叶李）相比。在没有 PSII 修复的情况下，花青素叶片（樱桃李）在红光下的 PSII 光失活率系数（ki）比绿叶（三叶李）高 1.8 倍，但在蓝光下显著降低（-18%）。两种类型的叶片的 PSI 在蓝光或红光下均未发生光失活。
在没有修复的情况下，花青素叶片在红光下表现出 PSII 光失活的加剧，而在蓝光下则减轻，这在一定程度上缓和了关于类黄酮光保护作用的现有争议。总的来说，研究结果表明，应用适当的方法来测试类黄酮的光保护假设是至关重要的。
