Sun Yongjiang, Geng Qingwei, Du Yuanpeng, Yang Xinghong, Zhai Heng
State Key Lab of Crop Biology, Tai'an 271018, Shandong, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
State Key Lab of Crop Biology, Tai'an 271018, Shandong, China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, Shandong, China.
Plant Sci. 2017 Mar;256:65-71. doi: 10.1016/j.plantsci.2016.12.004. Epub 2016 Dec 14.
Photosystem II (PSII) in plants is susceptible to high temperatures. The cyclic electron flow (CEF) around PSI is thought to protect both PSII and PSI from photodamage. However, the underlying physiological mechanisms of the photosynthetic electron transport process and the role of CEF in grape at high temperatures remain unclear. To investigate this issue, we examined the responses of PSII energy distribution, the P700 redox state and CEF to high temperatures in grape leaves. After exposing 'Cabernet Sauvignon' leaves to various temperatures (25, 30, 35, 40 and 45°C) in the light (600μmol photons ms) for 4h, the maximum quantum yield of PSII (Fv/Fm) significantly decreased at high temperatures (40 and 45°C), while the maximum photo-oxidizable P700 (Pm) was not affected. As the temperature increased, higher initial rates of increase in post-illumination Chl fluorescence were detected, which were accompanied by an increase in high energy state quenching (qE). The chloroplast NAD(P)H dehydrogenase-dependent CEF (NDH-dependent CEF) activities were different among grape cultivators. 'Gold Finger' with greater susceptibility to photoinhibition, exhibited lower NDH-dependent CEF activities under acute heat stress than a more heat tolerant 'Cabernet Sauvignon'. These results suggest that overclosure of PSII reaction centers at high temperature resulted in the photoinhibition of PSII, while the stimulation of CEF in grape played an important role in the photoprotection of PSII and PSI at high temperatures through contributing to the generation of a proton gradient.
植物中的光系统II（PSII）对高温敏感。围绕PSI的循环电子流（CEF）被认为可以保护PSII和PSI免受光损伤。然而，光合电子传递过程的潜在生理机制以及CEF在葡萄高温下的作用仍不清楚。为了研究这个问题，我们检测了葡萄叶片中PSII能量分布、P700氧化还原状态和CEF对高温的响应。将‘赤霞珠’叶片在光照（600μmol光子·m⁻²·s⁻¹）下暴露于不同温度（25、30、35、40和45°C）4小时后，PSII的最大量子产率（Fv/Fm）在高温（40和45°C）下显著降低，而最大可光氧化P700（Pm）不受影响。随着温度升高，检测到光照后叶绿素荧光的初始增加速率更高，同时伴随着高能态猝灭（qE）的增加。叶绿体NAD(P)H脱氢酶依赖性CEF（NDH依赖性CEF）活性在不同葡萄品种间存在差异。对光抑制更敏感的‘金手指’在急性热胁迫下表现出比更耐热的‘赤霞珠’更低的NDH依赖性CEF活性。这些结果表明，高温下PSII反应中心的过度关闭导致了PSII的光抑制，而葡萄中CEF的激活在高温下对PSII和PSI的光保护中发挥了重要作用，通过促进质子梯度的产生。
