Induction of cyclic electron flow around photosystem I during heat stress in grape leaves.
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 m-2s-1) 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.
State Key Lab of Crop Biology, Tai'an 271018, Shandong, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
Yongjiang
Y
Sun
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.
Qingwei
Q
Geng
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.
Yuanpeng
Y
Du
State Key Lab of Crop Biology, Tai'an 271018, Shandong, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
Xinghong
X
Yang
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. Electronic address: zhaih@sdau.edu.cn.
Heng
H
Zhai
D000222:Adaptation, Physiological; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D005453:Fluorescence; D006358:Hot Temperature; D008027:Light; D009252:NADPH Dehydrogenase / Q000378:metabolism; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D013045:Species Specificity; D013312:Stress, Physiological; D027843:Vitis / Q000145:classification / Q000378:metabolism*
D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D009252:NADPH Dehydrogenase
Cyclic electron flow; Grape; Heat stress; Photoinhibition