Drought-induced changes in photosynthetic electron transport in maize probed by prompt fluorescence, delayed fluorescence, P700 and cyclic electron flow signals

• Published in: Environmental and experimental botany 2019-02, Vol.158, p.51-62
• Main Authors: Zhou, Ronghua, Kan, Xin, Chen, Jianjian, Hua, Heliang, Li, Yue, Ren, Jiaojiao, Feng, Ke, Liu, Huanhuan, Deng, Dexiang, Yin, Zhitong
• Format: Article
• Language: English
• Subjects: Cyclic electron flow; Delayed fluorescence; Drought stress; Energy conversion efficiencies in photosystems (PS) I and II; Maize; Modulated 820 nm reflection; Prompt fluorescence OJIP
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2018.11.005

•PF, DF and P700 revealed complementary information on drought-induced changes.•Drought impaired OEC, PSII RCs and PSI acceptor side in maize photosynthetic chain.•Drought decreased maize photosynthetic forward, backward and cyclic electron flows.•Cyclic electron flows might play an important role in maize response to drought. The effect of drought on the prompt chlorophyll a fluorescence (PF) transient (OJIP), delayed chlorophyll a fluorescence (DF), modulated 820-nm reflection (MR), energy conversion efficiencies in photosystems (PS) I and II, and cyclic electron flow (CEF) activity in two maize hybrids with contrasting drought tolerance was investigated. Our aim was to identify the target site of drought stress on the photosynthetic electron transport chain and investigate the relevance of the CEF pathway to the drought tolerance of maize plants. The OJIP analysis showed that drought stress, depending on its duration, decreased FP, increased FJ, and induced a pronounced K-band and a positive L-band. Moreover, OJIP parameters, including PIABS, RC/CSO, TRO/ABS, and ETO/TRO, were significantly reduced. The DF analysis showed that the values of I1 and I2 in the induction curve and L1 and L2 derived from the decay curve decreased progressively with the duration of drought stress. The MR analysis showed that drought stress inactivated both the fast decrease and slow increase phases of the MR transient, resulting in a gradual decrease in both VPSI and VPSII-PSI. The energy conversion analysis showed that drought stress decreased the PSI photochemical quantum yield Y(I) and PSII photochemical quantum yield Y(II). Compared to the tolerant hybrid, the drought-induced changes in the sensitive hybrid were stronger and appeared at an earlier treatment stage. The CEF activity analysis showed that the CEF pathway under drought stress operated for a longer time in the tolerant hybrid than that in the sensitive hybrid. The above results indicate that drought stress damaged the donor and acceptor sides of PSII, the PSII reaction center and the acceptor side of PSI and decreased the efficiency of both PSI and PSII and the capacity of electron transfer. The CEF pathway might play an important role in the tolerance of the maize photosynthetic electron transport chain to drought stress.