气候变化领域集成服务门户

Plant growth and photosynthesis in response to water status have been extensively investigated. However, elucidating the photosynthetic process and its indicators under a drought episode and rewatering across the entire leaf lifespan is often neglected. In this experiment, three water treatments were set during two growth seasons: a control treatment, moderate persistent drought (T-1), and severe persistent drought (T-2). Maize leaf chlorophyll fluorescence emission was analyzed to determine the regulative responses of the photosynthetic potentials and photosystem II (PSII) photochemistry process to drought and rewatering in situ. A severe drought episode during the peak vegetative growth stage resulted in decreases in chlorophyll content, the maximal efficiency of PSII photochemistry (F-v/F-m), and photochemical quenching, but increases in non-photochemical quenching and the yield for dissipation by downregulation. Rewatering only restored partial PSII functions in plants that had undergone historical drought episodes. An analysis of non-photochemical pathways of thermal dissipation indicates that regulative photoprotection of the photosystem apparatus may occur through heat dissipation when an effect of severe drought episode appeared on a young leaf; however, rewatering did not enhance photoprotection with leaf aging. Compared to the control treatment, the yield of T-1 and T-2 decreased by 25.1% and 27.1% in 2015, and 26.4% and 54.3% in 2016, respectively. The chlorophyll content was significantly and closely correlated with F-v/F-m (R = 0.65, P < 0.001) and the maximum versus minimum fluorescence yield in the dark-adapted state (F-m/F-o)(R = 0.72, P < 0.001). Additionally, the two parameters can be suggested to feasibly track chlorophyll content changes and the degree of leaf senescence in responses to a drought episode and its interaction with leaf aging: F-m/F-o and the relative limitation to photosynthesis (RLP). The current results may provide a profound insight into better understanding the underlying mechanism of photosynthetic potentials and photochemistry efficiency and photoprotection in response to drought episodes and rewatering over the entire leaf lifespan.