Abstract
The drought tolerance and capacity to recover after drought are important for plant growth and yield. In this study, two maize lines with different drought resistance were used to investigate the effects of different drought durations and subsequent re-watering on photosynthetic capacity, electron transfer and energy distribution, and antioxidative defense mechanisms of maize. Under short drought, maize plants decreased stomatal conductance and photosynthetic electron transport rate, and increased NPQ (Non-photochemical quenching) to dissipate excess excitation energy in time and protect the photosynthetic apparatus. With the increased drought duration, NPQ, antioxidase activity, PItotal (total performance index), ∆I/Io, ψEo (quantum yield for electron transport), φEo (efficiency/probability that an electron moves further than QA−), δRo (efficiency/probability with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side) and φRo (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) were significantly reduced, while Y(NO) (quantum yield of nonregulated energy dissipation) and MDA (malondialdehyde) began to quickly increase. The photosynthetic rate and capacity of photosynthetic electron transport could not recover to the level of the plants subjected to normal water status after re-watering. These findings indicated that long drought damaged the PSI (photosystem I) and PSII (photosystem II) reaction center and decreased the electron transfer efficiency, and this damage could not be recovered by re-watering. Different drought resistance and recovery levels of photosynthetic performance were achieved by different maize lines. Compared with D340, D1798Z had higher NPQ and antioxidase activity, which was able to maintain functionality for longer in response to progressive drought, and it could also recover at more severe drought after re-watering, which indicated its higher tolerance to drought. It was concluded that the capacity of the energy dissipation and antioxidant enzyme system is crucial to mitigate the effects caused by drought, and the capacity to recover after re-watering was dependent on the severity and persistence of drought, adaptability, and recovery differences of the maize lines. The results provide a profound insight to understand the maize functional traits’ responses to drought stresses and re-watering.
Highlights
The IPCC (Intergovernmental Panel on Climate Change) expected climate change to result in abnormal changes in precipitation patterns, including increased severity and accelerated frequency of drought [1]
T4 recovered slowly after re-watering. These results suggested that the long-term drought constrained photosynthetic capacity, and that long-term drought might make non-stomatal factors play a dominant role in photosynthesis
Stomatal limitation was a major factor for photosynthetic reduction, and the photosynthetic performance could recover rapidly after re-watering
Summary
The IPCC (Intergovernmental Panel on Climate Change) expected climate change to result in abnormal changes in precipitation patterns, including increased severity and accelerated frequency of drought [1]. To improve irrigation management for agricultural systems [5] Both of these require a better understanding of the physiological responses to drought [6]. Drought can severely inhibit the growth and productivity of plants through affecting some key physiological processes, such as the photosynthesis rate [7]. Plants reduce the water vapor loss through reducing the stomatal opening [8]. It restricts CO2 entry in the leaf, which may lead to the decrease of the photosynthesis rate [9] and a decrease in primary photochemical processes [10], which will inhibit plant growth and even reduce dry matter accumulation and yield [11]
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