Cumulative effects of drought–flood abrupt alternation on the photosynthetic characteristics of rice

Abstract

The photosynthetic characteristics of crops under drought–flood abrupt alternation (DFAA) provide a foundation for the precise modeling of yield formation. However, current modeling practices are largely based on single water stress conditions or continuously well-watered conditions that differs considerably from the actual rice growing conditions in South China where DFAA occurs. This study aims to investigate the cumulative effects of DFAA on the photosynthetic characteristics of rice. The experiments were conducted in 2017 and 2018, and six DFAA groups with different combinations of drought and flooding were tested during the jointing–heading stage of rice. Three additional treatments were also used to compare the photosynthetic characteristics of rice under different water conditions, namely, those under continuous well-watered (CW), continuous drought (CD), and continuous flooded (CF) conditions. The results showed that there was photosynthetic inhibition after the DFAA stress, followed by recovery and compensation. Interestingly, two different kinds of interaction between the prior drought and the subsequent flooding were observed: the antagonistic effect of the preceding drought on the subsequent-flood-induced photosynthetic inhibition and the synergistic effect of the subsequent flooding on the preceding-drought-induced photosynthetic inhibition. In addition, the antagonistic effect on gs was more pronounced in DFAA groups that experienced prior mild or long-term drought, and the synergistic effect on gs was more deleterious in DFAA groups with severe subsequent flooding. These cumulative effects of DFAA were affected by the leaf-to-air vapor pressure difference (VPDleaf) and probably resulted in different leaf water use strategies in rice. This research increases our knowledge of the effects of the interaction between drought and flooding on rice photosynthesis and highlights the need to consider these complex interactions in future yield modeling and production practices.