Plant photosynthetic responses to drought, rewatering, and flooding.

The review discusses how plants modulate photosynthesis under contrasting water regimes, highlighting stress-specific limitations, recovery dynamics, and physiological indicators to inform breeding and management under climate change. Climate change is intensifying rainfall extremes, including prolonged droughts, sudden rewatering, and extended flooding, threatening crop productivity worldwide. Here, we present an integrative review synthesizing how major crops modulate photosynthesis under these contrasting water regimes. Drought restricts stomatal and mesophyll conductance, downregulates RuBisCo, and heightens photo-oxidative stress, whereas flooding impairs root structure, water transport, and ATP production. Both stresses can trigger oxidative processes and reduce root-to-shoot hydraulic conductance, imposing similar limitations on photosynthesis. Responses to drought and flooding, and recovery after rewatering and flooding depends on stress intensity and duration, plant species/genotype, and developmental stage. Chlorophyll stability, gas exchange, and PSII fluorescence emerge as robust indicators of photosynthetic resistance and resilience. Trade-offs between stress tolerance and recovery reflect coordinated adjustments in energy use, carbon allocation, and senescence process. Despite recent advances, critical gaps remain in long-term acclimation, compound heat-drought impacts, and canopy-scale carbon dynamics. Finally, we propose an innovative research framework linking photosynthetic plasticity to precipitation variability and highlight breeding and management practices to enhance plant resilience under future climate extremes.