Water stress is a key factor limiting sorghum growth and yield potential. This study investigated the changes in morphology, photosynthetic parameters, and fluorescence characteristics of sorghum under drought and waterlogging stress. The results indicated that these two types of water stress limited sorghum growth and led to a decrease in leaf chlorophyll (Chl), especially Chl a, which was accompanied by a decrease in net photosynthetic rate. In addition, under both types of water stress, the light-compensation point (LCP) and light-saturation point (LSP) both decreased, but the effect on these parameters was more obvious under drought. In terms of fluorescence parameters, the initial fluorescence and variable fluorescence increased under drought and waterlogging stress, while the maximum fluorescence did not change significantly, and the electron transport rate, photochemical quenching, and PSII actual quantum yield decreased. In summary, these results suggest that sorghum adapts to drought and waterlogging stress by reducing the leaf Chl a content, reducing LCP and LSP, and changing fluorescence parameters.

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