Critical Leaf Water Content for Maize Photosynthesis under Drought Stress and Its Response to Rewatering

Crop photosynthesis is closely related to leaf water content (LWC), and clarifying the LWC conditions at critical points in crop photosynthesis has great theoretical and practical value for accurately monitoring drought and providing early drought warnings. This experiment was conducted to study the response of LWC to drought and rewatering and to determine the LWC at which maize photosynthesis reaches a maximum and minimum and thus changes from a state of stomatal limitation (SL) to non-stomatal limitation (NSL). The effects of rehydration were different after different levels of drought stress intensity at different growth stages, and the maize LWC recovered after rewatering following different drought stresses at the jointing stage; however, the maize LWC recovered more slowly after rewatering following 43 days and 36 days of drought stress at the tasselling and silking stages, respectively. The LWC when maize photosynthesis changed from SL to NSL was 75.4% +/- 0.38%, implying that the maize became rehydrated under physiologically impaired conditions. The LWCs at which the maize V-cmax25 reached maximum values and zero differed between the drought and rewatering periods. After exposure to drought stress, the maize exhibited enhanced drought stress tolerance, an obviously reduced suitable water range, and significantly weakened photosynthetic capacity. These results provide profound insight into the turning points in maize photosynthesis and their responses to drought and rewatering. They may also help to improve crop water management, which will be useful in coping with the increased frequency of drought and extreme weather events expected under global climate change.

Automated summary

Crop photosynthesis is closely related to leaf water content (LWC), and understanding the LWC conditions during critical points in crop photosynthesis can provide accurate monitoring of drought and early warnings. This study showed that maize LWC recovery after drought stress varied at different growth stages, with different effects of rehydration. Maize photosynthesis transitioned from stomatal limitation to non-stomatal limitation at a LWC of 75.4% +/- 0.38%, indicating rehydration under physiologically impaired conditions. These findings shed light on the responses of maize photosynthesis to drought and rewatering, and may aid in improving crop water management in the face of increasing drought frequency and extreme weather events due to global climate change.