Drought tolerance in cowpea species is driven by less sensitivity of leaf gas exchange to water deficit and rapid recovery of photosynthesis after rehydration

• Two cowpea cultivars with contrasting behavior under drought stress
• Water relations, leaf biochemistry metabolism, and carboxylation activity
• Only stomatal control does not support drought tolerance in cowpea plants
• Rapid recovery of the photosynthesis after drought stress is a key point

Cowpea grains are the main protein source for many people in semi-arid regions. The goal of this study was to study the in vivo photosynthetic behavior of two cowpea cultivars under well-watered, drought stress, and recovery conditions. The cultivars differ in their sensitivity to drought stress, being classified as tolerant and sensitive based on grain production. After 10 days of water deficit, the leaf water potential of the tolerant cultivar was higher than in the sensitive cultivar, suggesting a mechanism of drought tolerance related to the maintenance of shoot water status. During drought stress, the leaf gas exchange and chlorophyll fluorescence parameters decreased faster in the sensitive cultivar as compared to the tolerant one. After 48 h of rehydration, the stressed plants of both cultivars did not recover the maximum rates of carboxylation, the maximum rate of electron transport driving the RuBP regeneration and photosynthetic capacity. However, tolerant cultivar recovered all photosynthetic parameters faster than the sensitive cultivar after 60 h of rehydration. Our results suggest that the tolerant cultivar was able to maintain higher photochemical activity and leaf gas exchange during water deficit for a longer period than the sensitive cultivar does, which could alleviate the stress effects to the photosynthetic machinery and improve its recovery ability. The consequences of this behavior are discussed.