Cowpea (Vigna unguiculata [L.] Walp.) plants display contrasting sulfur-mediated drought acclimation in greenhouse and field

Water restriction is a critical environmental condition for plants capable of promoting severe losses in agricultural yield. Our hypothesis was that sulfur (S) supplementation alleviates drought damage for enhanced performance of cowpea cultivars under semiarid conditions. Two parallel experiments were conducted in greenhouse and field, using two cowpea cultivars (Xique-xique and Novaera) subjected to two water regimes (control and drought) and three S levels (S-40, S-80 and S-120 kg ha−1). Drought had a more restrictive impact on cowpea in greenhouse than in field. Drought-stressed plants in greenhouse showed drastic reductions in net photosynthesis, stomatal conductance and dry mass, for both cowpea cultivars as compared to controls. S-80 supplementation in greenhouse and S-120 in field promoted growth recovery of stressed-Novaera plants as related to S-40 stressed ones, exhibiting a performance closer to that of well-irrigated plants. Superior performance of S-supplemented stressed Novaera plants was associated with activation of mechanisms for water retention, likely osmotic adjustment, evidenced by increased water content, stomatal conductance and transpiration. These physiological adjustments allowed plants to maintain elevated net photosynthesis and growth under drought. In conclusion, S supplementation proves effective in mitigating drought damage in Novaera cultivar, offering potential for cultivating cowpea plants in water-scarce environments.