Cowpea, a vital legume in the tropics, plays a crucial role in the diet of millions of people. However, its yield remains significantly low due to water deficit stress. The objective of this study was to evaluate the morphological and physiological responses of four cowpea varieties subjected to water deficit stress to establish their actual resistance capacities. Trials were conducted in a greenhouse at Nangui Abrogoua University, using three Fisher blocks in the experimental design. Water deficit conditions, at 25% field capacity (FC) and 12.5% FC (severe), were applied from seeding until the wilting of plants, in addition to a control condition (100% FC). Physiological (leaf moisture, leaf temperature) and morphological (number of branches, stem diameter, plant length) data were analyzed. The results showed that the highest leaf moisture rates were recorded at 12.5% FC for all varieties. Variety KVX745-11P recorded the highest leaf moisture rate (65.45%) and exhibited the lowest leaf temperatures, at 30.4°C. Leaf moisture rates increase as the degree of water deficit decreases, while leaf temperature increases as the degree of water deficit increases. The lowest numbers of branches, smallest stem diameters, and plant lengths were recorded at 12.5% FC for all varieties. It was concluded from this study that water deficit negatively impacted the physiology and morphological traits of the studied cowpea varieties.
