The intensity of the stress caused in crops by salinity will largely depend on the level of tolerance of the species or cultivar, and on the management strategies used. The aim of this study therefore, was to evaluate growth and Physiological response in two cultivars of the Cowpea, irrigated with saline water and subjective to different levels of potassium under Sheltered conditions. Seeds of the cultivars, EC 790 and EC 104 were used, which were explained to increase levels of salinity, using irrigation water with an electrical conductivity (CEa) of 0.8, 2.2, 3.6 and 5.0 dS m-1, and increasing rates of potassium (K) in the form of KCl (0.5,1.0, 2.0 and 4.0 g KCl per pot). Comments were taken of leaf gas exchange and plant growth (length of main STEM, stem diameter and total dry matter) at 47 and 55 days after planting (DAP) accordingly. Increases in the salinity of the irrigation water reduced the length of the main stem, the stem diameter and total dry matter in both cultivars. The large levels of potassium together with the salinity resulting in a depressive effect on the growth of the main stem and on stomatal conductance, compared to the isolated effect of salinity, indicating an enhanced osmotic effect. The existence of an interaction between salinity and potassium is an indication that the optimal level of the nutrient depends on salinity levels in the root zone of the plants, and is important information in the management of crops in saline environments. = The intensity of the straw caused by salinity in crops will depend mainly on the level of tolerance of the species or cultivate and on the management strategies used. The aim of this work was to assess the growth and physiological responses of two caupi bean cultivars, irrigated with salt water and subjected to different potassium levels, under protected environmental conditions. Seeds from the EC 790 and EC 104 cultivars have been used and have undergone increasing levels of salinity using irrigation water with electrical conductivity (ECa) of 0,8; 2,2; 3,6 and 5,0 dS m-1 and increasing doses of potassium (K) in the form of KCl (0,5; 1,0; 2,0 and 4.0 g per vessel KCl). At the age of 47 and 55 days after planting (DAP), readings were taken of foliar gas and plant growth exchanges (length of the main shank, stem diameter and total dry matter) respectively. The increase in salinity of irrigation water has reduced the length of the main shank, stem diameter and total dry matter in both cultivars. The highest doses of potassium together with salinity have provided a depressive effect on the growth of the main stem and on static conductance compared to the isolated effect of salinity and are indicative of intensification of osmotic effects. The existence of interactions between salinity and potassium is an indication that the optimal dose of that nutrient depends on salinity in the root zone of the plants and is an important information for the keeping of crops in saline environments.