Growth and water status of cowpea under salt stress and exogenous melatonin application

ABSTRACT Cowpea is a species considered sensitive to salt stress, with losses in growth and yield from the irrigation water electrical conductivity of 3.3 dS m⁻¹. Melatonin is a promising tool with an attenuating effect on abiotic stresses. Thus, this study aimed to evaluate the water status and growth of ‘BRS Tumucumaque’ cowpea as a function of irrigation water salinity and exogenous melatonin application. The experiment was conducted in a greenhouse, in a randomized block design, in a 3 × 3 factorial scheme, with three replicates and two plants in each experimental unit. The first factor consisted of three salinity levels in the irrigation water (0.5, 3.0, and 5.0 dS m⁻¹), and the second factor of three melatonin concentrations (0, 0.5, and 1 mM). At 41 days after sowing, plant height, stem diameter, number of leaves and leaflets, root length, leaf area, dry mass of leaves, petiole, stem and root, relative water content, electrolyte leakage, leaf mass per unit area and succulence were analyzed. Increasing salinity concentrations reduced most growth variables and increased electrolyte leakage. Exogenous application of melatonin did not have a significant effect on the attenuation of salt stress in cowpea.