Physiology and production components of cowpea under salt stress and chitosan application

Cowpea ( Vigna unguiculata (L.) Walp.) is one of the main grain crops that form part of Brazilian food consumption, but its production is affected by edaphoclimatic conditions and high salinity of the irrigation water. The aim of this research was to evaluate the effects of chitosan concentrations on the physiology and production components of cowpea grown under salt stress. The experiment was conducted in a greenhouse, adopting a completely randomized design, in a 2 x 5 factorial scheme, with two levels of electrical conductivity of irrigation water (ECw- 0.6 and 4.0 dS m(-1)) and five concentrations of chitosan (0, 0.25, 0.50, 0.75, and 1.00 g L-1), with four replicates, each of which consisting of three plants. Irrigation water with electrical conductivity of 4.0 dS m(-1) negatively affected the synthesis of photosynthetic pigments, chlorophyll a fluorescence, and grain production of cowpea cv. BRS Tapaihum. Foliar application of chitosan at concentrations between 0.46 and 0.71 g L-1 mitigated the deleterious effects of salt stress on photochemical efficiency, grain production, and grain index per plant. Chitosan applications under irrigation water of electrical conductivity of 0.6 dS m(-1) promoted an increase in the mean pod length, grain production and grain index of cowpea plants cv. BRS Tapaihum.