Morphophysiology of cowpea under salt stress and chitosan application in a semi-arid area

Abstract

In the Northeast region of Brazil, waters with high concentrations of soluble salts stand out as one of the main abiotic stress factors, significantly impacting plant growth and productivity. Therefore, it is necessary to use alternatives capable of mitigating the effects of salt stress on crops of great importance to the region, such as cowpea. In this context, the objective of present study was to evaluate the effects of chitosan concentrations on the morphophysiology of cowpea under saline stress. The experiment was conducted in a greenhouse, adopting a randomized design, in a 2 × 5 factorial scheme, with two levels of electrical conductivity of the 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 replications. Irrigation with ECw of 4.0 dS m^-1 decreased the relative water content and phytomass accumulation and increased electrolyte leakage in the leaf blade of cowpea plants. Chitosan applications on plants under ECw of 0.6 dS m^-1 inhibited the growth. Chitosan applications between concentrations of 0.46 and 0.71 g L^-1 mitigated the harmful effects of water salinity by reducing electrolyte leakage and increasing the relative water content, number of leaves, leaf area, and relative growth rate of stem diameter, and root/shoot ratio. Foliar application of chitosan in cowpea cultivation should only be carried out under conditions of high water salinity.