Morphophysiology of cucumber under saline nutrient solutions and salicylic acid application in hydroponic system1

In conventional systems, the use of saline water makes vegetable production unfeasible, so hydroponic cultivation is a promising alternative in semi-arid areas, as it minimizes socioeconomic impacts. An alternative for mitigating salt stress effects on plants is the application of salicylic acid. The objective of this study was to evaluate the effect of foliar application of salicylic acid on the physiological aspects and growth of 'Hiroshi' japanese cucumber under saline nutrient solutions in a hydroponic system. The studywas carried out in a greenhouse. The hydroponic system used was the Nutrient Film Technique- NFT. Treatments consisted of four values of electrical conductivity of the nutrient solution - ECns (2.1, 3.0, 3.9, and 4.8 dS m-1) and four concentrations of salicylic acid - SA (0, 1.8, 3.6, and 5.4 mM), distributed in a completely randomized design in split plots, with ECns levels considered the plots and SA concentrations considered the subplots, with four replicates. Growth, gas exchange, photosynthetic pigments, relative water content, and electrolyte leakage in the leaf blade were evaluated. Salicylic acid at concentrations ranging from 3.7 to 4.7 mM increased stomatal conductance and carotenoid synthesis, under ECns of 2.1 dS m-1. ECns above 2.1 dS m-1 reduced gas exchange, photosynthetic pigment content, relative water content, and growth of Japanese cucumber plants, at 23 days after transplanting.