Physiological indices and growth of hydroponic cucumber under saline nutrient solutions and salicylic acid

Abstract

The objective of this study was to evaluate the effect of foliar application of salicylic acid on the physiological indices and growth of Japanese cucumber cv. Hiroshi grown under saline nutrient solutions in a hydroponic system. The experiment was conducted in a greenhouse at the Center of Science and Agri-Food Technology of the Federal University of Campina Grande, Pombal, PB, Brazil, using the Nutrient Film Technique (NFT) hydroponic cultivation system. A completely randomized design was used in a split-plot scheme, with plots consisting of four levels of electrical conductivity of the nutrient solution - ECns (2.1, 3.6, 5.1, and 6.6 dS m-1) and subplots consisting of concentrations of salicylic acid - SA (0, 1.8, 3.6, and 5.4 mM), with four replicates and two plants per plot. ECns of 4.8 dS m-1 associated with foliar application of 3.6 mM of SA resulted in higher relative water content. Growth, photosynthetic pigment synthesis, and biomass accumulation in Japanese cucumber plants are inhibited by nutrient solution from 2.1 dS m-1. Salicylic acid at concentration of 2.0 mM promoted a higher relative growth rate of leaf area for plants under nutrient solution of 2.1 dS m-1. SA concentration of 5.4 mM associated with saline nutrient solution of 6.6 dS m-1 resulted in a higher root/shoot ratio, but intensified the deleterious effects of salt stress on the biomass accumulation of cucumber plants.