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Salicylic acid (SA) is a phenolic compound capable of inducing physiological and metabolic changes that enhance the tolerance of plants to saline stress associated with using a hydroponic system and enable the use of saline water in semi-arid regions. In this context, this assay aimed to evaluate the impact of the foliar application of SA on mitigating salt stress effects on Japanese cucumber cultivated in a hydroponic system. The experiment was carried out in a protected ambient (greenhouse), using the Nutrient Film Technique—NFT hydroponic system. A completely randomized design was performed in a 4 × 4 split-plot scheme, with four levels of electrical conductivity of the nutrient solution—ECns (2.1, 3.6, 5.1, and 6.6 dS m−1)—considered as plots and four SA concentrations (0, 1.8, 3.6, and 5.4 mM), regarded as subplots, with four replicates and two plants per plot. An increase in the ECns negatively affected the physiology, production components, and post-harvest quality of cucumber. However, the application of SA to leaves at concentrations between 1.4 and 2.0 mM reduced the deleterious effects of saline stress and promoted an increase in the production of and improvement in the post-harvest quality of cucumber fruits. [ABSTRACT FROM AUTHOR]

In order to study the effect of salicylic acid concentrations on the mitigation of salt stress in melon plants grown on a hydroponic system an experiment was conducted in a greenhouse at Pombal – PB, Brazil, using an NFT (Nutrient Film Technique) system. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution—ECns (2.1—control, 3.2, 4.3, and 5.4 dS m−1) and four concentrations of salicylic acid—SA (0, 1.5, 3.0, and 4.5 mM), with six replicates. Salicylic acid at the concentration of 3.2 mM attenuated the effect of nutrient solution salinity on the fresh weight of melon fruits. The saline nutrient solution impairs gas exchange and the relative water content and increases the intercellular electrolyte leakage in the leaf blade of melon plants. However, salicylic acid attenuates the deleterious effects of salinity and attains a maximum yield of melon fruits of 23.82 t ha−1 with foliar application of 1.5 mM at ECns of 3.1 dS m−1. Salicylic acid stimulated the synthesis of total chlorophyll, the CO2 assimilation rate, and the instantaneous water use efficiency of hydroponic melon up to a concentration of 4.5 mM. The results obtained indicate that the responses of the hydroponic melon plant grown with saline nutrient solution and the application of salicylic acid are not yet fully elucidated. [ABSTRACT FROM AUTHOR]