Hydroponic cultivation of okra using saline nutrition solutions under application of salicylic acid

ABSTRACT The limited availability of low-salinity water for irrigation in the Northeastern semi-arid region has restricted food production, making it necessary to use strategies to reduce the effects of salt stress on plants. Among the alternatives, the foliar application of salicylic acid stands out. In this context, the objective of this study was to evaluate the effects of foliar application of salicylic acid in mitigating salt stress on the gas exchange, chlorophyll a fluorescence, photosynthetic pigments, and growth of ‘Canindé’ okra in a hydroponic system. The experiment was carried out in a greenhouse, in Pombal - PB, using the Nutrient Film Technique - NFT hydroponic system. The experimental design used was completely randomized in a 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) as the plots and four concentrations of salicylic acid - SA (0, 1.2, 2.4, and 3.6 mM) as the subplots, with four replicates and two plants per plot. SA concentration of 3.6 mM was able to minimize the effect of nutrient solution salinity on chlorophyll a fluorescence and increase the synthesis of chlorophyll b in okra plants, 34 days after transplanting. Nutrient solution salinity above 2.1 dS m-1 negatively affected gas exchange, relative water content, photosynthetic pigments, and growth and increased electrolyte leakage in the leaf blade of okra plants.