Gas exchange, photosynthetic pigments, and growth of hydroponic okra under salt stress and salicylic acid

The high concentrations of salts present in the water sources of the Brazilian Northeastern semi-arid region stand out as one of the limiting factors for agricultural production, contributing to soil salinization and/or sodification. Thus, it is extremely important to identify strategies to mitigate the effects of salt stress on plants, such as the foliar application of salicylic acid. In this context, the objective of the present study was to evaluate the effect of foliar application of salicylic acid as an attenuator of salt stress on leaf gas exchange, water relations, photosynthetic pigments, and growth of okra cv. Caninde grown in a hydroponic system. The experiment was conducted in a greenhouse, in Pombal, PB, Brazil. The treatments consisted of four levels of electrical conductivity of the nutrient solution -ECns (3.0, 5.0, 7.0, and 9.0 dS m-1) and four concentrations of salicylic acid -SA (0, 1.2, 2.4, and 3.6 mM) distributed in a completely randomized design in a split-plot scheme, considering the ECns levels as the plots and SA concentrations as the subplots, with four replicates and two plants per plot. ECns from 3.0 dS m-1 inhibited the synthesis of photosynthetic pigments, leaf gas exchange, and growth of okra cv. Caninde. Foliar application of salicylic acid at concentrations of up to 3.6 mM does not alleviate the effects of salt stress on water relations, gas exchange and growth of okra. Salicylic acid at a concentration of 1.8 mM stimulates chlorophyll a and b biosynthesis in okra under ECns of 3.0 and 4.0 dS m-1, respectively.

Automated summary

The high concentrations of salts in the water sources of the Brazilian Northeastern semi-arid region limit agricultural production by causing soil salinization and/or sodification. This study evaluated the potential of foliar application of salicylic acid as a mitigation strategy for salt stress on okra plants grown hydroponically. The results showed that salicylic acid at a concentration of 1.8 mM stimulated chlorophyll synthesis in okra under specific electrical conductivity conditions.