Ameliorative role of salicylic acid in the growth, nutrient content, and antioxidative responses of salt-stressed lettuce

Plant responses to biotic and abiotic stresses are regulated by salicylic acid (SA), a signaling molecule. The goal of this study was to determine the efficacy of foliar SA treatments (0.25, 0.50, or 1.00 mM) in reducing salt stress in lettuce exposed to 100 mM NaCl. Salt-stressed plants given a foliar application of SA showed alleviation of the negative effects of salinity, resulting in higher growth performance (increases of 6%–198%). The positive impacts of SA were especially noticeable as an increase in the content of photosynthetic pigments, such as total chlorophyll (31–72%) and total carotenoids (49–141%). Application of SA also helped to reduce membrane damage, as seen by significantly lower levels of MDA (31–70%) in the leaves of salt-stressed lettuce plants. Moreover, the use of SA enhanced overall flavonoid and phenolic content, as well as nutrient absorption. SA treatment also increased the activities of antioxidant enzymes, such as ascorbate peroxidase, catalase, glutathione reductase, and superoxide dismutase, resulting in a considerable reduction in salt-induced oxidative damage. The most efficient SA application concentration was 0.50 mM. Overall, the use of SA as a foliar spray could be recommended as a long-term strategy for improving the defense systems of salt-stressed lettuce.