Evaluation of Salicylic Acid Effects on Growth, Biochemical, Yield, and Anatomical Characteristics of Eggplant (Solanum melongena L.) Plants under Salt Stress Conditions

Salt stress is a major issue in agriculture and crop production that influences global food security. Mitigation options to address salt stress through agronomic practices can help manage this issue. Experiments were performed in two summer seasons in an experimental farm to test the impact of three salinity levels (S): 300 (control), 1000, 2000, and 3000 ppm, and two salicylic acid (SA) levels, including 1.0 and 1.50 mM, and their interaction on growth and yield of eggplant (Solanum melongena L.) hybrid Suma. The results showed that increasing S levels up to 3000 ppm reduced plant and fruit physical characteristics, as well as leaf and fruit chemical characteristics, especially leaf total chlorophyll, carotenoids, relative water, fruit nitrogen, phosphorus, and potassium contents, which led to a reduction in total yield per plant. However, an insignificant effect was observed in the control level and 1000 ppm saline water in leaf area, fruit length, leaf total chlorophyll content, fruit phosphorus content, and total yield per plant. In contrast, leaf sugars, proline contents, electrolyte leakage, fruit TSS (total soluble solids), and ascorbic acid contents were improved with S levels up to the concentration of 3000 ppm compared to the control. However, tested parameters were significantly higher due to the SA foliar spray of 1.0 mM besides photosynthetic pigments of leaves enhanced by using 1.0 and 1.50 mM. Using 1.0 mM SA concentration alleviated the adverse impact of S on eggplant plants until 1000 ppm saline water, reflecting an increase in eggplant yield. The anatomical structure of eggplant leaves revealed positive variations in mature leaf blades in both the stressed and SA-treated plants. Based on these results, the use of SA at a concentration of 1.0 mM may lessen the negative impacts of salt on the growth of eggplant, which increases the overall yield.