Insights into salicylic acid-mediated redox homeostasis, carbohydrate metabolism and secondary metabolite involvement in improvement of photosynthetic performance, enzyme activities, ionomics, and yield in different varieties of Abelmoschus esculentus

Abstract

Salicylic acid (SA) is a well-known signaling molecule and phenolic plant hormone. However, the optimal concentration of SA required for beneficial effects may vary across different plant species. The objective of this study was to investigate the effects of salicylic acid (SA) on two different varieties of Abelmoschus esculentus (Sakata-713 and Neelam) in order to determine the optimal concentration of SA and its impact on the growth, physiology, and biochemical processes of the plants. We conducted an experiment applying different SA concentrations (0, 10−4, 10−5, 10−6, 10−7 M) at 25 days after sowing (DAS) and evaluated various plant parameters at different stages. To evaluate various parameters sampling was performed at 30 and 45 DAS; yield traits were calculated at 60 DAS. The results indicate that SA application increased cell division, trichome number, chlorophyll content, photosynthesis, gas exchange traits, and elemental status which further boosted plants growth and yield traits. SA application stimulated activity of several enzymes that participate in carboxylation/decarboxylation homeostasis (carbonic anhydrase), nitrogen metabolism (nitrate reductase), Calvin cycle (Rubisco), TCA cycle (succinate dehydrogenase and fumarase) and secondary metabolism (phenylalanine lyase). A gradual increase in the production of secondary metabolites (total phenol, total flavonoid, anthocyanin) and carbon metabolism (total reducing sugars, starch, glucose, fructose, sucrose) was observed. Notably, SA treatment also played a vital role in maintaining a balanced equilibrium between reactive oxygen species (ROS) and the scavenging system (catalase, peroxidase, superoxide dismutase). Based on our results, the optimal concentration of SA was determined to be 10−5 M, as it yielded the most favourable outcomes among the different concentrations tested. Moreover, when comparing the two varieties of okra, Sakata-713 exhibited a more promising response to SA treatment compared to Neelam.