Amelioration of Zinc Stress by Salicylic Acid in Soybean

Salicylic Acid (SA) is a key signaling molecule among naturally occurring plant hormones, known for its role in regulating various physiological processes. This study sought to investigate whether the application of SA could improve growth parameters including root length, shoot length, and dry weight of roots and shoots and alleviate zinc-induced stress in soybean seedlings during pre-, peak-, and post-flowering stages of plant growth. Zinc concentrations of 250, 500, 750, 1000, and 1250 mg/kg of soil were applied to the plants, along with 0.5 mM SA treatment, and compared with control groups. Soybean plants subjected to zinc stress and treated with SA exhibited improved growth and enhanced morphological parameters compared to those without treatment. Notably, the most pronounced positive effect on soybean biomass was observed at a zinc concentration of 500 mg/kg of soil. 0.5 mM SA treatment not only promoted growth but also mitigated the adverse effects of elevated Zinc levels (750-1250 mg/kg) although the reduction was less pronounced as compared to plants treated with Zinc alone, enhancing plant resilience. These findings suggest that SA may act as a protective agent against heavy metal toxicity, potentially enhancing the internal immunity of soybean plants and improving their resilience to environmental stressors, thereby offering valuable implications for agricultural practices.