Protective role of ZnO nanoparticles in soybean seedlings growth and stress management under Cr-enriched conditions

Chromium (Cr) is a venomous heavy metal and environmental concern which threatened the global food safety due to its carcinogenic and mutagenic effects on biological systems. Some researchers have investigated the ameliorative role of ZnO-NPs to manage heavy metal toxicity in agricultural systems; however, their protective role has never been explored. Therefore, the present research was performed to explore the protective role of ZnO-NPs application under severe Cr toxicity in soybean seedlings. Soybean seedlings were supplemented with 100 µM Cr stress which caused deleterious effects on seed germination, plant growth, biomass, photosynthetic rate, disturbed PSII system, total soluble sugar, total soluble protein, nutrient acquisition by increasing the lipid peroxidation, and electrolyte leakage. Moreover, Cr stress also negatively affected the enzymatic antioxidative activities (SOD, POD, and CAT), and non-enzymatic activities (GR, GSH, GSSH) activities in soybean seedlings due to increased metal accumulation. However, foliar spray of ZnO-NPs mitigated Cr stress by reducing root and shoot Cr uptake as well as plant concentration of oxidative stress markers (MDA and H2O2). Moreover, a higher biomass, altered enzymatic and non-enzymatic antioxidant activities and increased nutrient uptake was observed in ZnO-NPs treated plants. This protective role might be due to the competitive superiority of ZnO-NPs over Cr to use similar in-planta transport channels. Our results revealed that the application of ZnO-NPs can alleviate Cr toxicity in soybean and offers a sustainable solution of crop growth in Cr-contaminated agricultural soils.