Mitigation of heavy metal stress in maize (Zea mays L.) through application of silicon nanoparticles

Abstract

The ability of silicon to increase plant resistance to abiotic stress is well recognised, but less well known is the ability of silicon nanoparticles (SiNPs) to diminish abiotic stress. In this study, therefore, we compared the effect of sodium silicate and SiNPs on plant growth, biomass, pigments, soluble protein, proline, oxidative stress, antioxidant enzymes, and Cd accumulation in maize grown in cadmium (Cd) contaminated soil in a pot experiment arranged in randomized complete block design. Soils were contaminated with varying concentrations of Cd (0, 25, and 50 mg/kg). SiNPs showed specific agglomerated structure having remarkable surface area for nutrients adsorption. Cd stress caused a significant reduction in agronomic attributes by enhancing oxidative stress. Conversely, foliar spraying of Si and SiNPs significantly overcomes the Cd-induced decline in maize plants. Si and SiNPs significantly enhanced the agronomic and physiological attributes of maize by upregulating the activities of SOD, POD, CAT, and APX and reducing the MDA and H2O2 contents under Cd stress. Si significantly reduced the Cd contents in grains by 60.6% (TE) and 43.2% (TF) under Cd 25 and 50 mg/kg stress, respectively, whereas SiNPs decreased the Cd contents in grains by 62.2% (TH) and 48.7% (TI) under Cd 25 and 50 mg/kg stress, respectively. It was noted that the individual delivery of Si and SiNPs had no statistically significant influence on the protective nature. Thus, foliar application of both forms of silicon might be helpful in enhancing plant resilience under Cd stress conditions.