Abstract
The study examines the effect of rhizospheric application of hydrogen sulfide (H(2)S) on Spinacia oleracea (spinach) plants grown in pots containing metal-contaminated soil. Various concentrations of H(2)S, in the form of Sodium hydrosulfide (NaHS), (10, 50, 100, 200, and 500 µM), were applied to the rhizospheric zone to assess their effect on soil and plant physiology. Plants grown in control soil exhibited reduced fresh biomass along with increased production of oxidative biomarkers like hydrogen peroxide (H(2)O(2)), superoxide radical (SOR), and malondialdehyde (MDA), and antioxidative enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). The rhizospheric application of H(2)S resulted in a significant increase in fresh biomass, with the 200 µM dose showing the highest increase of 37% compared to plants in control soil. Additionally, H(2)O(2), SOR, and MDA production were maximally reduced by 38%, 52%, and 48%, respectively, in the 200 µM treatment group compared to the control. The activities of antioxidative enzymes, such as SOD, POD, and CAT, increased maximally at 200 µM dose. High-resolution mass spectrometry (HRMS) data and scanning electron microscopy (SEM) supported the superior performance of plants at this dose. Thus, among all the doses, the 200 µM dose of H(2)S significantly mitigated metal toxicity, promoting plant growth and functional traits. The correlation analysis further confirmed these results, revealing a dose-dependent decrease in metal residues in plants treated with H₂S. This approach holds significant potential for enhancing both the quality and yield of plants cultivated in metal-contaminated soils. Further, future research should be conducted for optimal application methods to increase the efficiency and promote widespread adoption of this strategy.