Green synthesis of iron oxide nanoparticles using Bacillus subtilis to mitigate salinity stress in rice (Oryza sativa L.) plants and enhance physiological activities

Abstract

Salinity stress significantly affects rice production worldwide. Therefore, this study investigated the potential of bacteria-mediated synthesized iron oxide nanoparticles (IONPs) to mitigate salinity stress in rice. IONPs were characterized using DLS, UV-vis spectroscopy, SEM, EDX, FTIR, and XRD and revealed 30–40 nm particles with cubic and spherical morphologies. Greenhouse studies showed enhanced growth parameters in IONP-treated plants under both normal and salt stress conditions. Treatment with 100 ppm IONPs under salinity stress resulted in enhanced shoot length (278.6%), root length (122.9%), and wet weight (180.0%) compared to the control plants. Similarly, post-harvest analysis revealed that IONPs improved chlorophyll content (206.8%), reduced proline accumulation (43.9–56% decrease), and modulated superoxide dismutase activity (9.2–22.6% decrease) compared to the control plants. Furthermore, IONPs enhanced soil dehydrogenase activity (185.5–479.5%) under salt stress, which indicated improved soil microbial activity. In addition, treatment with IONPs significantly reduced the accumulation of Na⁺ (58.49%) and Cl⁻ (35.5%) ions in rice plants and enhanced the availability of soil nitrogen and phosphorus compared with the salt-stressed control. KEGG pathway analysis suggested that these effects might be mediated by the modulation of peroxisomal functions. This study demonstrated the potential of IONPs as a promising tool for enhancing rice crop performance under saline conditions with implications for sustainable agriculture in salt-affected areas.