Physiological effects of silver nanoparticles and Pseudomonas stutzeri on Zea mays L. irrigated with effluent water from industry

This study aimed to measure the bioremediation potential of silver nanoparticles (AgNPs) and plant growth-promoting rhizobacteria (PGPR) in enhancing maize growth under contaminated conditions. The irrigation water used was effluent from tube well and Hitech Industries Taxila (HIT), both containing Fe and Mn levels exceeding permissible limits. Tap water irrigation served as the control. Notably, the Cr levels in HIT effluent water were 280% higher than the permissible limits set by the World Health Organization (WHO 2011). The HIT water showed 64.11%, 200%, and 24% higher content of Ca, K, and Na as compared to control. Seeds were soaked for 2h prior to sowing in 71-h old Pseudomonas stutzeri (P. stutzeri) (Gene bank accession no. KX574858) culture, at concentration of 10⁸ cells/mL. The toxic effects of chromium (Cr) leads to a reduction in photosynthetic activity. The results showed that the combined treatment of AgNPs and PGPR increased flavonoid, phenolic, and carotenoid activities by 78%, 167%, and 55%, respectively, in tube well-irrigated plants. Additionally, PGPR and AgNPs effectively reduced oxidative stress by enhancing the activities of enzymes, superoxide dismutase (SOD), phenylalanine ammonia-lyase (PAL), and peroxidase (POD) in maize irrigated with tube well water. The study demonstrates the potential of AgNPs and PGPR in mitigating the adverse effects of heavy metal (HM) toxicity on maize plants. The findings suggest that maize plants irrigated with high Cr-contaminated water exhibited enhanced metal tolerance when treated with PGPR. The key objective of this study was to explore the individual effects of P. stutzeri and AgNPs on the stabilization of Mn, Fe, and Cr, and their impact on maize physiological responses. This study also evaluated the role of AgNPs and P. stutzeri in enhancing the availability and uptake of phosphorus (P) and nitrogen (N) macronutrients in rhizospheric soil irrigated with HM-contaminated water.