Green-fabricated MnO₂ nanoparticles function as dual nanofertilizers and chromium remediators, enhancing antioxidant pathways, ionomic networks, and physiological resilience in wheat

Abstract

This study investigates the potential of green-fabricated manganese dioxide (MnO₂) nanoparticles (NPs) to mitigate chromium (Cr) toxicity in wheat, presenting a novel approach to enhancing ion homeostasis and physiological resilience under Cr stress. Chromium contamination in agricultural soils is a significant concern, severely impacting crop productivity and disrupting the physiological homeostasis of wheat. Chromium exposure compromises nutrient uptake, induces oxidative stress, and impairs plant growth and yield. This study explored the use of green-fabricated MnO₂ NPs to mitigate Cr-induced oxidative stress in two bread wheat cultivars, Borlaug-16 and SKD-1. Seed nano-priming with MnO₂ NPs (100, 250, and 500 mg kg⁻¹) was applied, followed by Cr (100 mg kg⁻¹) exposure, and key physiological, biochemical, and ionomic responses were evaluated. Manganese dioxide nanoparticles significantly reduced Cr uptake and improved ion transport. In Borlaug-16, NP250 enhanced seedling height by 74 %, while NP100 reduced H₂O₂ and TBARS by 60.28 % and 50.17 %, respectively, indicating improved oxidative stress tolerance. SKD-1 exhibited greater Cr stress tolerance, with NP250 improving root length by 31.03 % and relative water content by 56.66 %, supporting better water retention. Additionally, MnO₂ NP treatments boosted antioxidant enzyme activities, increasing APX and GPX by up to 12.47 %, and restored root and leaf anatomy, reversing Cr-induced structural damage. Furthermore, MnO₂ NPs enhanced the uptake of essential nutrients such as calcium, potassium, and magnesium, while restricting Cr translocation, improving overall nutrient efficiency. These findings emphasize the potential of MnO₂ NPs as an eco-friendly strategy for enhancing crop resilience and promoting sustainable agriculture in Cr-contaminated soils.