Arsenic (As) contamination poses a critical threat to agricultural productivity, affecting rapeseed (Brassica napus L.), an agronomically important crop. A comparative assessment was performed to evaluate the efficacy of chemogenic and biogenic manganese nanoparticles (C-MnNPs and B-MnNPs) for mitigating As toxicity. B-MnNPs were biosynthesized using cell-free filtrate of Bacillus pumilus MAY4, while C-MnNPs were obtained from Cwnano Co., Ltd. (Shanghai, China). Greenhouse assays demonstrated that both C-MnNPs and B-MnNPs alleviated detrimental effects of As; however, B-MnNPs exhibited superior performance compared to their chemical counterparts. Compared to As-stressed plants, B-MnNPs enhanced leaf and root biomass (26.4% and 56.15%, respectively), net photosynthetic rate (64.8%), and stomatal conductance (50%). B-MnNPs more effectively reduced oxidative stress markers by activating antioxidant defense systems in both leaf and root tissues. Furthermore, B-MnNPs reduced in planta As accumulation while significantly improving uptake of essential nutrients, including potassium, phosphorous, magnesium, and manganese, etc., in rapeseed plants. Expression studies revealed that B-MnNPs upregulated antioxidant defense and redox homeostasis related stress-responsive genes under induced As stress. Biochemical assays further confirmed the enrichment of stress-responsive phytohormones, including salicylic acid, jasmonic acid, and abscisic acid, in B-MnNP-treated As-stressed rapeseed plants, indicating activation of multi-tier defense response by B-MnNPs to cope with As stress. These findings establish B-MnNPs as a highly effective nano-enabled strategy for managing As toxicity in the rapeseed cultivation system. This research provides critical insights into the molecular and physiological mechanisms underlying MnNP-mediated stress tolerance and offers a promising green nanotechnology approach for heavy metal-resilient crops.
Skhawat Ali (2025) studied this question.