Nanoparticle-driven defense in wheat (Triticum aestivum L.): Enhancing antioxidant and rhizosphere responses under arsenic and microplastic stress

Soil contamination with toxic heavy metals such as arsenic (As) and microplastics (MPs) is becoming a serious global problem due to rapid industrial and agriculture expansion. Although nanoparticles (NPs) are the major protectants to alleviate metal toxicity. A pot-based study was conducted to evaluate the effects of silicon (Si-NPs), silicon dioxide (SiO₂-NPs), and silver (Ag-NPs) nanoparticles on wheat (Triticum. Aestivum L.) exposed to As and MPs stress, focusing on key physiological, biochemical, and molecular assessments including oxidative stress responses, antioxidant activities, proline metabolism, and rhizosphere microbiome dynamics. Our results depicted that As and MPs exposure significantly reduced plant biomass (by 42-46 %), photosynthetic efficiency (by 38 %), mineral uptake (by 35 %), and rhizosphere microbiome diversity (by 30 %), while increasing malondialdehyde (MDA) and H₂O₂ contents (by 55-60 %), indicating oxidative stress, health risk indices, and molecular mechanisms. Antioxidant enzymes (SOD, POD, CAT, and APX) were enhanced at 100 mg kg⁻¹ As and 2 mg L⁻¹ MPs but declined at 200 mg kg⁻¹ As and 4 mg L⁻¹ MPs. As and MPs stress also suppressed anthocyanins and soluble proteins while increasing As accumulation in roots and shoots (by up to 48 %). Application of Si-NPs, SiO₂-NPs, and Ag-NPs mitigated these adverse effects by improving growth (30-40 %), photosynthesis (25-33 %), antioxidant defenses (40-50 %), regulating AsA-GSH cycle, proline metabolism, and cellular fractionation, mineral uptake, reducing oxidative damage and HI indices (25-30 %). These treatments also lowered As retention in plant tissues (by 35-40 %). Research findings, therefore, suggested that application of Si-NPs, SiO₂-NPs, and Ag-NPs can ameliorate As toxicity in T. aestivum seedlings and resulted in improved plant growth and composition under metal stress.