Modulation of arsenic uptake and detoxification in maize (Zea mays L.) by plant-based iron oxide nanoparticles

Plant-based iron oxide nanoparticles (PIONs) were evaluated for regulating arsenic (As) stress responses and detoxification mechanisms in maize (Zea mays L.) under controlled conditions. A 40-day pot experiment was conducted using washed sand supplemented at sowing with sodium arsenate (30 mg As kg⁻¹) and foliar PIONs green-synthesized using Pinus roxburghii needle extract (100, 300, and 500 mg L⁻¹; three sprays at weekly intervals). PIONs improved maize growth and physiology, increasing root length from 23.77 cm (control) to > 34 cm at the highest PION dose and enhancing chlorophyll a and b to 0.85 and 1.75 mg g⁻¹ FW, respectively. PIONs also elevated stress metabolites (proline, soluble sugars, amino acids, phenolics) and antioxidant enzymes (APX, CAT, POD, SOD), indicating strengthened redox regulation. A key finding was the dual effect of PIONs on As accumulation: PIONs alone increased tissue As, with root As rising from 1.60 to 2.70 mg kg⁻¹ (+ 68.8%) and leaf As from 0.35 to 1.00 mg kg⁻¹ (+ 185.7%) at 500 mg L⁻¹, whereas under As stress the combined treatment (As + 500 mg L⁻¹ PIONs) reduced As relative to PION-only plants by 33.3% in roots (2.70 → 1.80 mg kg⁻¹) and 58.0% in leaves (1.00 → 0.42 mg kg⁻¹). Overall, PIONs enhanced maize performance and moderated As bioaccumulation under arsenic stress, supporting their potential as a sustainable nano-enabled approach for arsenic-affected systems.