Cold plasma and green magnetic nanocomposite mitigate arsenic and nanoplastic toxicity in wheat plants by up-regulating enzymatic and non-enzymatic antioxidants

Soil and water contamination by heavy metals and nanoplastics poses a critical environmental challenge, threatening agricultural productivity and food safety. This study investigated a novel strategy to mitigate the combined toxicity of arsenic (As) and polymethyl methacrylate nanoplastics (PMMANPs) in wheat using cold plasma (CP) seed priming and a green-synthesized Ag/Zn/Fe nanocomposite (NC). A randomized complete block design (RCBD) with three replications was employed. Wheat plants were exposed to As (0.05 g/L), PMMANPs (0.05 g/L), NC (0.05 g/L), and CP (2 min) in various combinations. Blocks represented different growth chambers, ensuring environmental variability (e.g., light intensity, temperature, humidity) was controlled. Each block contained all treatments, randomly assigned within chambers. Results revealed that As accumulated primarily in roots, with limited translocation to leaves. Both As and PMMANPs significantly inhibited plant growth and reduced photosynthetic efficiency. The pollutants induced oxidative stress, marked by elevated root cell death, malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) levels, though antioxidant defenses were activated. Notably, CP treatment enhanced germination by 5.34 %, while both CP and NC independently and synergistically reduced As uptake, improved growth, and lowered oxidative stress markers. Furthermore, these treatments modulated phenolic compound biosynthesis, particularly increasing: gallic acid (338 mg/kg DW and 229 mg/kg DW) and p-coumaric acid (219 mg/kg DW and 173 mg/kg DW) under As + PMMANPs + NC and As + PMMANPs + NC + CP, respectively.This suggests enhanced chelation and detoxification mechanisms. This study demonstrates that CP priming combined with green NC application provides an effective, eco-friendly solution to alleviate combined heavy metal and nanoplastic stress in crops. These findings have significant implications for sustainable agriculture in contaminated environments.