Phytotoxic effects of 6PPD on wheat: Insights into germination inhibition, oxidative stress, and metabolic disruptions

N-(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine (6PPD), a widely used antioxidant in the rubber industry, has been identified as a pervasive environmental contaminant with significant ecological risks. However, its effects on terrestrial plants remain poorly understood. This study systematically evaluates the impact of 6PPD (10 to 400 μg L −1 ) on seed germination, seedling growth, nutrient accumulation, oxidative stress, and metabolic responses in wheat ( Triticum aestivum L.). The findings demonstrate that 6PPD significantly inhibits seed germination, with rates declining by 19.64 % to 42.26 % across tested concentrations. Seed vigor and sprout length were notably reduced at higher concentrations (200 and 400 μg L −1 ) ( p < 0.05). Exposure to 400 μg L −1 6PPD suppressed chlorophyll content and shoot biomass, indicating disruptions in photosynthetic efficiency and growth. Nutrient analysis revealed a biphasic response, with increased Cu, Mg, Mn, and Zn in leaves at lower 6PPD concentrations (10, 50, and 100 μg L −1 ) and significant reductions in Cu at higher concentrations (200 and 400 μg L −1 ) ( p < 0.05). Elevated reactive oxygen species (ROS) levels, correlating with increasing 6PPD concentrations, indicated severe disruption of the antioxidant defense system. Metabolic profiling identified significant alterations in pathways related to fatty acids, carbohydrates, citrate, and d-amino acids. These findings suggest that 6PPD exposure compromises wheat metabolism and growth, highlighting the ecological risks posed by tire wear particle-derived compounds to crop plants. • 6PPD inhibits seed germination of wheat and reduces chlorophyll content and biomass. • Exposure to 6PPD induced oxidative stress in plants by increasing the ROS level. • 6PPD disrupts metabolic pathways in shoots and roots.