Interactive ecotoxicity of co-exposure to 2-ethylhexyl diphenyl phosphate (EHDPP) and cadmium on wheat (Triticum aestivum L.) seedling growth in simulated agricultural soil adjacent to plastic recycling areas

Aims To determine the phytotoxicity of EHDPP, alone and co-contaminated with Cd, in wheat seedlings, and to identify the nature of their interaction, as reflected in growth, photosynthesis, antioxidant defense, and bioaccumulation. Methods A pot experiment subjected wheat ( Triticum aestivum L.) seedlings to three EHDPP levels (50, 500, 1,000 ng·g − 1 ) and a combined EHDPP (500 ng·g − 1 ) + Cd treatment. Biomass was weighed; photosynthesis was assessed via chlorophyll fluorescence (F v /F m , F v /F 0 ) and pigment content; oxidative status via MDA and SOD, POD, CAT activities. Methods were spectrophotometry, kit assay and GC-MS; combined toxicity was evaluated by Abbott's formula and ANOVA with LSD tests. Results EHDPP (50–1,000 ng·g − 1 ) was phytotoxic to wheat seedlings, and co-exposure with Cd was mainly antagonistic. EHDPP alone reduced root, stem, and leaf biomass by 53%, 52%, and 38%, whereas Cd co-exposure raised biomass. Similarly, EHDPP decreased F v /F m and F v /F 0 by 4.62% and 41.16%, which Cd mitigated. Pigments increased but showed a biphasic response under combined stress, peaking at moderate EHDPP. MDA rose by 81% (EHDPP) and 97% (combined); under co-exposure, SOD peaked then fell, POD decreased with EHDPP, and CAT trended upward. EHDPP accumulated mainly in roots (RCFs 0.02–0.09); Cd raised RCFs but lowered TFs, enhancing root retention. Conclusions EHDPP and Cd interact mainly antagonistically in wheat seedlings, modulating photosynthetic efficiency, oxidative balance, and contaminant distribution. This interaction, which shifts toxicity away from a simple additive response, is significant for the risk assessment of mixed-contaminated soils.