Foliar Fate of Phthalate Esters in Lettuce: Uptake, Phytotoxicity, and Metabolic Responses

Phthalate esters (PAEs) are emerging atmospheric contaminants in facility agriculture, yet their foliar transformations and phytotoxic mechanisms remain unclear. We compared the uptake, translocation, metabolism, and physiological effects of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in lettuce after foliar exposure. The more hydrophobic DEHP accumulated in cuticular wax and leaves and caused oxidative lipid damage, whereas DBP was weakly retained in wax, translocated more readily to roots, and elicited stronger antioxidant responses. Both compounds were converted to monoesters, which accumulated at higher concentrations than their parent PAEs. Metabolomics revealed that DBP specifically upregulated arginine metabolism, suggesting an enhanced defense, whereas DEHP was associated with glutathione metabolism and ABC transporter pathways, consistent with responses to membrane peroxidation. These findings show that PAE physicochemical properties govern their fate in plants and drive compound-specific metabolic disturbances with important implications for crop safety under atmospheric PAE pollution.