Abstract
The mechanisms underlying phytohormonal disruptions caused by microplastic/plasticizer contamination in agricultural systems remain poorly understood. This study systematically investigates how polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and di-n-octyl phthalate (DOP) alter endogenous hormone networks in agricultural systems. Integrated transcriptomic-metabolomic analyses were conducted on cucumber plants grown in hydroponic and soil systems exposed to microplastics (PE, PS, PVC) and DOP. Hormonal pathways were deciphered via gene expression profiling of key biosynthesis regulators. Microplastics and DOP primarily affected the tryptophan-dependent auxin biosynthesis pathway. Differentially expressed genes (DEGs) related to cytokinin biosynthesis were involved in the de novo synthesis pathway. All treatments primarily regulated the expression of DEGs encoding the enzymes gibberellin-20-oxidase (GA20ox), gibberellin-2-oxidase (GA2ox), and gibberellin-3-oxidase (GA3ox) to maintain the balance of active gibberellins. Changes in abscisic acid metabolite levels were linked to the expression of DEGs for abscisic aldehyde oxidase (ABA2). All treatments reduced the ethylene biosynthesis rate. Cucumber plants regulate the expression of DEGs related to phytochrome B (PHYB)-activated inhibitor 1 (CYP734A1) to maintain a balance of endogenous brassinosteroids. Jasmonic acid levels significantly increased after PE, PS, and PS + DOP treatments. Salicylic acid pathways remained unaffected despite phenylalanine ammonia lyase gene variations. PE and PS exhibit significantly stronger impacts on endogenous hormone biosynthesis in cucumber plants compared with PVC. PS with the co-presence of DOP synergistically enhancing jasmonic acid biosynthesis. Notably, smaller PS particle sizes facilitate their absorption by cucumber roots while simultaneously suppressing auxin synthesis efficiency. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-025-01645-8.