Advancements in the absorption, metabolism, and transport mechanisms of HPPD inhibitor herbicides in soil-plant system

4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicides represent one of the most important classes of agricultural chemicals due to their unique mode of action, excellent bioactivity, and broad-spectrum weed control. However, their long-term and widespread application in major food crop fields, including corn, rice, and wheat, has raised growing concerns regarding environmental residues, ecological toxicity, and resistance evolution. This review critically examines recent advances in the absorption mechanisms, tissue distribution patterns, metabolic pathways, and molecular regulatory mechanisms of major HPPD inhibitor herbicides within soil-plant systems. Special emphasis is placed on elucidating the biological basis governing their environmental fate, including the roles of plant species-specific physiological traits, transporter systems, and detoxification enzymes such as cytochrome P450s and glutathione S-transferases. The toxicological effects of HPPD inhibitors on both target and non-target organisms are systematically evaluated, with particular attention to the higher ecotoxicity of certain transformation products compared to their parent compounds. Furthermore, this review summarizes the microbial degradation pathways of representative triketone herbicides, highlighting the predominance of nitroreduction as the primary degradation mechanism and the key enzymes involved. Current knowledge gaps are identified, including the limited understanding of enantioselective metabolism in crops and weeds, the insufficient characterization of metabolite toxicity, and the need for integrated multi-omics approaches to comprehensively assess sublethal and transgenerational effects. Future research directions are proposed, focusing on the development of low-residue crop varieties through genetic manipulation of key detoxification genes and the quantification of field-scale contributions of soil microbiota to herbicide degradation. This review provides theoretical and technical support for assessing the environmental behavior of HPPD inhibitor herbicides, controlling residual pollution in environmental media, and ensuring ecological and environmental safety.