Coordinated Responses of Barley in Photosynthesis, Antioxidative System, and Stomatal Regulation Under Flufenoxuron Stress

Flufenoxuron is extensively applied in agricultural pest control; however, its effects on plant physiological processes remain insufficiently understood. Hence, this study evaluated the effects of flufenoxuron on photosynthetic processes and stomatal regulation in barley. The findings indicated that flufenoxuron significantly reduced photosynthetic efficiency and gas-exchange capacity. Furthermore, flufenoxuron exposure markedly increased abscisic acid (ABA) in leaves but not in roots. Nonetheless, reactive oxygen species (ROS) generation and membrane lipid peroxidation were triggered by flufenoxuron. Concomitantly, defense responses were activated, including the upregulation of peroxidase activity and the accumulation of soluble sugars to mitigate osmotic imbalance. Correlation analysis revealed that stomatal conductance (Gs) showed significant negative correlations with ABA, H2O2 (hydrogen peroxide), and O2·− (superoxide anion) levels. Furthermore, flufenoxuron exposure altered the expression of genes associated with ABA biosynthesis and catabolism, accompanied by changes in the expression of genes related to ABA- and ROS-associated signaling. These findings suggest that ABA- and ROS-associated processes may be involved in stomatal regulation under flufenoxuron exposure. Overall, this study provides a conceptual and mechanistic basis for understanding the phytotoxicity of benzoylurea compounds.