Trace Levels of Triclosan May Affect Root Growth and Morphology in Cultivated Plants

Triclosan (TCS) is a micropollutant frequently detected in biosolids applied to agricultural soils. In soil solution-where it is potentially bioavailable to roots-it occurs at residual concentrations (ng L^-1). Nevertheless, the ecotoxicological implications of TCS exposure in agricultural crops at these concentrations are still not fully elucidated. In this context, the present study investigated the effects of TCS (25-200 ng L^-1) on seed germination and root development in Cucumis sativus, Solanum lycopersicum, Lactuca sativa, and Raphanus sativus, as well as its phytotoxic, cytotoxic, and genotoxic potential in Allium cepa root systems. All concentrations induced H₂O₂ accumulation in the roots and consumption of nonenzymatic antioxidants, and, under specific conditions, triggered lipid peroxidation, indicating oxidative stress as the primary mechanism associated with the observed adverse effects. In A. cepa, TCS induced a mitodepressive effect and morphological alterations in the roots at all tested concentrations, in addition to significant aneugenic effect at concentrations of 50-200 ng L^-1. In contrast, TCS concentrations of 25-100 ng L^-1 stimulated root growth in cucumber, tomato, lettuce, and radish; however, the resulting radicles were more susceptible to breakage and morphological changes, suggesting that root elongation may have been associated more with cell expansion than with coordinated proliferative growth. In these species, concentrations of 200 ng L^-1 caused a significant reduction in root growth and intensified morphological damage. These findings demonstrate that trace levels of TCS can impair early plant establishment by compromising root structural integrity, potentially affecting agronomic performance under environmentally realistic conditions.