Effects of Typical Herbicides on Growth and Cadmium Accumulation in Arabidopsis thaliana

Soil heavy metal contamination represents a significant environmental challenge. In many agricultural fields, mild-to-moderate heavy metal pollution often coexists with herbicide application. However, whether herbicide presence exacerbates safety risks in crop production remains unclear. This study investigated the effects of two typical herbicides widely used in agriculture, napropamide and metolachlor, on plant growth and heavy metal accumulation in the model plant Arabidopsis thaliana, under both individual and cadmium (Cd) co-exposure conditions. Results demonstrated that 0.2 mg/L napropamide significantly inhibited root length, fresh weight, and chlorophyll SPAD values. Notably, biomass decreased by 59.8% compared to the control, a reduction significantly greater than that observed with metolachlor treatment. Under Cd co-exposure, napropamide intensified phytotoxic symptoms, including severe root atrophy and leaf chlorosis, while metolachlor-induced symptoms resembled Cd stress alone. Notably, metolachlor significantly elevated the Cd translocation factor compared to the control. Collectively, napropamide exhibits higher growth toxicity to non-target plants, whereas metolachlor, despite lower direct phytotoxicity under Cd co-contamination, enhances Cd mobility to aerial tissues, posing ecological risks. These findings reveal important herbicide-specific effects on Cd accumulation patterns in model plants, establishing a foundation for future research on crop species in co-contaminated agricultural systems.