As common soil fungi that form symbioses with most terrestrial plants,arbuscular mycorrhizal(AM) fungi play an important role in plant adaptation to chromium(Cr) contamination.However,little information is available on the underlying mechanisms of AM symbiosis on plant Cr resistance.In this study,dandelion(Taraxacum platypecidum Diels.) was grown with and without inoculation of the AM fungus Rhizophagus irregularis and Cr uptake by extraradical mycelium(ERM) was investigated by a compartmented cultivation system using a Cr stable isotope tracer.The results indicated that AM symbiosis increased plant dry weights and P concentrations but decreased shoot Cr concentrations.Using the Cr stable isotope tracer technology,the work provided possible evidences of Cr uptake and transport by ERM,and confirmed the enhancement of root Cr stabilization by AM symbiosis.This study also indicated an enrichment of lighter Cr isotopes in shoots during Cr translocation from roots to shoots in mycorrhizal plants. As common soil fungi that form symbioses with most terrestrial plants, arbuscular mycorrhizal (AM) fungi play an important role in plant adaptation to chromium (Cr) contamination. However, little information is available on the underlying mechanisms of AM symbiosis on plant Cr resistance. In this study, dandelion (Taraxacum platypecidum Diels.) Was grown with and without inoculation of the AM fungus Rhizophagus irregularis and Cr uptake by extraradical mycelium (ERM) was investigated by a compartmented cultivation system using a Cr stable isotope tracer. The results indicated that AM symbiosis increased plant dry weights and P concentrations but decreased shoot Cr concentrations. Using the Cr stable isotope tracer technology, the work provides possible evidences of Cr uptake and transport by ERM, and confirmed the enhancement of root Cr stabilization by AM symbiosis. This study also shows an enrichment of lighter Cr isotopes in shoots during Cr translocation from roots to shoots in mycorrhizal p lants.