Effects of cadmium(Cd)on activities of key nitrogen metabolism enzymes in leaves of Arabis paniculata F. were studied.Arabis paniculata F.,a newly identified hyperaccumulator,was grown in soils varying in Cd content(0,10,20,40,80,160 and 240 mg kg^-1)for 135 days.Plants were analyzed for contents of NO₃^--N,NH₄⁺-N,soluble protein,proline and activities of nitrate reductase(NR),glutamine synthetase(GS),glutamate synthase(GOGAT),glutamate dehydrogenase (GDH).Results show that the biomass of Arabis paniculata F.increased with the Cd concentration in the soil and reached the highest in the treatment of 240 mg kg^-1.In the treatments with Cd content varying from 10 to 80 mg kg^-1,the contents of NO₃^--N and NH₄⁺-N in plant shoots were lower than in the control but did not show any significant variance(p>0.05),while in the treatments above 80 mg kg^-1 Cd,both the contents of NO₃^--N and NH₄⁺-N increased with the Cd concentration.Compared with the control,the treatments of Cd varying between 10～160 mg kg^-1 did not show any significant variance(p>0.05)in NR activity,but NR activity reduced sharply to 67% of the control in Treatment 240 mg kg^-1 Cd.Furthermore,the activities of GS, GOGAT and soluble protein in all the Cd treatments showed no significant variance(p>0.05)from the control.The GDH activity increased with the Cd concentration from 10 to 80 mg kg^-1 and then decreased dramatically when above 80 mg kg^-1.Compared with that of the control,the contents of free proline increased obviously in the Cd treatments except in treatment 10 mg kg^-1 Cd.