Abstract: Through pot experiment and physiological-biochemical analysis,the study showed that the electric conductivities of Conyza canadensis collected from heavy Cu pollution (Ⅰ),light Cu pollution (Ⅱ) and control (Ⅲ) sites were enhanced,while the chlorophyll (a+b) contents were reduced with increasing Cu concentration.The protein and proline contents in Ⅰ were increased at first and then reduced,but those in Ⅱ and Ⅲ were reduced with increasing Cu concentration.The activities of SOD,POD and CAT were intensified under Cu stresses.When the Cu concentration was 1 200 mg·kg^-1,their activities in Ⅰ,Ⅱ and Ⅲ were increased 194.1%,206.2% and 118.6%,170.1%,182.9% and 111.3%,and 115.1%,155.4% and 107.3%,respectively,in comparing with the control,which illustrated that the tolerance of Conyza canadensis was in order of heavy Cu pollution site>light Cu pollution site >control site,and the three ecotypes showed distinct differences in tolerance.

Key words: Exogenous selenium, Soil enzyme activity, Soybean