Abstract:In order to explain the relationship between the deformity of tobacco caused by quinclorac and the activity of peroxidase, a protective enzyme in the plant induced by the chemical, modeling the dose of quinclorac residue in soil, the seedling of tobacco was transplanted to the soil mixed with quinclorac of different concentrations. The deforming of tobacco growth appeared in different degrees after 7 d. Peroxidase (POD) was studied between deformity and normality of tobacco. The results showed that the activity of POD in tobacco leaf treated with quinclorac was obviously higher than that of the control and the activity increased continually with the increasing of concentration in 35 days. When treated with 1.04×10-3,2.08×10-3, 4.17×10-3 , 8.33×10-3 and 1.67×10-2 mg/kg, the specific activity of POD was 29.61, 23.73, 30.33, 41.00 and 57.73 OD · g-1 · min-1 respectively after 28 days; whereas that of the CK was 17.47 OD · g-1 · min-1. The rate of activation of POD was 69.47%, 35.80%, 73.61%, 134.69%, 230.45%, respectively. The assay of isoenzymes of POD showed that the enzyme band of deformed leaf treated with quinclorac was more than that of the control , and the color of enzyme band of the deformed leaf was stronger than the control. The relationship of the activity of POD and the growth deformation of tobacco caused by quinclorac was discussed.