In this paper,using in vitro leaf disc culture system,the changes of contents of chlorophylls,carotenoids,soluble protein,thiobarbituric acid reactive substance(TBARS),and activities of antioxidant enzymes were investigated during the incubation of leaf discs of P SAGl2 -IPT modified gerbera in 0,25,50μmol L-1 paraquat(PQ)under continuous light intensity of 130μmol m-2 s-1,compared with the control plant(wild type).The results showed that PQ treatment significantly decreased the contents of chlorophylls,carotenoids,and soluble protein,therefore,promoted leaf senescence.However, the decreases in the leaf discs of modified gerbera were considerably smaller.The activities of superoxide dismutase (SOD),catalase(CAT),and dehydroascorbate reductase(DHAR)were significantly increased by PQ treatment and with the increasing of PQ concentration,particularly in the modified plants.The activities of ascorbate peroxidase(APX)and guaiacol peroxidase(GPX)could not be detected in the leaf discs of PQ treatments,which suggested that they were labile to the oxidative stress induced by PQ.As a product of lipid peroxidation,TBARS significantly increased in content with the increase of PQ concentration,while its concentration in the modified plants was significantly lower than that of control plants.Therefore,it could be concluded that the chimeric gene P SAG12-IPT transformed gerbera leaves had higher antioxidative potential,thus causing the delay of senescence under oxidative stress induced by PQ. In this paper, using in vitro leaf disc culture system, the changes of contents of chlorophylls, carotenoids, soluble protein, thiobarbituric acid reactive substance (TBARS), and activities of antioxidant enzymes were investigated during the incubation of leaf discs of P SAG12-IPT The results showed that PQ treatment significantly decreased the contents of chlorophylls (PQ) under continuous light intensity of 130 μmol m-2 s-1. , decreased in the leaf discs of modified gerbera were smaller smaller.The activities of superoxide dismutase (SOD), catalase (CAT), and dehydroascorbate reductase (DHAR) were significantly increased by PQ treatment and with the increasing of PQ concentration, particularly in the modified plants. Activities of ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) could not be detected in the leaf discs of P Q treatments, which suggested that they were labile to the oxidative stress induced by PQ. As a product of lipid peroxidation, TBARS significantly increased in content with the increase of PQ concentration, while its concentration in the modified plants was significantly lower than that of control plants.Therefore, it could be that that chimeric gene P SAG12-IPT transformed gerbera leaves had a higher antioxidant potential, thus causing the delay of senescence under oxidative stress induced by PQ.