Objective: To discuss the effect of various nitrogen (N) concentrations on the antioxidase activity and the growth of Notopterygium incisum seedling. Method: Enzyme-labeled instrument was used to measure the activity of antioxidant enzymes[superoxide dismutase (SOD)

peroxidase (POD)

catalase (CAT) and ascorbate peroxidase (APX)] of N. incisum seedling rhizome that were treated with various concentrations (0

10

15

20 and 40 mmol · L-1) of N. Result: According to our findings

the growth of N. incisum seedling was effectively promoted with N with the concentrations between 15 mmol · L-1 and 20 mmol · L-1

while growing slowly in N with the concentration above 20 mmol · L-1. SOD and APX activities of N. incisum rhizome showed an obvious ‘V’ shape with the increase of concentration. In high-concentration N (40 mmol · L-1)

SOD and APX activities were the highest; and in middle-concentration N (15 mmol · L-1)

the activities were the lowest. For CAT and APX activities

there was no significantly difference in various concentrations of N in the early time

while the activities under the high concentration was significantly higher than those in the middle-concentration N (P<0.05) in 42 d. Conclusion: Therefore

it can conclude that low and high concentrations of N caused the slow growth of N. incisum seedling

and a dose-effect relationship was observed. The antioxidant enzyme activity of N. incisum rhizome was significantly increased in a high-concentration N stress.