Abstract: In order to reveal the effects of different nitrogen forms and nitrogen application amount on Picris japonica Thunb.growth, physiological and biochemical characteristics under the different concentrations of Pb stress, pot experiment was performed to study the effects on the Picris japonica Thunb. biomass, chlorophyll content and antioxidant enzyme activity.The results showed that, with increasing nitrogenous fertilizer, the biomass increased first and then reduced.Under the low concentrations of Pb stress (500 mg/kg), with NH₄⁺-N fertilizer, the chlorophyll content and the CAT activities in Picris japonica Thunb. increased first, and then reduced SOD activity increased gradually, POD activity decreased first and then increased.In the case of NO₃^--N fertilizer, the chlorophyll and SOD activity increased first, then decreased, the activity of POD and CAT decreased gradually.Under the high concentrations of Pb stress (2 000 mg/kg), with NH₄⁺-N fertilizer application, the chlorophyll content and the POD activity first increased and then decreased, meanwhile CAT and SOD activity decreased first and then increased, with increasing nitrogenous fertilizer.With NO₃^--N fertilizer, only CAT activity increased first and then decreased, and other indicators had no obvious changes.As a result, the appropriate NH₄⁺-N fertilizer was more useful to Picris japonica Thunb's growth.It not only helped to enhance the chlorophyll content, but also increased the activity of antioxidase.It was crucial to make efforts in increasing plant biomass and medicinal value, and it had practical significance on remediation of lead contaminated soil.

Key words: Picris japonica Thunb., Pb, NH₄⁺-N, NO₃^--N, Biomass, Chlorophyll, Antioxidant enzyme

CLC Number: 

• S143.1