Objective of this paper was to study changes in growth and antioxidant enzyme activity of Platycladus orientalis seedlings under drought and Pb stress. A potting experiment was conducted with four soil water regimes (40％,60％ ,80％ , 100％ of soil relative water content) and five Pb concentrations(0,300,500, 1 000, 2 000 mg·kg -1 ). The results showed that drought stress restrained growth and antioxidase activities of P. orientalis seedlings, and the effects were more significant with the drought aggravated. The distribution pattern of biomass changed under drought stress, manifested as root ＞ stem ＞ leaf. Pb promoted the growth of P. orientalis seedlings within 2 000 mg· kg-1. The drought stress imposed with 60％ , 80％ water regimes to P. orientalis seedlings was alleviated within 2 000 mg· kg-1 Pb. Growth index and antioxidase activities of P. orientalis seedlings under treatments with 1 000 mg·kg-1 Pb and 80％ of soil relative water content were higher than control, however growth index under other treatments were lower than control. With the soil relative water content decreasing, MDA concentrations increased continually, but with Pb concentration increasing, MDA concentrations increased first, then decreased, and reached the maxmum at 2 000 mg·kg-1. When Pb concentration was 1 000 mg· kg-1 , regardless of the water content, MDA content was significantly lower than control. In summary, the resistances of P. orientalis to drought stress could be strengthened under proper drought and Pb interaction.
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