Study On The Resistance Of Tilia Amurensis Seedlings To Heavy Metal Contamination In Urban Soil And Drought Stress

The physiological and biochemical reaction of 3-years seedling of Tilia amurensis Rupr. were studied under the heavy metals(cadrniurn, lead, mercury, chromium) pollution and drought stress to the seedling in pots in greenhouse. Four concentration gradients were designed respectively for the heavy metals pollution in the soil, Cd²⁺:0.05, 0.25, 0.5, 1mg·kg^-1, Pb²⁺:10, 50, 100, 200mg·kg^-1, Hg²⁺:0.05, 0.5, 1.5, 2.5mg·kg^-1, Cr²⁺:20, 40, 60, 80mg·kg^-1, comparison was designed at the same time. Four concentration gradients were designed for drought stress, relative water content in the soil:75±2%(CK), 65±2%(treatmentâ… ), 55±2%(treatmentâ…¡), 45±2%(treatmentâ…¢), 35±2% (treatmentâ…£)。The results were as follows:1. Effect on physiological and biochemical reaction of Tilia amurensis Rupr. with heavy metal treatmentsChlorophyll content of Tilia amurensis Rupr. Leaves were all lower than that of control with cadmium, lead, mercury and chromium treatments. The conductivity of Tilia amurensis Rupr. Leaves was equal to that of control with Cr²⁺ concentration 20 mg·kg^-1 treatment, which was lower than that of control with Hg²⁺ concentration 1.5 mg·kg^-1 and Pb²⁺ concentration 50 mg·kg^-1 treatments, and which was higher than that of control with other treatments. The POD activity of Tilia amurensis Rupr. Leaves was higher than that of control with mercury which was lower than that of control with chromium treatments, and which showed irregular change with cadmium and lead treatments. The SOD activity of Tilia amurensis Rupr. leaves was lower than that of control with Pb²⁺ concentration 10 mg·kg^-1 treatment, which was equal to that of control with Hg²⁺ concentration 0.05 mg·kg^-1 treatment, and which was higher than that of control by other treatments.2. Effect on physiological and biochemical reaction of Tilia amurensis Rupr. with drought stress treatmentsEffect on chlorophyll content of Tilia amurensis Rupr. leaves was obvious with drought stress treatments. With the decrease of water content with drought stress treatments, chlorophyll content decreased. The relative conductivity of Tilia amurensis Rupr. Leaves was higher than that of control with drought stress treatments. The POD activity of Tilia amurensis Rupr.leaves was high with drought stress treatments, and which was highest with water content 35% treatment. With the decrease of water content,The SOD activity of Tilia amurensis Rupr. Leaves increased gradually. The SOD activity of Tilia amurensis Rupr. Leaves was higher than that of control with the relative water content 45% and 35% treatments, and which was lower than that of control with the relative water content 65% and 55% treatments. MDA content of the four treatments was higher than that of control. With the decrease of relative water content with drought stress treatments, Pro content of Tilia amurensis Rupr. increased gradually, and which was maximal by the relative water content 35%.