Effects Of Simulated Acid Rain, Zn And Cd On Growth And Physiological-Biochemical Characteristics Of Brassica Chinensis L And Phaseolus Vulgaris L

In this dissertation, effects of different acidities of simulated acid rain and different concentrations of Zn or Cd on the fresh weights, contents of chlorophyll, activities of SOD, POD, CAT, and contents of MDA in Brassica chinensis L and Phaseolus vulgaris L were studied with a pot experiment. The main results were as follows:The contents of chlorophyll of Brassica chinensis L and Phaseolus vulgaris L had the same tendency as the biomass of these two plants treated with simulated acid rain, Zn and Cd. The fresh weights and contents of chlorophyll of Brassica chinensis L decreased with increasing in concentrations of Zn, Cd and acidity of simulated acid rain. While those of Phaseolus vulgaris L increased first and decreased afterward when concentrations of Zn, Cd and acidity of simulated acid rain increased. In the experiment, the fresh weights of Brassica chinensis L were lighter in the combination of simulated acid rain and Zn or Cd than those in the single pollution of simulated acid rain, Zn or Cd. It meaned that simulated acid rain made the toxic effects of Zn or Cd on growth of the plants more serious. The fresh weights and chlorophyll contents of Phaseolus vulgaris L were the highest when pH value of acid rain was 4.5, Zn concentration was 60 mg/kg, and or Cd concentration was 0.5 mg/kg. This showed that lower acidity of simulated acid rain and lower concentrations of Zn or Cd could promote growth of the plants. Toxic effects of high acidity of acid rain and high concentrations of Zn or Cd on growth of Brassica chinensis L and Phaseolus vulgaris L were obvious, which was showed in the fact that the leaves were smaller and narrower than the contrast, and the growth of the plants were inhibited.The contents of MDA in the roots and leaves of Brassica chinensis L and Phaseolus vulgaris L had a positive relation with concentrations of Zn or Cd in the soil. When Zn concentration was less than 20 mg/kg or Cd concentration was less than 2 mg/kg, the contents of MDA increased slowly. However, when concentrations of Zn or Cd increased, the contents of MDA increased quickly. Meanwhile, the contents of MDA increased with decreasing in pH value of simulated acid rain. The contents of MDA were higher when treated with the solutions of pH3.0 than those when treated with the solutions of pH3.5 or pH4.5.The activities of SOD in the roots of Brassica chinensis L treated with pH4.5 or pH 3.5 solutions increased faster than those treated with pH5.6. But with increasing in concentrations of Zn or Cd, the activities of SOD decreased. The activities of SOD in the leaves of Brassica chinensis L treated with pH4.5 had changed only a little, but had changed more when treated with pH3.5. The activities of SOD in the roots and leaves ofPhaseolus vulgaris L decreased with concentrations of Zn or Cd added to soils when treated with pH4.5, pH3.5 or pH3.0. There was a negative relation between SOD activity of Phaseolus vulgaris L and pH value of simulated acid rain when concentrations of Zn and/or Cd were high.The activities of POD in the roots of Brassica chinensis L increased with concentrations of Zn or Cd added to soils. While the activities of POD in the leaves of Brassica chinensis L increased first and decreased afterwards with increasing in concentrations of Zn, or increased with increasing in concentrations of Cd. On the other hand, the activities of POD in the roots of Phaseolus vulgaris L increased first and decreased afterwards with Zn concentrations, and those in the leaves increased with Zn concentrations.The activities of CAT in the roots and leaves of Brassica chinensis L increased first and decreased afterwards when treated with simulated acid rain and Cd. And the activities of CAT in the roots and leaves of Phaseolus vulgaris L had the same tendency as Brassica chinensis L when treated with pH3.5 or pH3.0 solutions.The contents of MDA, activities of SOD, POD and CAT of Brassica chinensis L, treated with the combination of simulated acid rain, Zn and Cd, had the same tendency as those when trea...