The Effects Of Artificial Acid And Pb Rain Pollution On Turf Grass Growth And Antioxidant Physiology

To understand the heavy metal Pb and acid rain's effect on turf grass, I studied the Pb, acid rain and the combined stress of Pb and acid Rain on tall fescue and perennial ryegrass. I use three potted plant to do the simulation test. During the experiment I determined some physical signs like the biomass, the chlorophyll content, the activity of SOD and POD, the content of malondialdehyde and soluble sugar and the leaves electric conductivity.Pb solution's stress tests show that high concentration of Pb obviously inhibited the growth of turf grass. It not only results in the decrease of plant biomass but also leads to the chlorosis of leaves. The leaves might be dying seriously. At the beginning of the test, under the stress of high concentration of Pb, the activity of antioxidant enzyme which exists in the cells of leaves is generally increased, and it also gradually increased with the stress time. It indicates that the level of intracellular free radical continues to rise, and induced the increasing activity of antioxidant enzymes. In high concentrations, the enzymes'activity increased dramatically, but with the stress time extension, the enzymes'activity declined sharply. It indicating that a large number of free radicals have led to the antioxidant enzyme lose its activity, the toxic effects of Pb has increased and the function of oxygen free radical eliminating antioxidant enzymes is gradually disappeared. And during this process, SOD and POD's activity are all become sensitive. This result shows that in the two kinds of lawn grass, tall fescue's ability to resist the stress is stronger than the perennial ryegrass.Stress test that simulated acid rain showed that with the increasing of acid rain intensity, the grass blades'SOD, POD activity was decreased, the level of lipid peroxidation was increasing and MDA's relatively content was also increased. The intensification of lipid peroxidation would reduce the unsaturation of membrane lipid, the membrane of cytoplasm would be ruptured, the membrane permeability would increase, the chloroplast would be destroyed and the amount of chlorophyll would decrease. With the increasing of acidity and the prolonging of stress time, the tall fescue and perennial ryegrass only shows the visible damage spot at the end of stress when the pH is 3.5. It shows that the acid rain's influence on turf grass is more sensitive than the visible damage on the blade. In addition, these two kinds of lawn grass have the different rate of changing on physical signs, so it indicates that there are some differences between the two varieties of turf grass on acid rain resistance. Heavy metals and acid rain combined stress test showed that with the increased acidity of acid rain and Pb concentration, the biomass and chlorophyll content of tall fescue and perennial ryegrass were decreased to varying degrees. The content of malondialdehyde increased. The activity of superoxide dismutase and peroxidase was increased at the beginning and then decreased. The concentration of soluble sugar and the electrical conductivity is increased with the rose up of Pb concentration and acid rain intensity. The result showed that Pb combined pollution with acid rain is even more serious than a single one's impact on the turf grass.