The Reaserch Of Physiological Characteristics And Accumulation Of Houttuynia Cordata Thunb Under Single Cadmium, Lead And Combination Pollution Stress

The Cd and Pb are main metal pollutants in the environment.The Cd is not necessary for the propagation, it is one of the heavy metals with the most strong toxicity;The Pb is a kind of poisonous heavy metal element and can cause various physiology abnormality. Most of Cd and Pb that got into the agriculture ecosystem system exist on the soil surface,which bring harm to crop. In this study, the effects of single and combined of Pb and Cd on growth of Houttuynia cordata Thunb,contents of Pb and Cd in Houttuynia,chlorophyll content, activities of SOD,POD,CAT in the leaves were studied. And we also studied the correlation of Pd or Cd and their contents in Houttuynia. Research results are listed as below:1 Single Pb under conentrations no more than 1000mg/kg in soil had no significant effects on growth,plant height, root length and biamass of Houttuynia. The biomass of Houttuynia reduced significantly by stress of Cd (0-50mg/kg) in soil. When treated with 500 mg/kg of Pb, plant height and root length of Houttuynia reach the maximum-41.7cm and 55.9cm, and the root length rise to the maximum of 35.7cm in concentration 50 mg/kg of Cd. Both high concentration of Pb (more than 2000mg/kg) and Cd in soil are proved to be harmful to Houttuynia.The toxic effects of combined pollution of Cd and Pb are related to their concentrations in soil. The toxicity of mixture of Pb and Cd could be explained as antagonistic action under compound pollution Pb 500mg/kg and Cd 10mg/kg. Cd toxicity was enhanced by lead under compound pollution of Pb (250mg/kg or500mg/kg) and Cd (50mg/kg or 50mg/kg).2 Concentration of Pb and Cd in aboveground and underground part of Houttuynia increased with the increasement of Pb or Cd concentration in soil. The concentration of Pb in the overground part and underground part of Houttuynia rise to the maximum of 441.93mg/kg and 869.48mg/kg as concentration of Pb is 2000mg/kg, respectively; Cd content rise to the maximum of 129.50mg/kg and 511.98 mg/kg as concentration of Cd was 50mg/kg, respectively.The maximum accumulation amount of Pb and Cd of Houttuynia were 1.34g/basin and 1.270mg/basin, respectively.Under Pb and Cd complex pollution,when Cd was less than 10mg/kg,Cd inhibited the absorption of Houttuynia on Pb,and then Pb and Cd showed antagonistic action. While Pb was less than 1000mg/kg, Pb concentration of Houttuynia were first increased and then decreased with increasing of Cd concentration. Cd could inhibited the cumulation of Houttuynia on Pb,under higher Pb stress.When Pb was 500mg/kg to 1000 mg/kg, Pb cumulation of Houttuynia were first increased and then decreased with increasing of Cd concentration. Cd concentration were decreased with increasing of Pb concentration,when Cd concentration were Omg/kg and 10mg/kg.And Pb inhibited the cumulation of Houttuynia on Cd.3 In the controls, The main ingredient was residua Pb and Cd. Addition of the Pb and Cd in soil the most speciation of Pb and Cd were exchange.The Houttuynia were sensitive to absorbed part of the organic bound Cd and carbonate bound Pb in the various forms of Pb and Cd of soil.4 The chlorophyll content of Houttuynia leaves had significant correlation with the concentration of Pb, Cd and their complex pollution. The toxicity of heavy metal are Cd> Pb> Pb-Cd complex pollution. Antioxidant enzyme system of Houttuynia leaves showed different activity in different concentration of Cd,Pb and Cd-Pb complex pollution stress. Activities of SOD and CAT in the Houttuynia leaves increased, while Cd concentration in soil was less than 10 mg/kg, and activity of POD in the Houttuynia leaves increased in high concentrations of Cd, Pb stress.Under single Pb, Cd and Pb-Cd complex pollution stress, content of MDA of Houttuynia leaves had no significantes correlation with the concentration of Pb and Cd in soil.5 The most part of Pb and Cd accumulated by Houttuynia were stored in cell coat of Houttuynia.The percentage of the accumulated Cd in root, stem and leaves were 78.2%, 85.2% and 88.3%, respectively. Under Pb-Cd complex pollution stress, the concentration of Pb in cell components of root, stem and leaves of Houttuynia had significant correlation with Pb in soil, and it had no correlation with concentration of Cd in soil. The sensitivity of Houttuynia for Pb and Cd was stem>root>leaf.