| Problems caused by human activities about Cd pollution in soil has become the current focus of environmental pollution problems. Due to its high toxicity and teratogenic properties, such as cancer and migration in ecological system, cadmium is is one of the most serious threats to food safety and human health. The scope of the current soil cadmium pollution in China has been involved in a large area including more than 10 provinces and 20 regions, besides the trend of its contamination is still spreading. Facing a wide range of pollution, the traditional physical and chemical cure methods are high-cost with huge make it difficult to be applied widely. Phytoremediation was known as a potential strategy using plants to minimize the damage which comes with many advantages such as economically applicable, high-effective and environmentally sustainable. In the phytoremediation research, chelating agents have been extensively used in enhancing the ability of uptake and accumulation of plant from heavy metals contaminated soils.In this research,Phytolacca americana L.（pokeweed） as a promising plant for phytoremediation on cadmium（Cd） contaminated soil was studied. First, pot experiments were conducted to investigate the resistance and absorption ability to cadmium of pokeweed at different levels of Cd with 0, 10, 30, 50 and 100 mg kg-1 dw soil（from solutions of Cd（NO3）2·4H2O）.Then pot experiments were conducted to investigate the effects of low-molecular-weight organic acids（LMWOA） at different levels(10, 20, 30, 40 mmol kg-1) on growth, oxidative stress and antioxidant system of pokeweed. Their role in Cd transportation and accumulation and the ameliorating effects of Cd-induced oxidative stress were also studied. This study has an important theoretical indication for improving the efficiency of phytoremediation in the practical and realizing the repairment of large area of soil contamination.The main conclusions has been present as follow:（1） The pokeweed in lower concentrations of Cd contaminated soils with vigorous growth and stronger plant. However, the pokeweed suffered serious stress when the concentration of Cd is 50 mg kg-1.（2） Under the different concentrations of Cd contaminated soils, pokeweed showed well tolerated and high accumulation ability to Cd. And the Cd concentration in its aboveground were more than 100 mg kg-1.When the pokeweed suffered serious Cd stress more tnan Cd is 50 mg kg-1, the biomass and chlorophyll content of pokeweed were significantly reduced, and malondialdehyde（MDA） con tent increased significantly, the activity of SOD, POD and CAT decreased.（3） There are different effects of low-molecular-weight organic acids（LMWOA） at different levels(10, 20, 30, 40 mmol kg-1) on growth, oxidative stress and antioxidant system of pokeweed under 50 mg kg-1 Cd contamination. The results showed that low concentration of exogenous citric acid(10 mmol kg-1), malic acid(20 mmol kg-1) and oxalic acid(10 mmol kg-1) had a better capability of enhancing Cd uptake and transport, and alleviating the physiological toxicity from Cd and showing the effect on the availability of cadmium in the soils. Including the increased of chlorophyll and the activity of SOD, POD,and CAT, and the decreased of MDA. Besides, the Cd accumulation and translation can be effectively enhanced by lower concentration(10 and 20 mmol kg-1 dw) of organic acids. However, the high concentration of organic acid might affect the soil p H value, make the plants under more serious stress and cause the inhibition of enzyme synthesis or a modificati on in the assemblage of enzyme subunits.In conclusion, this study provided an important reference for further application of the pokeweed to the actual soil remediation. the lower concentration of exogenous citric acid, malic acid and oxalic acid have capability of enhancing Cd uptake and transport, and alleviating the physiological toxicity from Cd.And the phytoremediation effective of pokeweed can be enhanced by them. |
PDF Full Text Request