| Phytoremediation has become a developed "green technology", in which hyperaccumulators were used to remove excess heavy metals in soil. It’s important for the phytoremediation to select new hyperaccumulators and built a complete set of technical measures and repair system based on the results. Although hundreds of heavy metal hyperaccumulators have been found, most have drawbacks, such as the selected plants may as alien species can cause biological invasion lead to the application of regional ecological deterioration and the problem of the plants can not grow normally under low temperature in winter, which limit the popularization and application of phytoremediation technology. This study is to solve the these problems.Capsella bursa-pastoris (L.) Medic was a winter growth of local farmland weeds. When the soil Cd was 60.10mg/kg, the plant accumulated 142.50mg/kg in shoots. When the soil Pb was 100.25mg/kg, the plant accumulated 69.72mg/kg. It came to a result that Capsella bursa-pastoris (L.) Medic may be a winter Cd-hyperaccumulator or Pb-hyperaccumulator.In the present study, two concentration gradient pot-experiments, in involving soil Cd concentration (0,25,50,75,100,125 mg/kg) and soil Pb concentration (0,200,400,600, 800,1000,1200,1400,1600 mg/kg), were conducted to study the growth, physiological responses, Cd and Pb accumulation characteristics, phytoremediation capability of Cd and Pb in Capsella bursa-pastoris (L.) Medic, The results were as follows:(1)C. bursa-pastoris showed strong tolerance and had great ability of accumulation to Cd and Pb, respectively, which were identifyed as a new Cd-accumulator and a new Pb-accumulator. The maximum concentration of Cd in shoot was 382.13 mg/kg, which was over the critical value of a Cd-hyperaccumulator. All BCF of Cd in root and shoot were higher than 1, which maximum BCF in root and shoot were 4.03 and 3.32. The maximum concentration of Pb in shoot was 1783.95 mg/kg, which was over the critical value of a Pb-hyperaccumulator. Parts of BCF of Pb in root and shoot were higher than 1, which maximum BCF in root and shoot were 1.24 and 1.11.(2)C bursa-pastoris was a good candidate for phytoextraction of Cd and Pb, which could be used to remediate Cd or Pb contaminated farmland soil in winter. When the Cd concentration in soil was not over 50 mg/kg, C.bursa-pastoris had a great phytoremediation capability. When the Pb concentration in soil was not over 400 mg/kg, C.bursa-pastoris also had a great phytoremediation capability.(3)When the Cd concentration in soil was not over 50 mg/kg, there was not obvious oxidative stress on plant. The MDA content, H2O2 content, O2- content in the leaves of C.bursa-pastoris were no significant difference compared with the control(P>0.05). When the Pb concentration in soil was not over 600 mg/kg, there was not obvious oxidative stress on plant. The MDA content, H2O2 content, O2- content in the leaves of C.bursa-pastoris were no significant difference compared with the control(P>0.05).(4)The antioxidative system of C.bursa-pastoris in response to different Cd or Pb treatments were not the same. Under the low level of Cd treatment (25-50mg/kg), C.bursa-pastoris cleaned up the excessive of H2O2 and O2- through enhanced the activity of antioxidant enzymes (SOD, CAT, APX and GPX) and increased the content of antioxidant substances (GSH and ASA). Under moderate level of Cd treatment (75-100mg/kg), C.bursa-pastoris cleaned up the excessive of H2O2 and O2- through enhanced the activity of antioxidant enzymes (SOD, CAT, APX and GPX) and stabilized the content of antioxidant substances (GSH and ASA). However, high level of Cd treatment (125-150mg/kg) decreased the activity of SOD, APX and GPX, by this time plant alleviated oxidative damage through stabilized the cativity of CAT and the content of GSH and ASA.Under the low level of Pb treatment (200-400mg/kg), C.bursa-pastoris cleaned up the excessive of H2O2 and O2- through enhanced the activity of antioxidant enzymes (SOD, CAT, APX and GPX) and increased the content of antioxidant substances (GSH and ASA). However, moderate level of Pb treatment (600-1000mg/kg) decreased the content of GSH and ASA, by this time plant alleviated oxidative damage through enhanced the activity of SOD, CAT, APX and GPX. High level of Pb treatment (1200-1600mg/kg) decreased the activity of SOD and CAT, by this time plant alleviated oxidative damage through stabilized the cativity of APX and GPX and the content of GSH and ASA. |
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