| An experiment was conducted in greenhouse to study the distribution and movement characteristics ofheavy metals in hyperaccumulators: Solanum photeinocarpum and Leersia hexandra by adding and dislodging Cd or Cr. The results showed that the biomass of S. photeinocarpum in 100 mg/L Cd pollution was significantly higher than that in control. The Cd concentration of roots, stems and leaves were 22 930, 3 250 and 94 mg/kg, respectively, and the enrichment coefficients were 229, 32.5 and 0.9, respectively. The distribution pattern of Cd in S. photeinocarpum changed, and Cd concentrations decreased by 31.2% and 35.9% in plant roots and stems, and increased by 90.3% in leaves after the external Cd source was removed. Cd concentration was the highest in mature leaves (the second and third leaf) in Cd addion treatment and was transferred to the old leaves (the first leaf) in cadmium treatment and new leaves (the fifth and sixth leaf) after the external Cd source was removed. Leaf biomasses of L. hexandra in 20 mg/L Cr(Ⅲ) and 20 mg/kg Cr(Ⅳ) treatments were significantly lower than that in control, but returned to normal after the external Cr source was removed. The Cr concentrations of plant roots, stems and leaves in 20 mg/L Cr (Ⅲ) and 20 mg/L Cr (Ⅳ) treatments were the same and accumulated 7 114, 1 021 and 223 mg/kg, respectively, and the enrichment coefficients were 352,51 and 6.8. There was no difference among leaves in different leaf position. The distribution pattern of Cr in L.hexandra unchanged after the external Cd source was removed. The results indicate that S. photeinocarpum and L. hexandra have very good remediation efficiency for Cd and Cr pollution. Cd has mobility in S. photeinocarpum and can be redistributed when the external environment changes after it enters into the plant roots, stems and leaves. The Cr absorption of L. hexandra is a one-way process and Cr is first accumulated in the plant roots, and then transported by transmembrane to the stems and leaves. Once Cr enters into L. hexandra, it could be difficult to redistribute. |
