| A screening experiment was planned with25kinds of ornamental plants in an in vitro system for the selection of hyperaccumulations, responses of Pharbitis nil seeds to Cd2+, Cr6+, Hg2+, As5+stress were evaluated by the germination, root length and root dry weight, the results revealed that Pharbitis nil seeds had a strong patience on Cd2+, Cr6+, Hg2+stress.Then a pot experiment was conducted to study the growth responses and accumulation characteristics of Pharbitis nil to Cd2+, Cr6+, Hg2+single pollution. The result showed that lower concentration played a promoting role in the growth and development of Pharbitis nil, but when it passes a certain concentration, it will produce poisonous effect. Different organs have different heavy metals accumulation, Cd2+in leaves, Cr6+and Hg2+in roots have a higher accumulation. Both TF and BF of the three heavy metals revealed a decreasing trend with the increasing concentrations of heavy metals in soil; in the case of the same lower concentration (20mg/kg), the accumulation capacity of heavy metals was in the following order: Cd2+>Cr6+>Hg2+, and the translocation capacity of heavy metals was in the following order: Cr6+>Cd2+> Hg2+; in the case of the same higher concentration (50mg/kg), the accumulation capacity of heavy metals was in the following order:Cd2+> Hg2+> Cr6+, and the translocation capacity of heavy metals was in the following order:Cr6+>Cd2+> Hg2+. Meanwhile, several kinds of defense enzyme activities (POD, CAT, PPO, PAL), conductivity, MDA, chlorophyll content and soluble protein content were measured. Based on the above results, the resistance capacity of Pharbitis nil to heavy metals was in the following order:Cr6+> Hg2+>Cd2+.At the same time, conducted to study the growth responses and accumulation characteristics of Pharbitis nil to Cd-Cr and Cd-Hg compound contamination, the results revealed that within a certain concentration range Cd-Cr (Cd2+<5, Cr6+<20) and Cd-Hg (Cd2+<5, Hg2+<20) compound treatments played a promoting role in the biomasses, plant height and stem diameter growth of Pharbitis nil, whereas prevented the plant growth at the higher concentration range Cd-Cr (Cd2+>20, Cr6+>50) and Cd-Hg (Cd2+>20, Hg2+>50). It was closely related with the influence of growth characteristics of Pharbitis nil and the absorption and transportation mechanism of heavy metal.Heavy metal accumulation ability is one of the most important indexes for the selection of hyperaccumulations. Compared with ornamentals, Pharbitis nil had a strong patience and accumulation capacity to heavy metals stress, possessed the characteristics of hyperaccumulations. Meanwhile, Pharbitis nil was annual herb, with characteristics of fast growth, landscaping and many other advantages. Therefore, it can be used as a kind of phytoremediation resources for the remediation of city heavy metals contaminated soil, which suitable for large-scale promotion. |
PDF Full Text Request