Search

Lead concentrations in roots, stems and leaves of accumulating and non accumulating ecotypes of Sedum alfredii (Hance) were studied through a hydroponic experiment with different Pb concentrations supplied as Pb(NO(3))(2). Lead concentrations in leaves and stems of the accumulating ecotype were 4 - 9 times and 3 - 5 times those of the non-accumulating ecotype, and Pb accumulated amounts in stems and leaves of the accumulating ecotype were 4 - 9 times and 8 - 11 times higher than those of the non-accumulating ecotype, respectively. The results indicated that the accumulating ecotype had better ability to transport Pb from roots to shoots. The subcellular distributions of Pb in the root, stem and leaf tissues were studied using sucrose differential centrifugation. Approximately 50% of Pb contents was found to be associated with the cell wall fraction in stems of the accumulating ecotype and the percentage increased to 80% both in roots and leaves, no matter when plants were grown with different levels of Pb. The results indicated that the distribution of Pb on cell walls of the accumulating ecotype could mainly account for the high tolerance to Pb.

Phytoremediation is becoming an established technology for environmental clean-up and protection. Hyperaccumulator plants are potential tools to remove excess metals from contaminated soils. As an efficient operational routine technology, phytoextraction requires a better knowledge of tolerance and accumulation for excess metals by particular plants. Based on the vegetation survey, a new zinc (Zn)-accumulating ecotype of Sedum alfredii Hance naturally-growing in an old Zn/lead (Pb) mining region in Quzhou City (29°17′ N, 118°56′ E) and a non-Zn-accumulating ecotype of Sedum alfredii Hance in the suburb of Hangzhou City (30°06′ N, 120°12′ E), Zhejiang province were found. To identify Zn tolerance and accumulation characteristics of the two ecotypes of Sedum alfredii Hance, a solution culture experiment was carried out with four treatments: 0.0325 (CK), 20, 80, 160 mg Zn L−1 in the basic nutrient solution. The biomass of root, stem and leaf for the ecotype of Sedum alfredii from Zn/Pb mining area, as well as of leaf of non-Zn-accumulating ecotype of Sedum alfredii, expressed as dry weight, were not significantly different among the treatments after 12 days. However, the biomass of root and stem for non-Zn-accumulating ecotype of Sedum alfredii in treatments with 80 and 160 mg Zn L−1 were significantly lower than that of the control treatment (CK). The results indicated that Zn concentrations in leaves, stems and roots of the test plants increased significantly with increasing Zn concentration in the nutrient solution. Zn concentrations in leaves and stems of the ecotype from Zn/Pb mining area were 25–34 and 7–48 fold higher than those in leaves and stems of the non-Zn-accumulating ecotype. The amounts of Zn accumulated in shoots (leaves and stem) of the ecotype from Zn/Pb mining area in 20, 80 and 160 mg Zn L−1 treatments were significantly larger than those of the non-Zn-accumulating ecotype. As the Zn concentrations on the dry weight in leaves and stems of the ecotype from Zn/Pb mining area were 16,740 and 19,567 mg kg−1 in the 80 mg Zn L−1 treatment, this ecotype can be regarded as a Zn hyperaccumulator. [ABSTRACT FROM AUTHOR]