Tolerance And Accumulation Characteristics Of Dicranostigma Leptopodum (Maxim.) Fedde Under Zinc, Cadmium, Copper And Lead Stress

Heavy metal pollution of soil has been a serious problem which could be toxic to environment and humans. Screening hyperaccumulator was the foundation of bioremediation. Based on the results of field investigation, combined with the distribution characteristics of Dicranostigma leptopodum (Maxim.) Fedde, we determined that Dicranostigma leptopodum (Maxim.) Fedde taken from Fuquan(FQ) and Xiatuo(XT) in western Sichuan as the research object, which had some differences in the ecological environment. A pot experiment was carried to study Zn, Cd, Cu and Pb tolerance and accumulation characteristics of Dicranostigma leptopodum (Maxim.) Fedde. The result showed as follows:(1)Dicranostigma leptopodum (Maxim.) Fedde in FQ and XT could grow normally and complete its life history.They have great patience to Zn, Cd, Cu and Pb, furthermore, they could enrich Zn and Cd. The average Zn and Cd concentrations of Dicranostigma leptopodum (Maxim.) Fedde in FQ were 1231.65mg kg-1 and 17.75mg kg-1, respectively. But for those in XT, the values were 386.45mg kg-1 and 3.59 mg kg-1. The hightest Zn and Cd BCFs of FQ population were 1.14 and 1.36. For XT, most of the values were lower than 1, the BCFs were 0.77-1.13 and 0.61-2.22。Correlation analysis showed that shoot concentration of the two populations had significant positive correlation with the soil concentration. This showed that the metal concentrations in soils could some extent affected the metal concentrations in plants.(2)Dicranostigma leptopodum (Maxim.) Fedde showed strong tolerance and enrich characteristics under Zn stress. When the treatment concentration< 1500 mg kg-1, the two did not express obvious toxicant phenomenon, and the plant height and shoot biomass increased significantly compared to CK(P<0.05). The SOD, POD and CAT activities of plants from the two sites increased when the treatment concentration<1500 mg kg-1. POD and CAT of FQ plant decreased when the treatment concentration>2500 mg kg-1, and POD showed a marked drop trends (P<0.05). POD, SOD and CAT of FQ showed significant differences compared to CK (P<0.05). When the treatment concentration was 3500 mg kg-1, the highest shoot Zn concentration of FQ plants were 4094.07 mg kg-1, the shoot BCF was 1.30. the highest shoot Zn concentration of XT plants were 2964.17 mg kg-1, the shoot BCF was 0.88. The shoot accumulation of plants from the two sites took up 92.8-98.9% and 95.4-98.0% of the total amount in the plant.(3)Dicranostigma leptopodum (Maxim.) Fedde showed tolerance and enrich characteristics at some extent under Cd stress. Plant height, shoot biomass and root biomass of the two sites increased along with the increasing of the treatment concentration when the treatment concentration<100 mg kg-1. However, Plant height and shoot biomass of plants from the two sites reduced evidently when the treatment concentration> 100 mg kg-1(P<0.05). When the treatment concentrations were 100-180 mg kg-1, the Cd concentrations in the shoots of FQ plant were 21.21-95.58 mg kg-1, the BCF in shoots under Cd stress were 0.24-0.59. But for those from XT, the accumulations of Cd in shoots were 61.80-93.54 mg kg-1 which took up 60.68-71.14% of the total amount in the plant, the shoot BCFs in shoots under Cd stress were 0.59-0.66. The tolerance and accumulation characteristics to Cd of the two plants did not showed significant differences.(4) Dicranostigma leptopodum (Maxim.) Fedde showed tolerance and enrich characteristics at some extent under Cu stress. Plant height, root length, shoot biomass and root biomass of the FQ plants decreased along with the increasing of the treatment concentration significantly (P<0.05). Cu concentration of plant Shoot from the two sites increased along with the increasing of the treatment concentration significantly (P<0.05), when the treatment concentration≥1000 mg kg-1, the Cu concentrations in the shoots of FQ plant were 120.47-236.90 mg kg-1, which took up 91.37-92.39% of the total amount in the plant, the shoot BCFs and TFs in shoots under Cu stress were 0.52-0.59 and 0.91-0.92. Cu concentrations in the shoots of XT plant were 74.62-175.45 mg kg-1, which took up 71.52-79.67% of the total amount in the plant, the shoot BCFs and TFs in shoots under Cu stress were 0.07-0.09 and 0.43-0.50. The tolerance and accumulation characteristics to Cu of the two plants did not showed significant differences.(5)Dicranostigma leptopodum (Maxim.) Fedde showed toxicant phenomenon under the Pb stress, but they had not enrich ability to Pb. Plant heights and root length of the two plants increased significantly compared to the CK when the treatment concentration≤1600 mg kg-1 (P<0.05), but decreased significantly when the treatment concentration>1600 mg kg-1 (P<0.05). The shoot Pb concentration of plants from the two sites increased with the increasing of the treatment concentration significantly (P<0.05). When the treatment concentration was 1900 mg kg-1, the Pb concentrations in the shoots of FQ and XT plant were 548.00 mg kg-1 and 322.48 mg kg-1, which took up 76.71% and 88.17% of the total amount in the plant. The TFs and shoot BCFs of plants from the two sites were lower than 1.Generally speaking, Dicranostigma leptopodum (Maxim.) Fedde showed strong tolerance and accumulation ability of Cd and Zn, and had weaker tolerance and accumulation ability of Cu and Pb.