Inorganic Pollutants Tolerance And Uptake By Rumex Acetosa Linn, Polygonum Microcephalum D.Don, Rumex Hastatus D.Don

Phytoremediation is an emerging environmental clean-up technique. It explores the nature with which plants can tolerate and hyperaccumulate some chemical elements, in combination with plant's natural ability and its associated microorganisms to remove the contaminants in the environment. Screening accumulators or hyperaccumulators with large biomass and strong ability to take up environmental pollutants is the key for successful phytoremediation practices. Plant species from the Polygonaceae are widely distributed with most of them having large biomass, and it is, therefore, possible to screen accumulators and hyperaccumulators from the Polygonaceae. A survey of literature shows that little study has been done on uptake of pollutants by plants from the Polygonaceae, and that the reports about their physiological and biochemical characteristics under heavy metal stress were sporadically seen. A batch of sand culture and soil culture experiments were carried out to investigate heavy metal and radiocesium uptake and accumulation by Rumex acetosa Linn, Polygonum Microcephalum D.Don, and Rumex hastatus D.Don widely distributed on copper mining areas, and their physiological and biochemical characteristics under Cu Zn stress, as well their potentials in application to phytoremediation. The major results were summarized as follows:1. R. acetosa, P. Microcephalum, R. hastatus were found to have comparatively strong ability to tolerate and accumulate copper and to maintain normal growth in Cu-contaminated environment. Sand culture experimental results show that theycould survive in 7 mg L-1'Cu treated nutrient solution and accumulate copper to a certain extent. P. Microcephalum had higher root copper concentration than R. acetosa and R. hastatus. The former has root copper concentrations averaging 4765.06+484.28 while the latter two have root copper concentrations averaging 1749.23 +154.98 and 890.26 +57.21 mg kg-1 respectively. P. Microcephalum also had higher shoot copper concentration averaging 214.04 +16.31 mg kg-1 than R. hastatus and R. acetosa which contain average shoot copper concentration 27.59+5.32 34.59+4.94 mg kg-1, respectively. Soil culture experiments also demonstrated that R. acetosa and R. hastatus can accumulate some amount of copper with root copper concentration averaging 101.16 + 10.26 132.13 + 73.46mg kg-1, respectively, and shoot copper concentration averaging 22.09+ 1.06 29.72+17.38mg kg-1, respectively when grown for 70 days on soils contaminated with 50 mg Cu kg-1. These results indicated that the three Polygonaceae can serve as pioneer species for phytoremediation of copper -contaminated soils.2. R. acetosa and R. hastatus also have comparatively strong ability to tolerate and accumulate zinc, and to survive well on Zn-contaminated environment. R. acetosa grown in 5 mg Zn L-1 treated culture solution has concentrations of zinc up to 852.53+48. 57, 1223.26+97.17 mg kg-1, and 956.90+54.36. 1136.85 +6.36 mg kg-1 in the root and shoot, respectively while R. hastatus grown in the similar condition has zinc concentrations of 956.90 +54.36 mg kg-1 and 1136.85 +6.36 mg kg-1 in the root and shoot, respectively. Although the concentration of zinc in both species has not reached the criterion set for zinc hyperaccumulator, their high zinc shoot/root ratio of more than or near 1 suggested that they were Zn accumulators. Therefore, both species have some high potential to remediate zinc-contaminated soils.3. R. acetosa and R. hastatus can grow in the environment contaminated with both Cu and Zn, and accumulate some amount of Cu and Zn. Although the combinedtreatments with both Cu and Zn decreased growth biomass compared with single Cu and single Zn treatments, they can also grow well in the combined polluted environment and accumulate certain amount of Cu and Zn. Under combined contamination, Cu and Zn showed obvious mutual interactions: Zn treatment decreased Cu uptake by R. acetosa and R. hastatus, and Cu treatment depressed Zn uptake by R. acetosa and...