Cu Tolerance And Accumulation Of Festuca Arundinacea, Paspalumnotatum And Cynodondactylon Under The Stress Of Cu And Cu-Zn

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 suceessful 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 batch of sand culture and soil culture experiments were carried out to investigate heavy metal uptake and accumulation by Rumexacetosa 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.Cynodondactylon,FestucaarundinaceaSchreb,and Paspalumnotatum 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 they could survive in 7 mg·L^-1 Cu treated nutrient solution and accumulate copper to a certain extent.FestucaarundinaceaSchreb had higher root copper concentration than Cynodondactylon and Paspalumnotatum.The former has root copper concentrations averaging 4765.06±484.28 while the latter two have root copper concentrations averaging 1749.23±254.95 and 590.26±57.21mg·kg^-1 respectively.FestucaarundinaceaSchreb also had higher shoot copper concentration averaging 214.04±16.31 mg·kg^-1 than Paspalumnotatum and Cynodondactylon which contain average shoot copper concentration 27.59±5.32,34.59±4.94mg·kg^-1,respectively.Soil culture experiments also demonstrated that Cynodondactylon and Paspalumnotatum can accumulate some amount of copper with root copper concentration averaging101.16±10.26,132.13±73.46 mg·kg^-1,respectively and shoot copper concentration averaging 22.09±1.06,29.72±17.38 mg·kg^-1,respectively when grown for 70 days on soils contaminated with 50mg Cu·kg^-1.These results indicated that the three Gramineae can serve as pioneer species for phytoremediation of coppercontaminated soil.2.Cynodondactylon and Paspalumnotatum can in the contaminated with both Cu and Zn,and accumulate some amount of Cu and Zn.Although the combined treatments 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 Cynodondactylon and Paspalumnotatum,and Cu treatment depressed Zn uptake by Cynodondactylon and Paspalumnotatum.3.It is found that copper and zinc contamination has effect on some physiological and biochemieal characteristics of Cynodondactylon and Paspalumnotatum.Sand culture experimental results showed that the chlorophyll content of Paspalumnotatum grown in only copper treatment decreased but its chlorophyll a/b radio increased remarkably.It was also shown that single Cu treatment significantly enhaced MDA in Cynodondactylon and Paspalumnotatum leave cells,and increased the activity of SOD and POD,with CAT activity increasing at beging,and then decreasing With time.The soil pot experiment in single copper treatment showed similar variation characteristics of physiological and biochemical for Cynodondactylon and Paspalumnotatum.Under combined contamination physiological and biochemical characteristics of Cynodondactylon and Paspalumnotatum showed more rem-arkable variation than single treatment:Compared with single Cu and single Zn treatments,the cmbined treatments with both Cu and Zn decreased the chlorophyll content and CAT activity of Paspalumnotatum,while increased the root and leaf cell MDA content, SOD and POD activity of Paspalumnotatum,meanwhile the root and leaf cell POD activity of Cynodondactylon is also increased under combined contamination.