Molecular characterization of Deschampsia cespitosa populations from metal contaminated areas in Northern Ontario: nickel and copper toxicity.

Abstract

The main objectives of the present study were to 1) reassess the level of genetic variation in D. cespitosa populations from three regions contaminated or uncontaminated with metals in Northern Ontario; 2) determine the degree of toxicity of nickel and copper in D. cespitosa genotypes; and 3) investigate cytological damages caused by metals in D. cespitosa plants growing in Northern Ontario. An insignificant change in the overall percent of polymorphic loci in populations from Little Current and Cobalt Cart Lake was found. On the other hand, a significant decrease was seen in the Coniston/Wahnapitae and Cobalt Nipissing Tailings sites. The degree of genetic relatedness among the populations has increased, compared to data from the analysis of samples 16 years ago. This strengthens the earlier theory that Sudbury populations of D. cespitosa might be from the Cobalt region. The degree of toxicity of nickel and copper in D. cespitosa was investigated under controlled conditions. It was found that copper is more toxic than nickel. Neither copper nor nickel caused damage to plants at low rates of 5.6 and 9.16 mg/kg respectively, corresponding to the bioavailable amounts. Higher dosages (1600 mg/kg) of nickel and (1312 mg/kg) copper equivalent to total elements in site, caused significant damages to plants. Cytological analysis for D. cespitosa revealed significant mitotic disruption from long term exposure of roots to high levels of metal frequently manifested through aneuploidy in metal-contaminated sites when compared to the reference sites. All plants from contaminated areas exhibited varying degrees of mixoploidy compared to the reference sites. These high levels of mitotic abnormalities did not seem to affect D. cespitosa survival and growth in highly metal-contaminated sites.