Genetic and Physiological Responses of Deschampsia Cespitosa to Soil Metal Contamination.

Excessive concentrations of metals in soil represent serious threats to plant ecosystem sustainability. Knowledge of the effects of long term exposure to high levels of metals on cytological stability and genetic variability in D. cespitosa population is lacking.  The objectives of present study are to determine how D. cespitosa plants cope with soil metal contamination. The effects of excessive copper and nickel on cytological stability and genetic variability were analyzed. Molecular analyses of D. cespitosa populations growing on metal contaminated sites were performed using microsatellites markers. The results of the present study provide strong evidence that D. cespitosa copes with metal contamination by accumulating them in its root system with limited translocation to their aerial plant parts.  The metal accumulation factors in roots compared to bioavailable metals in soils, were very high reaching 5.5, 35.2, 151.2, 24.8, and 127.4 for Cu, Fe, Mg, Ni, and Zn, respectively. Although the microsatellite analysis revealed no significant difference in genetic variation levels between metal contaminated and uncontaminated, cytological analysis clearly showed that long exposure of roots to high levels of metal contamination lead to significant mitotic disruptions. Overall, 83% of the plants from metal contaminated sites showed a high level of mixoploidy compared to 17% from the reference sites. Lagging chromosomes in mitotic anaphase were observed in most of the plants from metal contaminated sites. These mitotic abnormalities appear to have no detectable effects on plant growth and survival.  D. cespitosa is therefore well suitable for metal contaminated sites.