Toxic elements are present in polluted water from mines, industrial outlets, storm water etc. Wetland plants take up toxic elements and increase the pH of the medium. In this thesis was investigated how the shoots of submerged plants and roots of emergent plants affected the pH of the surrounding water in the presence of free toxic ions. The aim was to clarify the mechanisms by which these plants change the surrounding water pH in the presence of toxic ions. The influence of Elodea canadensis shoots on the pH of the surrounding water was studied in the presence of cadmium (Cd) at low initial pH (4-5). The involvement of photosynthetic activity in the pH changes was investigated in the presence and absence of Cd. The cytosolic, vacuolar and apoplasmic pH changes as well as cytosolic Cd changes in E. canadensis were monitored. The influence of Eriophorum angustifolium roots on the pH of the surrounding water was investigated in the presence of a combination of Cd, copper, lead, zinc and arsenic at low initial pH (3.5). Eriophorum angustifolium root exudates were analyzed for organic acids. Elodea canadensis shoots increased the pH of the surrounding water, an effect more pronounced with increasing Cd levels and/or increasing plant biomass and increased plant Cd uptake. The pH increase in the presence of free Cd ions was not due to photosynthesis or proton uptake across the plasmalemma or tonoplast. Cadmium was initially sequestered in the apoplasm of E. canadensis and caused its acidosis. Eriophorum angustifolium roots increased the surrounding water pH and this effect was enhanced in the presence of arsenic and metals. This pH increase was found to depend partly on the release of oxalic acid, formic acid and succinic acid by the plants. In conclusion, E. canadensis shoots and E. angustifolium roots were found to increase the low initial pH of the surrounding water. The pH modulation by these species was enhanced by low levels of free toxic ions in the surrounding water. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.

The role of Eriophorum vaginatum in carbon dioxide (CO 2) and methane (CH4) dynamics of two restored peatlands in eastern Canada was examined. Sites were established in Riviere-du-Loup, Quebec from May to October of 1999 and 2000, and Shippagan, New Brunswick from May to October of 2001. / CH4 emissions from E. vaginatum collars were positively related to maximum photosynthesis in 1999 and 2001, when the water table was close to the surface. CH4 emissions were also positively related to end of season above ground plant biomass at both sites. CH4 emissions from E. vaginatum collars ranged from -0.015 to 14.7 mg CH4-C m-2 h-1 at Riviere-du-Loup and -0.15 to 5.4 mg CH4-C m -2 h-1 at Shippagan. It is likely that E. vaginatum provides substrate for methanogenesis through plant production and acts as a conduit transporting CH4 to the atmosphere. / Patterns of NEE from E. vaginatum depended on site-specific and year-specific conditions. E. vaginatum was a net sink for CO2 at high and low light levels at Shippagan, and a net source of CO2 at low light levels at Riviere-du-Loup.

No description available.