Survey of Canadian native plant species for resistance to salt and metal stress

Abstract

There are over 21, 000 federally managed metal contaminated soil sites in Canada, not including sites managed by the private sector or sites affected by other contaminants requiring some level of remediation. One of the most economical remediation options, especially on a large scale, is phytoremediation. Phytoremediation is a process where plants and their associated microbes uptake, break down, or immobilize target soil contaminants. Native plant species are important to consider for phytoremediation since their lifecycles are acclimatized to local soil and weather and are not at risk of becoming invasive. The purpose of this thesis was to assess Canadian native plant species used in soil reclamation for their resistance to metals and salts found in oil sands mine tailings. To determine germination and growth inhibition concentrations of salts and metals, seeds were exposed to various metal and salt concentrations in semi-solid water agar. Germination and early growth of Achillea millefolium (common yarrow), Astragalus canadensis (Canadian milkvetch), Calamovilfa longifolia (Prairie sandreed), Koeleria macrantha (Prairie Junegrass), and Vicia americana (American vetch) were assessed in a lab bioassay using semi-solid water agar, and in a greenhouse experiment, using soil. The semi-solid water agar and soil were artificially contaminated with either a metal [Cd(NO3)2, Cr(NO3)2, Cu(NO3)2, Ni(NO3)2], or salt (KCl, NaCl, K2SO4, Na2SO4). In the bioassay, germination was inhibited by salts (0, 1000, 10 000, 100 000 mg kg-1) for all species at concentrations exceeding 1000 mg kg-1. Koeleria macrantha was the only species that was inhibited by metals at 20 and 50 mg kg-1 Cd and Cu. Roots and shoots exhibited stunting for many of the metal concentrations, and in salt concentrations exceeding 1000 mg kg-1. In the greenhouse experiment, metal concentrations (0, 10, 20, 50 mg kg-1) had no effect on germination and there was no significant difference (p<0.05) between the biomass of control plants and plants grown in the metal contaminated soil. Seeds struggled to germinate in salt contaminated soil (0, 1000, 5000 mg kg-1), mostly in the chloride amended soil, and produced very little biomass. The most promising candidate from the experiments was A. millefolium since it had the highest germination, and the longest root and shoot lengths in the bioassay study. Also, it produced the highest biomass in the greenhouse study, and was able to grow in chloride amended soil, which significantly inhibited other species. Results suggest A. millefolium should be the focus of future studies.