| This dissertation consists of four experimental studies examining effects of different soil chemical and physical properties on mycorrhizal tree seedlings. In Chapter II, ectomycorrhizal black spruce (Picea mariana), white spruce (Picea glauca) and jack pine (Pinus banksiana) seedlings were subjected to KF and NaCl treatments. Fluoride-induced needle injury was alleviated by 60 mM NaCl in black spruce and white spruce, but not jack pine. Chloride tissue concentrations in NaCl-treated plants were not affected by the presence of KF. However, shoot F concentrations in black spruce and white spruce treated with 5 mM KF + 60 mM NaCl were significantly reduced compared with the 5 mM KF treatment. The results point to a possible competitive inhibition of F transport by Cl. In Chapter III, inoculated and non-inoculated jack pine seedlings were subjected to boron and salt treatments. When applied with 60 mM NaCl, 2 mM H3BO3 aggravated needle necrosis while reducing Cl concentrations in shoots of non-inoculated plants. Plants inoculated with mycorrhizal fungi had lower shoot Na concentrations compared with non-inoculated seedlings. In Chapter IV, inoculated and non-inoculated American elm (Ulmus americana) seedlings were grown in non-compacted and compacted soil and subjected to NaCl treatment. When treated with 60 mM NaCl, ectomycorrhizal seedlings had several-fold lower Na leaf concentrations compared with the non-ectomycorrhizal plants. Soil compaction reduced Na leaf concentrations in non-ectomycorrhizal plants and decreased dry weights, gas exchange and root hydraulic conductance. However, in ectomycorrhizal plants, soil compaction had little effect on the leaf Na concentrations and on other measured growth and physiological parameters. In Chapter V, inoculated and non-inoculated American elm seedlings were subjected to different pH solutions (pH 3, 6 and 9) containing 0 and 60mM NaCl. NaCl treatment reduced leaf chlorophyll concentrations in non-ectomycorrhizal seedlings compared with ectomycorrhizal plants and the greatest decrease occurred at pH 6 treatment. Root Na concentrations were higher in ectomycorrhizal plants at pH 3 treatment compared with non-inoculated seedlings. However, there was no effect of inoculation on root Na concentrations at pH 6 and 9. The results of the above studies point to the importance of soil chemical and physical properties in the responses of mycorrhizal plants to NaCl. |
