THE EFFECT OF MYCORRHIZAL INFECTION ON THE RESPONSE OF BETULA PAPYRIFERA TO NICKEL AND COPPER

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Abstract
Summary: The role of ectomycorrhizas in the metal tolerance of birch seedlings from Sudbury, Ontario was investigated. Betula papyrifera Marsh, is one of the few tree species able to survive in the copper‐ and nickel‐polluted area near Sudbury. Two types of birch seedlings were tested; those inoculated with Laccaria proxima (Boud.) Pat., Lactarius hibbardae Peck, Lactarius rufus (Scop, ex Fr.) Fries, or Scleroderma flavidum E. & E. isolates originating from the Sudbury area, and those which were not inoculated. Once the seedlings were infected, they were grown in sand culture containing 34 or 85 μM Ni, 32 or 63 Cu, or a control solution. At the low nickel concentration, the mycorrhizal plants, especially those infected with S. flavidum, grew significantly better than did non‐mycorrhizal plants. At the higher nickel concentration, S. flavidum‐infected seedlings weighed 86% of controls without nickel, while the other seedlings weighed only 52 to 61 % of control. The good growth of S. flavidum‐infected birch seedlings may have been due to retention of nickel in the mycorrhizas. These seedlings had the highest root nickel contents and the lowest stem nickel contents. At the high concentration of copper, growth of the mycorrhizal seedlings was significantly reduced compared with the non‐mycorrhizal seedlings. This reduction in growth of infected seedlings did not relate to an increase in the uptake or translocation of copper. Under the low copper treatment, infection with mycorrhizal fungi did not affect seedling growth. The potential role of iron and phosphorus in affecting host metal tolerance was investigated. Changes in the tissue concentrations of these elements did not relate to the effect of the fungi on metal tolerance.