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

Abstract

SUMMARYThe 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 fiavidum 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 fiM Ni, 32 or 63 fiM Cu, or a control solution. At the low nickel concentration, the mycorrhizal plants, especially those infected with S. fiavidum, grew significantly better than did non-mycorrhizal plants. At the higher nickel concentration, S.flaviduminfected seedlings weighed 86 % of controls without nickel, while the other seedlings weighed only 52 to 61 % of control. The good growth of 5. fiavidum-'mfected 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.

ZINC TOLERANCE IN BETULA SPP.

“…(Brown & Wilkins, 1985). Similar amelioration has been noted in Betula papyrifera Marsh when it is associated with various ectomycorrhizal symbionts and exposed to Cu and Ni (Jones & Hutchinson, 1986), and in ericaceous mycorrhizas exposed to Cu and Zn toxicity (Bradley, Burt & Read, 1981, 1982. Gildon & Tinker (1983) have shown amelioration in vesicular-arbuscular mycorrhizas (VAM), although Killham & Firestone (1983) found that VAM infection led to enhanced metal toxicity to the associated vascular plant.…”

Nickel toxicity in mycorrhizal birch seedlings infected with Lactarius rufus or Scleroderma flavidum I. Effects on growth, photosynthesis, respiration and transpiration

“…However, not all fungi Infection by ectomycorrhizal fungi can increase the are equally effective at protecting the host. Further, tolerance of their hosts to Ni (Jones & Hutchinson, the relatiye tolerance of the fungus under axenic 1986), Zn (Brown & Wilkins, 1985) or Al (Jones, culture may not reflect its ability to enhance the Browning & Hutchinson, 1986). The mechanism by tolerance of the phytobiont (Jones & Hutchinson, which the fungi confer tolerance is unclear.…”

“…Fr. was not (Jones & Hutchinson, 1986). Comparison between the fungi was important not only to investigate the differences in their effectiveness in altering host tolerance but in addition, since paper birch is usually mycorrhizal under natural conditions (Malloch & Malloch, 1981), mycorrhizal plants made better controls for the S. jJavidum-miected plants than did uninoculated plants.…”

“…A further objective was to examine whether Betula papyrifera Marsh, seedlings derived from seed collected from an area uncontaminated by Ni responded to the fungi, and to Ni, in the same way as seedlings grown from seed from a Ni-contaminated site near Sudbury (Jones & Hutchinson, 1986). Since in previous experiments Ni-treated 5. flavidum-miected hirch had much heavier root systems than those itifected with other fungi, chitin analysis was used to determine whether this increased weight was due solely to fungal growth.…”

“…Since, in a previous experiment (Jones & Hutchinson, 1986), there had been an indication that some fungi had tolerance mechanisms that were limited in capacity, the development of Ni toxicity over time was studied. This was done by recording water use by the plants twice weekly, as well as by measuring growth at three harvests over 21 weeks.…”