title: Influence of pH on copper and zinc sensitivity of ericoid mycobionts in vitro.
abstract: The effect of pH on growth, metal uptake and toxicity in four isolates of ericoid mycobionts (two Hymenoscyphus ericae from unpolluted heathland sites and two H. ericae-type mycobionts from metal-contaminated mine spoil) was assessed in vitro. These isolates were incubated in liquid medium (10% Rorison's medium, glucose at 10 g l(-1)) containing either 0.25 mM Cu or 2.0 mM Zn and adjusted to pH 2, 3, 4, 5 or 6. After 30 days incubation, dry mass and mycelial metal content were determined and growth was expressed as tolerance index, i.e. dry mass in the presence of metal as a percentage of dry mass in the absence of metal. Initial medium pH had a significant effect on both tolerance index and metal accumulation. Tolerance indices were highest at pH 2, with several isolates showing a stimulation of growth (i.e. tolerance index >100%) at this pH. Tolerance index decreased at higher initial pH values and growth of two mycobionts was completely inhibited (tolerance index=0) in the Cu-supplemented media at pH 6. Reduction in tolerance index coincided with an increase in mycelial accumulation of Cu and Zn. Practical and environmental implications of these results are discussed.
authors.affiliation: Department of Botany, University College Dublin, Dublin 4, Ireland.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Gibson
authors.forename: Derek T
authors.initials: DT
authors.lastname: Mitchell
mesh_terms: D003300:Copper / Q000378:metabolism*; D029791:Ericaceae / Q000378:metabolism / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D025282:Mycelium / Q000378:metabolism; D038821:Mycorrhizae / Q000187:drug effects*; D015032:Zinc / Q000378:metabolism*
chemical_list: D003300:Copper; D015032:Zinc