THE EFFECTS OF ALUMINUM AND CALCIUM ON THE GROWTH AND NUTRITION OF SELECTED ECTOMYCORRHIZAL FUNGI OF JACK PINE

The influence of Al and Ca on the growth, in axenic culture, of three ectomycorrhizal fungi associated with jack pine (Pinus banksiana Lamb.) was examined. Isolates of Hebeloma crustuliniforme (St. Amans) Quel., Rhizopogon rubescens (Tul.) Tulasne, and Suillus tomentosus (Kauff.) Singer, Snell & Dick were obtained from basidiocarps collected in jack pine stands of different ages. Basidiocarps and the soil surrounding them were analyzed for Al and Ca, as well as other elements. Each fungal species was grown for 4 weeks in nutrient solutions containing 37, 185, 370, or 740-mu-M Al combined in a factorial design with 25, 125, 250, or 500-mu-M Ca and maintained at pH 3.8. Growth of all three fungal species was reduced at 370-mu-M Al. Significant interaction was found between fungal species and Al treatment for all six elements measured in mycelial tissue. Stepwise increments in external Al concentration resulted in reduced mycelial concentrations of Ca, Mg, and K, and increased mycelial concentrations of Al, P, and Fe in H. crustuliniforme. High external Al levels resulted in reduced mycelial concentrations of all elements measured except Al and P in R. rubescens. In contrast, for S. tomentosus the same external Al levels increased the mycelial concentrations of all elements except Ca. The response of the three ectomycorrhizal fungi to Ca also differed. Growth of H. crustuliniforme was stimulated by stepwise increments in external Ca concentrations from 25 to 500-mu-M. Increments in calcium had no effect on the growth of R. rubescens. High external levels of Ca acted synergistically with high external Al concentrations to reduce growth by S. tomentosus. Unlike the other two species, the response of S. tomentosus to Al and Ca could not have been predicted from the soil and basidiocarp analyses. Alterations in Ca to Al ratios of soils may influence the succession of ectomycorrhizal fungi on conifer root systems.