Utilization of organic nitrogen by ectomycorrhizal fungi (<e1>Hebeloma</e1> spp.) of arctic and temperate origin

Arctic and temperate strains of <e1>Hebeloma</e1> spp. were grown in axenic culture on glutamic acid, alanine, lysine and NH<inf>4</inf>⁺ as sole sources of nitrogen (N), with excess carbon (C) or deficient C (supplied as glucose). Their ability to utilize seed protein as a natural N source was also assessed. All strains tested had the capacity to assimilate amino acids and generally utilized alanine and glutamic acid more readily than NH<inf>4</inf>⁺. Some strains were able to utilize amino C when starved of glucose C, and could mineralize amino-N to NH<inf>3</inf>-N. Arctic strains, in particular, appeared to be pre-adapted to the utilization of seed protein N and glutamic acid N, which is often liberated in high concentrations after soil freezing. The results are discussed in relation to their possible ecological importance.