The ability of a range of commonly occurring ectomycorrhizal fungi to utilize peptides and proteins as sole sources of nitrogen at a range of pH levels was examined by determining patterns of growth and nitrogen uptake in liquid cultures. Differences in patterns of utilization of the nitrogenous substrates were found. Some of the fungi had little ability to grow on peptides or proteins but grew well on ammonium and were termed ‘non-protein fungi’. Others grew vigorously on peptide and protein, severely depleting N contents of the growth media. These were termed ‘protein fungi’. An intermediate category was also recognized in which some growth occurred on protein at most of the pH levels though final yields were lower than those of the ‘protein fungi’.
The implications of the results are discussed in relation to the ability of the fungi to sustain a saprotrophic or mycorrhizal habit in soils differing qualitatively in their nitrogen status.