The role of proteins in the nitrogen nutrition of ectomycorrhizal plants

V. Nitrogen transfer in birch (Betula pendula) grown in association with mycorrhizal and non-mycorrhizal fungi



Plants of Betula pendula L, were grown on a medium continuing protein as sole nitrogen source, and the ability of fungi representing a range of nutritional categories to provide them with access to protein-N was examined by determining changes of dry weight and nitrogen accumulation with time following sequential harvests.

Three fungi known to be ectomycorrhizal all gave access to the nitrogen but large differences in their effectiveness were observed, an ‘early stage’ fungus providing significantly more N than either a ‘late stage’ fungus or a facultative associate. The saprotroph Oidiodendron griseum Roback also facilitated N transfer to the plants whereas they obtained no such supply in the uninoculated condition, or when grown with an ericoid endophyte and a saprotroph isolated from the seed coat. The process of nutrient transfer from fungus to host is seen as the key rate limiting step determining growth response of the host. The physiological and ecological implications of the results are discussed.