THE ROLE OF PROTEINS IN THE NITROGEN NUTRITION OF ECTOMYCORRHIZAL PLANTS: III. PROTEIN UTILIZATION BY BETULA,PICEA AND PINUS IN MYCORRHIZAL ASSOCIATION WITH HEBELOMA CRUSTULINIFORME

Abstract

Summary: The ability of four major species of trees of boreal forests,Betula pendula, Picea mariana, P. sitchensis and Pitius contorta, to utilize protein as a sole nitrogen source was compared when the plants were grown in mycorrhizal association with the fungus Hebeloma crustuliniforme and in the non‐mycorrhizal condition. When mycorrhizal, all species used protein N readily, producing vigorous shoots with nitrogen contents ranging from 5% in birch to around 3% in the conifers, and consuming up to 53% of the nitrogen provided in the culture vessels. In the absence of infection birch, black spruce and pine were completely unable to use protein as an N source and Sitka spruce had only a minimal ability to do so. It is suggested that early infection by fungi with proteolytic capability may be of particular importance for small seeded species germinating in soils of boreal and arctic regions where mineralization of nitrogen is inhibited by low temperatures.