PREFERENTIAL USE OF ORGANIC NITROGEN FOR GROWTH BY A NONMYCORRHIZAL ARCTIC SEDGE

PLANT growth in arctic tundra is strongly nitrogen-limited despite large pools of soil organic nitrogen1-4. Here we report that field-collected roots of Eriophorum vaginatum, an arctic sedge, rapidly absorb free amino acids, accounting for at least 60% of the nitrogen absorbed by this species in the field. In solution culture, Eriophorum accumulates more nitrogen and biomass when supplied with amino acids than when grown on inorganic nitrogen, whereas Hordeum vulgare (a cereal adapted to mineral soils) grows least when nitrogen is supplied as amino acids. To our knowledge, this is the first documentation of preferential absorption and use of organic nitrogen by a non-mycorrhizal vascular plant. The direct absorption of amino acids by Eriophorum short-circuits the bottle-neck in arctic nitrogen cycles imposd by temperature-limited mineralization.