Role of Mycorrhiza in Nitrogen Fixation

Abstract

NONE of the higher fungi has yet been implicated in nitrogen fixation; at least no claims to this effect have been confirmed by the nitrogen-15 technique. It has often been suggested that the ectotrophic mycorrhizæ of certain coniferous trees might fix nitrogen, but there is no unequivocal evidence in support of this. The nitrogen-15 technique has been used to test for fixation in Pinus sylvestris L. with negative results¹ and in P. radiata D. Don. with positive results^3,4. In each of these investigations, plants were grown in soil or sand so that, even where evidence of fixation was obtained, the identity of the organism (or organisms) responsible for nitrogen fixation is unknown.