Corrêa, A., Cruz, C., Ferrol, N. (2015) Nitrogen and Carbon/Nitrogen dynamics in arbuscular mycorrhiza: the great unknown.Mycorrhiza, 25(7), 499-515. DOI:10.1007/s00572-015-0627-6 (IF2015 3,252; Q1 Mycology)
Many studies have established that arbuscular mycorrhizal fungi transfer N to the host plant. However, the role and importance of arbuscular mycorrhiza (AM) in plant N nutrition is still uncertain, as are the C/N interactions within the symbiosis. Published reports provide differing, and often contradictory, results that are difficult to combine in a coherent framework. This review explores questions such as: What makes the difference between a positive and a negative effect of AM on plant N nutrition? Is the mycorrhizal N response (MNR) correlated to the mycorrhizal growth response (MGR), and how or under which conditions? Is the MNR effect on plant growth C mediated? Is plant C investment on fungal growth related to N needs or N benefit? How is the N for C trade between symbionts regulated? The patternless nature of current knowledge is made evident, and possible reasons for this are discussed.