Plant δ15N associated with arbuscular mycorrhization, drought and nitrogen deficiency

Abstract

It has long been evident that plant 15N chiefly reflects the processes which fractionate 15N/14N rather than the 15N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant 15N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with 15N-depleted foliar 15N, commonly as low as −12‰. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant 15N by as much as 3.5‰. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar 15N found in field situations and do so by 15N enrichment rather than depletion.Scottish Crop Research Institute is grant-aided by the Scottish Officeof Agriculture, Environment and Fisheries Department.Peer reviewe