Quantifying inorganic nitrogen uptake capacity among ectomycorrhizal fungal species using MIFE microelectrode ion flux measurements: theory and applications

Abstract

A growing appreciation of the intimate association between trees and a wide diversity of mycorrhizal fungi in forest ecosystems is leading to the view that trees and their associated mycorrhizal symbionts should be considered meta-organisms or holobionts. For ectomycorrhizal associations, nitrogen (N) mobilization and uptake is a major contribution from the fungal partners. This paper reviews the traditional methods of measuring N uptake by ectomycorrhizae, and describes the application of microelectrode ion flux measurement of nitrogen uptake using the MIFETM technique to ectomycorrhizal fungi associated with forest trees. From results obtained with microelectrode ion flux measurement thus far, we argue that plant N uptake capacity should be considered an exogenous trait, related to the functional diversity among ectomycorrhizal species and communities, rather than a function of host plant root physiology, alone.