Signaling in Ectomycorrhizal Symbiosis Establishment

Abstract

This chapter focuses on the mutual relations between metal elements and the population biology, community composition and biodiversity of ectomycorrhizal fungi (ECMF) and on the contribution of ECMF to metal transfers in food webs. The ectomycorrhizal (ECM) association of trees and fungi is successful in recycling scarce essential metal elements and in colonizing soils with high levels of metal toxicity. Uptake and translocation of metal elements by ECMF may account for major deviations from simple models of soil metal budgets. Accumulation of certain essential and non-essential metals and metalloids (e.g. K, Rb, Cs, As, Se, Zn, Cd, Hg, Ag) is common in ECMF, while other elements tend to be excluded (e.g. Al, Pb). Bioconcentration factors (BCFs) are species, strain and metal specific. A negative correlation between environmental metal concentrations and BCFs appears to be the rule. The role of ECMF as a nutrient source of rare elements (e.g. Se) and as an important gateway of toxic metals to vertebrate foodwebs in polluted areas merits further study. ECM communities in metalliferous soils can be surprisingly diverse. The potential to colonize metalliferous soils is widespread in various phylogenetic groups of ECMF. The microevolution of metal tolerance does not require populational differentiation.