Ecto outside; myco fungus; rhizo root.

Ectomycorrhizal fungi are symbionts found on the roots of host plants. They often manifest themselves as mushrooms (as those shown on the left associated with a eucalypt) or truffles around the base of host plants. Photo credit: CSIRO Division of Forestry & Forest Products, Perth, W. Australia.

Ectomycorrhizal fungi form a mantle to the exterior of the roots of host plants as shown in this picture. The white fine, defuse area surrounding the more defined central core (the root) is the fungal network (mycelium) of the mantle. The structure comprising fungus and root is called an ectomycorrhiza and these are characteristically short, thickened, club roots with bifocations. Thus associated, ectomycorrhizal fungi increase the availability of soil nutrients to their host through an increased surface area for uptake. In exchange, the fungus receives energy from their host in the form of plant sugars.