D. Specificity of association 1. Usually association not of close specificity like with legume-rhizobium. Most hosts can form ectomycorrhiza with a number of different fungi and association may be with more than one species at a time. Relationships between particular conifer genera and certain sections of genus Rhizopogon suggest co-evolution. A. Structure 1.
Name comes from vesicles and arbuscules which are organs of the fungus inside the plant cells.
Relationship between VA fungus and plant root. Arbuscules are thought to be site where nutrient transfer occurs. Plant cell membrane is highly invaginated and weight of cytoplasm may be up to 20x that of uninfected cells. Effect on plant root not as obvious as with ectos. Fungus exists in soil as chlamydospores .