Ectomyeorrhiza formation in Eucalyptus

SUMMARY The structure of mature tubercles collected from a Eucalyptus pilularis forest in Queensland, Australia, is described. The smooth, pale yellow tubercles (5‐20 mm diam.) consisted of a rind (200‐250 μm thick) enclosing a dense coralloid mass of ectornycorrhizas (150‐300 μm diam.) and rhizomorphs (200‐300 μm diam.). The outer rind region was cemented together with an interhyphal matrix of carbohydrate containing embedded lipid deposits. Dolipores were common in the inner rind indicating the fungal component to be a basidiomycete. Mycorrhizas had thin mantles and well‐formed Hartig nets. Protein and lipid reserves were present in mantle hyphae. Rhizomorphs formed around non‐mycorrhizal roots inside the tubercles. The central zone of rhizomorph tissue contained thick‐walled hyphae which stained positively for lignin‐like material. The tubercles are similar to structures formed in associations between Rhizopogon and conifers in the northern hemisphere.