Ectomycorrhiza Formation in Eucalyptus

Summary Ultrastmcture of Eucalyptus ectomycorrhizas initiated by compatible, host‐specific fungi and by broad‐host range fungi was compared with that of roots inoculated with incompatible, conifer‐specific ectomycorrhizal fungi. The results indicate little difference in morphology between ectomycorrhizas formed by compatible, host‐specific fungi and those formed by broad‐host‐range fungi. However, interaction between eucalypt roots and incompatible fungus species known to be conifer‐specific induced either deposition of tannins in root tissue or, in the case of the Pseudotsuga‐speciiic Suillus lakei, a characteristic hypersensitive reaction which resulted in lysis of hyphae and of epidermal and outer cortical cells of roots.