Ectendomycorrhizas

Mycorrhizas can be broadly classified into three groups, viz. ecto-, ectendo- and endo-mycorrhizas. Within the ectendomycorrhizas are the arbutoid and monotropoid mycorrhizas and the ectendomycorrhizas of trees.

Ectendomycorrhizas caused by E-strain fungi are often found in the early seedling stages of species of Pinus and other conifers. The sheath is very thin, almost absent in some cases. A well developed Hartig net is found just behind the meristematic region. Further back, the cells are penetrated by the fungus and almost filled by coiled hyphae surrounded by host plasmalemma. In the sapling or adult stage of tree growth they are usually replaced by ectomycorrhizas but, according to Harley and Harley (1987), ectoendomycorrhizas have been found in adult trees. Similar mycorrhizas have been reported from some angiosperms (Harley and Harley, 1987). A few experiments (Harley and Smith, 1983) have shown improved growth, presumably with enhanced mineral nutrition, of the plant host.

References

• Harley, J.L. and Harley, E.L. (1987) A check-list of mycorrhiza in the British flora. New Phytol. (Suppl.) 105:1-102.
• Harley, J.L and Smith, S.E. (1983) Mycorrhizal Symbiosis. Academic Press, London, U.K..