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n. pl. mycorrhi·zae (-zē) or mycorrhi·zas
The symbiotic association of the mycelium of a fungus with the roots of a plant, as is found in the majority of vascular plants.

my′cor·rhi′zal adj.


(Greek myco- fungus, rhiza root) an association between a FUNGUS and the roots of a higher plant. In some cases the fungus breaks down PROTEINS or AMINO ACIDS that are soluble and can be absorbed by the higher plant. In most cases, only nitrogen and phosphorus compounds result from fungal activity. Carbohydrates synthesized by the higher plants are absorbed by the fungus, so the relationship is a form of SYMBIOSIS. Some plants which lack chlorophyll, such as the bird's nest orchid, rely on mycorrhizas for carbohydrates in addition to protein.

There are two types of mycorrhiza: ectomycorrhiza and endomycorrhiza. In an ectomycorrhiza the infecting fungus occurs on the surface of the root and possibly between the cells of the root cortex, but does not penetrate such cells. The root becomes covered by a sheath of fungal tissue and looks different from an uninfected root. It is thicker, has no root hairs or root cap and may be a different colour. Ectomycorrhizae are found mainly on trees, such as oak and pine. In an endomycorrhiza the fungus develops within the cells of the root cortex. Subsequently the root cells digest the fungus leaving only knots of fungal material in the cells. There is usually little difference in the morphology of the root and a sheath of fungal tissue is not normally formed.

References in periodicals archive ?
Pine trees cannot survive without ectomycorrhizae, while members of the mustard family are often parasitized by mycorrhizal fungi.
Ectomycorrhizae infect most deciduous plants and shrubs.
Miller OKJr (1983) Ectomycorrhizae in the Agaricales and Gasteromycetes.
Ectomycorrhizae can be grown artificially in the laboratory.
Identification of a far red reflectance response to ectomycorrhizae in slash pine.
Douglas-fir ectomycorrhizae in 40- and 400- year-old stands: mycobiont availability to late successional western hemlock.
Headspace solid-phase microextraction with gas chromatography and mass spectrometry in the investigation of volatile organic compounds in an ectomycorrhizae synthesis system.
Impacts of atmospheric deposition on New Jersey pine barrens forest soils and communities of ectomycorrhizae.
Ectomycorrhizae (Chapter 9)--A type of mycorrhizal association in which the symbiotic fungi forms an extensive mantle around the plant roots.
LePage BA, Currah RS, Stockey RA, Rothwell GW (1997) Fossil ectomycorrhizae from the Middle Eocene.