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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.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


(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.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Martin, "Identification of symbiosis-regulated genes in Eucalyptus globulus--Pisolithus tinctorius ectomycorrhiza by differential hybridization of arrayed cDNAs," The Plant Journal, vol.
Singer R, Araujo I (1979) Litter decomposition and ectomycorrhiza in Amazonian forest.
In the "Colour Atlas of Ectomycorrhiza" by Agerer (1987-2012) most morphotypes documented are from coniferous trees.
patula seedlings effectively induces the establishment of ectomycorrhizas features in the roots in comparison with the spontaneous and natural colonization from native propagules [2, 7, 10].
In temperate forests, ectomycorrhiza (ECM) serve as a major organ for controlling nutrient uptake by trees, and it was estimated that up to 95% of the short roots in these trees contain ECM (Smith and Read 1997).
The upper layer of these woody savannahs is dominated by species that share the formation of ectomycorrhiza: species of the genera Brachystegia and Julbernardia (both Leguminosae) in the African miombo, dipterocarps in Indochina, and eucalyptus in Australia.
Hogberg P, Johannisson C, Yarwood S, Callesen I, Nasholm T, Myrold DD, Hogberg MN (2011) Recovery of ectomycorrhiza after 'nitrogen saturation' of a conifer forest.
Ectomycorrhiza is a mutualistic symbiotic relationship between the roots of higher plants and fungi.
On morphoanatomical basis, mycorrhizas are categorised into three different groups, namely ectomycorrhiza, endomycorrhiza and ectendomycorrhiza.
One of the major types of mycorrhiza, the ectomycorrhiza, involves an estimated 5000 species of fungi in the subphyla Ascomycotina and Basidiomycotina (Kendrick 1992, Molina et al.
This is the first detailed report on molecular identification of aboveground fruiting body as well as its ectomycorrhiza, Lactarius species, associated with wide host range.