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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 ?
Better conditions in sandy loam environments could enable pinyons growing there to provide sufficient photosynthate to sustain normal levels of ectomycorrhizae following short-term herbivory.
Ectomycorrhizae are being identified using color, shape, macroscopic (ramification and presence of rhizomorphs) and microscopic (mantle organization and features of cystidia) characters (Agerer, 2002).
Structure of ectomycorrhizae formed by Wilcoxina mikolae var.
Ectomycorrhizae as biological deterrents 3558 to pathogenic root infections.
Due to their such importance in forest trees, scientists have been researching this genus for their role as ectomycorrhizae, their diversity and phylogeny (Kretzer and Bruns, 1997; Wu et al., 2000; Manian et al., 2001; Beatriz et al., 2006; Feng et al., 2008; Sarwar et al., 2011, 2012a, b; Sarwar, 2013; Sarwar and Khalid, 2014; Sarwar et al., 2015).
Riffle, "Commercial vegetative inoculum of Pisolithus tinctorius and inoculation techniques for development of ectomycorrhizae on container-grown tree seedlings," Forest Science, vol.
Ectomycorrhizae are a type of mycorrhizae that procedure a dense sheath around the physical structure of plant roots, from which the hyphae grow; in endomycorrhizae, mycelium is entrenched within the root tissue, not forming a sheath around the root system.
(2013) failed to find the short term effect of N-deposition on root vitality and ectomycorrhizae presence in black spruce (Picea mariana) stands of the boreal forest of Quebec.
Negative effects of scale insect herbivory on the ectomycorrhizae of juvenile pinyon pine.
More than 5000 fungi can form ECM symbionts with over 2000 woody plants [6], showing the importance of ectomycorrhizae in plant-soil interactions.
Detection of summer truffle (Tuber aestivum Vittad.) in ectomycorrhizae and in soil using specific primers.