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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 ?
Survival in the soil of the ectomycorrhizal fungus Laccaria bicolor and the effects of a mycorrhiza helper Pseudomonas fluorescens.
TABLE 1: Height, shoot dry mass (SDM), percentage of root colonization (PRC) and ratio of height/stem diameter (H/D) of Eucalyptus saligna grown in copper concentrations, and with and without inoculation of ectomycorrhizal fungus Pisolithus microcarpus.
Muller et al., "The ectomycorrhizal fungus Scleroderma bermudense alleviates salt stress in seagrape (Coccoloba uvifera L.) seedlings," Mycorrhiza, vol.
Key words: Lyophyllum shimeji; Ectomycorrhizal fungus; Commercial cultivation; Bottle culture; Liquid spawn
The monokaryotic strain the ectomycorrhizal fungus Hebeloma cylindrosporum (h1) was obtained from single spore germination [13].
Bonello P, Bruns TD, Gardes M (1998) Genetic structure of a natural population of the ectomycorrhizal fungus Suillus pungens.
For example, based upon RFLP analysis, we observed that 42% of the root tips at one site, Sunset Crater, were colonized by a single type of ectomycorrhizal fungus. Similarly, using morphological techniques, Natarajan et al.
Effects of Ectomycorrhizal Fungus Astraeus Odoratus onDipterocarpus Alatus Seedlings.
Bending and Read (1995) were able to show mobilization of N from patches of organic material from the fermentation horizon of a pine forest soil by mycelia of the ectomycorrhizal fungus Suillus bovinus.
According to P accumulation, mycorrhizal plants associated with the ectomycorrhizal fungus H.