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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 ?
Effects of arbuscular mycorrhizal fungus and humic acid on the seedling development and nutrient content of pepper grown under saline soil conditions.
To date, 75 mycorrhizal fungus strains have been recovered from Platanthera leucophaea protocorms, seedlings and mature plants spanning nine populations in Illinois (Fig.
However, in the present work, it was unclear whether the mycorrhizal fungus induced the expression of the H+-ATPase gene under the salt-treated conditions.
Contribution of arbuscular mycorrhizal fungus to red kidney and wheat plants tolerance grown in heavy metal-polluted soil.
versiforme is the best effective mycorrhizal fungus in alleviating salt stress of trifoliate orange and G.
The present work tried to determine the effects of the three polyamine (PA) species (100 mg L-1), putrescine (Put), spermidine (Spd) and spermine (Spm), on root colox`nization, root morphology and phosphorus (P) uptake of three- month-old citrus (Citrus tangerine) seedlings inoculated with arbuscular mycorrhizal fungus (AMF), Glomus mosseae.
A New Record of Arbuscular Mycorrhizal Fungus in China.
Bacterial associations with the mycorrhizosphere and hyphosphere of the arbuscular mycorrhizal fungus Glomus mosseae.
To incorporate mycorrhizal technology in nursery conditions, the mycorrhizal associations are three way interactions between plants, fungi and growing media (Brundrett et al., 1996), since the effectiveness of a particular mycorrhizal fungus varies with the plant and the growing conditions (Corkidi et al., 2004).
Some studies have reported increased benefits for plants species, like angico plants, inoculated with more than one species of mycorrhizal fungus, with the plants exhibiting increased growth when inoculated with both Glomus etunicatum and Gigaspora albida (Sugai et al., 2011).