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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 vesicular-arbuscular mycorrhizal inoculation at different soil P availabilities on growth and nutrient uptake of in vitro propagated coffee (Coffea arabica L.) plants.
Mycorrhizal spores were extracted with minor modifications with the procedures of [16, 17] as follows: 100 g of soil sample was suspended in 100 ml and left resting for 60 min; soil suspensions were liquefied for 10 s and sequentially sieved through 500 and 53 [micro]m mesh sieves; spores were recovered in tubes with 70% sucrose solution and centrifuged for four min twice and then sieved for 250 and 50 [micro]m mesh sieves.
Plant species often vary dramatically in the rate at which they form mycorrhizal associations, leading to differential success in communities of interacting species (Janos, 1980; Grman, 2012; Bennett et al, 2006).
Inocula of the mycorrhizal fungi Acaulospora longula, Gigaspora albida, Glomus clarum, and Claroideoglomus etunicatum were obtained from the Federal Rural University of Pernambuco (UFRPE).
Arbuscular mycorrhiza (AM) is a symbiotic association formed with arbuscular mycorrhizal fungi (AMF) and 80% of terrestrial plant roots.
In particular, earthworms and arbuscular mycorrhizal fungi (AMF) have a major influence on soil physical properties and nutrient availability (Milleret et al.
Inoculation with arbuscular mycorrhizal fungi (AMF) has been studied in some fruits (FARIAS et al., 2014: RITER NETO et al., 2014; SOARES et al., 2012; NUNES et al., 2013; COELHO et al., 2012; ANZANELLO et al., 2011), including soursop (SAMARAO et al., 2011).
<B Paul Thomas with truffles that have been cultivated in the UK for the first time Mycorrhizal Systems Ltd/Simon