Mycorrhizas Among Plant Species

Figure. 1 - Abundance of various types of mycorrhizas among plant species, literature review from 128 publications (Brundrett, 2009) includes ca 8000 plant species, AM – arbuscular mycorrhiza, EcM – ectomycorrhiza, NM – nonmycorrhizal, Ericoid – ErM, Orchid – OrM.

Arbuscular mycorrhiza

The most common and abundant mycorrhiza is AM which belongs into the endomycorrhizas and inter alia associates with approximately 74% of all Angiosperm plant species, number of Gymnosperm species and some Cryptogamic species (Brundrett, 2009). AM is formed only by one obligatory mycorrhizal fungal clade called Glomeromycota. AMf and are generalists and they form mycorrhizal symbiosis with various plants species. Glomeromycota are vitally dependent on their autotrophic hosts since the early time of plant evolution. Some authors enforce a theory, that mycorrhizal fungi allowed the plants to leave the water environment and colonize the land (Selosse & Le Tacon, 1998).

The colonization of plant root cells by AM fungi starts with an attraction by strigolactone molecules released by the plant roots (Besserer et al., 2006) and afterwards continues with a cascade of signals which are induced by the fungal hyphae and gradually leads to penetration of the cortical plant cell walls (Oldroyd et al., 2005). The plants recognize the AMf as a mutualist organism and allows them to enter into its living cells. The plasmatic membrane of penetrated root cells remains untouched and covers the whole surface of fungal hyphae which gradually forms a typical tree like structure called arbuscule. The branched structure of arbuscule builds a highly multiplied surface between the fungal and plant phospolipid membranes, which gives formation of space called interfacial matrix ...

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...resentatives form mutualistic symbiosis with EcMf, AMf and Actinobacteria (Benson & Clawson, 2000). A different example is EcM Quercus ilex from the Fagaceae family in whose roots ErMf can be also found but they do not form ErM (Bergero et al., 2000).

The typical anatomical characteristic of EcM is the fungal intercellular structure called Hartig net, hyphal sheet covering the outer surface of the host plant roots and emanating mycelial hyphae which are able to create more complex structures called rhizomorphs (Peterson et al., 2004). The mycelial hyphae and rhizomorphs greatly increase the surface and radius of the whole root and mycorrhizal system and enables to reach further (Anderson & Cairney, 2007) and acquire more nutrients from the soil. Nutrients provided from the EcM fungi for its host plants are as mentioned P and mainly N, aminoacids, enzymes, water etc.