Orchidaceous Mycorrhizal Fungi

Abstract

The underground world harbors one of the most common symbiotic associations between plant root and fungus called ‘mycorrhiza’ (Smith and Read 1995; Vanna 1998, 1999) which is the beneficial association between soil-borne fungus and the roots of about as many as ninety percent of terrestrial plants. Trappe (1996) defined mycorrhizas as ‘dual organs of absorption formed when symbiotic fungi inhabit healthy organs of most terrestrial plants’. More than 6000 fungal species are capable of establishing mycorrhizas with about 240,000 plant species, but relatively few anatomical types of plant-fungus interactions result from such impressive biodiversity (Bonfante and Perotto 1995; Vanna 1995; 1998). Mycorrhizae are classified on the basis of extent of root penetration, production of external mantle or sheath and the inter-and intracellular structures they form once inside the plant root (Read, 1999) (Fig. 1).