THE ROLE OF ROOT EXUDATES IN ARBUSCULAR MYCORRHIZA INITIATION

摘要: The rhizosphere is a complex environment, the home to numerous microorganisms and ecosystems, site of many chemical physical reactions, substrate that supports terrestrial plants via anchorage roots. Plant roots continually elongate through this heterogeneous area, absorbing water minerals vital for sustaining plant growth development, exuding various sub stances into (Fig. 1). root exudate constituents include actively secreted polysaccharides form layer mucilage around root, enzymes such as acid phosphatases; volatile compounds including ethylene CO2; low molecular weight metabolites sugars, organic acids, amino acids phytosiderophores, phenolics; cells sloughed off cap, dead cell lysates (Marschner, 1995; Rovira, 1969). vary between different plants, composition changes in same at ages or when grown under environmental conditions (Hale et al., 1971; Marschner, Exudation levels particular are not always along axis, generally greater apical regions exudates alter by changing pH mineral availability desorption chelation, also influence interactions populate One important inhabitants fungi from order Glomales, which arbuscular mycorrhizae. Arbuscular mycorrhizal (AM) estimated colonize than 80% land species (Bonfante Perotto, 1995) apparently responsive wide diversity exuded (Rovira, AM symbiosis enhances uptake plant, particularly phosphorus (P), confers other benefits health, increased additional minerals, drought tolerance, resistance pathogens (Newsham