Progress on material exchange between arbuscular mycorrhizal(AM) fungi and host plant: A review

Arbuscular mycorrhizal (AM) fungi can form symbiosis with 80% of terrestrial plant species. The exchange between mineral nutrients of AM fungi and carbohydrate of host plant is important for material cycle in whole ecosystem. Nowadays, there are many studies on the AM fungi promoting host plant mineral nutrient absorption. The AM fungi can enhance availability of mineral nutrients by small diameter of extraradical hyphae, activate soil nutrients by releasing organic acids and soil enzymes, ensure the efficiency of soil nutrition transport into extraradical hyphae by the lower value of Km nutrient transporter on extraradical hyphae, ensure the rate of nutrition transport in intraradical hyphae by converting nutrients ions to suitable forms, and promote the efficiency of the nutrition transport into host plant by inducing symbiotic plant nutrients transporters. However, the progress of plant feedback carbohydrate to fungi is few. As the important role of AM symbiosis in whole ecosystem, researches about the locations (arbuscule, intraradical hyphae and extraradical hyphae), the forms (ionic forms, polymer, amino acid, sucrose and monosaccharide) and the process (active transport) of the mineral nutrients and carbohydrate exchange are significant. This review summarizes the characteristics of membrane system of arbuscule and intraradical hyphae, the forms of nitrogen (N), phosphate (P) and carbohydrate within the exchange, and the process of exchange which relates to transmembrane, energy expenditure and N or P coupling with carbohydrate. Finally, the prospect of AM fungi and host plant materials exchanges is proposed.