Efficiency of vam hyphae in utilisation of organic phosphorus by wheat plants

Abstract

In a pot experiment wheat (Triticum aestivum L.) was grown under axenic conditions in two soils differing in organic matter and phosphorus contents. The pots were separated by 30.urn nylon nets and a 0.45.urn membrane into five compartments, a central one for root growth, two adjacent to the central compartment for hyphal growth and two outer ones for control. The treatments consisted of sterilized soil, supply of organic (Na-phytate) or inorganic phosphorus (P) and of soil either non-inoculated or inoculated with Glomus mosseae. Shoot dry weight increased by mycorrhizal inoculation in the range between 2.2 and 4.5 g pot−1depending on the soil and treatment. Organic P was depleted by V A-mycorrhizal hyphae throughout the hyphal compartment (15 mm). The maximum depletion was 106 mg kg−1soil within a 0.5 mm distance from the root surface. The depletion of organic P depended on the soil type, hyphal length density, phosphatase activities and the amount of organic P present in the system. The maximum hyphal contribution to the hydrolysis of organic P was concentrated in the zone within 3 mm from the root surface. In the mycorrhizal treatment, shoot concentrations of P, Cu, and Zn increased. In general, a slight decrease in the Mn and Fe concentrations was noticed. A significant increase in the concentration of K in the mycorrhizal plants was observed only in the presence of organic P. Calcium and Mg concentrations were not affected by mycorrhizal inoculation. The results obtained clearly demonstrated that V A-mycorrhizal phosphatase is effective in the hydrolysis of Na-phytate and confirmed the important direct contribution of VAM hyphae to plant P, Cu, and Zn nutrition. © Taylor & Francis Group, LLC.