Biochemical changes and zinc fractions in arbuscular mycorrhizal fungus (Glomus intraradices) inoculated and uninoculated soils under differential zinc fertilization

Greenhouse experiment was conducted to assess the biochemical changes and zinc fractionation pattern in soils of arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) inoculated (+Myc) and uninoculated (-Myc) maize plants fertilized with varying levels of Zn (0, 1.25, 2.5,3.75 and 5.0 mg kg(-1)). Soil samples collected at 45 and 75 days after sowing (DAS) were analyzed for biomass carbon, soil enzymes and glomalin besides Zn fractions and available Zn and P contents. AM fungus inoculated (+Myc) soil had significantly (P <= 0.01) higher organic C and biomass C than -Myc soil but the response was more pronounced at 75 DAS fororganic C and at 45 DAS for biomass carbon. As a result, higher dehydrogenase and phosphatase activities were detected in +Myc soil consistently. Mycorrhizal symbiosis increased the glomalin protein concentration of inoculated (+Myc) soil by 40% in comparison to -Myc soil. Zinc fractionation studies revealed that more than 50% of total Zn was measured in residual fraction. AM symbiosis increased the organically bound Zn while reduce crystalline oxide and residual Zn fractions indicating enhancement in plant available Zn by slow transformation of unavailable forms into available forms. The data suggest that mycorrhizal inoculation orchestrates biochemical changes and Zn release pattern in soils, which may facilitate increased availability of Zn even under deficient conditions. (C) 2009 Elsevier B.V. All rights reserved.