This work was undertaken at the State University of North Fluminense (UENF), State of Rio de Janeiro, Brazil, under greenhouse conditions, in the first semester of 1996, to evaluate the role of arbuscular mycorrhizal fungi (AMF) in the process of nitrogen transfer from bean to maize plants using the isotope 15N. Special pots divided in three sections (A, B and C), were constructed and either no barrier and a nylon mesh screen (40 ∝m) (which allowed the AMF hyphae to pass but not the plant roots) or 1 ∝m (which acted as barrier to AM hyphae and plant roots) was inserted between the sections B and C. It was added 25 mg kg-1 of N only into the section A, using as source (15NH4)2SO4. Two bean plants pre-germinated and inoculated with Rhizobium tropici were planted with their root systems divided between the sections A and B. Ten days later, 2 seeds of maize were sown into the section C and the inoculation was made by adding inoculum (Glomus etunicatum) into the substrate. Thirty-five days after the transplanting of the legume plants the experiment was harvested and the results revealed that the mycorrhizal colonization was satisfactory in maize and bean plants. The inoculation with AMF increased the dry weight and the 15N and P content of maize plant shoots. The direct transfer of 15N via AM hyphae was 16.6%; the indirect transfer of 15N mediated by AM mycelium network, was 34.1%, and the indirect transfer not mediated by AM mycelium network was 49.3%..
mycorrhizae; bean; maize; nitrogen