ABSTRACT
Numerous scientific publications on the benefits of arbuscular mycorrhizal (AM) symbioses to plant growth and productivity were published during the past few decades (Harley and Smith, 1983; Howeler, 1985; Siqueira and Franco, 1988; Gianinazzi-Pearson and Gianinazzi, 1989; Marschner and Dell, 1994; George, 2000). The vast majority of the experiments reported were conducted under con trolled or greenhouse conditions and perhaps without a system per spective. These experiments failed to clarify the mechanisms regulat ing the AM symbiosis, which could hardly be used to increase agricultural plant productivity.
