Novel in-growth core system enables functional studies of grassland mycorrhizal mycelial networks

A novel in-growth core system, enabling functional studies of natural commu nities of arbuscular mycorrhizal (AM) mycelia in soil is described and test ed. The cores have windows covered with nylon mesh of 35 mum pore size that pre vent in-growth of roots but permit penetration of AM hyphae. They were inse rted into grassland turf and contained either sterilized sand and a 'bait' seedling of Trifolium repens or nonsterile natural soil without bait plants . The impacts of hyphal severance, achieved by periodic rotation of some of the cores, upon AM colonization of bait plants (experiment 1) and transfer of P-33 from soil to plants outside the cores (experiment 2) were examined . Severance of AM hyphae reduced both AM colonization of bait plants and thei r shoot P concentrations. The shoot P-33 concentrations of plants with myce lial access to (PO4)-P-33-labelled cores were 10-fold greater than those wh ich had no mycelial access. It is concluded that this novel approach enables the functioning of mycorrh izal mycelial networks to be evaluated under conditions closely simulating those occurring in nature. (C) New Phytologist (2001).