Influence of arbuscular mycorrhizal fungi, inoculum level and phosphorus placement on growth and phosphorus uptake of Phyllanthus calycinus under jarrah forest soil

Phosphorus uptake and biomass production may vary between arbuscular mycorrhizas (AM) species of contrasting life cycles and their modes of interaction with host plants. This research investigated differences among three AM fungi from different genera isolated from the jarrah forest with respect to their colonisation, biomass production and P uptake over time. The understorey plant Phyllanthus calycinus, has been shown to be extensively mycorrhizal. We examined differences in the capacity of fungi associated with this plant to access a P point source from increasing distances from the root. The methodology simulated “pockets” of P in forest soil. Phosphorus sources in root-exclusion mesh bags were inserted 2, 4 and 6 cm from plant roots restrained in separate mesh bags. Acaulospora laevis colonised plants to the greatest extent, producing higher plant biomass and P uptake compared to the other two fungi. Plant biomass and P uptake were enhanced where P sources were closest to the root, as expected, but there were differences among fungi in response to level of inoculum used for each fungus. The capacity of individual AM fungi to access a point source of P at different distances varied in a highly mycorrhizal native forest understorey plant in parallel with plant growth and P uptake.