Phosphate transport by hyphae of field communities of arbuscular mycorrhizal fungi at two levels of P fertilization

This study was conducted to elucidate the effect of P fertilisation on the function of field communities of arbuscular mycorrhizal fungi (AMF) measure d as P transport to flax. Two methods were applied to soil from a long-term field experiment with NaHCO3-extractable soil P levels of 24 and 50 mg kg( -1) in an experiment under controlled conditions: i) Measurement of plant g rowth and P uptake in the presence or absence of the fungicide benomyl and ii) measurement of hyphal P transport from a root-free compartment labelled with P-32. Benomyl successfully prevented mycorrhizal function. The absolu te contribution of AMF to plant P uptake was of the same magnitude with or without P fertilisation at 27 days after sowing. Therefore, even though pla nts grown at the higher soil P level had greater P uptake, the relative con tribution of AMF to P uptake was greater at the lower P level than at the h igher P level (77 and 49% of total P uptake, respectively). The AMF in P-fe rtilized soil transported less P-32 from the root-free compartment to the p lant after 23 days than the AMF in unfertilized soil, but this difference d isappeared in plants harvested after 27 and 32 days. The production of hyph ae was largely similar in both fertilization treatments, indicating that th e capacity for P uptake and transport by hyphae of the two AMF communities was similar.