Growth and phosphorus nutrition of a Paris-type arbuscular mycorrhizal symbiosis

Paris-type arbuscular mycorrhizas (AM) are reportedly the most common morphological type of AM; however, most research has focused on the Arum-type. Asphodelus fistulosus , a common weed in southern Australia, forms Paris-type AM when colonised by Glomus coronatum . It is often found in sites with low nutrient levels, and may therefore be dependent on its AM associations for growth and phosphorus (P) nutrition. A. fistulosus was inoculated with G. coronatum and grown in pots containing a soil/sand mixture with P added to give five soil P concentrations. The plants were grown in a glasshouse and harvested 6 and 9 wk after planting, at which times growth, P nutrition and colonisation were measured. At low soil P, A. fistulosus showed very marked positive responses to colonisation both in P uptake and growth; both responses decreased with increasing P supply. Colonisation was not greatly reduced by increasing P supply. This study appears to be one of the first detailed investigations of P responses in a Paris-type AM, providing insight into what is reportedly the more common but less well studied morphological type of AM.