Root morphology acclimation to phosphorus supply by six cultivars of Trifolium subterraneum L

Aims: Trifolium subterraneum L. is the predominant annual pasture legume in southern Australia. Cultivars with improved phosphorus (P) foraging ability would improve the P-use efficiency of agricultural systems. We therefore investigated variation in root traits related to Puptake among six cultivars. Methods: Micro-swards were grown at six levels of P in field soil with indigenous arbuscular mycorrhizal (AM) fimgi for six weeks. Dry matter yield, tissue P concentration, rhizosphere carboxylates, AM fungal colonisation and root morphological traits were measured. Results: The cultivars showed similar shoot and root yield responses to P supply. Average root diameter did not change, specific root length (SRL) increased and root tissue density (RTD) decreased with increased P supply. Amounts of total rhizosphere carboxylates were low (