The uptake and translocation of phosphate by mycelial strands of pine mycorrhizas

Abstract

Uptake and rapid translocation of 32P-orthophosphate to Pinus radiata mycorrhizas from soil by mycelial strands of Rhizopogon luteolus was demonstrated. In greenhouse material, translocation occurred from soil for at least 12 mm and some 30–80 per cent of phosphate absorbed from 5 × 10 −6 M as KH 2PO 4 was translocated. In the field, translocation occurred for 12 cm. Uptake by excised mycelial strands was metabolically mediated. Translocation occurred more rapidly when the untreated ends of strands were placed in an osmoticum: polarity in translocation was also observed. It was concluded that uptake and translocation by mycelial strands (as distinct from individual hyphae) provide an effective method for mycorrhizal exploitation of large inter-root soil volumes and assist the plants in competition for nutrients. Large differences occurred between strains of the same species in mycelial strand growth in soil. Mycelial strands of R. luteolus grew through the test soil at 1.3-2.9 mm/day and along P. radiata roots at 1.7 mm/day at 25°C day and 16°C night temperatures.