Using perspex observation chambers, the uptake, translocation and distribution of ^ap-labelled
phosphorus was studied in ectomycorrhizal mycelial networks of Suillus bovinus (Fr.) O. Kuntze
interconnecting plants of Pinus contorta Dougl. ex Loud and Pinus sylvestris L. Label was fed
either directly to the cut ends of individual mycelial strands, to plant roots, or to the unsterile
peat in the vicinity of advancing mycelial fans. Where ^^V was fed to individual strands or
mycelial fans it was taken up and translocated through the mycelium, over distances exceedmg
40 cm, to all host plants connected to the mycelial network. Ectomycorrhizal roots acted as major
sinks for phosphate but the label did not move exclusively towards the plant and was distributed
throughout the mycelial system. Calculated translocation rates and flux rates suggest that
transport is primarily by symplastic flow rather than turgor driven bulk flow. The amount of
label accumulated by each plant was signiflcantly related both to the size of the plant shoot and
to the number of mycorrhizal root tips but did not appear to be influenced by the transpiration
rates of individual plants. Phosphorus supplied directly to plant roots did not move to other
plants via the mycelial connections suggesting that movement of phosphorus between the fungus
and host is unidirectional.
Key words: Ectomycorrhiza, mycelial strands, phosphate uptake, Pinus spp., Suillus bovinus.