The structure and function of the vegetative mycelium of ectomycorrhizal plants .3. Ultrastructural and autoradiographic analysis of inter-plant carbon distribution through intact mycelial systems

Plants of Pinus sylvestris L. were grown in mycorrhizal association with Suillus bovinus (Fr.) O. Kuntze in
observation chambers until an interconnecting mycelial network had developed between the seedlings. The shoot
of an individual seedling was then sealed in a perspex cuvette and exposed to 14CO2. After incubation for 48 h, the
'donor' shoot was removed and components of the mycelial network and mycorrhizal roots of connected and
unconnected 'receiver' seedlings were harvested, fixed, embedded and sectioned prior to being autoradiographed
and examined by transmission electron microscopy. The patterns of distribution of 14C-labelled material within
the mycelial strands, the sheath and root tissues was examined. The results are discussed in relation to carbon
metabolism of the fungus and of the interconnected host plant.