Distribution of photosynthetically fixed carbon within root systems of Eucalyptus pilularis plants ectomycorrhizal with Pisolithus tinctorius.

In intact seedlings of Eucalyptus pilularis Stn. ectomycorrhizal with Pisolithus tinctorius (Pers.) Coker & Couch in growth pouches, and labelled photosynthetically with C more radioactivity was translocated into mycorrhizal than to non-mycorrhizal roots. Results from autoradiography of intact root systems were supported by data from scintillation counting of individual root tips. Greater C accumulation occurred in young than in older mycorrhizas. It is proposed that individual mycorrhizal roots act most strongly as carbon sinks early in their life and that there is a progressive reduction in the amount of photosynthate translocated to them as they age.