INTRASPECIFIC TRANSFER OF CARBON BETWEEN PLANTS LINKED BY A COMMON MYCORRHIZAL NETWORK

To quantify the involvement of arbuscular mycorrhiza (AM) fungi in the intraspecific transport of carbon (C) between plants we fumigated est ablished Festuca ovina turf for one week with air containing depleted C-13. This labelled current assimilate in a section of mycorrhizal or non-mycorrhizal turf. Changes in the C-13/12 ratio of adjacent, unfumi gated plants, therefore, allowed the movement of C between labelled an d unlabelled plants to be estimated. In mycorrhizal turves, 41% of the C exported to the roots from the leaves was transported to neighbouri ng plants. The most likely explanation of this is was the transport of C via a common hyphal network connecting the roots of different plant s. No inter-plant transport of C was detected in non-mycorrhizal turve s. There was no evidence that the C left fungal structures and entered the roots of receiver plants. Mycorrhizal colonisation increased carb on transport from leaves to root from 10% of fixed carbon when non-myc orrhizal to 36% in mycorrhizal turves. These results suggest that AM f ungi impose a significantly greater C drain on host plants than was pr eviously thought.