The magnitude and control of carbon transfer between plants linked by a common mycorrhizal network

Various claims have been made about the ecological significance of plant-to-plant carbon movement through common mycorrhizal networks (CMNs). Most suggest that resource competition among interconnected plants should be less important than previously thought. If true, that would profoundly alter our...

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Bibliographic Details
Published in:	Journal of experimental botany 1999-01, Vol.50 (330), p.9-13
Main Authors:	Robinson, David, Fitter, Alastair
Format:	Article
Language:	eng
Subjects:	Agronomy. Soil science and plant productions Animal and plant ecology Animal, plant and microbial ecology Arbuscular mycorrhiza Biological and medical sciences Carbon common mycorrhizal network Economic plant physiology Ecophysiology ectomycorrhiza Fundamental and applied biological sciences. Psychology Fungi Hyphae Parasitism and symbiosis Perspectives on Stabilizing Processes in Mixed Plant Communities Plant communities Plant physiology and development Plant roots Plants Radiocarbon Soil ecology Symbiosis Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...) Synecology Terrestrial ecosystems
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Summary:	Various claims have been made about the ecological significance of plant-to-plant carbon movement through common mycorrhizal networks (CMNs). Most suggest that resource competition among interconnected plants should be less important than previously thought. If true, that would profoundly alter our perception of how plants interact among themselves and with their environment. However, there are difficulties in quantifying the amounts of resource transferred via CMNs, ensuring that transfer is genuinely through hyphae, not soil, and understanding its control. Carbon movement has not been quantified in many of the published studies. Where it has, its likely functional role has not been clarified. Some recent, well-publicized research suggests that carbon transferred to trees via an ectomycorrhizal (EcM) network may be physiologically and ecologically important. Our view, however, is that the evidence for this remains equivocal. Appropriate controls for the possibility of carbon transfer via soil were not used under field conditions. In laboratory experiments, controls failed to clarify the role of EcM links in carbon transfer. To resolve some areas of uncertainty, abundances of 13C have been measured to estimate carbon transfers via an arbuscular mycorrhizal (AM) network connecting grasses and forbs of the same or different species. Permeable barriers to roots and hyphae allowed any direct carbon transfer via soil to be detected. Large amounts of carbon (typically 10% of that in roots) were transferred between linked plants via the CMN. Transferred carbon was never transported into shoots of ‘receiver’ plants. It remained in roots, probably inside fungal structures and, therefore, unavailable to the plants into which it was apparently transferred. Carbon transfer via an AM network does not allow ‘resource sharing’ among linked plants. It is probably irrelevant to the botanical components of a community, but it may be fundamental for fungal members. The ‘mycocentric’ view is that fungal structures within roots are parts of extended mycelia through which fungi move carbon according to their own carbon demands, not those of their autotrophic hosts.
ISSN:	0022-0957 1460-2431