ScienceDaily (Aug. 22, 2009) — Three Thai orchids have been found to rely on a wide range of fungi to help them take carbon out of the soil instead of producing their own organic carbon. A detailed study of the relationship, published in the open access journal BMC Biology, also features stunning pictures of the plants.

Marc-André Selosse and Mélanie Roy, from the Centre d'Ecologie Fonctionnelle et Evolutive, Montpellier, France, studied Aphyllorchis montana, A. caudata and Cephalanthera exigua orchids with Suyanee Vessabutr and Santi Watthana from the Queen Sirikit Botanic Garden, Thailand. These orchids have no chlorophyll and rely on fungi colonizing their roots for their carbon supply.

The plants, which grow on the ground in mountain forests, were collected from 10 different sampling sites in diverse parts of Thailand. The two Aphyllorchis orchids studied were found to associate with a wide range of fungi, while the Cephalanthera was much more specific.

Selosse said: "We show for the first time that certain tropical orchids associate with highly diverse soil fungi colonizing their roots; using stable isotopes, we show that they are likely to use these fungi as a carbon source." Most importantly for conservation concerns, all these fungi associate in turn with the roots of nearby green trees, where they collect carbon for the orchids.

Speaking about the results of the study, Selosse said: "Plants really interact with fungi in an unexpectedly diverse way - the impression one gains is that there is a great need for more research on biological interactions in the tropics to unravel this diversity."

Story Source:

Adapted from materials provided by BioMed Central, via EurekAlert!, a service of AAAS.

Journal Reference:

1. Mélanie Roy, Santi Watthana, Anna Stier, Franck Richard, Suyanee Vessabutr and Marc-André Selosse. Two mycoheterotrophic orchids from Thailand tropical dipterocarpacean forests associate with a broad diversity of ectomycorrhizal fungi. BMC Biology, 2009; (in press) [link]

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This is an Aphyllorchis montana orchid. (Credit: Roy et al., BMC Biology)

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