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Integrated peloton and fruiting body isotope data shed light on mycoheterotrophic interactions in Gastrodia pubilabiata (Orchidaceae)

Summary

Some orchids don’t photosynthesize and instead get their nutrients directly from fungi they associate with. This study examined an unusual orchid species whose roots grow in direct contact with mushroom fruiting bodies. By analyzing the chemical signatures of different parts of this system, researchers confirmed that examining fungal threads extracted from orchid roots accurately reflects the fungal partner’s composition, validating a method that helps scientists study these fascinating plant-fungus partnerships when mushrooms cannot be easily found.

Background

Mycoheterotrophic orchids acquire carbon from fungal partners through mycorrhizal associations. Recent stable isotope analyses of fungal pelotons isolated from orchid roots have advanced understanding of this nutritional strategy, but concerns persist regarding potential isotopic biases, particularly 15N depletion during extraction.

Objective

This study tested whether peloton tissues reliably reflect fungal isotope signatures by comparing δ13C and δ15N values between pelotons and fruiting bodies from the same fungal individual. The unique system studied involved Gastrodia pubilabiata orchid roots in direct contact with fruiting bodies of their fungal partner Cyanotrama gypsea.

Results

δ13C values were nearly identical between pelotons and fruiting bodies, while δ15N values were slightly higher in pelotons. The 13C and 15N enrichment observed in the orchid relative to fungal fractions was consistent with expected trophic-level fractionation, supporting a predator-prey-like mode of nutrient transfer.

Conclusion

The findings validate the reliability of peloton-based stable isotope analysis as a method to represent fungal isotopic signatures. The study supports broader use of extracted pelotons in mycoheterotrophic studies when fruiting bodies are unavailable, and suggests that observed 15N enrichment differences between plants and pelotons likely reflect physiological specialization rather than methodological artifacts.
  • Published in:Mycorrhiza,
  • Study Type:Field Study with Experimental Analysis,
  • Source: 10.1007/s00572-025-01213-8; PMID: 40498228
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