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

Summary

This study examined how a special orchid called Gastrodia pubilabiata obtains nutrients from fungi by comparing the chemical signatures of fungal cells found inside the orchid’s roots with those of mushroom fruiting bodies. The researchers found that the fungal cells inside the roots had nearly identical chemical signatures to the mushroom fruiting bodies, confirming that scientists can accurately study this relationship by analyzing extracted fungal cells. This finding helps validate a scientific method that has been increasingly used to understand how orchids feed on fungi without performing photosynthesis.

Background

Mycoheterotrophic plants acquire carbon from fungi through a symbiotic relationship. Recent studies use stable isotope analysis of fungal pelotons extracted from orchid roots, but concerns exist about whether extracted pelotons reliably reflect fungal isotope signatures, particularly regarding 15N depletion during extraction.

Objective

To test whether peloton tissues reliably reflect fungal isotope signatures by comparing δ13C and δ15N values between pelotons extracted from Gastrodia pubilabiata roots and fruiting bodies of its fungal partner Cyanotrama gypsea, a unique system where roots occur in direct contact with fruiting bodies.

Results

δ13C values were nearly identical between pelotons and fruiting bodies, while δ15N values were slightly higher in pelotons. The orchid showed expected trophic-level enrichment relative to fungal sources, with 13C and 15N patterns consistent with predator-prey-like nutrient transfer. Metabarcoding confirmed C. gypsea accounted for 99.98% of fungal reads.

Conclusion

Peloton-derived isotopic data reliably reflect fungal source signatures, supporting the validity of peloton-based isotope approaches in mycoheterotrophic studies. The findings suggest that large 15N enrichment differences in some orchids result from physiological specialization rather than methodological artifacts during extraction.
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