Annals of Botany

An orchid with a partially mycoheterotrophic taste for truffles

Partially mycoheterotrophic nutrition is a widespread trophic strategy in green-leaved Orchidaceae species in forest habitats. Owing to the light limitation of their habitats, many forest orchids meet carbon demands though autotrophy, and by tapping into the nutritional reserves provided by mycorrhizal fungi.

Epipactis neglecta at forest site 9 in the Nördliche Frankenalb in July 2009
(A) Epipactis neglecta at forest site 9 in the Nördliche Frankenalb in July 2009. Scale bar = 5 cm. Image courtesy of Florian Fraaß. (B) Light micrograph showing a transverse section of a root of Epipactis neglecta. Fungal colonization is visible as exodermal, outer and inner cortex cells filled with fungal hyphae, indicated by white arrows. Scale bar = 100 µm. (C) Ascocarps of Tuber excavatum. Scale bar = 1 cm. (D) Cross-section of an ascocarp of Tuber brumale. Scale bar = 1 cm.

Schiebold et al. analysed the food webs of 12 taxa in the orchid genus Epipactis, obtaining stable isotope natural abundance measurements of Epipactis leaf tissue and fungal sporocarps, and molecular identification of mycorrhizal fungi. The pronounced gradient in 15N enrichment observed in Epipactis species is strongly driven by type and by the 15N abundance of the orchids’ mycorrhizal fungi.

Reference

Schiebold, J. M.-I., Bidartondo, M. I., Karasch, P., Gravendeel, B., & Gebauer, G. (2017). You are what you get from your fungi: nitrogen stable isotope patterns in Epipactis species. Annals of Botany, 119(7), 1085–1095. https://doi.org/10.1093/aob/mcw265