Orchids exhibit a unique type of mycorrhizal symbiosis, but the exact role of these fungal partners in the acquisition of inorganic and organic N by terrestrial orchids remains unclear. Wu et al. use 15N labelling to investigate inorganic and amino acid N uptake by non-mycorrhizal and mycorrhizal Cymbidium goeringii seedlings. They find that non-mycorrhizal seedlings preferentially take up NO3– from tracers injected into the soil, while seedlings inoculated with mycorrhizas show a strong preference for NH4+ uptake. This difference indicates that mycorrhizal fungi switch the N source uptake of C. goeringii from NO3– to NH4+.
Wu et al. investigate the role of mycorrhizal symbiosis in the acquisition of inorganic and organic N by terrestrial orchids.