Orchid mycorrhiza

Orchid mycorrhiza are a symbiotic relationship between the roots of plants of the family Orchidaceae and a variety of fungi. All orchids are mycoheterotrophic at some point in their life cycle. Orchid mycorrhiza are critically important during orchid germination, as orchid seed has virtually no energy reserve and obtains its carbon from the fungal symbiont. Many adult orchids retain their fungal symbionts, although the benefits to the adult photosynthetic orchid and the fungus remain largely unexplored.

Fungi forming orchid mycorrhiza
The fungi that form orchid mycorrhiza are typically basidiomycetes. These fungi come from a range of taxa including Ceratobasidium (Rhizotoctonia), Sebacina, Tulasnella and Russula species. Some orchids associate with saprotrophic, or pathogenic fungi, while other orchids associate with ectomycorrhizal fungal species. These latter associations are often called tripartate associations as they involve the orchid, the ectomycorrhizal fungus and the ectomycorrhizal host plant.