Orchid “mycorrhizae”
Coiled hyphae - pelotons Common mycorrhizal networks
Many plant-mycorrhizal associations have low host- specificity. One ectomycorrhizal fungus species may be capable of forming a mycorrhizal association with multiple plant species.
Mutiple plant individuals may be interconnected by the same mycorrhizal hyphal network, also potential for interspecific connections, e.g. Pseudotsuga - Lithocarpus
Hypothesized that photosynthetically fixed carbon and inorganic nutrients can be shared via common mycorrhizal networks, allow exploitation of larger nutrient supply Plant-Plant connections via EcM networks
Host specificity: narrow to broad according to species; most EcM fungi can occur on more than one host
Interconnections: common mycorrhizal networks link individuals of same or different species
“Host receptivity”: number & diversity of mycorrhizal fungi accepted by a particular host
Individuals of the same and different species can be connected by a common dikaryon
Guild concept - shared compatibility for mycorrhizal fungal associates by co-occurring plant species (e.g., Douglas-fir & Arctostaphylos) Myco-heterotrophic plants
About 400 plant species in 85 genera are dependent directly on a fungal symbiont for carbon. Other plants, notably orchids, are dependent directly on a fungal symbiont during the early stages of growth immediately following seed germination before the first leaves form.
Where does the carbon come from? From another (autotrophic) plant host with which the fungus is a mycorrhizal symbiont
Mycotrophic plant-fungus associations highly host-specific, in contrast to typical mycorrhizal associations Mycoheterotrophic plants
Monotropoidae Achlorophyllous plants
Example: Monotropa Base of Monotropa uniflora inflorescence and mycorrhizal roots of M. uniflora and Russula brevipes. Allotropa virgata and Tricholoma magnivelare, matsutake or pine mushroom Sarcodes sanguinea, Pterospora andromeda
Pterospora – Rhizopogon mycorrhizae Mycoparasitic orchids Example Corallorhiza Parasitic on Russula spp, Thelephora Mycoparasitic orchids
Parasites of “Rhizoctonia” (Sebacina)
Hexalectris spicata Neottia nudus-avis