Orchid mycorrhiza
Encyclopedia
Orchid mycorrhizae are symbiotic relationships between the root
s of plant
s of the family Orchidaceae
and a variety of fungi. All orchids are myco-heterotrophic at some point in their life cycle
. Orchid mycorrhizae 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.
(Rhizoctonia
), Sebacina
, Tulasnella
and Russula
species. Most orchids associate with saprotrophic or pathogenic fungi, while a few 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.
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s of plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s of the family Orchidaceae
Orchidaceae
The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...
and a variety of fungi. All orchids are myco-heterotrophic at some point in their life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
. Orchid mycorrhizae are critically important during orchid germination, as orchid seed has virtually no energy reserve and obtains its carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
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 mycorrhizae
The fungi that form orchid mycorrhiza are typically basidiomycetes. These fungi come from a range of taxa including CeratobasidiumCeratobasidium
Ceratobasidium is a genus of fungi in the order Cantharellales. Basidiocarps are effused and the genus is sometimes grouped among the corticioid fungi, though species also retain features of the heterobasidiomycetes. Rhizoctonia-like anamorphs of Ceratobasidium species are placed in the genus...
(Rhizoctonia
Rhizoctonia
Rhizoctonia is a genus of anamorphic fungi in the order Cantharellales. Species do not produce spores, but are composed of hyphae and sclerotia and are asexual states of fungi in the genus Thanatephorus. Rhizoctonia species are saprotrophic, but are also facultative plant pathogens, causing...
), Sebacina
Sebacina
Sebacina is a genus of fungi in the family Sebacinaceae. Its species are mycorrhizal, forming a range of associations with trees, orchids, and other plants. Basidiocarps are produced on soil and litter, sometimes partly encrusting stems of living plants. The fruit bodies are cartilaginous to...
, Tulasnella
Tulasnella
Tulasnella is a genus of effused fungi in the Tulasnellaceae family. The widespread genus is estimated to contain around 50 species...
and Russula
Russula
Around 750 worldwide species of mycorrhizal mushrooms compose the genus Russula. They are typically common, fairly large, and brightly colored - making them one of the most recognizable genera among mycologists and mushroom collectors...
species. Most orchids associate with saprotrophic or pathogenic fungi, while a few 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.
External links
- "Orchid Mycorrhiza", from Fungal Biology (online textbook), School of Biological Sciences, University of SydneyUniversity of SydneyThe University of Sydney is a public university located in Sydney, New South Wales. The main campus spreads across the suburbs of Camperdown and Darlington on the southwestern outskirts of the Sydney CBD. Founded in 1850, it is the oldest university in Australia and Oceania...
, June 2004: - "Orchidoid mycorrhizae" from Mycorrhizae and Plant Phylogeny (website) by Frank C. Landis, Botany Department, University of Wisconsin–MadisonUniversity of Wisconsin–MadisonThe University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...
, January 11, 2002.