HOME

TheInfoList



OR:

Myco-heterotrophy (from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
μύκης , "fungus", ἕτερος ', "another", "different" and τροφή ', "nutrition") is a
symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
relationship between certain kinds of
plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
and
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
, in which the plant gets all or part of its food from
parasitism Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
upon fungi rather than from
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
. A myco-heterotroph is the
parasitic plant A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...
partner in this relationship. Myco-heterotrophy is considered a kind of
cheating Cheating generally describes various actions designed to subvert rules in order to obtain unfair advantages. This includes acts of bribery, cronyism and nepotism in any situation where individuals are given preference using inappropriate cr ...
relationship and myco-heterotrophs are sometimes informally referred to as "mycorrhizal cheaters". This relationship is sometimes referred to as mycotrophy, though this term is also used for plants that engage in mutualistic
mycorrhizal   A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plan ...
relationships.


Relationship between myco-heterotrophs and host fungi

Full (or obligate) myco-heterotrophy exists when a non-photosynthetic plant (a plant largely lacking in
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
or otherwise lacking a functional
photosystem Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems ...
) gets all of its food from the fungi that it parasitizes. Partial (or facultative) myco-heterotrophy exists when a plant is capable of photosynthesis, but parasitizes fungi as a supplementary food supply. There are also plants, such as some
orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...
species, that are non-photosynthetic and obligately myco-heterotrophic for part of their
life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis, ...
, and photosynthetic and facultatively myco-heterotrophic or non-myco-heterotrophic for the rest of their life cycle. Not all non-photosynthetic or "
achlorophyllous Myco-heterotrophy (from Greek μύκης , "fungus", ἕτερος ', "another", "different" and τροφή ', "nutrition") is a symbiotic relationship between certain kinds of plants and fungi, in which the plant gets all or part of its food fro ...
" plants are myco-heterotrophic – some non-photosynthetic plants like
dodder ''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
directly parasitize the
vascular tissue Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There ...
of other plants. The partial or full loss of photosynthesis is reflected by extreme physical and functional reductions of plastid genomes in mycoheterophic plants, an ongoing evolutionary process. In the past, non-photosynthetic plants were mistakenly thought to get food by breaking down
organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
in a manner similar to
saprotrophic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...
fungi. Such plants were therefore called " saprophytes". It is now known that these plants are not physiologically capable of directly breaking down organic matter and that in order to get food, non-photosynthetic plants must engage in parasitism, either through myco-heterotrophy or direct parasitism of other plants. The interface between the plant and fungal partners in this association is between the roots of the plant and the mycelium of the fungus. Myco-heterotrophy therefore closely resembles
mycorrhiza   A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...
(and indeed is thought to have evolved from mycorrhiza), except that in myco-heterotrophy, the flow of carbon is from the fungus to the plant, rather than vice versa. Most myco-heterotrophs can therefore be seen as ultimately being
epiparasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
, since they take energy from fungi that in turn get their energy from
vascular plants Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...
. Indeed, much myco-heterotrophy takes place in the context of common
mycorrhizal network A Mycorrhizal network (also known as a common mycorrhizal network or CMN) is an underground network found in forests and other plant communities, created by the hyphae of mycorrhizal fungi joining with plant roots. This network connects individu ...
s, in which plants use mycorrhizal fungi to exchange carbon and nutrients with other plants. In these systems, myco-heterotrophs play the role of "mycorrhizal cheaters", taking carbon from the common network, with no known reward. A special form of mycoheterotrophic association, which appears to be a chimera between the haustorial parasitism of a
parasitic plant A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...
and mycoheterotrophy, is observed in ''
Parasitaxus usta ''Parasitaxus usta'' is a rare species of conifer of the family Podocarpaceae, and the sole species of the genus ''Parasitaxus''. It is a woody shrub up to 1.8 m found only in the remote, densely forested areas of New Caledonia, first discovered ...
'', the only mycoheterotrophic gymnosperm. In congruence with older reports, it has been recently shown that some myco-heterotrophic orchids can be supported by saprotrophic fungi, exploiting litter- or wood-decaying fungi. In addition, several green plants (evolutionarily close to myco-heterotrophic species) have been shown to engage in partial myco-heterotrophy, that is, they are able to take carbon from mycorrhizal fungi, in addition to their photosynthetic intake.


Species diversity of myco-heterotrophs and host fungi

Myco-heterotrophs are found among a number of plant groups. All
monotropes Monotropoideae, sometimes referred to as monotropes, are a flowering plant subfamily in the family Ericaceae. Members of this subfamily are notable for their mycoheterotrophic and non-photosynthesizing or achlorophyllous characteristics. Descript ...
and non-photosynthetic
orchids Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...
are full myco-heterotrophs, as is the non-photosynthetic
liverwort The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of g ...
''
Cryptothallus ''Cryptothallus'' is a previously recognized genus of liverworts in the family Aneuraceae. The plants are small, and are white to pale green as a result of lacking chlorophyll. This feature led to the creation of a separate genus. The morphology o ...
''. Partial myco-heterotrophy is common in the
Gentian family Gentianaceae is a family of flowering plants of 103 genera and about 1600 species. Etymology The family takes its name from the genus ''Gentiana'', named after the Illyrian king Gentius. Distribution Distribution is cosmopolitan. Characteristi ...
, with a few genera such as ''
Voyria ''Voyria'', commonly known as ghostplants, is a genus of 20 species of herbaceous perennial plants, belonging to the family Gentianaceae. They are mostly native to warm temperate and tropical regions of the Caribbean, Central America and South A ...
'' being fully myco-heterotrophic; in photosynthetic orchids; and in a number of other plant groups. Some
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...
s and
clubmosses Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
have myco-heterotrophic
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...
stages.Taylor DL, Bruns TD, Leake JR, Read DJ. 2002
Mycorrhizal specificity and function in myco-heterotrophic plants.
In: ''Mycorrhizal Ecology'' (Sanders IR, van der Heijden M, eds.), Ecological Studies vol. 157, pp 375–414. Berlin: Springer-Verlag. . (NOTE: this PDF is from the page proofs, and is not identical to the published version)
The fungi that are parasitized by myco-heterotrophs are typically fungi with large energy reserves to draw on, usually mycorrhizal fungi, though there is some evidence that they may also parasitize parasitic fungi that form extensive mycelial networks, such as ''
Armillaria ''Armillaria'' is a genus of fungi that includes the '' A. mellea'' species known as honey fungi that live on trees and woody shrubs. It includes about 10 species formerly categorized summarily as ''A. mellea''. ''Armillarias'' are long-l ...
''. Examples of fungi parasitized by myco-heterotrophic plants can be found among the
ectomycorrhizal An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; pl. ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobi ...
,
arbuscular mycorrhizal An arbuscular mycorrhiza (AM) (plural ''mycorrhizae'', a.k.a. ''endomycorrhiza'') is a type of mycorrhiza in which the symbiont fungus (''AM fungi'', or AMF) penetrates the cortical cells of the roots of a vascular plant forming arbuscules. ( ...
, and
orchid mycorrhizal Orchid mycorrhizae are endomycorrhizal fungi which develop symbiotic relationships with the roots and seeds of plants of the family Orchidaceae. Nearly all orchids are myco-heterotrophic at some point in their Biological life cycle, life cycle. Orch ...
fungi. The great diversity in unrelated plant families with myco-heterotrophic members, as well as the diversity of fungi targeted by myco-heterotrophs, suggests multiple
parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and paral ...
s of myco-heterotrophs from mycorrhizal ancestors.


References


Further reading

* * * Werner PG. 2006
Myco-heterotrophs: hacking the mycorrhizal network.
''
Mycena News The Mycological Society of San Francisco (MSSF) is an amateur club based in the San Francisco Bay Area, "dedicated to promoting the understanding and enjoyment of fungi." Meetings are held every third Tuesday, and the society newsletter, ''Mycen ...
'' 57(3): 1,8.
Dr. Martin Bidartondo: Selected publications





External links



''The Parasitic Plant Connection'', SIU Carbondale, College of Science.
''Wayne's Word'' Noteworthy Plant For June 1997: Fungus Flowers – Flowering Plants that Resemble Fungi
by WP Armstrong.

by Tom Volk, ''TomVolkFungi.net''

– images of myco-heterotrophs by mycologist Martín Bidartondo. {{DEFAULTSORT:Myco-Heterotrophy Botany Ecology Mycology * Parasites of fungi Symbiosis