Editing Mycorrhiza (section)

== Types==
The mycorrhizal lifestyle has independently [[convergent evolution|convergently evolved]] multiple times in the history of Earth.<ref name="Ericoid mycorrhizal fungi and their">{{cite journal |last1=Perotto |first1=Silvia |last2=Daghino |first2=Stefania |last3=Martino |first3=Elena |title=Ericoid mycorrhizal fungi and their genomes: another side to the mycorrhizal symbiosis? |journal=New Phytologist |date=2018 |volume=220 |issue=4}}</ref> There are multiple ways to categorize mycorrhizal symbiosis. One major categorization is the division between ''ectomycorrhizas'' and ''endomycorrhizas''. The two types are differentiated by the fact that the hyphae of ectomycorrhizal fungi do not penetrate individual [[cell (biology)|cells]] within the root, while the [[hypha]]e of endomycorrhizal fungi penetrate the cell wall and [[wikt:invaginate|invaginate]] the [[cell membrane]].<ref>Harley, J. L.; Smith, S. E. 1983. Mycorrhizal symbiosis (1st ed.). Academic Press, London.</ref><ref name="Allen, Michael F 1991">Allen, Michael F. 1991. The ecology of mycorrhizae. Cambridge University Press, Cambridge.</ref>

===Similar symbiotic relationships===
Some forms of plant-fungal symbiosis are similar to mycorrhizae, but considered distinct. One example is fungal endophytes. Endophytes are defined as organisms that can live within plant cells without causing harm to the plant. They are distinguishable from mycorrhizal fungi by the absence of nutrient-transferring structures for bringing in nutrients from outside the plant.<ref name="Ericoid mycorrhizal fungi and their"/> Some lineages of mycorrhizal fungi may have evolved from endophytes into mycorrhizal fungi,<ref>{{cite journal |last1=Selosse |first1=Marc-Andre |last2=Petroli |first2=Remi |last3=Mujica |first3=Maria |last4=Laurent |first4=Liam |last5=Perez-Lamarque |first5=Benoit |last6=Figura |first6=Tomas |last7=Bourceret |first7=Amelia |last8=Jaquemyn |first8=Hans |last9=Li |first9=Taiqiang |last10=Gao |first10=Jiangyun |last11=Minasiewicz |first11=Julita |last12=Martos |first12=Florent |title=The Waiting Room Hypothesis revisited by orchids: were orchid mycorrhizal fungi recruited among root endophytes? |journal=Annals of Botany |date=2021 |volume=129 |issue=3}}</ref> and some fungi can live as mycorrhizae or as endophytes.

===Ectomycorrhiza===

[[File:Grib skov.jpg |thumb |[[Beech]] is [[ectomycorrhiza]]l ]]
[[File:Raudonvirsis1-vi.jpg |thumb |''[[Leccinum aurantiacum]]'', an [[#Ectomycorrhiza|ectomycorrhizal]] fungus]]

{{Main|Ectomycorrhiza}}

Ectomycorrhizae are distinct in that they do not penetrate into plant cells, but instead form a structure called a [[Hartig net]] that penetrates between cells.<ref name="The potential role of Mucoromycotin">{{cite journal |last1=Howard |first1=Nathan |last2=Pressel |first2=Silvia |last3=Kaye |first3=Ryan S. |last4=Daniell |first4=Tim J. |last5=Field |first5=Katie J. |title=The potential role of Mucoromycotina ‘fine root endophytes’ in plant nitrogen nutrition |journal=Physiologia Plantarum |date=2022 |volume=174 |issue=3}}</ref> Ectomycorrhizas consist of a hyphal sheath, or mantle, covering the root tip and the Hartig net of hyphae surrounding the plant cells within the root [[Cortex (botany)|cortex]]. In some cases the hyphae may also penetrate the plant cells, in which case the mycorrhiza is called an endomycorrhiza. Outside the root, [[ectomycorrhizal extramatrical mycelium]] forms an extensive network within the soil and [[leaf litter]]. Other forms of mycorrhizae, including arbuscular, ericoid, arbutoid, monotropoid, and orchid mycorrhizas, are considered endomycorrhizae.<ref name="Peterson et al. 2004">{{Cite book |last1=Peterson |first1=R. L. |first2=H. B. |last2=Massicotte |name-list-style=amp |first3=L. H. |last3=Melville |date=2004 |url=http://pubs.nrc-cnrc.gc.ca/eng/books/books/9780660190877.html |title=Mycorrhizas: anatomy and cell biology |publisher=National Research Council Research Press |isbn=978-0-660-19087-7 |url-status=dead |archive-url=https://web.archive.org/web/20071225163327/http://pubs.nrc-cnrc.gc.ca/eng/books/books/9780660190877.html |archive-date=2007-12-25 }}</ref>

Ectomycorrhizas, or EcM, are symbiotic associations between the roots of around 10% of plant families, mostly woody plants including the [[Betulaceae|birch]], [[Dipterocarpaceae|dipterocarp]], [[Myrtaceae|eucalyptus]], [[Fagaceae|oak]], [[Pinaceae|pine]], and [[Rosaceae|rose]]<ref name=Wang2006/> families, [[Orchidaceae#Ecology|orchids]],<ref>{{cite web |url=http://esciencenews.com/articles/2011/07/12/orchids.and.fungi.an.unexpected.case.symbiosis |title=Orchids and fungi: An unexpected case of symbiosis |date=July 12, 2011 |publisher=American Journal of Botany |access-date=24 July 2012 |archive-url=https://web.archive.org/web/20110715013341/http://esciencenews.com/articles/2011/07/12/orchids.and.fungi.an.unexpected.case.symbiosis |archive-date=2011-07-15 |url-status=live }}</ref> and fungi belonging to the [[Basidiomycota]], [[Ascomycota]], and [[Zygomycota]]. Ectomycorrhizae associate with relatively few plant species, only about 2% of plant species on Earth, but the species they associate with are mostly trees and woody plants that are highly dominant in their ecosystems, meaning plants in ectomycorrhizal relationships make up a large proportion of plant biomass.<ref name="The functional role of ericoid myco">{{cite journal |last1=Ward |first1=Elisabeth B. |last2=Duguid |first2=Marlyse C. |last3=Kuebbing |first3=Sara E. |last4=Lendemer |first4=James C. |last5=Bradford |first5=Mark A. |title=The functional role of ericoid mycorrhizal plants and fungi on carbon and nitrogen dynamics in forests |journal=New Phytologist |date=2022 |volume=235 |issue=5}}</ref> Some EcM fungi, such as many ''[[Leccinum]]'' and ''[[Suillus]]'', are symbiotic with only one particular genus of plant, while other fungi, such as the ''[[Amanita]]'', are generalists that form mycorrhizas with many different plants.<ref name=bak04/> An individual tree may have 15 or more different fungal EcM partners at one time.<ref name=saari04/> While the diversity of plants involved in EcM is low, the diversity of fungi involved in EcM is high. Thousands of ectomycorrhizal fungal species exist, hosted in over 200 genera. A recent study has conservatively estimated global ectomycorrhizal fungal species richness at approximately 7750 species, although, on the basis of estimates of knowns and unknowns in macromycete diversity, a final estimate of ECM species richness would probably be between 20,000 and 25,000.<ref>{{cite journal |last1=Rinaldi |first1=A. C. |last2=Comandini |first2=O. |last3=Kuyper |first3=T. W. |date=2008 |title=Ectomycorrhizal fungal diversity: separating the wheat from the chaff |journal=Fungal Diversity |volume=33 |pages=1–45 |url=http://www.fungaldiversity.org/fdp/sfdp/33-1.pdf |access-date=2011-05-23 |archive-url=https://web.archive.org/web/20110724163606/http://www.fungaldiversity.org/fdp/sfdp/33-1.pdf |archive-date=2011-07-24 |url-status=live }}</ref> Ectomycorrhizal fungi evolved independently from saprotrophic ancestors many times in the group's history.<ref>{{cite journal |last1=Martin |first1=Francis M. |last2=van der Heijden |first2=Marcel G. A. |title=The mycorrhizal symbiosis: research frontiers in genomics, ecology, and agricultural application |journal=New Phytologist |date=2024 |volume=242 |issue=4}}</ref>

Nutrients can be shown to move between different plants through the fungal network. Carbon has been shown to move from [[Betula papyrifera|paper birch]] seedlings into adjacent [[Coast Douglas-fir|Douglas-fir]] seedlings, although not conclusively through a common mycorrhizal network,<ref>{{Cite journal |last1=Karst |first1=Justine |last2=Jones |first2=Melanie D. |last3=Hoeksema |first3=Jason D. |date=2023-02-13 |title=Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests |url=https://www.nature.com/articles/s41559-023-01986-1 |journal=Nature Ecology & Evolution |language=en |volume=7 |issue=4 |pages=501–511 |doi=10.1038/s41559-023-01986-1 |pmid=36782032 |bibcode=2023NatEE...7..501K |s2cid=256845005 |issn=2397-334X}}</ref> thereby promoting [[Ecological succession|succession]] in [[ecosystem]]s.<ref>{{cite journal |last1=Simard |first1=Suzanne W. |last2=Perry |first2=David A. |last3=Jones |first3=Melanie D. |last4=Myrold |first4=David D. |last5=Durall |first5=Daniel M. |last6=Molina |first6=Randy |name-list-style=amp |title=Net transfer of carbon between ectomycorrhizal tree species in the field |journal=Nature |volume=388 |issue=6642 |date=1997 |pages=579–582 |doi=10.1038/41557 |bibcode=1997Natur.388..579S |s2cid=4423207 |doi-access=free }}</ref> The ectomycorrhizal fungus ''[[Laccaria bicolor]]'' has been found to lure and kill [[springtail]]s to obtain nitrogen, some of which may then be transferred to the mycorrhizal host plant. In a study by Klironomos and Hart, [[Eastern White Pine]] inoculated with ''L. bicolor'' was able to derive up to 25% of its nitrogen from springtails.<ref>[https://archive.today/20120710035451/http://findarticles.com/p/articles/mi_m1200/is_14_159/ai_104730213/ Fungi kill insects and feed host plants] BNET.com</ref><ref>{{cite journal |last1=Klironomos |first1=J. N. |last2=Hart |first2=M. M. |date=2001 |title=Animal nitrogen swap for plant carbon |journal=Nature |volume=410 |issue=6829 |pages=651–652 |doi=10.1038/35070643 |pmid=11287942 |bibcode=2001Natur.410..651K |s2cid=4418192 }}</ref> When compared with non-mycorrhizal fine roots, ectomycorrhizae may contain very high concentrations of trace elements, including toxic metals (cadmium, silver) or chlorine.<ref>{{cite journal |last1=Cejpková |first1=J. |last2=Gryndler |first2=M. |last3=Hršelová |first3=H. |last4=Kotrba |first4=P. |last5=Řanda |first5=Z. |last6=Greňová |first6=I. |last7=Borovička |first7=J. |title=Bioaccumulation of heavy metals, metalloids, and chlorine in ectomycorrhizae from smelter-polluted area |journal=Environmental Pollution |volume=218 |pages=176–185 |doi=10.1016/j.envpol.2016.08.009 |pmid=27569718 |year=2016|bibcode=2016EPoll.218..176C }}</ref>

The first genomic sequence for a representative of symbiotic fungi, the ectomycorrhizal basidiomycete ''L. bicolor'', was published in 2008.<ref>{{cite journal |last1=Martin |first1=F. |date=2008 |title=The genome of ''Laccaria bicolor'' provides insights into mycorrhizal symbiosis |doi=10.1038/nature06556 |journal=Nature |volume=452 |issue=7183 |pages=88–92 |pmid=18322534 |first2=A. |last3=Ahrén |first3=D. |last4=Brun |first4=A. |last5=Danchin |first5=E. G. J. |last6=Duchaussoy |first6=F. |last7=Gibon |first7=J. |last8=Kohler |first8=A. |last9=Lindquist |first9=E. |display-authors=2 |last2=Aerts |bibcode=2008Natur.452...88M |url=https://nootropicsfrontline.com/wp-content/uploads/2021/07/wiki_martin2008.pdf |doi-access=free }}</ref> An expansion of several multigene families occurred in this fungus, suggesting that adaptation to symbiosis proceeded by gene duplication. Within lineage-specific genes those coding for symbiosis-regulated secreted proteins showed an up-regulated expression in ectomycorrhizal root tips suggesting a role in the partner communication. ''L. bicolor'' is lacking enzymes involved in the degradation of plant cell wall components (cellulose, hemicellulose, pectins and pectates), preventing the symbiont from degrading host cells during the root colonisation. By contrast, ''L. bicolor'' possesses expanded multigene families associated with hydrolysis of bacterial and microfauna polysaccharides and proteins. This genome analysis revealed the dual [[saprotrophic]] and [[biotrophic]] lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. Since then, the genomes of many other ectomycorrhizal fungal species have been sequenced further expanding the study of gene families and evolution in these organisms.<ref>{{Cite journal |last1=Miyauchi |first1=Shingo |last2=Kiss |first2=Enikő |last3=Kuo |first3=Alan |last4=Drula |first4=Elodie |last5=Kohler |first5=Annegret |last6=Sánchez-García |first6=Marisol |last7=Morin |first7=Emmanuelle |last8=Andreopoulos |first8=Bill |last9=Barry |first9=Kerrie W. |last10=Bonito |first10=Gregory |last11=Buée |first11=Marc |last12=Carver |first12=Akiko |last13=Chen |first13=Cindy |last14=Cichocki |first14=Nicolas |last15=Clum |first15=Alicia |date=2020-10-12 |title=Large-scale genome sequencing of mycorrhizal fungi provides insights into the early evolution of symbiotic traits |journal=Nature Communications |language=en |volume=11 |issue=1 |pages=5125 |doi=10.1038/s41467-020-18795-w |issn=2041-1723 |pmc=7550596 |pmid=33046698|bibcode=2020NatCo..11.5125M }}</ref>

====Arbutoid mycorrhiza====

This type of mycorrhiza involves plants of the Ericaceae subfamily [[Arbutoideae]]. It is however different from ericoid mycorrhiza and resembles ectomycorrhiza, both functionally and in terms of the fungi involved.<ref name="Brundrett 2004 pp. 473–495">{{cite journal |last=Brundrett |first=Mark |title=Diversity and classification of mycorrhizal associations |journal=Biological Reviews |publisher=Wiley |volume=79 |issue=3 |year=2004 |issn=1464-7931 |doi=10.1017/s1464793103006316 |pages=473–495|pmid=15366760 |s2cid=33371246 }}</ref> It differs from ectomycorrhiza in that some hyphae actually penetrate into the root cells, making this type of mycorrhiza an ''ectendomycorrhiza''.<ref>{{cite news |url=https://www.business-standard.com/article/pti-stories/some-plants-may-depend-more-on-friendly-fungi-than-own-leaves-study-119102900751_1.html |title=Some plants may depend more on friendly fungi than own leaves: Study |work=Business Standard |date=20 October 2019 |agency=Press Trust of India }}</ref>

===Arbuscular mycorrhiza===

{{Main|Arbuscular mycorrhiza}}

[[File:Wheat field.jpg|thumb|upright|[[Wheat]] has [[arbuscular mycorrhiza]]. ]]

[[Arbuscular mycorrhiza]]s, (formerly known as vesicular-arbuscular mycorrhizas), have hyphae that penetrate plant cells, producing branching, tree-like structures called arbuscules within the plant cells for nutrient exchange. Often, balloon-like storage structures, termed vesicles, are also produced. In this interaction, fungal [[hyphae]] do not in fact penetrate the [[protoplast]] (i.e. the interior of the cell), but invaginate the [[cell membrane]], creating a so-called peri-arbuscular membrane. The structure of the arbuscules greatly increases the contact surface area between the hypha and the host cell [[cytoplasm]] to facilitate the transfer of nutrients between them. Arbuscular mycorrhizas are obligate biotrophs, meaning that they depend upon the plant host for both growth and reproduction; they have lost the ability to sustain themselves by decomposing dead plant material.<ref>{{Cite journal |last1=Lanfranco |first1=Luisa |last2=Bonfante |first2=Paola |last3=Genre |first3=Andrea |date=2016-12-23 |editor-last=Heitman |editor-first=Joseph |editor2-last=Howlett |editor2-first=Barbara J. |title=The Mutualistic Interaction between Plants and Arbuscular Mycorrhizal Fungi |url=https://journals.asm.org/doi/10.1128/microbiolspec.FUNK-0012-2016 |journal=Microbiology Spectrum |language=en |volume=4 |issue=6 |pages=4.6.14 |doi=10.1128/microbiolspec.FUNK-0012-2016 |pmid=28087942 |hdl=2318/1627235 |issn=2165-0497|hdl-access=free }}</ref> Twenty percent of the photosynthetic products made by the plant host are consumed by the fungi, the transfer of carbon from the terrestrial host plant is then exchanged by equal amounts of phosphate from the fungi to the plant host.<ref>{{Cite journal |last1=Kiers |first1=E. Toby |last2=Duhamel |first2=Marie |last3=Beesetty |first3=Yugandhar |last4=Mensah |first4=Jerry A. |last5=Franken |first5=Oscar |last6=Verbruggen |first6=Erik |last7=Fellbaum |first7=Carl R. |last8=Kowalchuk |first8=George A. |last9=Hart |first9=Miranda M. |last10=Bago |first10=Alberto |last11=Palmer |first11=Todd M. |last12=West |first12=Stuart A. |last13=Vandenkoornhuyse |first13=Philippe |last14=Jansa |first14=Jan |last15=Bücking |first15=Heike |date=2011-08-12 |title=Reciprocal Rewards Stabilize Cooperation in the Mycorrhizal Symbiosis |url=https://www.science.org/doi/10.1126/science.1208473 |journal=Science |language=en |volume=333 |issue=6044 |pages=880–882 |doi=10.1126/science.1208473 |pmid=21836016 |bibcode=2011Sci...333..880K |s2cid=44812991 |issn=0036-8075}}</ref>

Contrasting with the pattern seen in ectomycorrhizae, the species diversity of AMFs is very low, but the diversity of plant hosts is very high; an estimated 78% of all plant species associate with AMFs.<ref name="The functional role of ericoid myco"/> Arbuscular mycorrhizas are formed only by fungi in the [[Division (mycology)|division]] [[Glomeromycota]]. Fossil evidence<ref name="Remy et al."/> and DNA sequence analysis<ref name=simon1993>{{cite journal |last1=Simon |first1=L. |last2=Bousquet |first2=J. |last3=Lévesque |first3=R. C. |last4=Lalonde |first4=M. |date=1993 |title=Origin and diversification of endomycorrhizal fungi and coincidence with vascular land plants |journal=Nature |volume=363 |issue=6424 |pages=67–69 |doi=10.1038/363067a0 |bibcode=1993Natur.363...67S |s2cid=4319766 }}</ref> suggest that this mutualism appeared [[Devonian|400-460 million years ago]], when the first plants were colonizing land. Arbuscular mycorrhizas are found in 85% of all plant families, and occur in many crop species.<ref name=Wang2006/> The hyphae of arbuscular mycorrhizal fungi produce the glycoprotein [[glomalin]], which may be one of the major stores of carbon in the soil.<ref>{{Cite web |url=https://phys.org/news/2019-11-fungi-climate.html |title=Plants and fungi together could slow climate change |last=International Institute for Applied Systems Analysis |date=2019-11-07 |website=phys.org -us |access-date=2019-11-12}}</ref> Arbuscular mycorrhizal fungi have (possibly) been asexual for many millions of years and, unusually, individuals can contain many genetically different nuclei (a phenomenon called [[heterokaryosis]]).<ref name="Hijri">{{cite journal |last1=Hijri |first1=M. |last2=Sanders |first2=I. R. |date=2005 |title=Low gene copy number shows that arbuscular mycorrhizal fungi inherit genetically different nuclei |doi=10.1038/nature03069 |journal=Nature |volume=433 |issue=7022 |pages=160–163 |pmid=15650740 |bibcode=2005Natur.433..160H |s2cid=4416663 }}</ref>

===Mucoromycotina fine root endophytes===
Mycorrhizal fungi belonging to [[Mucoromycotina]], known as “fine root endophytes" (MFREs), were mistakenly identified as arbuscular mycorrhizal fungi until recently. While similar to AMF, MFREs are from subphylum Mucoromycotina instead of Glomeromycotina. Their morphology when colonizing a plant root is very similar to AMF, but they form fine textured hyphae.<ref name="The potential role of Mucoromycotin"/> Effects of MFREs may have been mistakenly attributed to AMFs due to confusion between the two, complicated by the fact that AMFs and MFREs often colonize the same hosts simultaneously. Unlike AMFs, they appear capable of surviving without a host. This group of mycorrhizal fungi is little understood, but appears to prefer wet, acidic soils and forms symbiotic relationships with liverworts, hornworts, lycophytes, and angiosperms.<ref>{{cite journal |last1=Prout |first1=James N. |last2=Williams |first2=Alex |last3=Wanke |first3=Alan |last4=Schornack |first4=Sebastian |last5=Ton |first5=Jurriaan |last6=Field |first6=Katie J. |title=Mucoromycotina ‘fine root endophytes’: a new molecular model for plant–fungal mutualisms? |journal=Trends in Plant Science |date=2023 |volume=29 |issue=6}}</ref>

===Ericoid mycorrhiza===

[[File:Ericoid mycorrhizal fungus.jpg|thumb|An [[ericoid]] mycorrhizal fungus isolated from ''[[Woollsia pungens]]''<ref name="Midgley">{{cite journal |last1=Midgley |first1=DJ |last2=Chambers |first2=SM |last3=Cairney |first3=J. W. G. |date=2002 |title=Spatial distribution of fungal endophyte genotypes in a Woollsia pungens (Ericaceae) root system |doi=10.1071/BT02020 |journal=Australian Journal of Botany |volume=50 |issue=5 |pages=559–565 }}</ref>]]

{{Main |Ericoid mycorrhiza}}

[[Ericoid mycorrhiza]]e, or ErMs, involve only plants in [[Ericales]] and are the most recently evolved of the major mycorrhizal relationships. Plants that form ericoid mycorrhizae are mostly woody understory shrubs; hosts include blueberries, bilberries, cranberries, mountain laurels, rhododendrons, heather, neinei, and giant grass tree. ErMs are most common in [[boreal forest]]s, but are found in two-thirds of all forests on Earth.<ref name="The functional role of ericoid myco"/> Ericoid mycorrhizal fungi belong to several different lineages of fungi. Some species can live as endophytes entirely within plant cells even within plants outside the Ericales, or live independently as saprotrophs that decompose dead organic matter. This ability to switch between multiple lifestyle types makes ericoid mycorrhizal fungi very adaptable.<ref name="Ericoid mycorrhizal fungi and their"/>

Plants that participate in these symbioses have specialized roots with no root hairs, which are covered with a layer of epidermal cells that the fungus penetrates into and completely occupies.<ref name="The potential role of Mucoromycotin"/> The fungi have a simple intraradical (growth in cells) phase, consisting of dense coils of hyphae in the outermost layer of root cells. There is no periradical phase and the extraradical phase consists of sparse hyphae that don't extend very far into the surrounding soil. They might form sporocarps (probably in the form of small cups), but their reproductive biology is poorly understood.<ref name="Allen, Michael F 1991"/>

Plants participating in ericoid mycorrhizal symbioses are found in acidic, nutrient-poor conditions.<ref name="Ericoid mycorrhizal fungi and their"/> Whereas AMFs have lost their [[saprotrophic]] capabilities, and EcM fungi have significant variation in their ability to produce enzymes needed for a saprotrophic lifestyle,<ref name="The functional role of ericoid myco"/> fungi involved in ErMs have fully retained the ability to decompose plant material for sustenance. Some ericoid mycorrhizal fungi have actually expanded their repertoire of enzymes for breaking down organic matter. They can extract nitrogen from cellulose, hemicellulose, lignin, pectin, and chitin. This would increase the benefit they can provide to their plant symbiotic partners.<ref>{{Cite journal |last1=Read |first1=D. J. |name-list-style=amp |first2=J. |last2=Perez-Moreno |title=Mycorrhizas and nutrient cycling in ecosystems—a journey towards relevance? |journal=New Phytologist |date=2003 |volume=157 |issue=3 |pages=475–492 |doi=10.1046/j.1469-8137.2003.00704.x |pmid=33873410 |doi-access=free }}</ref>

===Orchid mycorrhiza===

{{Main |Orchid mycorrhiza}}

All [[Orchidaceae|orchids]] are [[myco-heterotrophy|myco-heterotrophic]] at some stage during their lifecycle, meaning that they can survive only if they form [[orchid mycorrhiza]]e. Orchid seeds are so small that they contain no nutrition to sustain the germinating seedling, and instead must gain the energy to grow from their fungal symbiont.<ref name="The potential role of Mucoromycotin"/> The OM relationship is asymmetric; the plant seems to benefit more than the fungus, and some orchids are entirely mycoheterotrophic, lacking chlorophyll for photosynthesis. It is actually unknown whether fully autotrophic orchids that do not receive some of their carbon from fungi exist or not.<ref>{{cite journal |last1=Li |first1=Taiqiang |last2=Yang |first2=Wenke |last3=Wu |first3=Shimao |last4=Selosse |first4=Marc-Andre |last5=Gao |first5=Jiangyun |title=Progress and Prospects of Mycorrhizal Fungal Diversity in Orchids |journal=Frontiers in Plant Science |date=2021 |volume=12}}</ref> Like fungi that form ErMs, OM fungi can sometimes live as endophytes or as independent saprotrophs. In the OM symbiosis, hyphae penetrate into the root cells and form pelotons (coils) for nutrient exchange.

===Monotropoid mycorrhiza===

{{Main |Myco-heterotrophy}}

This type of mycorrhiza occurs in the subfamily [[Monotropoideae]] of the [[Ericaceae]], as well as several genera in the [[Orchidaceae]]. These plants are [[heterotrophic]] or [[mixotrophic]] and derive their carbon from the fungus partner. This is thus a non-mutualistic, [[Parasitism|parasitic]] type of mycorrhizal symbiosis.{{citation needed |date=November 2014}}