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{{Short description|Genus of flowering plants}}
{{italictitle}}
{{taxobox
{{Automatic taxobox
|name = Underground Orchid
| name = Underground orchids
|image = Rhizanthella gardneri 201206.jpg
| image = Rhizanthella gardneri — Fred Hort.jpg
|image_caption = ''Rhizanthella gardneri''
| image_caption = ''[[Rhizanthella gardneri]]''
| display_parents = 3
|regnum = [[Plantae]]
| parent_authority = R.S.Rogers
|unranked_divisio = [[Angiosperms]]
⚫
| taxon = Rhizanthella
|unranked_classis = [[Monocots]]
| authority = [[Richard Sanders Rogers|R.S.Rogers]]<ref name="POWO">{{cite web |title=''Rhizanthella'' |url=http://powo.science.kew.org/results?q=Rhizanthella |publisher=Kew Science - Plants of the World Online |access-date=25 September 2020}}</ref>
|ordo = [[Asparagales]]
⚫
| type_species = ''Rhizanthella gardneri''
|familia = [[Orchidaceae]]
⚫
| type_species_authority = [[R.S.Rogers]] (1928)
|subfamilia = [[Epidendroideae]]
| synonyms_ref = <ref name="Kew">{{WCSP | 178054 | ''Rhizanthella'' | access-date =20 July 2016 }}</ref>
|tribus = [[Gastrodieae]]
| synonyms = ''Cryptanthemis'' <small>[[Herman Rupp|Rupp]]</small>
|subtribus = [[Rhizanthellinae]]
⚫
}}
⚫
|genus = '''''Rhizanthella'''''
|genus_authority = [[Richard Sanders Rogers|R. S. Rogers]]
⚫
|type_species = ''Rhizanthella gardneri''
⚫
|type_species_authority = [[R. S. Rogers]] (1928)
|subdivision_ranks = Species
|subdivision = *''[[Rhizanthella gardneri]]'' - Gardner's Underground Orchid
*''[[Rhizanthella omissa]]'' - Lamington's Underground Orchid
*''[[Rhizanthella slateri]]'' - Eastern Underground Orchid
⚫
|}}


'''''Rhizanthella''''', commonly known as '''underground orchids''', is a small epiparasitic, achlorophyllous, subterranean [[genus]] of [[orchid]] [[Endemism|endemic]] native to [[Australia]]. It is abbreviated in trade journals as Rhi.
'''''Rhizanthella''''', commonly known as '''underground orchids''',<ref name="Hoffman" /> is a [[genus]] of flowering plants in the orchid family, [[Orchidaceae]] and is [[Endemism|endemic]] to Australia. All are leafless, living underground in [[symbiosis]] with [[mycorrhiza]]l fungi. The [[inflorescence]] is a head of flowers held at, or just above the ground but mostly covered by soil or leaf litter and little is known about the mechanism of [[pollination]].


==Description==
These orchids are rare and their status is considered vulnerable to critical, mostly due to loss of [[Habitat (ecology)|habitat]]. They live underground in [[symbiosis]] with [[mycorrhiza]]l fungi. These subterranean [[rhizome]]s or [[tuber]]s are short and thickened, without roots, serving as storage for the orchid. The leaves are absent.
Orchids in the genus ''Rhizanthella'' are mostly underground, [[Perennial plant|perennial]], [[sympodial]], [[mycotrophic]] [[Herbaceous plant|herbs]] with fleshy underground stems which produce new shoots at [[Plant stem|nodes]] where there are colourless leaf-like [[cataphyll]]s. There are no roots and new [[tuber]]s form at the end of short stems. The leaves are reduced to scale-like structures lacking [[chlorophyll]], pressed against and sheathing the stems.<ref name="Hoffman">{{cite book|last1=Hoffman|first1=Noel|last2=Brown|first2=Andrew|title=Orchids of South-West Australia.|date=2011|publisher=Noel Hoffman|location=Gooseberry Hill|isbn=9780646562322|pages=386–389|edition=3rd}}</ref><ref name="Orchids">{{cite book|editor1=Alec M. Pridgeon |editor2=Phillip J. Cribb |editor3=Mark W. Chase |editor4=Finn N. Rasmussen |title=Genera Orchidacearum, Volume 2, Orchidoideae (part 1)|date=2001|publisher=Oxford University Press|location=Oxford, England|isbn=0198507100|pages=186–193}}</ref><ref name=FloraBase>{{FloraBase|name=''Rhizanthella''|id=21295}}</ref><ref name="RBGS">{{cite web|last1=Weston|first1=Peter H.|title=Genus ''Rhizanthella''|url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&showsyn=&dist=&constat=&lvl=gn&name=Rhizanthella|publisher=Royal Botanic Garden Sydney: plantnet|access-date=20 July 2016}}</ref>


The inflorescence is a head containing many flowers and is held at, or just above ground level but the head is usually covered with leaf litter or soil. The head is surrounded by a large number of overlapping [[bract]]s and each flower has an erect, elongated bract at its base. The flowers are non-[[Resupination#Orchidaceae|resupinate]], arranged in a spiral, inward-facing, dull coloured and lack a stalk. The [[sepal]]s and [[petal]]s form a short, curved hood over the [[Labellum (botany)|labellum]] and [[Column (botany)|column]], open on one side. The [[wikt:lateral|lateral]] sepals are joined to each other and to the [[wikt:dorsal|dorsal]] sepal at their bases. The petals are joined at their bases to the [[Column (botany)|column]] and are shorter than the sepals. The labellum is different in size, shape and colouration from the other petals and sepals, is thick, fleshy and has no [[nectar]]. The column is short with short wings. Flowering time depends on species and is followed by the fruit which is a berry that does not split open ([[Dehiscence (botany)|indehiscent]]) and which contains 50 to 100 seeds.<ref name="Hoffman" /><ref name="Orchids" /><ref name="FloraBase" /><ref name="RBGS" />
When the orchid prepares to flower, the solitary [[inflorescence]]s break through the surface, beneath the leaf litter. The terminal inflorescence is [[racemose]]. It gives rise to a cluster of small, tubular, [[hermaphroditic]] [[flower]]s. The fragrant flowerheads are about 5&nbsp;cm wide and contain numerous, inward-facing, small flowers.


Underground orchids do not possess chloroplasts but they retain [[plastid]] genes, although ''[[Rhizanthella gardneri|R. gardneri]]'' possesses one of the smallest [[organelle]] [[genome]] yet described in land plants.<ref name="Oxford">{{cite journal|last1=Delannoy|first1=Etienne|last2=Fujii|first2=Sota|last3=Colas des Francs-Small|first3=Catherine|last4=Brundrett|first4=Mark|last5=Small|first5=Ian|title=Rampant Gene Loss in the Underground Orchid Rhizanthella gardneri Highlights Evolutionary Constraints on Plastid Genomes|journal=Molecular Biology and Evolution|date=2 February 2011|volume=28|issue=7|pages=2077–2086|doi=10.1093/molbev/msr028|pmid=21289370|pmc=3112369}}</ref>
Pollination is carried out by small [[fly|flies]] or [[insect]]s, even underground by [[termite]]s or [[gnat]]s. The fruit is a fleshy, indehiscent [[drupe]] with about 250 minute seeds.


==Taxonomy and naming==
Their discovery in 1928 caused such an excitement among orchid lovers, that a wax model had to be toured around [[UK|Britain]].
The first formal description of an underground orchid was by [[Richard Sanders Rogers]] who published his description of ''[[Rhizanthella gardneri|R. gardneri]]'' in the ''[[Royal Society of Western Australia|Journal of the Royal Society of Western Australia]]'' in 1928.<ref name=APNI>{{cite web|title=''Rhizanthella gardneri''|url= http://id.biodiversity.org.au/instance/apni/477139|publisher=APNI|access-date=20 July 2016}}</ref><ref name="R.S.Rogers">{{cite journal |last1=Rogers |first1=Richard Sanders |title=A New Genus of Australian Orchid |journal=Journal of the Royal Society of Western Australia |date=1928 |volume=15 |issue=1 |page=1 |url=https://www.biodiversitylibrary.org/item/173678#page/53/mode/1up |access-date=26 September 2020}}</ref> The name "''Rhizanthella''" is a diminutive of ''[[Rhizanthes]]'', a parasitic plant in the Family [[Rafflesiaceae]].<ref name="Quattrocchi">{{cite book|last1=Quattrocchi|first1=Umberto|title=R - Z.|date=2000|publisher=CRC World Dictionary of Pant Names (R-Z)|location=Boca Raton, FL|isbn=0849326788|page=2296}}</ref> The name "''Rhizanthes''" is derived from the [[Ancient Greek]] words ''rhiza'' meaning "root"<ref name="RWB">{{cite book|last1=Brown|first1=Roland Wilbur|title=The Composition of Scientific Words|date=1956|publisher=Smithsonian Institution Press|location=Washington, D.C.}}</ref>{{rp|666}} and ''anthos'' meaning "flower".<ref name="RWB" />{{rp|338}}


===Species list===
== Reference works ==
Four species are recognised by the [[World Checklist of Selected Plant Families]] and a fifth species has been formally described, but not as yet accepted by other authorities:
* George, A. S. (1981). ''Rhizanthella-The Underground Orchid of Western Australia''. Proceedings of the Orchid Symposium, 13th International Botanical Congress 77-78.
* ''[[Rhizanthella gardneri]]'' <small>[[R.S.Rogers]]</small><ref name="POWO1">{{cite web |title=''Rhizanthella gardneri'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:655670-1 |publisher=Kew Science - Plants of the World Online |access-date=25 September 2020}}</ref> – western underground orchid (W.A.)
* Dixon, K. W., et al. (1990). ''The Western Australian fully subterranean orchid Rhizanthella gardneri''. Orchid Biology, Reviews and Perspectives. V. J. Arditti. Portland, Oregon, Timber Press. 5: 37-62.
* ''[[Rhizanthella johnstonii]]'' <small>[[Kingsley Wayne Dixon|K.W.Dixon]] & [[Maarten J. M. Christenhusz|Christenh.]]</small><ref name="POWO2">{{cite web |title=''Rhizanthella johnstonii'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77176525-1 |publisher=Kew Science - Plants of the World Online |access-date=25 September 2020}}</ref> – south coast underground orchid (W.A.)
* Dixon, K. (2003) ''Underground Orchids on the Edge''. Plant Talk, 31: 34-35.
* ''[[Rhizanthella omissa]]'' <small>[[David L. Jones (botanist)|D.L.Jones]] & [[Mark Alwin Clements|M.A.Clem.]]</small><ref name="POWO3">{{cite web |title=''Rhizanthella omissa'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77077242-1 |publisher=Kew Science - Plants of the World Online |access-date=25 September 2020}}</ref> (Qld.)
* Jones, D.L. & Clements, M.A. (2006). ''Rhizanthella omissa, a new species of underground orchid from south eastern Australia''. The Orchadian, vol. 15, no. 3, pp.&nbsp;131-133.
* ''[[Rhizanthella slateri]]'' <small>([[Herman Rupp|Rupp]]) M.A.Clem. & [[Phillip James Cribb|P.J.Cribb]]</small><ref name="POWO4">{{cite web |title=''Rhizanthella slateri'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:75519-3 |publisher=Kew Science - Plants of the World Online |access-date=25 September 2020}}</ref> – eastern Australian underground orchid (N.S.W.)

In 2020, a fifth species, ''[[Rhizanthella speciosa]]'', found in New South Wales, was described by [[Mark Alwin Clements|Mark Clements]] and [[David L. Jones (botanist)|David Jones]] in the journal ''Lankesteriana'' but as at September 2020, the name has not been accepted by the World Checklist of Selected Plant Families.<ref name=APNInew>{{cite web|title=''Rhizanthella speciosa''|url= https://id.biodiversity.org.au/instance/apni/51365480|publisher=APNI|access-date=27 September 2020}}</ref>

==Distribution and habitat==
''[[Rhizanthella gardneri]]'' occurs in the south-west of [[Western Australia]] where it grows in association with broombush (''[[Melaleuca uncinata]]'').<ref name="Hoffman" /> [[Rhizanthella johnstonii|R. johnstonii]], also from WA, was split from R. gardneri in 2018.<ref>{{Cite journal|last=Dixon|first=Kingsley W.|last2=Christenhusz|first2=Maarten J. M.|date=2018-01-12|title=Flowering in darkness: a new species of subterranean orchid Rhizanthella (Orchidaceae; Orchidoideae; Diurideae) from Western Australia|url=https://www.biotaxa.org/Phytotaxa/article/view/phytotaxa.334.1.12|journal=Phytotaxa|language=en|volume=334|issue=1|pages=75–79|doi=10.11646/phytotaxa.334.1.12|issn=1179-3163}}</ref><ref name="ClementsJones2020" /> ''[[Rhizanthella omissa]]'' has only been collected once, at an elevation of {{convert|1200|m|ft|sigfig=1|abbr=on}} in the [[Lamington National Park]] in [[Queensland]].<ref name="orchidspecies">{{cite web|title=''Rhizanthella omissa''|url=http://www.orchidspecies.com/rhizomissa.htm|publisher=Internet Orchid Species Photo Encyclopedia|access-date=20 July 2016}}</ref> ''[[Rhizanthella slateri]]'', formerly known as ''Cryptanthemis slateri,'' occurs in the [[Blue Mountains (New South Wales)|Blue Mountains]] and similar ranges in [[New South Wales]] where it grows in [[sclerophyll]] forest.<ref name="RBGS" /> ''[[Rhizanthella speciosa|R. speciosa]]'' was discovered in 2016 in wet sclerophyll forest in [[Barrington Tops]], which contrasts with the more-open dry forest habitat of ''R. slateri''.<ref name="ClementsJones2020">{{Cite journal|last=Clements|first=Mark A.|last2=Jones|first2=David L.|date=2020-07-30|title=Notes on Australasian Orchids 6: A new species of Rhizanthella (Diurideae, subtribe Prasophyllinae) from Eastern Australia|url=https://revistas.ucr.ac.cr/index.php/lankesteriana/article/view/43271|journal=Lankesteriana|language=en|pages=221–227–221–227|doi=10.15517/lank.v20i2.43271|issn=2215-2067|doi-access=free}}</ref>

==Ecology==
The pollination mechanism of ''Rhizanthella'' is not known. A single specimen of a small fly from the genus ''[[Megaselia]]'', some small wasps and termites are the only observations of insects carrying [[pollinia]] of ''Rhizanthella''.<ref name="Orchids" />

==References==
{{Reflist}}


==Further reading==
==Further reading==
*Hoffman, N., Brown, A. (1998). ''Orchids of South-west Australia''. University of Western Australia Press, Nedlands.Rev. 2nd ed. with suppl. ISBN 1876268182
* Jones, David L. (2006).'' A complete guide to native orchids of Australia: including the island territories''. Frenchs Forest. {{ISBN|1-877069-12-4}}.
⚫
* [https://web.archive.org/web/20080311222734/http://www.arkive.org/species/GES/plants_and_algae/Rhizanthella_gardneri/ Underground orchid - Rhizanthella gardneri] at ARKive.org (includes photographs)
*Jones, David L. (2006).'' A complete guide to native orchids of Australia: including the island territories''. Frenchs Forest. ISBN 1-8770-6912-4.
* {{Commons-inline|Rhizanthella|''Rhizanthella''}}
⚫
*[http://www.arkive.org/species/GES/plants_and_algae/Rhizanthella_gardneri/ Underground orchid - Rhizanthella gardneri] at ARKive.org (includes photographs)


{{Taxonbar|from1=Q137012|from2=Q21447122}}
{{commons}}
{{Authority control}}


[[Category:Rhizanthella| ]]
[[Category:Rhizanthella| ]]
[[Category:Orchid genera]]
[[Category:Diurideae genera]]
[[Category:Angiosperms of Western Australia]]
[[Category:Endemic orchids of Australia]]
[[Category:Orchidaceae of Australia]]
[[Category:Myco-heterotrophic orchids]]
[[Category:Plants with indehiscent fruit]]

[[de:Rhizanthella]]
[[es:Rhizanthella]]
[[kv:Ризантелла]]
[[mrj:Ризантелла]]
[[koi:Ризантелла]]
[[pt:Rhizanthella]]
[[fi:Rhizanthella]]
[[udm:Ризантелла]]

Latest revision as of 20:16, 25 October 2023

Underground orchids
Rhizanthella gardneri
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Subtribe: Rhizanthellinae
R.S.Rogers
Genus: Rhizanthella
R.S.Rogers[1]
Type species
Rhizanthella gardneri
R.S.Rogers (1928)
Synonyms[2]

Cryptanthemis Rupp

Rhizanthella, commonly known as underground orchids,[3] is a genus of flowering plants in the orchid family, Orchidaceae and is endemic to Australia. All are leafless, living underground in symbiosis with mycorrhizal fungi. The inflorescence is a head of flowers held at, or just above the ground but mostly covered by soil or leaf litter and little is known about the mechanism of pollination.

Description

[edit]

Orchids in the genus Rhizanthella are mostly underground, perennial, sympodial, mycotrophic herbs with fleshy underground stems which produce new shoots at nodes where there are colourless leaf-like cataphylls. There are no roots and new tubers form at the end of short stems. The leaves are reduced to scale-like structures lacking chlorophyll, pressed against and sheathing the stems.[3][4][5][6]

The inflorescence is a head containing many flowers and is held at, or just above ground level but the head is usually covered with leaf litter or soil. The head is surrounded by a large number of overlapping bracts and each flower has an erect, elongated bract at its base. The flowers are non-resupinate, arranged in a spiral, inward-facing, dull coloured and lack a stalk. The sepals and petals form a short, curved hood over the labellum and column, open on one side. The lateral sepals are joined to each other and to the dorsal sepal at their bases. The petals are joined at their bases to the column and are shorter than the sepals. The labellum is different in size, shape and colouration from the other petals and sepals, is thick, fleshy and has no nectar. The column is short with short wings. Flowering time depends on species and is followed by the fruit which is a berry that does not split open (indehiscent) and which contains 50 to 100 seeds.[3][4][5][6]

Underground orchids do not possess chloroplasts but they retain plastid genes, although R. gardneri possesses one of the smallest organelle genome yet described in land plants.[7]

Taxonomy and naming

[edit]

The first formal description of an underground orchid was by Richard Sanders Rogers who published his description of R. gardneri in the Journal of the Royal Society of Western Australia in 1928.[8][9] The name "Rhizanthella" is a diminutive of Rhizanthes, a parasitic plant in the Family Rafflesiaceae.[10] The name "Rhizanthes" is derived from the Ancient Greek words rhiza meaning "root"[11]: 666  and anthos meaning "flower".[11]: 338 

Species list

[edit]

Four species are recognised by the World Checklist of Selected Plant Families and a fifth species has been formally described, but not as yet accepted by other authorities:

In 2020, a fifth species, Rhizanthella speciosa, found in New South Wales, was described by Mark Clements and David Jones in the journal Lankesteriana but as at September 2020, the name has not been accepted by the World Checklist of Selected Plant Families.[16]

Distribution and habitat

[edit]

Rhizanthella gardneri occurs in the south-west of Western Australia where it grows in association with broombush (Melaleuca uncinata).[3] R. johnstonii, also from WA, was split from R. gardneri in 2018.[17][18] Rhizanthella omissa has only been collected once, at an elevation of 1,200 m (4,000 ft) in the Lamington National Park in Queensland.[19] Rhizanthella slateri, formerly known as Cryptanthemis slateri, occurs in the Blue Mountains and similar ranges in New South Wales where it grows in sclerophyll forest.[6] R. speciosa was discovered in 2016 in wet sclerophyll forest in Barrington Tops, which contrasts with the more-open dry forest habitat of R. slateri.[18]

Ecology

[edit]

The pollination mechanism of Rhizanthella is not known. A single specimen of a small fly from the genus Megaselia, some small wasps and termites are the only observations of insects carrying pollinia of Rhizanthella.[4]

References

[edit]
  1. ^ "Rhizanthella". Kew Science - Plants of the World Online. Retrieved 25 September 2020.
  2. ^ "Rhizanthella". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 20 July 2016.
  3. ^ a b c d Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia (3rd ed.). Gooseberry Hill: Noel Hoffman. pp. 386–389. ISBN 9780646562322.
  4. ^ a b c Alec M. Pridgeon; Phillip J. Cribb; Mark W. Chase; Finn N. Rasmussen, eds. (2001). Genera Orchidacearum, Volume 2, Orchidoideae (part 1). Oxford, England: Oxford University Press. pp. 186–193. ISBN 0198507100.
  5. ^ a b "Rhizanthella". FloraBase. Western Australian Government Department of Biodiversity, Conservation and Attractions.
  6. ^ a b c Weston, Peter H. "Genus Rhizanthella". Royal Botanic Garden Sydney: plantnet. Retrieved 20 July 2016.
  7. ^ Delannoy, Etienne; Fujii, Sota; Colas des Francs-Small, Catherine; Brundrett, Mark; Small, Ian (2 February 2011). "Rampant Gene Loss in the Underground Orchid Rhizanthella gardneri Highlights Evolutionary Constraints on Plastid Genomes". Molecular Biology and Evolution. 28 (7): 2077–2086. doi:10.1093/molbev/msr028. PMC 3112369. PMID 21289370.
  8. ^ "Rhizanthella gardneri". APNI. Retrieved 20 July 2016.
  9. ^ Rogers, Richard Sanders (1928). "A New Genus of Australian Orchid". Journal of the Royal Society of Western Australia. 15 (1): 1. Retrieved 26 September 2020.
  10. ^ Quattrocchi, Umberto (2000). R - Z. Boca Raton, FL: CRC World Dictionary of Pant Names (R-Z). p. 2296. ISBN 0849326788.
  11. ^ a b Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
  12. ^ "Rhizanthella gardneri". Kew Science - Plants of the World Online. Retrieved 25 September 2020.
  13. ^ "Rhizanthella johnstonii". Kew Science - Plants of the World Online. Retrieved 25 September 2020.
  14. ^ "Rhizanthella omissa". Kew Science - Plants of the World Online. Retrieved 25 September 2020.
  15. ^ "Rhizanthella slateri". Kew Science - Plants of the World Online. Retrieved 25 September 2020.
  16. ^ "Rhizanthella speciosa". APNI. Retrieved 27 September 2020.
  17. ^ Dixon, Kingsley W.; Christenhusz, Maarten J. M. (2018-01-12). "Flowering in darkness: a new species of subterranean orchid Rhizanthella (Orchidaceae; Orchidoideae; Diurideae) from Western Australia". Phytotaxa. 334 (1): 75–79. doi:10.11646/phytotaxa.334.1.12. ISSN 1179-3163.
  18. ^ a b Clements, Mark A.; Jones, David L. (2020-07-30). "Notes on Australasian Orchids 6: A new species of Rhizanthella (Diurideae, subtribe Prasophyllinae) from Eastern Australia". Lankesteriana: 221–227–221–227. doi:10.15517/lank.v20i2.43271. ISSN 2215-2067.
  19. ^ "Rhizanthella omissa". Internet Orchid Species Photo Encyclopedia. Retrieved 20 July 2016.

Further reading

[edit]
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