Editing Orchid (section)

=== Pollination ===
{{Main|Pollination of orchids}}
The complex mechanisms that orchids have evolved to achieve [[Allogamy|cross-pollination]] were investigated by [[Charles Darwin]] and described in ''[[Fertilisation of Orchids]]'' (1862). Orchids have developed highly specialized [[pollination]] systems, thus the chances of being pollinated are often scarce, so orchid flowers usually remain receptive for very long periods, rendering unpollinated flowers long-lasting in cultivation. Most orchids deliver pollen in a single mass. Each time pollination succeeds, thousands of ovules can be fertilized.

Pollinators are often visually attracted by the shape and colours of the labellum. However, some ''[[Bulbophyllum]]'' species attract male fruit flies (''[[Bactrocera]]'' and ''[[Zeugodacus]]'' spp.) solely via a floral chemical which simultaneously acts as a floral reward (e.g. [[methyl eugenol]], raspberry [[ketone]], or [[zingerone]]) to perform pollination.<ref>{{cite journal |author1=Tan K.H. |author2=Nishida R. | year = 2000 | title = Mutual reproductive benefits between a wild orchid, ''Bulbophyllum patens'', and ''Bactrocera'' fruit flies via a floral synomone | doi = 10.1023/A:1005477926244 | journal = Journal of Chemical Ecology | volume = 26 | issue = 2| pages = 533–546 |bibcode=2000JCEco..26..533T }}</ref><ref>{{cite journal |last1=Tan |first1=Keng-Hong |last2=Nishida |first2=Ritsuo |last3=Toong |first3=Yock-Chai |title=Floral Synomone of a Wild Orchid, Bulbophyllum cheiri, Lures Bactrocera Fruit Flies for Pollination |journal=Journal of Chemical Ecology |date=June 2002 |volume=28 |issue=6 |pages=1161–1172 |doi=10.1023/A:1016277500007 |pmid=12184394 |bibcode=2002JCEco..28.1161T }}</ref><ref>{{cite journal |last1=Raina |first1=Ashok K. |last2=Bland |first2=John M. |last3=Osbrink |first3=Weste |title=Hydroquinone Is Not A Phagostimulant For The Formosan Subterranean Termite |journal=Journal of Chemical Ecology |date=March 2005 |volume=31 |issue=3 |pages=509–517 |doi=10.1007/s10886-005-2026-5 |pmid=15898498 |bibcode=2005JCEco..31..509R }}</ref> The flowers may produce attractive odours. Although absent in most species, [[nectar]] may be produced in a [[spur (biology)|spur]] of the labellum ('''8''' in the illustration above), or on the point of the sepals, or in the septa of the ovary, the most typical position amongst the [[Asparagales]].

[[File:Phalaenopsis pollinia on toothpick.jpg|thumb|right|''[[Phalaenopsis]]'' pollinia (orange) attached to a toothpick with its sticky [[viscidium]]]]

In orchids that produce pollinia, pollination happens as some variant of the following sequence: when the pollinator enters into the flower, it touches a viscidium, which promptly sticks to its body, generally on the head or abdomen. While leaving the flower, it pulls the pollinium out of the anther, as it is connected to the viscidium by the caudicle or stipe. The caudicle then bends and the pollinium is moved forwards and downwards. When the pollinator enters another flower of the same species, the pollinium has taken such position that it will stick to the stigma of the second flower, just below the rostellum, pollinating it. In horticulture, [[Hand-pollination|artificial orchid pollination]] is achieved by removing the pollinia with a small instrument such as a toothpick from the pollen parent and transferring them to the seed parent.

[[File:Ophrys apifera flower2.jpg|thumb|right|''[[Ophrys apifera]]'' is about to self-pollinate]]

Some orchids mainly or totally rely on [[self-pollination]], especially in colder regions where pollinators are particularly rare. The caudicles may dry up if the flower has not been visited by any pollinator, and the pollinia then fall directly on the stigma. Otherwise, the anther may rotate and then enter the stigma cavity of the flower (as in ''[[Holcoglossum amesianum]]'').

The slipper orchid ''[[Paphiopedilum parishii]]'' reproduces by [[Self-pollination|self-fertilization]]. This occurs when the anther changes from a solid to a liquid state and directly contacts the stigma surface without the aid of any pollinating agent or floral assembly.<ref>{{cite journal |vauthors=Chen LJ, Liu KW, Xiao XJ, Tsai WC, Hsiao YY, Huang J, Liu ZJ |title=The anther steps onto the stigma for self-fertilization in a slipper orchid |journal=PLOS ONE|volume=7 |issue=5 |pages=e37478 |year=2012 |pmid=22649529 |pmc=3359306 |doi=10.1371/journal.pone.0037478 |bibcode=2012PLoSO...737478C |doi-access=free }}</ref>

The labellum of the [[Cypripedioideae]] is [[Poke bonnet|poke bonnet-shaped]], and has the function of trapping visiting insects. The only exit leads to the anthers that deposit pollen on the visitor.

In some extremely specialized orchids, such as the Eurasian genus ''[[Ophrys]]'', the labellum is adapted to have a colour, shape, and odour which attracts male insects via [[mimicry]] of a receptive female. Pollination happens as the insect attempts to mate with flowers.

Many neotropical orchids are pollinated by male [[euglossini|orchid bees]], which visit the flowers to gather volatile chemicals they require to synthesize [[pheromone|pheromonal]] attractants. Males of such species as ''[[Euglossa imperialis]]'' or ''[[Eulaema meriana]]'' have been observed to leave their territories periodically to forage for aromatic compounds, such as cineole, to synthesize pheromone for attracting and mating with females.<ref>{{cite journal | author = Kimsey Lynn Siri | year = 1980 | title = The behaviour of male orchid bees (Apidae, Hymenoptera, Insecta) and the question of leks | doi = 10.1016/s0003-3472(80)80088-1| journal = Animal Behaviour | volume = 28 | issue = 4| pages = 996–1004 }}</ref><ref>{{cite journal |last1=Zimmermann |first1=Yvonne |last2=Roubik |first2=David W. |last3=Eltz |first3=Thomas |title=Species-specific attraction to pheromonal analogues in orchid bees |journal=Behavioral Ecology and Sociobiology |date=October 2006 |volume=60 |issue=6 |pages=833–843 |doi=10.1007/s00265-006-0227-8 |bibcode=2006BEcoS..60..833Z }}</ref> Each type of orchid places the pollinia on a different body part of a different species of bee, so as to enforce proper cross-pollination.

A rare [[wikt:achlorophyllous|achlorophyllous]] [[Saprophyte|saprophytic]] orchid growing entirely underground in Australia, ''[[Rhizanthella slateri]]'', is never exposed to light, and depends on [[ant]]s and other terrestrial insects to pollinate it.

''[[Catasetum]]'', a genus discussed briefly by [[Charles Darwin|Darwin]], actually launches its viscid pollinia with explosive force when an insect touches a [[seta]], knocking the pollinator off the flower.

After pollination, the sepals and petals fade and wilt, but they usually remain attached to the ovary.

In 2011, <!-- a member of the genus ''[[Bulbophyllum]]'', --> ''[[Bulbophyllum nocturnum]]'' was discovered to flower nocturnally.<ref>{{cite web |url=http://www.australiangeographic.com.au/journal/worlds-first-night-flowering-orchid-discovered-in-papua-new-guinea.htm/ |title=World's first night-flowering orchid discovered |author=Tom Lawrie |publisher=[[Australian Geographic]] |date=23 November 2010 |access-date=26 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20111130073555/http://www.australiangeographic.com.au/journal/worlds-first-night-flowering-orchid-discovered-in-papua-new-guinea.htm |archive-date=30 November 2011 }}</ref>