View source for Biology:Operculum (botany)

{{Short description|Botanical term for a protective covering, hood or lid}} [[File:Eucalyptus erythrocorys operculum.jpg|thumb|right|Red operculum of ''[[Biology:Eucalyptus erythrocorys|Eucalyptus erythrocorys]]'']]
[[File:Operculum scar.jpg|thumb|right|Operculum and scar of ''[[Biology:Eucalyptus blakelyi|Eucalyptus blakelyi]]'']]
[[File:Tortula muralis kalyptra.jpeg|thumb|Calyptra of ''[[Biology:Tortula muralis|Tortula muralis]]'']]
[[File:Physcomitrella Sporophyt.JPG|thumb|Calyptra on top of the brown spore capsule (sporophyte) of the moss ''[[Biology:Physcomitrella patens|Physcomitrella patens]]''. The brownish archegonial venter is still visible.]]

In [[Biology:Botany|botany]], an '''operculum''' ({{plural form}}: '''opercula''') or '''calyptra''' ({{etymology|grc|''{{wikt-lang|grc|καλύπτρα}}'' ({{grc-transl|καλύπτρα}})|veil}}) is a cap-like structure in some [[Biology:Flowering plant|flowering plant]]s, [[Biology:Moss|moss]]es, and [[Biology:Fungus|fungi]]. It is a covering, hood or lid, describing a feature in [[Biology:Plant morphology|plant morphology]].

==Flowering plants==
In flowering plants, the operculum, also known as a calyptra, is the cap-like covering or "lid" of the flower or fruit that detaches at maturity. The operculum is formed by the fusion of [[Biology:Sepal|sepal]]s and/or [[Biology:Petal|petal]]s and is usually shed as a single structure as the flower or fruit matures.<ref name="RBGS">{{cite web |title=Glossary of Botanical Terms |url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&glossary=yes&alpha=M-O |publisher=Royal Botanic Garden Sydney |access-date=27 December 2019}}</ref> The name is also used for the capping tissue of [[Biology:Root|root]]s, the [[Biology:Root cap|root cap]].

In [[Biology:Eucalypt|eucalypt]]s, (including ''[[Biology:Eucalyptus|Eucalyptus]]'' and ''[[Biology:Corymbia|Corymbia]]'' but not ''[[Biology:Angophora|Angophora]]'') there may be two opercula – an outer operculum formed by the fusion of the united sepals and an inner operculum formed by the fusion of the sepals. In that case, the outer operculum is shed early in the development of the bud leaving a scar around the bud. In those species that lack an outer operculum, there is no bud scar. The inner operculum is shed just before flowering, when the [[Biology:Stamen|stamen]]s expand and shed their [[Biology:Pollen|pollen]].<ref name="CANBR">{{cite web |title=Learn about eucalypts |url=http://keyserver.lucidcentral.org:8080/euclid/data/02050e02-0108-490e-8900-0e0601070d00/media/Html/learn.htm |publisher=Euclid: Centre for Australian National Biodiversity Research |access-date=27 December 2019}}</ref>

In some species of [[Biology:Monocotyledon|monocotyledon]], the operculum is an area of [[Biology:Pollen#Structure|exine]] covering the pollen aperture.<ref name=Furness2001>{{cite journal |last1=Furness|first1=Carol A.|last2=Rudall|first2=Paula J.|title=Pollen and anther characters in monocot systematics|journal=Grana|date=January 2001|volume=40|issue=1–2|pages=17–25|doi=10.1080/00173130152591840|doi-access=free}}</ref>

In ''[[Biology:Plantago|Plantago]]'', the [[Biology:Capsule (fruit)|capsule]] has an opening covered by an operculum. When the operculum falls, the seed is sticky and is easily carried by animals that come into contact with it.<ref name="Soekarjo">{{cite book |editor-last1=Kuiper |editor-first1=Pieter J.C. |editor-last2=Bos |editor-first2=Marten |editor-last3=Soekarjo |editor-first3=R. |title=''Plantago'': A multidisciplinary study |date=1992 |publisher=Springer-Verlag |location=Berlin |isbn=3540536329 |pages=6–12 }}</ref>

[[Biology:Pitcher plant|Pitcher plant]]s have an operculum above the pitcher that serves to keep out rainwater that would otherwise dilute the digestive juices in the pitcher.<ref name="BBC">{{cite web |title=The giant plants that eat meat |url=http://www.bbc.com/earth/story/20150420-the-giant-plants-that-eat-meat |publisher=BBC |access-date=27 December 2019}}</ref>

==Bryophytes==
In [[Biology:Bryophyte|bryophytes]], the '''calyptra''' (''plural'' calyptrae) is an enlarged [[Biology:Archegonium|archegonial]] venter that protects the capsule containing the embryonic [[Biology:Sporophyte|sporophyte]].<ref>[[Biography:Ralf Reski|Ralf Reski]] (1998): Development, genetics and molecular biology of mosses. In: Botanica Acta. 111, 1-15.</ref> The calyptra is usually lost before the spores are released from the capsule. The shape of the calyptra can be used for identification purposes.<ref>{{Citation| last=Malcolm; Malcolm| first= Bill; Nancy| title= Mosses and other Bryophytes, an Illustrated Glossary| year=2006| publisher=Micro-Optics Press| page=65| isbn=0-9582224-7-9}}</ref>

The [[Biology:Sporangium|sporangium]] of mosses usually opens when its operculum or "lid" falls off, exposing a ring of teeth that control the release of spores.<ref name="EB">{{cite web |title=Form and function |url=https://www.britannica.com/plant/bryophyte/Form-and-function#ref211422 |publisher=Encyclopædia Britannica, Inc. |access-date=27 December 2019}}</ref>

==Fungi==
There are two types of sexual spore-bearing [[Biology:Ascus|asci]] of [[Biology:Ascomycota|ascomycete]] [[Biology:Fungi|fungi]] – those that have an operculum at the top of the ascus, and those that do not.<ref name="Reynolds">{{cite book |last1=Reynolds |first1=Don R. |last2=van Brummelen |first2=J. |title=Ascomycete Systematics : the Luttrellian Concept (Chapter 3 - The Operculate Ascus and Allied Forms) |date=1981 |publisher=Springer-Verlag |location=New York |isbn=9781461258469 |pages=27–31}}</ref>

==See also==
*Operculum (disambiguation)

==References==
{{Reflist}}

==External links==
* {{Cite NSRW|wstitle=Calyptra|short=x}}

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[[Category:Plant anatomy]]

{{Sourceattribution|Operculum (botany)}}