{{Short description|Butterfly-like flowers}} {{multiple image | align = right | direction = vertical | header = | header_align = center | image1 = Wisteria sinensis anatomia rev en.svg<!--Awaiting renaming!!--> | alt1 = | width1 = 250 | caption1 = Flower parts of a Chinese wisteria. It has a diadelphous stamen morphology (one stamen not fused with the remaining nine), which Linnaeus classed as the Diadelphia. | image2 = Sesbanea bispinosa, crop.jpg | alt2 = | width2 = 250 | caption2 = Dissected flower parts of ''Sesbania bispinosa'' | background color=;border:none; }} '''Papilionaceous flowers''' (from Latin: ''papilion'', a butterfly) are flowers with the characteristic irregular and butterfly-like corolla found in many, though not all, plants of the species-rich subfamily Faboideae of legumes. Tournefort suggested that the term ''Flores papilionacei'' originated with Valerius Cordus,<ref name=Rees/> who applied it to the flowers of the bean.<ref name=cordus>{{cite book|last1=Cordus|first1=Valerius |title=Historia Stirpium et Sylva |chapter=162 |date=1561}}</ref>
==Structure== ===Corolla=== The flowers have a bilateral symmetry with the corolla consisting of five petals. A single, large, upper petal is known as the '''banner''' (also '''vexillum''' or '''standard''' petal). The semi-cylindrical base of the banner embraces and compresses two equal and smaller lateral '''wings''' (or '''alae'''). The wings in turn enclose a pair of small keel petals, that are situated somewhat lower than the wings, but are interior to them.<ref name=Rees/> They have concave sides and correspond with the shape of the wings. The two '''keel''' petals are fused at their bases<ref name=reddy/> or stuck together<ref name=nswfs>{{cite web |title=Botanical term: papilionaceous |url=http://www.nswildflora.ca/glossary/papilionaceous.html |website=nswildflora.ca |publisher=Nova Scotia Wild Flora Society |date=2007 |access-date=24 March 2015 |archive-url=https://web.archive.org/web/20160304044830/http://www.nswildflora.ca/glossary/papilionaceous.html |archive-date=4 March 2016 }}</ref> to form a boat-shaped structure that encloses the essential flower organs,<ref>{{cite book |last1=Gupta |first1=P.K. |title=Genetics: classical to modern |date=2007 |publisher=Rastogi Publications |location=Meerut, India |isbn=978-81-7133-896-2 |pages=146–147 |edition=1}}</ref> namely the androecium and gynoecium. Typically these flowers have a vexillary (i.e. descendingly imbricate or overlapping) aestivation.<ref name=reddy>{{cite book |last1=Reddy |first1=S. M. |title=University Botany III: (Plant Taxonomy, Plant Embryology, Plant Physiology) |volume = 3 |date=2007 |publisher=New Age International |isbn=978-81-224-1547-6 |pages=60–64}}</ref>
===Stamens=== The stamens often have a diadelphous morphology, meaning that they are united in two sets with a distinct filament shape in each set.<ref name=Rees/> The inferior set forms a membranous sheath at its base, that envelops the single, superior pistil in a tube. The tube divides into nine filaments, which trace the base of the keel petals that enclose them.<ref name=Rees/> The single free filament lies above them. In ''Smithia'' the two sets are equal, with 5 stamens in each.<ref name=Rees/>
Many papilionaceous flowers however have ten distinct stamens. Genera that conform to the latter morphology include ''Sophora'', ''Anagyris'', ''Cercis'', ''Daviesia'', ''Dillwynia'', ''Gompholobium'', ''Mirbelia'' and ''Pultenaea''.<ref name=Rees/>
==Ecology== [[File:Bee bossiaea cinerea cropped.jpg|thumb|upright=1.2|A bee pollinating the flower of ''Bossiaea cinerea''.]] Charles Darwin observed that the fertility of plants with papilionaceous flowers depend to an important extent on visits by bees,<ref name=darw>{{cite book |last1=Darwin |first1=Charles |title=On the origin of species by means of natural selection, or, The preservation of favored races in the struggle for life | chapter = IV: On the advantage |date=2007 |publisher=Cosimo Classics |location=New York |isbn=978-1-60206-144-6 |page=62}}</ref> and it is accepted that this corolla structure evolved under selective pressure of bee pollinators.<ref name=swj>{{cite journal |last1=Aronne |first1=Giovanna |last2=Giovanetti |first2=Manuela |last3=De Micco |first3=Veronica |title=Morphofunctional Traits and Pollination Mechanisms of Coronilla emerus L. Flowers (Fabaceae) |journal=The Scientific World Journal |date=2012 |volume=2012 |article-number=381575 |doi=10.1100/2012/381575|pmid=22666114 |pmc=3361249 |doi-access=free }}</ref> Linnaeus remarked that they produce hardly any scent, but the flowers of Spanish broom, sweet pea, scorpion vetch, European yellow lupine, fava bean and various species of clover are notable exceptions.<ref name=Rees>{{cite book | last1=Rees | first1=Abraham | title=The Cyclopædia: Or, Universal Dictionary of Arts, Sciences, and Literature | date=1819 | publisher=Longman, Hurst, Rees, Orme & Brown [etc.] | page=PAP |volume= 26 }}</ref>
Four different mechanisms of pollen release are known in papilionaceous flowers, which are respectively known as the explosive, valvular, piston and brush mechanisms.<ref name=swj/> In the explosive or tripping mechanism (''cf.'' alfalfa, common broom, ox-eye bean<ref name=mos>{{cite web |last1=Mosquin |first1=Ted |title=The explosive pollination mechanism in Cornus canadensis L. |url=http://www.ou.edu/cas/botany-micro/ben/ben194.html |website=Botanical Electronic News |publisher=The Canadian Field-Naturalist, Volume 99, Number I, Jan.-Mar. 1985 |access-date=25 March 2015}}</ref>) all pollen is instantly released when pressure on the staminal column is permanently released (usually by an insect) causing it to snap against the standard petal. In the valvular mechanism pollen is released repeatedly when pollinators unseal the upper rim of the keel petals, and force them downwards. In the piston mechanism (''cf.'' scorpion senna<ref name=swj/>) pollen is released repeatedly when the keel tip is moved by an insect so as to release pollen through a hole in the tip. The brush mechanism employs a pistil which is longer than the stamens, so as to avoid self-pollination. When a pollinator presses against the standard and wing petals, a brush on the temporarily lifted pistil brushes pollen onto the pollinator, while the stigma receives external pollen.<ref name=swj/>
==Examples and exceptions== Well-known plant genera in the Faboideae which exhibit this corolla morphology include beans, peas, sweet peas, alfalfa (lucerne), clovers, lupines, smoke trees, black locusts, locoweeds and coral trees.<ref name=ww1>{{cite web |last1=Armstrong |first1=W. P. |title=Flower Terminology Part 2, 14. Flower Definitions |url=http://waynesword.palomar.edu/termfl2.htm |website=Wayne's Word, Botany 115 Terminology |access-date=25 March 2015 |archive-date=20 March 2015 |archive-url=https://web.archive.org/web/20150320005605/http://waynesword.palomar.edu/termfl2.htm }}</ref><ref name=ww2/> The flowers of coral trees are diadelphous and are considered papilionaceous, but the wings are much reduced, suggesting a flower with three petals.<ref name=Rees/><ref name=ww2>{{cite web |last1=Armstrong |first1=W. P. |title=1. Family Fabaceae - Subfamily Papilionoideae |url=http://waynesword.palomar.edu/legume1.htm |website=Wayne's Word, Botany 115 Terminology |access-date=25 March 2015 |archive-date=9 March 2015 |archive-url=https://web.archive.org/web/20150309223721/http://waynesword.palomar.edu/legume1.htm }}</ref> Their keel petals are elongate, fused together and sometimes tubular to facilitate pollination by certain bird groups,<ref name=ww2/> while secondary compounds in their nectar seem to repel bees.<ref name="nic">{{cite journal |last1=Nicolson |first1=Susan W. |last2=Lerch-Henning |first2=Sara |last3=Welsford |first3=Megan |last4=Johnson |first4=Steven D. |title= Nectar palatability can selectively filter bird and insect visitors to coral tree flowers |journal=Evolutionary Ecology |date=16 May 2015 |volume=29 |issue=3 |pages=405–417 |doi=10.1007/s10682-014-9718-7 |bibcode=2015EvEco..29..405N |url=https://www.researchgate.net/publication/276543352 |access-date=1 July 2016|hdl=2263/51251 |s2cid=254468205 |hdl-access=free }}</ref>
The false indigo genus, though belonging to the Faboideae, does not exhibit a papilionaceous corolla morphology, as it has only one petal per flower,<ref name=aquatic>{{cite book |last1=Wooten |first1=Robert K. Godfrey; Jean, W.|title=Aquatic and wetland plants of southeastern United States: Dicotyledons |date=1981 |publisher=University of Georgia Press |location=Athens, Ga. |isbn=0-8203-4243-2|page=236}}</ref> namely the banner.<ref name=Rees/><ref name=reddy/> The corolla of clovers tends to be monopetalous, as all five petals are often fused below to form a tube.<ref name=Rees/>
<gallery mode="packed" heights="180" style="font-size:100%; line-height:130%"> 2011-07-25 21-30-17-flower.jpg|Common bean flower Vicia faba.jpg|Fava bean flowers with purple banners and pied wings Starr 081009-0043 Pisum sativum var. macrocarpum.jpg|Pea flower with pink banner and maroon wings Medicago sativa (5183007138).jpg|Alfalfa flowers with staminal column of central flower tripped </gallery>
==Other legume subfamilies== To the contrary, plants in the Mimosoideae subfamily of legumes have the petals reduced, and have numerous stamens arranged in showy spikes. In the Caesalpinioideae subfamily of legumes the upper petal is initially enveloped by the lateral petals, before the petals unfold to assume a radial five-fold symmetry.<ref name=ww1/> The aestivation of Mimosoideae, Caesalpinioideae and Faboideae is presented in diagram below. border|frameless|center|upright=3
==See also== * Pollination syndrome * Zoophily
==References== {{reflist}}
Category:Plant morphology Category:Faboideae