Inflorescence
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Terms confused according to Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada
An '''inflorescence''' is a group or cluster of [[flower]]s arranged on a [[Plant stem|stem]] that is composed of a main [[branch]] or a complicated arrangement of branches. Strictly, it is the part of the [[shoot]] of [[spermatophytes|seed plants]] where [[flower]]s are formed and which is accordingly modified. The modifications can involve the length and the nature of the [[internode]]s and the [[phyllotaxis]], as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes.
The stem holding the whole inflorescence is called a '''peduncle''' and the main stem holding the flowers or more branches within the inflorescence is called the '''rachis'''. The stalk of each single flower is called a '''pedicel'''.
The [[fruit]]ing stage of an inflorescence is known as an '''infructescence'''.
A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle.
== General characteristics ==
Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it. These terms are general representations as plants in nature can have a combination of types.
=== Bracts ===
Inflorescences usually have modified foliage different from the vegetative part of the plant. Considering the broadest meaning of the term, any leaf associated with an inflorescence is called a '''[[bract]]''' <!--- This broad definition of bract is required to keep consistency within the article --->. A bract is usually located at the node where the main stem of the inflorescence forms, joined to the main stem of the plant, but other bracts can exist within the inflorescence itself. They serve a variety of functions which include attracting pollinators and protecting young flowers. According to the presence or absence of bracts and their characteristics we can distinguish:
* '''Ebracteate inflorescences''': No bracts in the inflorescence.
* '''Bracteate inflorescences''': The bracts in the inflorescence are very specialised, sometimes reduced to small scales, divided or dissected.
* '''Leafy inflorescences''': Though often reduced in size, the bracts are unspecialised and look like the typical leaves of the plant, so that the term '''flowering stem''' is usually applied instead of inflorescence. This use is not technically correct, as, despite their 'normal' appearance, these ''leaves'' are considered, in fact, ''bracts'', so that 'leafy inflorescence' is preferable.
* '''Leafy-bracted inflorescences''': Intermediate between bracteate and leafy inflorescence.
If many bracts are present and they are strictly connected to the stem, like in the family [[Asteraceae]], the bracts might collectively be called an '''involucre'''. If the inflorescence has a second unit of bracts further up the stem, they might be called an '''involucel'''.
<gallery>
Image:Brakteose beblätterung (inflorescence).PNG|Ebracteate inflorescence.
Image:Wisteria sinensisPNPG.jpg|Ebracteate of ''[[Wisteria sinensis]]''
Image:Brakteose beblätterung2 (inflorescence).PNG|Bracteate inflorescence.
Image:Pedicularis verticillata a3.jpg|Bracteate inflorescence of ''[[Pedicularis verticillata]]''.
Image:Frondobrakteose Beblätterung (inflorescence).PNG|Leafy-bracted inflorescence.
Image:Rhinanthus angustifolius.jpg|Leafy-bracted inflorescence of ''[[Rhinanthus angustifolius]]''.
Image:Frondose beblätterung (inflorescence).PNG|Leafy inflorescence.
Image:Unknown plant 01 bgiu.jpg|Leafy inflorescence of ''[[Aristolochia clematitis]]''.
</gallery>
=== Terminal flower ===
Plant organs can grow according to two different schemes, namely [[monopodial]] and [[sympodial]]. In inflorescences these two different growth patterns are called indeterminate or determinate, and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
* '''Indeterminate inflorescence''': [[Monopodial]] growth. The terminal bud keeps growing and forming lateral flowers. A terminal flower is never formed.
* '''Determinate inflorescence''': [[Sympodial]] growth. The terminal bud forms a terminal flower and then dies out. Other flowers then grow from lateral buds.
Indeterminate and determinate inflorescences are sometimes referred to as '''open''' and '''closed''' inflorescences respectively.
In '''determinate inflorescences''' the terminal flower is usually the first to mature (praecursive development), while the others tend to mature starting from the bottom of the stem. This pattern is called '''acropetal''' maturation. When flowers start to mature from the top of the stem , maturation is '''basipetal''', while when the central mature first, '''divergent'''.
<gallery>
Image:Akropetale Effloration (inflorescence).PNG|Determinate inflorescence with acropetal maturation
Image:Basipetale effloration (inflorescence).PNG|Determinate inflorescence with basipetal maturation
Image:Divergente effloration (inflorescence).PNG|Determinate inflorescence with divergent maturation
</gallery>
In '''indeterminate inflorescence''' there is no true terminal flower and the stem usually has a rudimentary end. In many cases the last true flower formed by the terminal bud ('''subterminal''' flower) straightens up, appearing to be a terminal flower. Often a vestige of the terminal bud may be noticed higher on the stem.
<gallery>
Image:Offener Blütenstand2 (inflorescence).PNG|Indeterminate inflorescence with a perfect acropetal maturation.
Image:Offener Blütenstand (inflorescence).PNG|Indeterminate inflorescence with a acropetal maturation and lateral flower buds.
Image:Pseudoterminalblüte (inflorescence).PNG|Indeterminate inflorescence with the subterminal flower to simulate the terminal one (vestige present)
</gallery>
=== Phyllotaxis ===
As with [[leaf|leaves]], flowers can be arranged on the stem according to many different patterns. See '[[Phyllotaxis]]' for in-depth descriptions.
<gallery>
Image:Inflorescences Raceme Kwiatostan Grono.svg|Alternate flowers
Image:Traube dekussiert (inflorescence).PNG|Opposite flowers
</gallery>
=== Metatopy ===
Metatopy is the placement of organs out of there normally expected position: typically metatopy occurs in inflorescences when unequal growth rates alter different areas of the axis and the organs attached to the axis.
When a single or a cluster of flower(s) is located at the axil of a bract, the location of the bract in relation to the stem holding the flower(s) is indicated by the use of different terms and may be a useful diagnostic indicator.
Typical placement of bracts include:
* Some plants have bracts that subtend the inflorescence, were the flowers are on branched stalks, the bracts are not connected to the stalks holding the flowers but are [[adnation|adnate]] or attached to the main stem (Adnate describes the fusing together of different unrelated parts. When the parts fused together are the same, they are connately joined)
* Other plants have the bracts subtend the [[pedicel]] or peduncle of single flowers.
Metatopic placement of bracts include:
* When the bract is attached to the stem holding the flower (the pedicel or peduncle), it is said to be '''recaulescent''', sometimes these bracts or bracteoles are highly modified and appear to be appendages of the flower calyx. Recaulescences is the fusion of the subtending leaf with the stem holding the bud or the bud its self,<ref>Kubitzki, Klaus, and Clemens Bayer. 2002. ''Flowering plants, Dicotyledons: Malvales, Capparales, and non-betalain Caryophyllales. The Families and genera of vascular plants, 5.'' Berlin: Springer. p. 77</ref> thus the leaf or bract is adnate to the stem of flower.
* When the formation of the bud is shifted up the stem distinctly above the subtending leaf, it is described as '''concaulescent'''.
<gallery>
Image:Bluete und Tragblatt (inflorescence).PNG|Flower and subtending bract
Image:Türkenbund dunkel.jpg|''[[Lilium martagon]]'' (flower and subtending bract)
Image:Konkauleszenz (inflorescence).PNG|Concaulescence
Image:Tomato scanned.jpg|''[[Solanum lycopersicum]]'' (concaulescence)
Image:Rekauleszenz (inflorescence).PNG|Recaulescence
Image:Tilia cordata Owoce lipy 656.jpg|''[[Tilia cordata]]'' (recaulescence)
</gallery>
== Organisation ==
There is no general consensus in defining the different inflorescences. The following is based on [[Focko Weberling]]'s ''Morphologie der Blüten und der Blütenstände'' (Stuttgart, 1981).
The main groups of inflorescences are distinguished by branching. Within these groups, the most important characteristics are the intersection of the axes and different variations of the model.
Inflorescences can be '''simple''' or '''compound'''.
=== Simple inflorescences ===
Indeterminate simple inflorescences are generally called '''racemose'''. The main kind of racemose inflorescence is the '''raceme''', the other kind of racemose inflorescences can all be derived from this one by dilation, compression, swelling or reduction of the different axes. Some passage forms between the obvious ones are commonly admitted.
* A '''[[raceme]]''' is an unbranched, indeterminate inflorescence with pedicellate (having short floral stalks) flowers along the axis.
* A '''[[raceme|spike]]''' is a type of raceme with flowers that do not have a pedicel.
* A racemose '''[[corymb]]''' is an unbranched, indeterminate inflorescence that is flat-topped or convex due to their outer pedicels which are progressively longer than inner ones.
* An '''[[umbel]]''' is a type of raceme with a short axis and multiple floral pedicels of equal length that appear to arise from a common point.
* A '''[[spadix]]''' is a spike of flowers densely arranged around it, enclosed or accompanied by a highly specialised bract called a '''[[spadix|spathe]]'''. It is characteristic of the [[Araceae]] family.
* A '''[[flower head]]''' or '''capitulum''' is a very contracted raceme in which the single sessile flowers share are borne on an enlarged stem. It is characteristic of [[Dipsacaceae]].
* A '''[[catkin]]''' or '''ament''' is a scaly, generally drooping spike or raceme. Cymose or other complex inflorescences that are superficially similar are also generally called thus.
<gallery>
Image:Traube.PNG|[[Raceme]]
Image:Epilobe feuilles etroites 01.jpg|''[[Epilobium angustifolium]]''
Image:Inflorescences Spike Kwiatostan Kłos.svg|[[Spike]]
Image:Plantagomedia.JPG|''[[Plantago media]]'' (spike)
Image:Schirmtraube.PNG| Racemose [[corymb]]
Image:Schleifenblume06.jpg|''[[Iberis umbellata]]'' (racemose corymb)
Image:Inflorescences Umbel Kwiatostan Baldach.svg|[[Umbel]]
Image:Astrantia minor.jpg|''[[Astrantia minor]]'' (umbel)
Image:Kolben (inflorescence).PNG|[[Spadix]]
Image:Arum maculatum.jpeg|''[[Arum maculatum]]'' (spadix)
Image:Koepfchen (inflorescence).PNG|[[head (botany)|Head]] (round)
Image:Fleur 9 - VTdJ.JPG|''[[Dipsacus fullonum]]'' (head)
Image:Kätzchen (inflorescence).PNG|[[Catkin]] (racemose or spicate)
Image:Alnus incana rugosa catkin.jpg|''[[Alnus incana]]'' (ament)
</gallery>
Determinate simple inflorescences are generally called '''cymose'''. The main kind of cymose inflorescence is the '''[[cyme]]'''. Cymes are further divided according to this scheme:
* Only one secondary axis: '''monochasium'''
** Secondary buds always develop on the same side of the stem: '''helicoid cyme''' or '''bostryx'''
*** The successive pedicels are aligned on the same plane: '''drepanium'''
** Secondary buds develop alternately on the stem : '''scorpioid cyme'''
*** The successive pedicels are arranged in a sort of spiral: '''cincinnus''' (characteristic of the [[Boraginaceae]])
*** The successive pedicels follow a zig-zag path on the same plane: '''rhipidium''' (many [[Iridaceae]])
* Two secondary axes: '''dichasial cyme'''
** Secondary axis still dichasial: '''dichasium''' (characteristic of [[Caryophyllaceae]])
** Secondary axis monochasia: '''double scorpioid cyme''' or '''double helicoid cyme'''
* More than two secondary axes: '''pleiochasium'''
Although it is commonly said to be a scorpioid cyme, the typical inflorescence of the family [[Boraginaceae]] is in fact the cincinnus, a helicoid cyme.
<gallery>
Image:Dichasium (inflorescence).PNG|Dichasium
Image:Dichasium (top view) (inflorescence).PNG|Dichasium, top view
Image:2006-10-22Silene dioica07.jpg|''[[Silene dioica]]'' (dichasium)
Image:Doppelwickel (inflorescence).PNG|Double cyme
Image:Doppelschraubel (inflorescence).PNG|Double cyme
Image:Schicht.jpg|Cincinnus (lateral and top view)
Image:Symphytum officinale 02.jpg|''[[Symphytum officinale]]'' (cincinnus)
Image:Schroef (bloeiwijze).jpg|Bostryx (lateral and top view)
Image:Saint johns wart flowers.jpg|''[[Hypericum perforatum]]'' (bostryx)
Image:Waaier (bloeiwijze).jpg|Rhipidium (lateral and top view)
Image:Canna Endeavour 01.jpg| ''[[Canna (plant)|Canna]] sp.'' (rhipidium)
Image:Sikkel (bloeiwijze).jpg|Drepanium (lateral and top view)
Image:Gladiolus imbricatus a1.jpg|''[[Gladiolus imbricatus]]'' (drepanium)
</gallery>
A cyme can also be so compressed that it looks like an umbel. Strictly speaking this kind of inflorescence could be called '''umbelliform cyme''', although it is normally called simply 'umbel'.
Another kind of definite simple inflorescence is the raceme-like cyme or '''botryoid'''; that is as a raceme with a terminal flower and is usually improperly called 'raceme'.
<gallery>
Image:Inflorescences Umbel Kwiatostan Baldach.svg|Umbelliform cyme
Image:Fiore di geranio.JPG|''[[Pelargonium zonale]]'' (umbelliform cyme)
Image:Botryoid.png|Botryoid
Image:Berberis vernae MS 4426.jpg|''Berberis vernae'' (botryoid)
</gallery>
A reduced raceme or cyme that grows in the [[axil]] of a bract is called a '''fascicle'''. A '''verticillaster''' is a fascicle with the structure of a dichasium; it is common among the [[Lamiaceae]]. Many verticillasters with reduced bracts can form a spicate (spike-like) inflorescence that is commonly called a '''spike'''.
<gallery>
Image:Gentiana lutea1.JPG|''[[Gentiana lutea]]'' (fascicles)
Image:Lamium orvala3.jpg|''[[Lamium orvala]]'' (verticillaster)
Image:Mentha longifolia 2005.08.02 09.53.56.jpg|''[[Mentha longifolia]]'' ('spike')
</gallery>
=== Compound inflorescences ===
Simple inflorescences are the basis for compound inflorescences or '''synflorescences'''. The single flowers are there replaced by a simple inflorescence, which can be both a racemose or a cymose one. Compound inflorescences are composed of branched stems and can involve complicated arrangements that are difficult to trace back to the main branch.
A kind of compound inflorescence is the '''double inflorescence''', in which the basic structure is repeated in the place of single florets. For example a double raceme is a raceme in which the single flowers are replaced by other simple racemes; the same structure can be repeated to form triple or more complex structures.
Compound raceme inflorescences can either end with a final raceme ('''homoeothetic'''), or not ('''heterothetic'''). A compound raceme is often called a '''panicle'''. Note that this definition is very different from that given by [[Focko Weberling|Weberling]].
Compound umbles are umbels in which the single flowers are replaced by many smaller umbles called '''umbellets'''. The stem attaching the side umbellets to the main stem is called a '''ray'''.
<gallery>
Image:Doppeltraube2.PNG|Homeothetic compound raceme
Image:Melilotus officinalis01.jpg|''[[Melilotus officinalis]]'' (homoeothetic compound raceme)
Image:Doppeltraube (inflorescence).PNG|Heterothetic compound raceme
Image:Hebe albicans.jpg|''[[Hebe albicans]]'' (heterothetic compound raceme)
Image:Inflorescences Muktispike Kwiatostan KłosZłożony.svg|Compound spike
Image:Lolium multiflorum detail.jpeg|''[[Lolium temulentum]]'' (compound spike)
Image:Doppelkoepfchen.PNG|Compound capitulum
Image:Echinops Ain France.jpg|''[[Echinops ritro]]'' (compound capitulum)
Image:Inflorescences Umbel Kwiatostan BaldachZłożony.svg|Compound (double) umbel
Image:Laserpitium latifolium2.jpg|''[[Laserpicium latifolium]]'' (double umbel)
Image:Dreifachdolde.PNG|Compound (triple) umbel
</gallery>
The most common kind of definite compound inflorescence is the '''panicle''' (of Webeling, or 'panicle-like cyme'). A panicle is a definite inflorescence that is increasingly more strongly and irregularly branched from the top to the bottom and where each braching has a terminal flower.
The so called cymose '''corymb''' is similar to a racemose corymb but has a panicle-like structure. Another type of panicle is the '''anthela'''. An anthela is a cymose corymb with the lateral flowers higher than the central ones.
<gallery>
Image:Inflorescences Panicle Kwiatostan Wiecha.svg|[[Panicle]]
Image:Vigne inflorescence 2.jpg|[[Vitis vinifera]]'' (panicle)
Image:Schirmrispe (inflorescence).PNG|Cymose [[corymb]]
Image:Sambucus nigra 003.jpg|''[[Sambucus nigra]]'' (cymose corymb)
Image:Spirre (inflorescence).png|Anthela
Image:Juncus inflexus.jpeg|''[[Juncus inflexus]]'' (anthela)
</gallery>
A raceme in which the single flowers are replaced by cymes is called a (indefinite) '''thyrse'''. The secondary cymes can of course be of any of the different types of dichasia and monochasia. A botryoid in which the single flowers are replaced by cymes is a '''definite thyrse''' or '''thyrsoid'''. Thyrses are often confusingly called '''panicles'''.
<gallery>
Image:Homöokladische Thyrse (inflorescence).PNG|Thyrse
Image:Aesculus hippocastanum flori.jpg|''[[Aesculus hippocastanum]]''
Image:Dichasialer zymus (inflorescence).PNG|Thyrsoid
Image:Syringa11.jpg|''[[Syringa vulgaris]]''
</gallery>
Other combinations are, of course, possible. For example, heads or umbels may be arranged in a corymb or a panicle.
<gallery>
Image:Achillea (yarrow) - 16.JPG|''[[Achillea]]'' sp. (heads in a corymb)
Image:Hedera helix.jpg|''[[Hedera helix]]'' (umbels in a panicle)
</gallery>
=== Other ===
The family [[Asteraceae]] is characterised by a highly specialised head technically called a '''[[calathid]]''' (but usually referred to as 'capitulum' or 'head'). The family [[Poaceae]] has a peculiar inflorescence of small spikes ('''spikelets''') organised in panicles or spikes that are usually simply and improperly referred to as '''spike''' and '''panicle'''. The genus ''[[Ficus]]'' ([[Moraceae]]) has an inflorescence called '''[[syconium]]''' and the genus ''[[Euphorbia]]'' has '''[[cyathium|cyathia]]''' (sing. ''cyathium''), usually organised in umbels. For detailed descriptions, see the respective articles.
<gallery>
Image:Chamomile@original size.jpg|''[[Matricaria chamomilla]]'' (calathid)
Image:Wheat close-up.JPG|''[[Triticum aestivum]]'' (compound spikes, "spikes")
Image:Lemont rice.jpg|''[[Oryza sativa]]'' (spikes in a panicle, "panicle")
Image:Some figs.jpg|''[[Ficus carica]]'' (syconium)
Image:Euphorbia tridentata ies.jpg|''[[Euphorbia tridentata]]'' (cyathium)
Image:Euphorbia cyparissias 02 bgiu.jpg|''[[Euphorbia cyparissias]]'' (cyathia in an umbel)
</gallery>
== References and external links ==
{{Commons|Inflorescence}}
{{de}}
* Focko Weberling: ''Morphologie der Blüten und der Blütenstände; Zweiter Teil''. Verlag Eugen Ulmer, Stuttgart 1981
* Wilhelm Troll: ''Die Infloreszenzen; Erster Band''. Gustav Fischer Verlag, Stuttgart 1964
* Wilhelm Troll: ''Die Infloreszenzen; Zweiter Band, Erster Teil''. Gustav Fischer Verlag, Stuttgart 1969
* Wilhelm Troll: ''Praktische Einführung in die Pflanzenmorphologie''. Gustav Fischer Verlag, Jena 1957
* Bernhard Kausmann: ''Pflanzenanatomie''. Gustav Fischer Verlag, Jena 1963
* Walter S. Judd, Christopher S. Campbell, Elizabeth A. Kellogg, Peter F. Stevens, Michael J. Donoghue: ''Plant Systematics: A Phylogenetic Approach'', Sinauer Associates Inc. 2007
*Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 7, May 2006 [and more or less continuously updated since]. [http://www.mobot.org/MOBOT/research/APweb/]
* Strasburger, Noll, Schenck, Schimper: Lehrbuch der Botanik für Hochschulen. 4. Auflage, Gustav Fischer, Jena 1900, p. 459
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[[Category:Plant morphology]]
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[[cs:Květenství]]
[[de:Blütenstand]]
[[et:Õisik]]
[[es:Inflorescencia]]
[[eo:Floraro]]
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[[it:Infiorescenza]]
[[lt:Žiedynas]]
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[[nl:Bloeiwijze]]
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[[ru:Соцветие]]
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