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In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis (peduncle) and by the timing of its flowering (determinate and indeterminate).

Morphologically, an inflorescence is the modified part of the shoot of seed plants where flowers are formed on the axis of a plant. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes.[citation needed]
One can also define an inflorescence as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.[citation needed]
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. Because flowers facilitate plant reproduction, inflorescence characteristics are largely a result of natural selection.
The stem holding the whole inflorescence is called a peduncle. The main axis (also referred to as major stem) above the peduncle bearing the flowers or secondary branches is called the rachis. The stalk of each flower in the inflorescence is called a pedicel. A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle. Any flower in an inflorescence may be referred to as a floret, especially when the individual flowers are particularly small and borne in a tight cluster, such as in a pseudanthium. The fruiting stage of an inflorescence is known as an infructescence. Inflorescences may be simple (single) or complex (panicle). The rachis may be one of several types, including single, composite, umbel, spike or raceme. [citation needed]
In some species the flowers develop directly from the main stem or woody trunk, rather than from the plant's main shoot. This is called cauliflory and is found across a number of plant families. An extreme version of this is flagelliflory where long, whip-like branches grow from the main trunk to the ground and even below it. Inflorescences form directly on these branches.
Terminal flower
Plant organs can grow according to two different schemes, namely monopodial or racemose and sympodial or cymose. In inflorescences these two different growth patterns are called indeterminate and determinate respectively, and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
- Indeterminate inflorescence: Monopodial (racemose) growth. The terminal bud keeps growing and forming lateral flowers. A terminal flower is never formed.
- Determinate inflorescence: Sympodial (cymose) 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. The indeterminate patterning of flowers is derived from determinate flowers. It is suggested that indeterminate flowers have a common mechanism that prevents terminal flower growth. Based on phylogenetic analyses, this mechanism arose independently multiple times in different species.
In an 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.
- Indeterminate inflorescence with a perfect acropetal maturation
- Indeterminate inflorescence with an acropetal maturation and lateral flower buds
- Indeterminate inflorescence with the subterminal flower to simulate the terminal one (vestige present)
In determinate inflorescences the terminal flower is usually the first to mature (precursive development), while the others tend to mature starting from the base of the stem. This pattern is called acropetal maturation. When flowers start to mature from the top of the stem, maturation is basipetal, whereas when the central mature first, maturation is divergent.
- Determinate inflorescence with acropetal maturation
- Determinate inflorescence with basipetal maturation
- Determinate inflorescence with divergent maturation
Phyllotaxis
As with leaves, flowers can be arranged on the stem according to many different patterns. See 'Phyllotaxis' for in-depth descriptions.
- Alternate flowers
- Opposite flowers
Similarly arrangement of leaf in bud is called Ptyxis.
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, where the flowers are on branched stalks; the bracts are not connected to the stalks holding the flowers, but are 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 itself, 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.
- Flower and subtending bract
- Lilium martagon (flower and subtending bract)
- Concaulescence
- Solanum lycopersicum (concaulescence)
- Recaulescence
- Tilia cordata (recaulescence)
Organization
There is no general consensus in defining the different inflorescences. The following is based on '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. They may contain many flowers (pluriflor) or a few (pauciflor). Inflorescences can be simple or compound.
Simple inflorescences
Indeterminate or racemose
Indeterminate simple inflorescences are generally called racemose /ˈræsɪmoʊs/. The main kind of racemose inflorescence is the raceme (/ˈræsiːm/, from classical Latin racemus, cluster of grapes). 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 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. It is characteristic of Umbelliferae.
- A spadix is a spike of flowers densely arranged around it, enclosed or accompanied by a highly specialised bract called a spathe. It is characteristic of the family Araceae.
- 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.
- Raceme
- Epilobium angustifolium
- Spike
- Plantago media (spike)
- Racemose corymb
- Iberis umbellata (racemose corymb)
- Umbel
- Astrantia minor (umbel)
- Spadix
- Arum maculatum (spadix)
- Head (round)
- Dipsacus fullonum (head)
- Catkin (racemose or spicate)
- Alnus incana (ament)
Determinate or cymose
Determinate simple inflorescences are generally called cymose. The main kind of cymose inflorescence is the cyme (pronounced /saɪm/), from the Latin cyma in the sense 'cabbage sprout', from Greek kuma 'anything swollen'). 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 and Commelinaceae)
- The successive pedicels follow a zig-zag path on the same plane: rhipidium (many Iridaceae)
- Secondary buds always develop on the same side of the stem: helicoid cyme or bostryx
- 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
- Simple dichasium
- Double cyme
- Double cyme
- Bostryx (lateral and top view)
- Hypericum perforatum (bostryx)
- Drepanium (lateral and top view)
- Gladiolus imbricatus (drepanium)
- Cincinnus (lateral and top view)
- Symphytum officinale (cincinnus)
- Rhipidium (lateral and top view)
- Canna sp. (rhipidium)
- Dichasium
- Dichasium, top view
- Silene dioica (dichasium)
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'.
- Umbelliform cyme
- Pelargonium zonale (umbelliform cyme)
- Botryoid
- Berberis vernae (botryoid)
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.
- Gentiana lutea (fascicles)
- Lamium orvala (verticillaster)
- Mentha longifolia ('spike')
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. This definition is very different from that given by .
Compound umbels are umbels in which the single flowers are replaced by many smaller umbels called umbellets. The stem attaching the side umbellets to the main stem is called a ray.
- Homeothetic compound raceme
- Melilotus officinalis (homoeothetic compound raceme)
- Heterothetic compound raceme
- Veronica albicans (heterothetic compound raceme)
- Compound spike
- Lolium temulentum (compound spike)
- Compound capitulum
- Echinops ritro (compound capitulum)
- Compound (double) umbel
- Laserpitium latifolium (double umbel)
- Compound (triple) umbel
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 branching 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.
- Panicle
- Vitis vinifera (panicle)
- Cymose corymb
- Sambucus nigra (cymose corymb)
- Anthela
- Juncus inflexus (anthela)
A raceme in which the single flowers are replaced by cymes is called a (indefinite) thyrse. The secondary cymes can 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.
- Thyrse
- Aesculus hippocastanum
- Thyrsoid
- Syringa vulgaris
Other combinations are possible. For example, heads or umbels may be arranged in a corymb or a panicle.
- Achillea sp. (heads in a corymb)
- Hedera helix (umbels in a panicle)
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 a hypanthodium, which bears numerous flowers on the inside of a convex or involuted compound receptacle. The genus Euphorbia has cyathia (sing. cyathium), usually organised in umbels.
- Matricaria chamomilla (calathid)
- Triticum aestivum (compound spikes, "spikes")
- Oryza sativa (spikes in a panicle, "panicle")
- Ficus carica (hypanthodium)
- Euphorbia tridentata (cyathium)
- Euphorbia cyparissias (cyathia in an umbel)
- Coleus (false spike)
Some species have inflorescences reduced to composite flowers or pseudanthia, in which case it is difficult to differentiate between inflorescences and single flowers.
Development and patterning
Development
Genetic basis
Genes that shape inflorescence development have been studied at great length in Arabidopsis. LEAFY (LFY) is a gene that promotes floral meristem identity, regulating inflorescence development in Arabidopsis. Any alterations in timing of LFY expression can cause formation of different inflorescences in the plant. Genes similar in function to LFY include APETALA1 (AP1). Mutations in LFY, AP1, and similar promoting genes can cause conversion of flowers into shoots. In contrast to LEAFY, genes like terminal flower (TFL) support the activity of an inhibitor that prevents flowers from growing on the inflorescence apex (flower primordium initiation), maintaining inflorescence meristem identity. Both types of genes help shape flower development in accordance with the ABC model of flower development. Studies have been recently conducted or are ongoing for homologs of these genes in other flower species.
Environmental influences
Inflorescence-feeding insect herbivores shape inflorescences by reducing lifetime fitness (how much flowering occurs), seed production by the inflorescences, and plant density, among other traits. In the absence of these herbivores, inflorescences usually produce more flower heads and seeds. Temperature can also variably shape inflorescence development. High temperatures can impair the proper development of flower buds or delay bud development in certain species, while in others an increase in temperature can hasten inflorescence development.
Meristems and inflorescence architecture
The shift from the vegetative to reproductive phase of a flower involves the development of an inflorescence meristem that generates floral meristems. Plant inflorescence architecture depends on which meristems becomes flowers and which become shoots. Consequently, genes that regulate floral meristem identity play major roles in determining inflorescence architecture because their expression domain will direct where the plant's flowers are formed.
On a larger scale, inflorescence architecture affects quality and quantity of offspring from selfing and outcrossing, as the architecture can influence pollination success. For example, Asclepias inflorescences have been shown to have an upper size limit, shaped by self-pollination levels due to crosses between inflorescences on the same plant or between flowers on the same inflorescence. In Aesculus sylvatica, it has been shown that the most common inflorescence sizes are correlated with the highest fruit production as well.
References
- Guertin, P., Barnett, L., Denny, E.G., Schaffer, S.N. 2015. USA National Phenology Network Botany Primer. USA-NPN Education and Engagement Series 2015-001. www.usanpn.org.
- "Inflorescence | Racemes, Spikes & Cymes | Britannica". www.britannica.com. 2023-09-26. Retrieved 2023-11-03.
- Kirchoff, Bruce K.; Claßen-Bockhoff, Regine (2013). "Inflorescences: concepts, function, development and evolution". Annals of Botany. 112 (8): 1471–6. doi:10.1093/aob/mct267. PMC 3828949. PMID 24383103.
- "PlantNET - NSW Flora Online - Glossary". Retrieved May 17, 2022.
- Fernanda Martínez-Velarde, Maria; 6 others, and (2023). "Desmopsisterriflora, an extraordinary new species of Annonaceae with flagelliflory". PhytoKeys (227): 181–198. doi:10.3897/phytokeys.227.102279. PMC 10314296. PMID 37396012.
{{cite journal}}
: CS1 maint: numeric names: authors list (link) - Bradley, Desmond; Ratcliffe, Oliver; Vincent, Coral; Carpenter, Rosemary; Coen, Enrico (1997-01-03). "Inflorescence Commitment and Architecture in Arabidopsis". Science. 275 (5296): 80–83. doi:10.1126/science.275.5296.80. ISSN 0036-8075. PMID 8974397. S2CID 20301629.
- 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
- Oxford English Dictionary. Raceme 2. Bot. A type of inflorescence in which the flowers are arranged on short, nearly equal, lateral pedicels, at equal distances along a single elongated axis
- Collins English Dictionary. 8th Edition first published in 2006
- Oxford English Dictionary. Cyme(1) Bot. A species of inflorescence wherein the primary axis bears a single terminal flower which develops first, the system being continued by axes of secondary and higher orders which develop successively in like manner; a centrifugal or definite inflorescence: opposed to Raceme. Applied esp. to compound inflorescences of this type forming a more or less flat head.
- Simpson, M. G. 2010. Plant Systematics Burlington: Academic Press. p. 509
- Tucker, Shirley C.; Grimes, James (1999-10-01). "The inflorescence: Introduction". The Botanical Review. 65 (4): 303–316. Bibcode:1999BotRv..65..303T. doi:10.1007/BF02857752. ISSN 0006-8101. S2CID 29599096.
- Shannon, S.; Meeks-Wagner, D. R. (1993-06-01). "Genetic Interactions That Regulate Inflorescence Development in Arabidopsis". The Plant Cell. 5 (6): 639–655. doi:10.1105/tpc.5.6.639. ISSN 1040-4651. PMC 160302. PMID 12271079.
- Schultz, E. A.; Haughn, G. W. (1991-08-01). "LEAFY, a Homeotic Gene That Regulates Inflorescence Development in Arabidopsis". The Plant Cell. 3 (8): 771–781. doi:10.1105/tpc.3.8.771. ISSN 1040-4651. PMC 160044. PMID 12324613.
- Alvarez, John; Guli, Catherine L.; Yu, Xiang-Hua; Smyth, David R. (1992-01-01). "terminal flower: a gene affecting inflorescence development in Arabidopsis thaliana". The Plant Journal. 2 (1): 103–116. doi:10.1111/j.1365-313X.1992.00103.x. ISSN 1365-313X.
- Louda, Svata M.; Potvin, Martha A. (1995-01-01). "Effect of Inflorescence-Feeding Insects on the Demography and Lifetime of a Native Plant". Ecology. 76 (1): 229–245. Bibcode:1995Ecol...76..229L. doi:10.2307/1940645. ISSN 1939-9170. JSTOR 1940645.
- Moss, G (27 November 2015). "Influence of Temperature and Photoperiod on Flower Induction and Inflorescence Development in Sweet Orange (Citrus Sinensis L. Osbeck)". Journal of Horticultural Sciences. 44 (4): 311–320. doi:10.1080/00221589.1969.11514314.
- Bjorkman, T.; Pearson, K. J. (1998-01-01). "High temperature arrest of inflorescence development in broccoli (Brassica oleracea var. italica L.)". Journal of Experimental Botany. 49 (318): 101–106. doi:10.1093/jxb/49.318.101. ISSN 0022-0957.
- BREWSTER, J. L. (1983-04-01). "Effects of Photoperiod, Nitrogen Nutrition and Temperature on Inflorescence Initiation and Development in Onion (Allium cepa L.)". Annals of Botany. 51 (4): 429–440. doi:10.1093/oxfordjournals.aob.a086487. ISSN 0305-7364.
- Souer, E.; Krol, A. van der; Kloos, D.; Spelt, C.; Bliek, M.; Mol, J.; Koes, R. (1998-02-15). "Genetic control of branching pattern and floral identity during Petunia inflorescence development". Development. 125 (4): 733–742. doi:10.1242/dev.125.4.733. ISSN 0950-1991. PMID 9435293.
- Benlloch, R.; Berbel, A.; Serrano-Mislata, A.; Madueno, F. (2007-09-01). "Floral Initiation and Inflorescence Architecture: A Comparative View". Annals of Botany. 100 (3): 659–676. doi:10.1093/aob/mcm146. ISSN 0305-7364. PMC 2759223. PMID 17679690.
- WYATT, ROBERT (1980-05-01). "The Reproductive Biology of Asclepias Tuberosa: I. Flower Number, Arrangement, and Fruit-Set". New Phytologist. 85 (1): 119–131. Bibcode:1980NewPh..85..119W. doi:10.1111/j.1469-8137.1980.tb04453.x. ISSN 1469-8137.
- Wyatt, Robert (1982-04-01). "Inflorescence Architecture: How Flower Number, Arrangement, and Phenology Affect Pollination and Fruit-Set". American Journal of Botany. 69 (4): 585–594. doi:10.1002/j.1537-2197.1982.tb13295.x. ISSN 1537-2197. JSTOR 2443068.
Bibliography
- 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 [1]. Version 7, May 2006 [and more or less continuously updated since].
- Strasburger, Noll, Schenck, Schimper: Lehrbuch der Botanik für Hochschulen. 4. Auflage, Gustav Fischer, Jena 1900, p. 459
- R J Ferry. Inflorescences and Their Names. The McAllen International Orchid Society Journal.Vol. 12(6), pp. 4-11 June 2011 Archived 14 September 2018 at the Wayback Machine
External links
Media related to Inflorescence at Wikimedia Commons
This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Inflorescence news newspapers books scholar JSTOR November 2023 Learn how and when to remove this message In botany an inflorescence is a group or cluster of flowers arranged on a plant s stem that is composed of a main branch or a system of branches An inflorescence is categorized on the basis of the arrangement of flowers on a main axis peduncle and by the timing of its flowering determinate and indeterminate Aloe hereroensis showing inflorescence with branched peduncleAmorphophallus titanum has the world s largest unbranched inflorescence Photo of the plant in bloom in 2000 at Fairchild Tropical Botanic Garden in Miami Florida US Morphologically an inflorescence is the modified part of the shoot of seed plants where flowers are formed on the axis of a plant The modifications can involve the length and the nature of the internodes and the phyllotaxis as well as variations in the proportions compressions swellings adnations connations and reduction of main and secondary axes citation needed One can also define an inflorescence as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern citation needed General characteristicsInflorescences 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 Because flowers facilitate plant reproduction inflorescence characteristics are largely a result of natural selection The stem holding the whole inflorescence is called a peduncle The main axis also referred to as major stem above the peduncle bearing the flowers or secondary branches is called the rachis The stalk of each flower in the inflorescence is called a pedicel A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle Any flower in an inflorescence may be referred to as a floret especially when the individual flowers are particularly small and borne in a tight cluster such as in a pseudanthium The fruiting stage of an inflorescence is known as an infructescence Inflorescences may be simple single or complex panicle The rachis may be one of several types including single composite umbel spike or raceme citation needed In some species the flowers develop directly from the main stem or woody trunk rather than from the plant s main shoot This is called cauliflory and is found across a number of plant families An extreme version of this is flagelliflory where long whip like branches grow from the main trunk to the ground and even below it Inflorescences form directly on these branches Terminal flower Plant organs can grow according to two different schemes namely monopodial or racemose and sympodial or cymose In inflorescences these two different growth patterns are called indeterminate and determinate respectively and indicate whether a terminal flower is formed and where flowering starts within the inflorescence Indeterminate inflorescence Monopodial racemose growth The terminal bud keeps growing and forming lateral flowers A terminal flower is never formed Determinate inflorescence Sympodial cymose 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 The indeterminate patterning of flowers is derived from determinate flowers It is suggested that indeterminate flowers have a common mechanism that prevents terminal flower growth Based on phylogenetic analyses this mechanism arose independently multiple times in different species In an 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 Indeterminate inflorescence with a perfect acropetal maturation Indeterminate inflorescence with an acropetal maturation and lateral flower buds Indeterminate inflorescence with the subterminal flower to simulate the terminal one vestige present In determinate inflorescences the terminal flower is usually the first to mature precursive development while the others tend to mature starting from the base of the stem This pattern is called acropetal maturation When flowers start to mature from the top of the stem maturation is basipetal whereas when the central mature first maturation is divergent Determinate inflorescence with acropetal maturation Determinate inflorescence with basipetal maturation Determinate inflorescence with divergent maturationPhyllotaxis As with leaves flowers can be arranged on the stem according to many different patterns See Phyllotaxis for in depth descriptions Alternate flowers Opposite flowers Similarly arrangement of leaf in bud is called Ptyxis 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 where the flowers are on branched stalks the bracts are not connected to the stalks holding the flowers but are 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 itself 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 Flower and subtending bract Lilium martagon flower and subtending bract Concaulescence Solanum lycopersicum concaulescence Recaulescence Tilia cordata recaulescence OrganizationThere is no general consensus in defining the different inflorescences The following is based on s Morphologie der Bluten und der Blutenstande 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 They may contain many flowers pluriflor or a few pauciflor Inflorescences can be simple or compound Simple inflorescences Inflorescence of sessile disc florets forming the capitulumIndeterminate or racemose Indeterminate simple inflorescences are generally called racemose ˈ r ae s ɪ m oʊ s The main kind of racemose inflorescence is the raceme ˈ r ae s iː m from classical Latin racemus cluster of grapes 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 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 It is characteristic of Umbelliferae A spadix is a spike of flowers densely arranged around it enclosed or accompanied by a highly specialised bract called a spathe It is characteristic of the family Araceae 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 Raceme Epilobium angustifolium Spike Plantago media spike Racemose corymb Iberis umbellata racemose corymb Umbel Astrantia minor umbel Spadix Arum maculatum spadix Head round Dipsacus fullonum head Catkin racemose or spicate Alnus incana ament Determinate or cymose Determinate simple inflorescences are generally called cymose The main kind of cymose inflorescence is the cyme pronounced s aɪ m from the Latin cyma in the sense cabbage sprout from Greek kuma anything swollen 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 and Commelinaceae 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 pleiochasiumSimple dichasium Double cyme Double cyme Bostryx lateral and top view Hypericum perforatum bostryx Drepanium lateral and top view Gladiolus imbricatus drepanium Cincinnus lateral and top view Symphytum officinale cincinnus Rhipidium lateral and top view Canna sp rhipidium Dichasium Dichasium top view Silene dioica dichasium 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 Umbelliform cyme Pelargonium zonale umbelliform cyme Botryoid Berberis vernae botryoid 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 Gentiana lutea fascicles Lamium orvala verticillaster Mentha longifolia spike 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 This definition is very different from that given by Compound umbels are umbels in which the single flowers are replaced by many smaller umbels called umbellets The stem attaching the side umbellets to the main stem is called a ray Homeothetic compound raceme Melilotus officinalis homoeothetic compound raceme Heterothetic compound raceme Veronica albicans heterothetic compound raceme Compound spike Lolium temulentum compound spike Compound capitulum Echinops ritro compound capitulum Compound double umbel Laserpitium latifolium double umbel Compound triple umbel 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 branching 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 Panicle Vitis vinifera panicle Cymose corymb Sambucus nigra cymose corymb Anthela Juncus inflexus anthela A raceme in which the single flowers are replaced by cymes is called a indefinite thyrse The secondary cymes can 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 Thyrse Aesculus hippocastanum Thyrsoid Syringa vulgaris Other combinations are possible For example heads or umbels may be arranged in a corymb or a panicle Achillea sp heads in a corymb Hedera helix umbels in a panicle 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 a hypanthodium which bears numerous flowers on the inside of a convex or involuted compound receptacle The genus Euphorbia has cyathia sing cyathium usually organised in umbels Matricaria chamomilla calathid Triticum aestivum compound spikes spikes Oryza sativa spikes in a panicle panicle Ficus carica hypanthodium Euphorbia tridentata cyathium Euphorbia cyparissias cyathia in an umbel Coleus false spike Some species have inflorescences reduced to composite flowers or pseudanthia in which case it is difficult to differentiate between inflorescences and single flowers Development and patterningDevelopment Genetic basis Genes that shape inflorescence development have been studied at great length in Arabidopsis LEAFY LFY is a gene that promotes floral meristem identity regulating inflorescence development in Arabidopsis Any alterations in timing of LFY expression can cause formation of different inflorescences in the plant Genes similar in function to LFY include APETALA1 AP1 Mutations in LFY AP1 and similar promoting genes can cause conversion of flowers into shoots In contrast to LEAFY genes like terminal flower TFL support the activity of an inhibitor that prevents flowers from growing on the inflorescence apex flower primordium initiation maintaining inflorescence meristem identity Both types of genes help shape flower development in accordance with the ABC model of flower development Studies have been recently conducted or are ongoing for homologs of these genes in other flower species Environmental influences Inflorescence feeding insect herbivores shape inflorescences by reducing lifetime fitness how much flowering occurs seed production by the inflorescences and plant density among other traits In the absence of these herbivores inflorescences usually produce more flower heads and seeds Temperature can also variably shape inflorescence development High temperatures can impair the proper development of flower buds or delay bud development in certain species while in others an increase in temperature can hasten inflorescence development Meristems and inflorescence architecture The shift from the vegetative to reproductive phase of a flower involves the development of an inflorescence meristem that generates floral meristems Plant inflorescence architecture depends on which meristems becomes flowers and which become shoots Consequently genes that regulate floral meristem identity play major roles in determining inflorescence architecture because their expression domain will direct where the plant s flowers are formed On a larger scale inflorescence architecture affects quality and quantity of offspring from selfing and outcrossing as the architecture can influence pollination success For example Asclepias inflorescences have been shown to have an upper size limit shaped by self pollination levels due to crosses between inflorescences on the same plant or between flowers on the same inflorescence In Aesculus sylvatica it has been shown that the most common inflorescence sizes are correlated with the highest fruit production as well ReferencesGuertin P Barnett L Denny E G Schaffer S N 2015 USA National Phenology Network Botany Primer USA NPN Education and Engagement Series 2015 001 www usanpn org Inflorescence Racemes Spikes amp Cymes Britannica www britannica com 2023 09 26 Retrieved 2023 11 03 Kirchoff Bruce K Classen Bockhoff Regine 2013 Inflorescences concepts function development and evolution Annals of Botany 112 8 1471 6 doi 10 1093 aob mct267 PMC 3828949 PMID 24383103 PlantNET NSW Flora Online Glossary Retrieved May 17 2022 Fernanda Martinez Velarde Maria 6 others and 2023 Desmopsisterriflora an extraordinary new species of Annonaceae with flagelliflory PhytoKeys 227 181 198 doi 10 3897 phytokeys 227 102279 PMC 10314296 PMID 37396012 a href wiki Template Cite journal title Template Cite journal cite journal a CS1 maint numeric names authors list link Bradley Desmond Ratcliffe Oliver Vincent Coral Carpenter Rosemary Coen Enrico 1997 01 03 Inflorescence Commitment and Architecture in Arabidopsis Science 275 5296 80 83 doi 10 1126 science 275 5296 80 ISSN 0036 8075 PMID 8974397 S2CID 20301629 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 Oxford English Dictionary Raceme 2 Bot A type of inflorescence in which the flowers are arranged on short nearly equal lateral pedicels at equal distances along a single elongated axis Collins English Dictionary 8th Edition first published in 2006 Oxford English Dictionary Cyme 1 Bot A species of inflorescence wherein the primary axis bears a single terminal flower which develops first the system being continued by axes of secondary and higher orders which develop successively in like manner a centrifugal or definite inflorescence opposed to Raceme Applied esp to compound inflorescences of this type forming a more or less flat head Simpson M G 2010 Plant Systematics Burlington Academic Press p 509 Tucker Shirley C Grimes James 1999 10 01 The inflorescence Introduction The Botanical Review 65 4 303 316 Bibcode 1999BotRv 65 303T doi 10 1007 BF02857752 ISSN 0006 8101 S2CID 29599096 Shannon S Meeks Wagner D R 1993 06 01 Genetic Interactions That Regulate Inflorescence Development in Arabidopsis The Plant Cell 5 6 639 655 doi 10 1105 tpc 5 6 639 ISSN 1040 4651 PMC 160302 PMID 12271079 Schultz E A Haughn G W 1991 08 01 LEAFY a Homeotic Gene That Regulates Inflorescence Development in Arabidopsis The Plant Cell 3 8 771 781 doi 10 1105 tpc 3 8 771 ISSN 1040 4651 PMC 160044 PMID 12324613 Alvarez John Guli Catherine L Yu Xiang Hua Smyth David R 1992 01 01 terminal flower a gene affecting inflorescence development in Arabidopsis thaliana The Plant Journal 2 1 103 116 doi 10 1111 j 1365 313X 1992 00103 x ISSN 1365 313X Louda Svata M Potvin Martha A 1995 01 01 Effect of Inflorescence Feeding Insects on the Demography and Lifetime of a Native Plant Ecology 76 1 229 245 Bibcode 1995Ecol 76 229L doi 10 2307 1940645 ISSN 1939 9170 JSTOR 1940645 Moss G 27 November 2015 Influence of Temperature and Photoperiod on Flower Induction and Inflorescence Development in Sweet Orange Citrus Sinensis L Osbeck Journal of Horticultural Sciences 44 4 311 320 doi 10 1080 00221589 1969 11514314 Bjorkman T Pearson K J 1998 01 01 High temperature arrest of inflorescence development in broccoli Brassica oleracea var italica L Journal of Experimental Botany 49 318 101 106 doi 10 1093 jxb 49 318 101 ISSN 0022 0957 BREWSTER J L 1983 04 01 Effects of Photoperiod Nitrogen Nutrition and Temperature on Inflorescence Initiation and Development in Onion Allium cepa L Annals of Botany 51 4 429 440 doi 10 1093 oxfordjournals aob a086487 ISSN 0305 7364 Souer E Krol A van der Kloos D Spelt C Bliek M Mol J Koes R 1998 02 15 Genetic control of branching pattern and floral identity during Petunia inflorescence development Development 125 4 733 742 doi 10 1242 dev 125 4 733 ISSN 0950 1991 PMID 9435293 Benlloch R Berbel A Serrano Mislata A Madueno F 2007 09 01 Floral Initiation and Inflorescence Architecture A Comparative View Annals of Botany 100 3 659 676 doi 10 1093 aob mcm146 ISSN 0305 7364 PMC 2759223 PMID 17679690 WYATT ROBERT 1980 05 01 The Reproductive Biology of Asclepias Tuberosa I Flower Number Arrangement and Fruit Set New Phytologist 85 1 119 131 Bibcode 1980NewPh 85 119W doi 10 1111 j 1469 8137 1980 tb04453 x ISSN 1469 8137 Wyatt Robert 1982 04 01 Inflorescence Architecture How Flower Number Arrangement and Phenology Affect Pollination and Fruit Set American Journal of Botany 69 4 585 594 doi 10 1002 j 1537 2197 1982 tb13295 x ISSN 1537 2197 JSTOR 2443068 BibliographyFocko Weberling Morphologie der Bluten und der Blutenstande 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 Einfuhrung 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 1 Version 7 May 2006 and more or less continuously updated since Strasburger Noll Schenck Schimper Lehrbuch der Botanik fur Hochschulen 4 Auflage Gustav Fischer Jena 1900 p 459 R J Ferry Inflorescences and Their Names The McAllen International Orchid Society Journal Vol 12 6 pp 4 11 June 2011 Archived 14 September 2018 at the Wayback MachineExternal linksLook up inflorescence in Wiktionary the free dictionary Media related to Inflorescence at Wikimedia Commons