A pseudanthium (Greek for "false flower"; ) is an
inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...
that resembles a flower.
The word is sometimes used for other structures that are neither a true flower nor a true inflorescence.
Examples of pseudanthia include flower heads, composite flowers,
or capitula, which are special types of inflorescences
in which anything from a small cluster to hundreds or sometimes thousands of
flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s are grouped together to form a single flower-like structure. Pseudanthia take various forms. The real flowers (the florets) are generally small and often greatly reduced, but the pseudanthium itself can sometimes be quite large (as in the heads of some varieties of
sunflower
The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), as ...
).
![Flower July 2011-2 1 cropped](https://upload.wikimedia.org/wikipedia/commons/3/38/Flower_July_2011-2_1_cropped.jpg)
Pseudanthia are characteristic of the daisy and sunflower
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
(
Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...
), whose flowers are differentiated into ray flowers and disk flowers, unique to this family. The disk flowers in the center of the pseudanthium are
actinomorphic
Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts.
Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirall ...
and the
corolla is fused into a tube. Flowers on the periphery are
zygomorphic
Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts.
Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirall ...
and the corolla has one large lobe (the so-called "petals" of a daisy are individual ray flowers, for example). Either ray or disk flowers may be absent in some plants: ''
Senecio vulgaris
''Senecio vulgaris'', often known by the common names groundsel and old-man-in-the-spring, is a flowering plant in the family Asteraceae. It is an annual herb, native to Europe and widely naturalised as a ruderal species in suitable disturbed hab ...
'' lacks ray flowers
and ''
Taraxacum officinale
''Taraxacum officinale'', the dandelion or common dandelion, is a flowering herbaceous perennial plant of the dandelion genus in the family Asteraceae (syn. Compositae). The common dandelion is well known for its yellow flower heads that turn i ...
'' lacks disk flowers.
The individual flowers of a pseudanthium in the family Asteraceae (or Compositae) are commonly called ''florets''.
The pseudanthium has a whorl of
bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
s below the flowers, forming an
involucre
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
.
In all cases, a pseudanthium is superficially indistinguishable from a flower, but closer inspection of its anatomy will reveal that it is composed of multiple flowers. Thus, the pseudanthium represents an evolutionary convergence of the inflorescence to a reduced reproductive unit that may function in
pollination
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...
like a single flower, at least in plants that are animal pollinated.
Pseudanthia may be grouped into types. The first type has units of individual flowers that are recognizable as single flowers even if fused. In the second type, the flowers do not appear as individual units and certain organs like stamens and carpels can not be associated with any individual flowers.
History
The term pseudanthium was originally applied to flowers with stamens in two whorls with the outer whorl opposite the petals (obdiplostemonate) or polyandric flowers; by the early 1900s the term was repurposed by the advocates of the 'pseudanthium theory' which assumed flower evolution originated from a polyaxial instead of a monoaxial configuration.
Related terms
Synorganization
The collection of independent organs into a complex structure is called ''
synorganization''.
Head
''Head'' is an equivalent term for flower head and pseudanthium when used in the botanical sense.
Capitulum
''Capitulum'' (plural ''capitula'') can be used as an exact synonym for pseudanthium and flower head; however, its use is generally but not always restricted to the family Asteraceae. At least one source defines it as a small flower head. In addition to its botanical use as a term meaning flower head it is also used to mean the top of the
sphagnum
''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, peat moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store wa ...
plant.
Calathid
''Calathid'' (plural ''calathids'' or ''calathidia'') is a very rarely used term. It was defined in the 1966 book, ''The genera of flowering plants (Angiospermae)'', as a specific term for a flower head of a plant in the family Asteraceae.
[ However, on-line botanical glossaries do not define it, and ]Google Scholar
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes p ...
does not link to any significant usage of the term in a botanical sense.
Plant families
Pseudanthia occur in 40 plant families including:
*Adoxaceae
Adoxaceae, commonly known as moschatel family, is a small family of flowering plants in the order Dipsacales, now consisting of five genera and about 150–200 species. They are characterised by opposite toothed leaves, small five- or, more rare ...
— in some ''Viburnum
''Viburnum'' is a genus of about 150–175 species of flowering plants in the moschatel family Adoxaceae. Its current classification is based on molecular phylogeny. It was previously included in the honeysuckle family Caprifoliaceae.
The membe ...
'' spp.
*Apiaceae
Apiaceae or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus ''Apium'' and commonly known as the celery, carrot or parsley family, or simply as umbellifers. It is the 16th-largest family of flowering plants ...
— pseudanthia are called ''umbel
In botany, an umbel is an inflorescence that consists of a number of short flower stalks (called pedicels) that spread from a common point, somewhat like umbrella ribs. The word was coined in botanical usage in the 1590s, from Latin ''umbella'' "p ...
s''
*Araceae
The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...
— pseudanthia are called '' spadices''
*Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...
— The ''capitula'' (singular ''capitulum'') or ''flower heads'', which are collections of different types of flowers, is a pseudanthium. The individual flowers of a capitulum are called ''florets''.[ Commonly the capitulum has ray flowers specialized to attract pollinators arranged surrounding disc flowers responsible for ]sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
, perianth symmetry can be varailbe within the family.
*Campanulaceae
The family Campanulaceae (also bellflower family), of the order Asterales, contains nearly 2400 species in 84 genera of herbaceous plants, shrubs, and rarely small trees, often with milky sap. Among them are several familiar garden plants belon ...
*Centrolepidaceae
Centrolepidaceae are a family of flowering plants now included in Restionaceae following APG IV (2016). The botanical name has been recognized by most taxonomists.
The APG II system, of 2003 (unchanged from the APG system, 1998), also recognis ...
— Where individual male and female flowers are grouped together and wrapped in bracts forming a pseudanthium appearing as a bisexual flower.
*Cornaceae
The Cornaceae are a cosmopolitan family of flowering plants in the order Cornales. The family contains approximately 85 species in two genera, ''Alangium'' and ''Cornus''. They are mostly trees and shrubs, which may be deciduous or evergreen, alt ...
*Cyperaceae
The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' w ...
— In subfamily Mapanioideae, pseudanthia are termed ''spicoids''. In ''Lepironia
''Lepironia'' is a genus of the sedge family, comprising only one species, ''Lepironia articulata'', known as the grey sedge.Govaerts, R. & Simpson, D.A. (2007). World Checklist of Cyperaceae. Sedges: 1-765. The Board of Trustees of the Royal Bo ...
'' sp the pseudanthium is greatly condensed with staminate flowers surrounding a central terminal pistillate female flower.
*Dipsacaceae
The Dipsacaceae have been recognized as a family (the teasel family) of the order Dipsacales containing 350 species of perennial or biennial herbs and shrubs in eleven genera. The species are currently placed in the family Caprifoliaceae. Native ...
*Euphorbiaceae
Euphorbiaceae, the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of a genus in the family. Most spurges, such as ''Euphorbia paralias'', are herbs, but some, e ...
— pseudanthia are called ''cyathia
A cyathium (plural: cyathia) is one of the specialised pseudanthia ("false flowers") forming the inflorescence of plants in the genus ''Euphorbia'' (Euphorbiaceae). A cyathium consists of:
* Five (rarely four) bracteoles. These are small, uni ...
'', composed of a single carpal flower with few to many single stamen staminate flowers contained within a cup-shaped structure or bracts; the bracts are often rimmed with nectar
Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...
ies and less commonly petal-like structures. The central cyathia maybe composed of all male flowers.
*Eriocaulaceae
The Eriocaulaceae are a family of monocotyledonous flowering plants in the order Poales, commonly known as the pipewort family. The family is large, with about 1207 known species described in seven genera. They are widely distributed, with the ce ...
*Hamamelidaceae
Hamamelidaceae, commonly referred to as the witch-hazel family, is a family of flowering plants in the order Saxifragales. The clade consists of shrubs and small trees positioned within the woody clade of the core Saxifragales. An earlier system ...
— in ''Rhodoleia
''Rhodoleia'' is a genus of plants in the family Hamamelidaceae. Together with its sister genus ''Exbucklandia'', ''Rhodoleia'' forms the sister clade to the other 25 genera of Hamamelidaceae. Flowers of ''Rhodoleia'' are bird-pollinated. Nectar ...
''
*Marcgraviaceae
The Marcgraviaceae are a neotropical angiosperm family in the order Ericales. The members of the family are shrubs, woody epiphytes, and lianas, with alternate, pinnately nerved leaves. The flowers are arranged in racemes. The flowers are accompa ...
*Moraceae
The Moraceae — often called the mulberry family or fig family — are a family of flowering plants comprising about 38 genera and over 1100 species. Most are widespread in tropical and subtropical regions, less so in temperate climates; however ...
*Myrtaceae
Myrtaceae, the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All speci ...
— in ''Actinodium
''Actinodium cunninghamii'', commonly known as swamp daisy or Albany daisy, is the only formally described species in the genus of flowering plants in the family Myrtaceae, ''Actinodium'' and is endemic to Western Australia.
Description
''Actin ...
'' — the pseudanthia is a head-like structure with fertile flowers in the center and showy ray-like structures along the outside.
*Nothofagaceae
''Nothofagus'', also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere in southern South America (Chile, Argentina) and Australasia (east and southeast Australia, New Zealand, New Gui ...
in subgenus Lophozonia - a three‐flowered dichasium without branches.
*Nyssaceae
Nyssaceae is a family of flowering trees sometimes included in the dogwood family (Cornaceae). Nyssaceae is composed of 37 known species in the following five genera:Averyanov, L. V. & Hiep, N. T. (2002). ''Diplopanax vietnamensis'', a New Specie ...
— in '' Davidia''
*Poaceae
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...
*Pontederiaceae
Pontederiaceae is a family of flowering plants.
The APG IV system of 2016 (unchanged from the APG III system of 2009, the APG II system of 2003 and the APG system of 1998) places the family in the order Commelinales, in the commelinid clade, in ...
— in ''Hydrothrix
''Hydrothrix'' Hook.f. was previously a monotypic flowering plant genus of Pontederiaceae, but is currently included in a broader and monophyletic '' Heteranthera''.
The highly modified ''Heteranthera gardneri'' is a submerged aquatic with a tw ...
''
*Proteaceae
The Proteaceae form a family of flowering plants predominantly distributed in the Southern Hemisphere. The family comprises 83 genera with about 1,660 known species. Together with the Platanaceae and Nelumbonaceae, they make up the order Pro ...
*Rubiaceae
The Rubiaceae are a family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with interpetiolar stipules ...
*Saururaceae
Saururaceae is a plant family comprising four genera and seven species of herbaceous flowering plants native to eastern and southern Asia and North America. The family has been recognised by most taxonomists, and is sometimes known as the "lizard ...
— in ''Anemopsis
The monotypic genus ''Anemopsis'' has only one species, ''Anemopsis californica'', with the common names yerba mansa or lizard tail.
It is a perennial herb in the lizard tail family (Saururaceae) and prefers very wet soil or shallow water.Flow ...
''
In some families, it is not yet clear whether the "flower" represents a pseudanthium because the anatomical work has not been done (or is still ambiguous due to considerable evolutionary reduction). Possible pseudanthia of this type may occur in the following families:
*Hydatellaceae
Hydatellaceae are a family of small, aquatic flowering plants. The family consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order Poales), but has b ...
*Lemnaceae
Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose ...
*Pandanaceae
Pandanaceae is a family of flowering plants native to the tropics and subtropics of the Old World, from West Africa through the Pacific. It contains 982 known species in five genera, of which the type genus, ''Pandanus'', is the most important, wi ...
*Triuridaceae
Triuridaceae are a family of tropical and subtropical flowering plants, including nine genera with a total of approximately 55 known species. All members lack chlorophyll and are mycoheterotrophic (obtain food by digesting intracellular fungi, o ...
*Phyllanthaceae
Phyllanthaceae is a family of flowering plants in the eudicot order Malpighiales. It is most closely related to the family Picrodendraceae.Kenneth J. Wurdack and Charles C. Davis. 2009. "Malpighiales phylogenetics: Gaining ground on one of the ...
[Petra Hoffmann, Hashendra S. Kathriarachchi, and Kenneth J. Wurdack. 2006. "A Phylogenetic Classification of Phyllanthaceae (Malpighiales)." ''Kew Bulletin.'' 61(1):40.]
Gallery
File:Ubor hoofdie.svg, Diagram of a flower head. Note bracts surrounding the flowers, which would be absent on a capitulum.
File:Bellis perennis white (aka).jpg, Flower head of a common daisy (''Bellis perennis
''Bellis perennis'' (), the daisy, is a European species of the family Asteraceae, often considered the archetypal species of the name daisy. To distinguish this species from other plants known as daisies, it is sometimes qualified as common dai ...
'')
File:Flower head.jpg, Flowers open in succession in head of a sunflower (''Helianthus annuus
The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), as b ...
''), with ray florets forming the 'petals'
File:Hieracium 2007-1.jpg, Close up of the ray corolla of ''Hieracium lachenalii
''Hieracium lachenalii'', also known as common hawkweed or yellow hawkweed, is a species of plant in the tribe Cichorieae within the family Asteraceae. It is native to Europe but has become established as a weed in Australia and parts of North A ...
''; every "petal" is actually a separate five-petaled flower complete with its own stamens and making its own fruit.
File:EricameriaNauseosa 8691.JPG, Discoid (having only disk flowers) flower heads of ''Ericameria nauseosa
''Ericameria nauseosa'' (formerly ''Chrysothamnus nauseosus''), commonly known as Chamisa, rubber rabbitbrush, and gray rabbitbrush, is a shrub in the sunflower family (Aster) found in the arid regions of western North America.
Two subspeci ...
'' (rubber rabbitbrush)
File:Senecio_angulatus_kz11.jpg, Flower head of creeping groundsel (''Senecio angulatus
''Senecio angulatus'', also known as creeping groundsel
and Cape ivy,
is a Succulent plant, succulent flowering plant in the family Asteraceae that is native to South Africa. Cape ivy is a scrambling and a vine, twining herb that can become an N ...
'') with petaloid ray florets and tubular disc florets in the middle
References
{{Reflist
Plant morphology
Flowers