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 forme ...

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 mechanis ...

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), ...

Pseudanthia are characteristic of the daisy and sunflower

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

(

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 ...

), 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 and the

corolla Corolla may refer to: *Corolla (botany), the petals of a flower, considered as a unit *Toyota Corolla, an automobile model name *Corolla (headgear) A ''corolla'' is an ancient headdress in the form of a small circlet or crown.zygomorphic 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 ...

'' lacks ray flowers and '' Taraxacum officinale'' 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 bracts below the flowers, forming an involucre. 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 Stamen, anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by Anemophily, wind. Pollinating agents can ...

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 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 ...

does not link to any significant usage of the term in a botanical sense.

Plant families

Pseudanthia occur in 40 plant families including: * Adoxaceae — in some '' Viburnum'' spp. * Apiaceae — pseudanthia are called '' umbels'' * Araceae — pseudanthia are called '' spadices'' *

— 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 th ...

, perianth symmetry can be varailbe within the family. * Campanulaceae * Centrolepidaceae — 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, a ...

* Cyperaceae — In subfamily Mapanioideae, pseudanthia are termed ''spicoids''. In '' Lepironia'' sp the pseudanthium is greatly condensed with staminate flowers surrounding a central terminal pistillate female flower. * Dipsacaceae * Euphorbiaceae — pseudanthia are called '' cyathia'', 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 nectaries and less commonly petal-like structures. The central cyathia maybe composed of all male flowers. Euphorbia caput-medusae 01

* Eriocaulaceae *

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 sy ...

— in '' Rhodoleia'' * Marcgraviaceae * Moraceae Actinodium cunninghamii - Flickr - Kevin Thiele

* Myrtaceae — in '' Actinodium'' — the pseudanthia is a head-like structure with fertile flowers in the center and showy ray-like structures along the outside. * Nothofagaceae in subgenus Lophozonia - a three‐flowered

dichasium 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 on ...

without branches. * Nyssaceae — in '' Davidia'' * Poaceae * Pontederiaceae — 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 * Rubiaceae * Saururaceae — in '' Anemopsis'' 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 *

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 fr ...

* Pandanaceae * Triuridaceae * PhyllanthaceaePetra 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'') File:Flower head.jpg, Flowers open in succession in head of a sunflower ('' Helianthus annuus''), 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 subspecies ...

'' (rubber rabbitbrush) File:Senecio_angulatus_kz11.jpg, Flower head of creeping groundsel ('' Senecio angulatus'') with petaloid ray florets and tubular disc florets in the middle

References

{{Reflist Plant morphology Flowers