"Flower head" redirects here. For the band, see Flowerhead
(Greek for "false flower") is an inflorescence
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 head
, composite flower
, which are special types of inflorescences
in which anything from a small cluster to hundreds or sometimes thousands of flowers
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
What appear to be "petals" of an individual flower, are actually each individual complete ray flowers
, and at the center is a dense pack of individual tiny disc flowers
. Because the collection has the overall appearance of a single flower, the collection of flowers in the head of this sunflower
is called a pseudanthium
or a composite.
Pseudanthia are characteristic of the daisy and sunflower family
), 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
is fused into a tube. Flowers on the periphery are 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
lacks ray flowers
and Taraxacum officinale
lacks disk flowers.
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
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.
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 1900's the term was repurposed by the advocates of the 'pseudanthium theory' which assumed flower evolution originated from a polyaxail instead of a monoaxial configuration.
The collection of independent organs into a complex structure is called synorganization
is an equivalent term for flower head and pseudanthium when used in the botanical sense
) can be used as an exact synonym for pseudanthium and flower head;
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
) 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,[when?]
and Google Scholar
does not link to any significant usage of the term in a botanical sense.[when?]
Pseudanthia occur in 40 plant families including:
- 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.
- 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
Actinodium cunninghamii pseudanthia
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:
The individual flowers of a pseudanthium in the family Asteraceae (or Compositae) are commonly called florets
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Last edited on 31 July 2021, at 19:12
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