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Pseudanthium

"Flower head" redirects here. For the band, see Flowerhead.

A pseudanthium (Ancient Greek for 'false flower'; pl.: pseudanthia) is an inflorescence that resembles a flower.[1] The word is sometimes used for other structures that are neither a true flower nor a true inflorescence.[1] Examples of pseudanthia include flower heads, composite flowers,[2]: 514  or capitula, which are special types of inflorescences[3] 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 (Asteraceae), 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[4] and Taraxacum officinale lacks disk flowers.[4][5] The individual flowers of a pseudanthium in the family Asteraceae (or Compositae) are commonly called florets.[6] 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.[7]

  1. ^ a b Louis P. Ronse De Craene (4 February 2010). Floral Diagrams: An Aid to Understanding Flower Morphology and Evolution. Cambridge University Press. p. 23. ISBN 978-1-139-48455-8.
  2. ^ Chester, Sharon (2016), The Arctic Guide: Wildlife of the Far North, Princeton University Press, ISBN 9781400865963.
  3. ^ Hutchinson, John (1964). The genera of flowering plants (Angiospermae). Oxford: Clarendon Press. LCCN 65000676.
  4. ^ a b "Senecio vulgaris L." Missouri Plants. Archived from the original on 27 June 2012. Retrieved 2 December 2012.
  5. ^ "Taraxacum Officinale". Florida Data. Retrieved 2 December 2012.
  6. ^ "calflora Botanical Terms". Retrieved 2012-02-26.
  7. ^ Sokoloff, Dmitry; Rudall, Paula J.; Remizowa, Margarita (2006-10-01). "Flower-like terminal structures in racemose inflorescences: a tool in morphogenetic and evolutionary research". Journal of Experimental Botany. 57 (13): 3517–3530. doi:10.1093/jxb/erl126. ISSN 0022-0957. PMID 17005921.

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