Pseudanthium
From Wikipedia, the free encyclopedia
A pseudanthium (Greek: false flower) is a special type of inflorescence, in which several flowers are grouped together to form a flower-like structure. The real flowers are generally small and greatly reduced, but can sometimes be quite large (as in the sunflower flower-head). Pseudanthia take various forms.
Pseudanthia are particularly widely distributed in the family Asteraceae, which includes the sunflowers. There the individual central flowers of the pseudanthium (called a flower head or capitulum in Asteraceae) typically have no petals. Individual flowers on the edge of the capitulum, however, may have single petals pointing outwards. The capitulum has a whorl of bracts below the structure forming an involucre. The rest of the capitulum comprises a collection of individual 'true' flowers, borne on a platform or more or less stiff cone arising from the inflorescence stem. However, in other plant groups there is no obvious cone or involucre.
In all cases, a pseudanthium (inflorescence) 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 occur in the following plant families:
- Apiaceae
- Asteraceae
- Campanulaceae
- Centrolepidaceae
- Cornaceae
- Cyperaceae
- Dipsacaceae
- Euphorbiaceae - there the pseudanthia are called cyathia
- Eriocaulaceae
- Hamamelidaceae
- Moraceae
- Poaceae
- Pontederiaceae -- in Hydrothrix
- 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:
