A pseudanthium (Greek for "false flower") or flower head 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. The individual flowers of a pseudanthium can be called florets.
Pseudanthia are characteristic of the sunflower family (Asteraceae). Flowers in the asteraceae family are differentiated into ray and disk flowers, which are unique to the 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 (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.
A pseudanthium (Greek for "false flower") or flower head 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. The individual flowers of a pseudanthium can be called florets.
Pseudanthia are characteristic of the sunflower family (Asteraceae). Flowers in the asteraceae family are differentiated into ray and disk flowers, which are unique to the 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 (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.