The perianth (sometimes called perigonium or perigon) is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs. The term perianth is derived from the Greek peri, meaning around, and anthos, meaning flower, while perigonium is derived from gonos, meaning seed, i.e sexual organs.
In flowering plants, the perianth consists of the calyx, consisting of sepals and the corolla consisting of petals. These may be described as being either dichlamydeous in which the two components are clearly separate, or homochlamydeous, in which they are indistinguishable. In this case the perianth is described as a Perigonium (perigon), and the sepals and petals are collectivley referred to as tepals. When the perianth is in two whorls, it is described as biseriate. While the calyx may be green, it may also be brightly coloured, and is then described as petaloid. The corolla and petals have role in attracting pollinators, but this may be augmented by more specilised structures like the corona (see below).
When the corolla consists of separate petals the term apotepalous is used, or polypetalous where there are many petals. In contrast the petals may be united to form a tubular corolla (gamopetalous or sympetalous).
|Types of perianth|
Both sepals and petals may have stomata and veins, even if vestigial. In some taxa, for instance some Magnolias and water lilies the perianth is arranged in a spiral on nodes, rather than whorls. Flowers with spiral perianths tend to also be those with undifferentiated perianths.
An additional structure in some plants (e.g. Narcissus, Passiflora (Passion flower), some Hippeastrum, Liliaceae) is the Corona (Paraperigonium, or Paraperigon), a ring of adaxial tissue arising from the corolla, perianth or filaments. This may consist of separate appendages, or be united. Strap shaped Ligules, as in Asteraceae are an example.
- Simpson, Michael G. (2011). Plant Systematics. Academic Press. ISBN 0-08-051404-9. Retrieved 12 February 2014.
- The dictionary definition of perianth at Wiktionary
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