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In a mature flower, the perianth consists of a calyx (sepals) and the corolla it supports. A sepal (/ ˈ s ɛ p əl, ˈ s iː p əl /) [1] [2] [3] is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom. [4]
Petals are usually surrounded by an outer whorl of modified leaves called sepals, that collectively form the calyx and lie just beneath the corolla. The calyx and the corolla together make up the perianth, the non-reproductive portion of a flower. When the petals and sepals of a flower are difficult to distinguish, they are collectively called ...
Instead, a typical angiosperm flower possesses verticils or ordered whorls that, from the outside in, are composed first of sterile parts, commonly called sepals (if their main function is protective) and petals (if their main function is to attract pollinators), and then the fertile parts, with reproductive function, which are composed of ...
These gene functions are called A, B, and C. Genes are expressed in only the outer and lower most section of the apical meristem, which becomes a whorl of sepals. In the second whorl, both A and B genes are expressed, leading to the formation of petals.
These functions are exclusive and the absence of one of them means that the other will determine the identity of all the floral verticils. The B function allows the differentiation of petals from sepals in the secondary verticil, as well as the differentiation of the stamen from the carpel on the tertiary verticil.
The outer series (calyx of sepals) is usually green and leaf-like, and functions to protect the rest of the flower, especially the bud. [58] [59] The inner series (corolla of petals) is, in general, white or brightly colored, is more delicate in structure, and attracts pollinators by colour, scent, and nectar. [60] [61]
First, at the base, are those non-reproductive structures involved in protecting the flower when it is still a bud, the sepals, then are those parts that play a role in attracting pollinators and are typically coloured, the petals, which together with the sepals make up the perianth (perigon, perigonium).
A mature flower. In this example, the perianth is separated into a calyx (sepals) and corolla (petals) The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepals when called a perigone.