A petal or petalum (plural: petals ) is a leaf of the inner flower envelope in the flower of flowering plants . The totality of the petals of a flower is called the crown or corolla . Petals are only spoken of in the case of irregular flower envelopes, if the flower envelope is differentiated into calyx and crown. If all the bloom cladding sheets are of the same type, then one speaks of a perigone (tepalum, tepalum). Most commonly the term petal is used, but in botanical usage this can have a broader meaning.
Structure and functions
A petal is typically flat and larger than a sepal of the same flower. It is to be addressed as a leaf organ. Phylogenetically , the petals in most clans emerged from stamens, in some more primitive families they rather emerged from the differentiation of a perianth into calyx and crown. Examples of the latter are the Magnoliaceae , Calycanthaceae and Himantandraceae . Petals emerging from stamens can be recognized anatomically by the same vascular bundle structure as in stamens.
The petals are often conspicuously colored or shaped. They usually have the function of attracting insects for pollination (cf. entomophilia ), and sometimes also serve to form or store nectar . Often the petals pointing downwards are enlarged or conspicuously colored and, as a lip or lower lip, forms a "landing place" for insects (e.g. violets , orchids , see also labellum ) or for the secondary presentation of pollen .
Petals can grow together or be free, multi-leaf (apo-, choripetal, eleutheropetal, pohlpetal). Overgrown -leaved, single-leaved ( sym- , gamopetal, monopetal) flower crowns are found especially in asterids . The free petals can be divided into sitting or stalked, nailed (unguiculate). The nailed petals are composed of a nail (unguis, stem-like narrowed lower section) and a plate (lamina, wider upper section), e.g. B. in the Silenoideae of the carnation family (Caryophyllaceae).
At the junction between the nail and the plate, tongue-shaped, lobed outgrowths, so-called " ligules ", can arise and together form a secondary crown (paracorolla). Such a secondary crown can also arise with fused-leaf crowns, e.g. B. in the yellow daffodil ( Narcissus pseudonarcissus ). The "corolla tube" is a tubular, lower section, and the "hem" is a widened or spread out, upper section of the calyx, crown or perigone in plants with an overgrown flower envelope. The transition point from the hem to the tube is the "throat" (faux). The free secondary corolla of fused-leaf crowns are therefore also called "pharynx scales". B. in the predatory plants (Boraginaceae).
The upper, more or less spreading edge (ridge) of an overgrown crown is also known as the limbus . If the upper edge is divided, then the individual parts are the lobes (lobes, laciniae). If the overgrown petals are folded in or folded out (pinched folds), the wider, thinner folds, bulges or humps on the limbus are called plica (e), the narrower, thicker area, the zone (intermediate fold) in between is called interplica ( e). A nectar groove (honey fold or furrow) (Plica nectarifera) is a furrow secreting honey on the petals → nectarium .
Like all flower organs, the petals can be arranged helically or whorled , the former being regarded as the original feature. Due to the strong compression of the flower axis, the screwy arrangement is often difficult to see.
The petals are located in the flower between the sepals on the outside and the stamens that follow on the inside . In various kinship groups, the petals are connected to the sepals by gradual transitions, for example in the cactus family (Cactaceae) or in the peonies (Paeoniaceae). In other clans there are again transitions from petals to stamens, for example in Nymphaea alba . The double flower that occurs in many cultivated forms is based on the transformation of stamens into petals. For the genetic development of the flower organs during flower formation, see flower formation .
Petal-free, so-called apetaloid flowers (perigon) are a derived feature of flowering plants and are often found in wind-flowered ( anemophilic ) clans, such as Salicaceae , Betulaceae , Juglandaceae , Urticaceae and Fraxinus .
The petals can also develop spurs .
The Latin term corolla goes back to Carl von Linné , who first used it in 1735; previously the Latin flos ("blossom") was common. The German term Krone is long -established, as early as 1781 in Giseke's Caroli a Linné Termini botanici . The Latin equivalent of crown would actually be corona . The diminutive form corolla literally means “crown” or “wreath”.
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