In botany, a whorl is an arrangement of leaves in which two or more leaves are attached to a node . When three or more sheets will also whisk spoken. The side branches, which arise from the leaf axils, are also whorled. If these branches have blossoms , they are called whorls. The kitchen appliances of the same name used to be made from lively standing branches ("Astquirl") .
If several leaves appear on a node, one speaks of numerous (polymer) whorls. One example is the pine frond ( Hippuris vulgaris ). Usually there are a few leaves on a node, with the loosestrife ( Lysimachia vulgaris ) there are three. In the case of twofold (dimeric) whorls, one usually speaks of opposite foliage .
For the arrangement of the leaves in whorls, two rules of whorl position apply:
- Equidistance rule: The leaves of a whorl always have the same lateral distance, i.e. the same angle. With opposite foliage, the angle is 180 °.
- Rule of alternation: The leaves of successive whorls stand in such a way that the leaves of the following whorl are in the leaf gaps of the preceding whorl. Opposite foliage results in the cross-opposed foliage characteristic of mint plants.
In most species , the petals are also arranged in whorls, they are then referred to as cyclic flowers. They are also sometimes referred to as circles. The whorls are usually 2, 3, 4 or 5-fold. Most hermaphroditic flowers consist of four (tetracyclic, with two bract whorls, one stamen whorl and one carpel whorl) or five whorls (pentacyclic, with two bract whorls, two stamen whorls and one carpel whorl).
- Wilhelm Troll: Practical introduction to plant morphology. First part: the vegetative structure . VEB Gustav Fischer Verlag, Jena 1954, pp. 78-83. (without ISBN)
- Manfred A. Fischer , Karl Oswald, Wolfgang Adler: Excursion flora for Austria, Liechtenstein and South Tyrol. 3rd, improved edition. State of Upper Austria, Biology Center of the Upper Austrian State Museums, Linz 2008, ISBN 978-3-85474-187-9 , p. 91f.