Heterostyly
Heterostyly or anisostyly , the different pen , is a term from flower biology . It is a form of reciprocal herogamy , in which different flower types ( heteromorphism ) are formed within a species to promote cross-pollination. Another form is the enantiostyly (slanted grip). Heterostyly can occur together with heteranthia , the different formation of the anthers, here z. B. with different functions. This also serves to make self-pollination more difficult or to prevent it. The opposite of heterostyly is homostyly .
Heterostyly is the occurrence of different types of flowers (polymorphism) within a plant species . These flower types differ in a different ratio of the length of the stylus to the length of the stamens , or also with regard to the attachment height of the anthers, i.e. the stamen position.
A distinction is made between the occurrence of two ( dimorphic heterostyly, distyly also heterodistyly ) or three ( trimorphic heterostyly, tristyly also heterotristyly ) different flowers. In short-styled (micro- or brachystylen; Brachystylie ) flowers are the pen and the short stamens long and medium length, with long-styled (macro- or dolichostylen) flowers pen the long and medium stamens and short. In between are the mesostyle , medium- styled flowers, here one half of the stamens is long, the other short, the stylus is shorter than the long ones and longer than the short ones.
For example, with numerous representatives of the genus Primula there are roughly the same number of individuals with a short stylus and high stamen position, or with a long stylus and deep stamen position. Such a dimorphic heterostyly or distyly occurs, for example, also in some representatives of the knotweed family ( Polygonaceae ), sorrel family ( Oxalidaceae ) or reddened family ( Rubiaceae ). Examples of tristyly are found in purple loosestrife ( Lythrum salicaria ) and most members of the genus Oxalis .
Charles Darwin was already able to show that optimal fruit set only takes place when both types are cross-pollinated, i.e. that heterostyly serves to promote cross- pollination .
In the meantime it has been found that in so-called heterostyly not only the stylus length and stamen position are decisive. Rather, different sized pollen and scar papillae also influence this pollination process. For this reason there is a tendency to replace the term heterostyly with the term heteromorphism .
See also
Individual evidence
- ↑ Pat Willmer: Pollination and Floral Ecology. Princeton Univ. Press, 2011, ISBN 978-0-691-12861-0 , p. 74.
- ↑ H. Potonié : Illustrated flora of northern and central Germany. 4th edition. Springer, 1889, p. 348, archive.org .
- ↑ Gustav Hegi: Illustrated flora of Central Europe . Volume 5, part 2, Lehmanns, 1926, p. 743.
- ↑ D. Heß : Systematic Botany. Ulmer Verlag, 2005, ISBN 3-8001-2850-0 , pp. 97, 172.