Apomixis

From Academic Kids

In botany, apomixis is biological reproduction without fertilization, meiosis or production of gametes, with the result that the seeds are genetically identical to the parent plant. An apomict or apomictic plant is an organism which chiefly reproduces this way. Although the evolutionary advantages of sexual reproduction are lost, apomixis does pass along traits fortuitous for individual evolutionary fitness.

As the plants are genetically identical from one generation to the next, each apomictic plant has the characters of a true species, maintaining their distinction from each other, despite having much smaller differences from other similar apomicts than is normal between species. They are therefore often called microspecies. In some genera, it is possible to identify and name hundreds or even thousands of microspecies, which may be grouped together as aggregate species, typically listed in Floras with the convention "Genus species agg." (e.g., the bramble, Rubus fruticosus agg.).

Good examples of apomixis can be found in the genera Crataegus (hawthorns), Sorbus (rowans and whitebeams), Rubus (brambles or blackberries), Hieracium (hawkweeds) and Taraxacum (dandelions).

A unique example of male apomixis has recently been discovered in the Saharan Cypress (Cupressus dupreziana), where the seeds are derived entirely from the pollen with no contribution from the female "parent" (Pichot et al., 2000, 2001).

Parthenogenesis is the animal equivalent of apomixis.

See also:

References

  • Gvaladze G.E. Forms of Apomixis in the genus Allium L. In: S.S. Khokhlov (Ed.): Apomixis and Breeding, Amarind Pub., New Delhi-Bombay-Calcutta-New York, 1976, pp. 160-165
  • Pichot, C., Fady, B., & Hochu, I. 2000. Lack of mother tree alleles in zymograms of Cupressus dupreziana A. Camus embryos. Ann. For. Sci. 57: 17Ė22. Full article (pdf file) (http://www.edpsciences.org/articles/forest/pdf/2000/01/asf0103.pdf)
  • Pichot, C., El MaŠtaoui, M., Raddi, S. & Raddi, P. 2001. Surrogate mother for endangered Cupressus. Nature 412: 39.de:Apomixis

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