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Apomixis asexual

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In botanyapomixis was defined Apomixis asexual Hans Winkler as replacement of the normal sexual reproduction by asexual reproductionwithout fertilization. This definition notably does Apomixis asexual mention meiosis. Apomixis asexual "normal asexual reproduction " of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis, but replacement of the seed by a plantlet or replacement of the flower by bulbils were categorized as types of apomixis.

Apomictically produced offspring are genetically identical to the parent plant.

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Some authors included all Apomixis asexual of asexual reproduction within apomixis, but that generalization of the term has since died out. In flowering plants, the term "apomixis" is commonly used in a restricted sense to mean agamospermyi. Although agamospermy could theoretically occur in gymnospermsit appears to be Apomixis asexual in that group.

Apomixis (asexual seed formation) is...

Apogamy is a related term that has had various meanings over time. In plants with independent gametophytes notably fernsthe term is still Apomixis asexual interchangeably with "apomixis", and both refer to the formation of sporophytes by parthenogenesis of gametophyte cells. Male apomixis paternal apomixis involves replacement of the Apomixis asexual material of the egg cell by that from the pollen.

Because apomictic plants are genetically identical from one generation to the next, each lineage has some of the characters of a true speciesmaintaining distinctions from other apomictic lineages within the same genuswhile having much smaller differences than is normal between species of most genera. 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 species aggregatestypically listed in floras with the convention " Genus species Apomixis asexual. In some plant familiesgenera with apomixis are quite common, for example in AsteraceaePoaceaeand Rosaceae.

Examples of apomixis can be found in the genera Crataegus hawthornsAmelanchier shadbushSorbus rowans and whitebeamsRubus brambles or blackberriesPoa meadow grassesNardus stricta MatgrassHieracium hawkweeds and Taraxacum dandelions. Although the evolutionary advantages of sexual reproduction are lost, apomixis can pass along traits fortuitous for evolutionary fitness.

As Jens Clausen put it [4]: The apomicts actually have discovered the effectiveness of mass production long before Mr Henry Ford applied it to the production of the Apomixis asexual. Facultative apomixis means that apomixis does not always occur, i. It appears likely [5] that all apomixis in plants is facultative; in other words, that "obligate Apomixis asexual is an artifact of insufficient observation missing uncommon sexual reproduction.

The gametophytes of bryophytesand less commonly ferns and lycopods can develop a group of cells that grow to look like a sporophyte of the species but with the ploidy level of the gametophyte, a phenomenon known as apogamy. The sporophytes of plants of these groups may also have the ability to form a plant that looks like a gametophyte but with the ploidy level of the sporophyte, a phenomenon known as apospory.

See also androgenesis and androclinesis described below, a type of male apomixis that occurs in a conifer, Cupressus dupreziana. Agamospermy, asexual reproduction through seeds, occurs in flowering plants through many different mechanisms [5] and a simple hierarchical classification of the different types is not possible.

Consequently, there are almost as many different usages of Apomixis asexual for apomixis in angiosperms as there Apomixis asexual authors on the subject. For English speakers, Maheshwari [8] is very influential.

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German speakers might prefer to consult Rutishauser Agamospermy occurs mainly in two forms: In gametophytic apomixisthe embryo arises from an unfertilized egg cell i. In adventitious embryony sporophytic apomixisan embryo is formed directly not from a gametophyte Apomixis asexual nucellus or Apomixis asexual tissue see nucellar embryony.

Maheshwari [8] used the following simple classification of types of apomixis in flowering plants:.

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Gametophytic apomixis in flowering plants develops in several different ways. The central cell of the megagametophyte may require fertilization to form the endospermpseudogamous gametophytic apomixisor in autonomous gametophytic apomixis fertilization is not required. Considerable confusion has resulted because diplospory is often defined to involve the megaspore mother cell only, but a number of plant families have a multicellular archesporium and the megagametophyte could originate from another archesporium Apomixis asexual. Apomixis Apomixis asexual in at least 33 families of flowering plants, and has evolved multiple times from sexual relatives.

In plants with both apomictic and meiotic embryology, the proportion Apomixis asexual the different types can differ at different times of year, [11] and photoperiod can Apomixis asexual change the proportion. The genetic control of apomixis can Apomixis asexual a single genetic change that affects all the major developmental components, formation of the megagametophyte, parthenogenesis of the egg cell, Apomixis asexual endosperm development.

From Wikipedia, the free encyclopedia. For androgenetic alopecia, see Pattern hair loss. This article is about plants. For similar processes in animals and Oomycetes, see Parthenogenesis. Not to be confused Apomixis asexual automixis or autogamy.

Recent Advances and Remaining Conundrums". A Case Study from Polystichoid Ferns. The evolutionary biology of plants. The University of Chicago press. An introduction to the embryology of the angiosperms. Embryologie und Fortpflanzungsbiologie der Angiospermen: Textbook of Apomixis asexual Strasburger's textbook of botany, rewritten. In Embryology of angiosperms. Biological Journal of the Apomixis asexual Society. Rivera Nava; Julien B. Annals of Forest Science.

Surrogate mother for endangered Cupressus ". Retrieved from " https: Plant reproduction Asexual reproduction. Wikipedia articles with GND identifiers. Views Read Edit Apomixis asexual history.

This page was last edited on 23 Juneat By using this site, you agree to Apomixis asexual Terms of Use and Privacy Policy. Apomixis: Apomixis, reproduction by special generative tissues without Apomixis, the development of asexual seed (seed not formed via the normal sexual. Reproduction is asexual (apomictic) when it occurs without recombination. Apomixis (Greek apo = without, mixis= mingling) is the general term for it. In botany, apomixis was defined by Hans Winkler Apomixis asexual replacement Apomixis asexual the normal sexual reproduction by asexual reproduction, without fertilization.

Its etymology is .

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