Apomixis is the formation of new individuals by asexual methods which mimic sexual reproduction including seed formation but do not involve fusion of gamets or sex cells.
Context
- Apomixis(information)
- Methods Of Apomixis
1. Apomixis(information)
The organism reproducing through apomixis is called apomict. Apomixis is controlled by genes. In apomixis the new individuals are genetically similar to the parent producing them. They are, therefore, clone of their parent. Members of a clone are called ramets. Apomixis can be recurrent or noncurrent. It occurs by the following methods:
2. Methods Of Apomixis
(i) Agamospermy (Gk. agamos-without marriage, sperme-seed).
It is mide of apomixis in which seeds ned but are asexual in nature as the embryo develops directly without gametic fusion. It is commonly el from a diploid nucellar cell (apospory) or megaspore mother cell (diplospory). The term apospory is ged for development of embryo sac or gametophyte directly from sporophyte tissue.
The term sporophytic budding is used if the embryo develops adventitiously from diploid cells of aellas or integument... Mango, Orange. Opuntia. Onion. The embryo is pushed into the area of sac to replace the normal embryo.
(ii) Parthenogenesis (Gk parthenon-virgin genesis-descent, Owen, 1848).
It is the development sew individual from a single gamete without fusion with daughter gamete In lower plants both the of gametes can undergo parthenogenesis but in higher plants, usually the female gamete shows this ty Depending upon the ploidy of the gamete, there are tw types of parthenogenesis, diploid and In haploid parthenogenesis, the embryo sac and its egg are haploid. The egg grows to form ad embryo. Such embryos do not survive in higher plants but in lower plants, the plant body is plid so that haploid embryo has survival value in diploid parthenogenesis, the embryo sa as well womained egg is diploid. undergoes parthenogenesis and forms diploid embryo. Diploid mogenesis is generally accompanied by failure of meiosis during megasporogenesis as well as et formation of embryo sac from a nucellar cell, eg. Rubus, Poa, Apple. In Apple, self pollination promotes diploid parthenogenesis.
(iii) Apogamy (Gk. apo-without, gamos-marriage).
It is formation of sporophyte or embryo directly from cells of gametophyte. In higher plants, the only diploid apogamy is successful is the gametophytic cell forming the sporophyte is diploid. In lower plants, haploid apogamy is equally successful.
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