Formulae on Sexual Reproduction In Flowering Plants


 


1
Gametic fusion or Syngamy is also referred to as Amphimixis. Reproduction avoiding gametic fusion is termed apomixis or asexual reproduction. As for instance in Citrus the supernumerary embryos produced by nucellus and finally lodged in the embryo-sac are referred to as apomictic embryos, and even adventive embryos.



2
Apogamy is development of sporophyte form gametophyte without gametic fusion. Apogamous sporophytes are thus abnormal in being haploid. They are of no consequence in the life cycle of the plant. Apospory, likewise, is formation of gametophte from sporophyte without meiosis. Aposporous gametophytes are thus abnormal in being diploid. Both apogamy and apospory are only of academic significance as they reveal that ploidy of a cell does not seal the developmental destiny of the cell; a diploid cell can develop like a haploid one (in apospory) and hapoid, like a diploid-one. Parthenogenesis which is development of embryo or individual from the gamete without fertilization, is a form of apogamy. Apogamy (preceded by meiosis) is the only example of asexual reproduction producing variation among the progeny.



   3
Formation of diploid embryo-sac (abnormally, without the meiosis), also call diplospory is an example of apospory. Parthenogenesis from diplosporous embryo-sac would produce no variation in progeny (due to lack of meiosis) and amount to cloning.



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