The substitution of usual sexual reproduction by a form of reproduction which does not involve meiosis and syngamy is called apomixis, a term introduced by Winkler in 1908
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However in normal sexual cycle, fertilization (Amphimixis i.e., fusion of male and female gametes), leads to the formation of embryo and later on seed. Seed germinates to produce new plant where male and female gametophytes are formed after meiosis. This normal sexual cycle involves fertilization and meiosis.
There are two main types of apomixis.
Types of apomixis
1. Vegetative reproduction : New plant is produced from stem, leaf, buds, etc. (Seed not required).
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2. Agamospermy : Seeds are produced and embryo is formed but meiosis and fertilization are eliminated. It may be :
(a) Adventive embryony : Embryo formed from cells of nucellus or integuments.
(b) Diplospory : Megaspore mother cell develops into an unreduced embryosac. The embryo is formed from unfertilized egg, (parthenogenesis) or some other cell of embryosac (apogamety).
(c) Apospory : A somatic cell in the nucellus directly forms an unreduced embryosac and the diploid egg parthenogenetically develops into embryo.