Apomixis

Reproduction that genuinely involves fertilization in flowering plants is called amphimixis; wherever reproduction happens without any union of male and female gametes, it is instead called apomixis - a term introduced by Winkler in 1908 and defined as the substitution of the normal sexual (amphimictic) system by a mode of reproduction that involves neither meiosis nor syngamy. Maheswari (1950) classified apomixis into two broad types. Recurrent apomixis includes both ordinary vegetative reproduction (where a plant simply propagates via a non-seed organ, such as bulbils in Fritillaria imperialis, bulbs in Allium, runners in Mentha arvensis or suckers in Chrysanthemum) and agamospermy, the broader category of processes by which seeds still form but their embryos develop while eliminating both meiosis and syngamy; agamospermy itself splits further into adventive embryony, in which an embryo arises directly from a diploid sporophytic cell of the nucellus or integument - also called sporophytic budding, since the gametophytic phase is skipped entirely (found in Citrus and Mangifera); diplospory (also called generative apospory), in which a diploid embryo sac forms straight from the megaspore mother cell without any regular meiotic division taking place (Eupatorium, Aerva); and apospory (somatic apospory), in which the megaspore mother cell does undergo normal meiosis and forms four megaspores, but these gradually degenerate while a nearby nucellar cell instead becomes a …