Editing Apomixis (section)

=== Types in flowering plants ===
[[File:Agave angustifolia (Caribbean Agave) in Hyderabad W IMG 8660.jpg|thumb|right|[[Caribbean agave]] producing plantlets on the old flower stem.]]
Maheshwari<ref name=Maheshwari/> used the following simple classification of types of apomixis in flowering plants:
*'''Nonrecurrent apomixis''': In this type "the megaspore mother cell undergoes the usual meiotic divisions and a haploid embryo sac [[megagametophyte]] is formed. The new embryo may then arise either from the egg (haploid parthenogenesis) or from some other cell of the gametophyte (haploid apogamy)." The haploid plants have half as many [[chromosomes]] as the mother plant, and "the process is not repeated from one generation to another" (which is why it is called nonrecurrent). See also '''parthenogenesis''' and '''apogamy''' below.
*'''Recurrent apomixis''', is now more often called '''gametophytic apomixis''': In this type, the megagametophyte has the same number of chromosomes as the mother plant because meiosis was not completed. It generally arises either from an [[archesporium|archesporia]]l cell or from some other part of the [[nucellus]].
*'''Adventive embryony''', also called '''sporophytic apomixis''', '''sporophytic budding''', or [[nucellar embryony]]: Here there may be a megagametophyte in the [[ovule]], but the embryos do not arise from the cells of the gametophyte; they arise from cells of nucellus or the integument. Adventive embryony is important in several species of ''[[Citrus]]'', in ''[[Garcinia]]'', ''[[Euphorbia dulcis]]'', ''[[Mangifera indica]]'' etc.
*'''Vegetative apomixis''': In this type "the flowers are replaced by [[bulbils]] or other vegetative propagules which frequently germinate while still on the plant". Vegetative apomixis is important in ''[[Allium]]'', ''[[Fragaria]]'', ''[[Agave]]'', and some grasses, among others.

====Types of gametophytic apomixis====
Gametophytic apomixis in flowering plants develops in several different ways.<ref name=Nogler>Nogler, G.A. 1984. Gametophytic apomixis. In Embryology of angiosperms. Edited by B.M. Johri. Springer, Berlin, Germany. pp. 475–518.</ref> A megagametophyte develops with an egg cell within it that develops into an embryo through [[parthenogenesis]]. The central cell of the megagametophyte may require fertilization to form the [[endosperm]], '''pseudogamous gametophytic apomixis''', or in '''autonomous gametophytic apomixis''' endosperm fertilization is not required. 
*In '''diplospory''' (also called '''generative apospory'''), the megagametophyte arises from a cell of the [[archesporium]].
* In '''apospory''' (also called '''somatic apospory'''), the megagametophyte arises from some other (somatic) cell of the nucellus.

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 cell.

Diplospory is further subdivided according to how the megagametophyte forms:
* ''[[Allium]] odorum''–''A. nutans'' type. The chromosomes double (endomitosis) and then meiosis proceeds in an unusual way, with the chromosome copies pairing up (rather than the original maternal and paternal copies pairing up).
* ''[[Taraxacum]]'' type: Meiosis I fails to complete, meiosis II creates two cells, one of which degenerates; three mitotic divisions form the megagametophyte.
* ''[[Ixeris]]'' type: Meiosis I fails to complete; three rounds of nuclear division occur without cell-wall formation; wall formation then occurs.
* ''[[Blumea]]''–''[[Elymus (plant)|Elymus]]'' types: A mitotic division is followed by degeneration of one cell; three mitotic divisions form the megagametophyte.
* ''[[Antennaria]]''–''[[Hieracium]]'' types: three mitotic divisions form the megagametophyte.
* ''[[Eragrostis]]''–''[[Panicum]]'' types: Two mitotic division give a 4-nucleate megagametophyte, with cell walls to form either three or four cells.