Question

What is the difference between apomixis, agamospermy, and apospory?

Answer 1

The method of reproduction that does not involve fertilization and meiosis is called asexual reproduction. Asexual reproduction is also known as apomixis and is of two types, namely agamospermy and vegetative propagation.
Apo = without and mixis = mixing.
It is characterized by speedy multiplication and reproduction of genetically identical plants from a single parent.

Complete answer

Agamospermy	Apomixis	Apospory
It is an asexual reproduction in which seeds are produced from unfertilized ovules.	Apomixis is a form of asexual reproduction that occurs via seeds, in which embryos develop without fertilization.	Apospory is the development of 2n gametophytes, without meiosis and spores, from vegetative, or nonreproductive, cells of the sporophyte.
Agamospermy takes place mainly in gymnosperms and gives rise to the production of clonal seeds.	Apomixis happens predominantly in flowering plants or angiosperms and replaces the flower structures with vegetative parts like bulbils.	It is the direct generation of gametophytes from sporophyte diploid cells without the need for spore formation (as in certain ferns and mosses).
Vegetative asexual reproduction does not occur in agamospermy.	Vegetative asexual reproduction occurs in apomixis.	Vegetative asexual reproduction occurs in apospory.

Genetically similar plants produced from an individual are called clones and each member of the clone is known as a ramet.
Agamospermy is a kind of plant apomixis method in which an embryo is formed without meiotic gametogenesis and fertilization. It takes place widely in ferns and flowering plants. Plants belonging to this category, propagate through seeds, yet embryo formation does not involve syngamy and meiosis. There are three different types of agamospermy, namely, adventive embryony, diplospory, and apospory.
Apospory is a method of agamospermy where a female gametophyte or embryo sac is formed from any diploid cell of the sporophyte, except the megaspore mother cell. Whether the apospory is somatic or generative, the gametophyte always remains diploid. Examples are Ranunculus and Hieracium.
In somatic apospory, the embryo sac is formed from somatic cells, and in generative apospory, the embryo sac is formed from archesporium without meiosis.

Note:
Apomixis, agamospermy, and apospory possess one similar aspect that none of them are involved in the act of fertilization or fusion of gametes. Apomixis and agamospermy are asexual methods of reproduction. Both of them do not involve in the production of gametes. Both of the methods produce genetically identical offspring to their parents. Both of them serve as adaptations by plants for survival and maintenance of their genetic composition.