Define apomixis.

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Hint: It is considered as a substitution to sexual reproduction by the means of such type of reproduction in which there is no involvement of processes like meiosis and fusion of gametes.

Complete answer:
In plants, sometimes the involvement of usual sexual gametes does not take place but the offspring are formed due to a kind of asexual reproduction which is known as Apomixis. The plants in which this occurs are known as apomictic plants. Some examples of such apomictic plants are some citruses, grasses, etc. The term Apomixis was introduced by Wrinkler in 1908. According to him, it is the substitution of the actual sexual reproduction in plants by the means of a type of reproduction where meiosis and syngamy are not involved. There are two main categories of Apomixis –
Vegetative reproduction – It is the process of asexual reproduction in plants where a part of the plant body becomes detached from the parent plant and develops into a new self-supporting individual. Propagation by Rhizome, Corm, Suckers, etc. are examples of vegetative reproduction.
Agamospermy – Plants belonging to this category retain the seeds as a source of propagation but they do not involve the usual steps of meiosis and syngamy. Adventive embryony is an example of agamospermy.

Note: -Vegetative reproduction occurs by many two means – natural and artificial. In natural means, it occurs through roots, stems, leaves while in the artificial means it occurs through cutting, bud grafting, layering, and stem grafting like methods.
-Agamospermy involves diplospory, adventive embryony, and apospory.