Apomixis - An Overview, Types

What Is Apomixis?

We can see many plants possessing vegetative and sexual reproduction (amphimixis). Sometimes there are some plants which show particular and special types of reproduction and these reproductions are known as apomixis and polyembryony. Apomixis is defined to be as a type of asexual reproduction and polyembryony is defined to be as a type of sexual reproduction. The apomixis, its meaning and the method of apomixis are described in the article.

When the formation of seeds occurs without the fusion of gametes (or fertilization) then it is defined as apomixis. Polyembryony is defined as the occurrence of many embryos and these embryos are present in the same seed of a flower. Apomixis and Polyembryony are observed in most of the plants. This type of reproductive process in botany has been given a detailed explanation in this article below with apomixis examples.

Apomixis Meaning

• Apomixis word is taken from two Greek words, that is, “apo” possesses the meaning away from and “mixed” means the act of mixing.

• The term apomixis was first introduced in botany by Winkler botanist in 1908

• Apomixis is commonly observed in higher plants mostly in the case of flowering plants and these plants are those plants in which the embryo may be produced from an unfertilised egg cell.

• The embryo can also be produced from a cell other than the egg cell within the embryo sac or can be produced from the cell outside the embryo sac.

• The plant that is produced by apomixis is genetically identical to the mother plant from which it is developed.

• There are more than 35 families present in the environment of plants which reproduce by means of Apomixis.

• Examples of Apomictic seeds include Gramineae and Rosaceae.

• It also included Compositae and Rutaceae.

Types Of Apomixis

The types of Apomixis are listed below-

Agamospermy

It is apomixis in which seeds are developed with no fertilisation, and the embryo arises from an unfertilised egg cell.

Examples: Dandelions, certain grasses

Adventive Embryony

In adventive embryony, directly from somatic cells, for example, nucellus or integuments, the embryos develop bypassing the gametic cells.

Examples: Citrus plants

Vegetative Apomixis

In vegetative apomixis, the new plants are produced from vegetative parts or organs such as bulbs, tubers, or rhizomes.

Examples: Onion, Garlic

Recurrent And Non-Recurrent Apomixis

In recurrent apomixis seeds are produced of the same ploidy degree as that of the mother plant; in nonrecurrent apomixis, the seeds would be of different ploidy

Examples: Poa species

Diplospory

It is that type of apomixis in which the embryo sac is developed from the diploid cell without any reduction division. The chromosome number remains unreduced.

Examples: Poa species

Apospory

In apospory the embryo sac develops from somatic cells, for example, nucellus cells, while bypassing the normal sexual process and not involving the megaspore mother cell.

Examples: Poa species

Apomixis Significance

There are different significance of apomixis are as follows:

Genetic Uniformity

• Ensures offspring produced are genetically identical to the parent plant.

• Favourable features passed down to subsequent generations remain.

Hybrid Vigour

• The desirable characteristics in hybrid plants remain in a non-segregated fashion.

• High yielding and vigour in subsequent generations remained.

Inexpensive Plant Breeding

• Reduces the repeated occurrence of hybridisation processes.

• Time and resources are saved in breeding programmes.

Stable Production Of Crops

• Consistency in quality and performance of the crops produced.

• Reduced variability in plant populations

• Fast Clonal Multiplication

• Improved multiplication of the clonal plant varieties happens fast.

• Faster adaptation to market demand

• Adaptability to Diverse Environments

• Wide adaptability of well-adjusted clones to other different areas is made possible

• Agriculture in variable climatic and soil conditions is facilitated.

Disease Resistance

• The resistance features to pests and pathogens are maintained.

• The pathogen-induced crop failure instances decrease.

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