Apomixis – Class 12 | Chapter – 2 | Biology Short Notes Series PDF

Apomixis: Apomixis is the process of identifying and developing diploid embryos or seeds found in a plant without fertilization or the term Apomixis can also be explained as a form of asexual reproduction that occurs via seeds, in which embryos develop without fertilization that occurs naturally in other plants.

Apomixis Important Points

• It is referred to as the process of formation of the plant from a seed without fertilization or normal sexual reproduction.
• They are also directly developed from diploid eggs present in the embryo sac.
• Sometimes there will be no proper mitotic & meiotic divisions in the embryo sac that leads to the formation of a diploid egg.
• This diploid egg directly develops into a new organism.
• As there is no fertilization, the newly formed embryo is genetically similar to the parent and is otherwise also known as the clone. Hence, they will be Genetically similar.

Types of Apomixis

• Diplospory: In diplospory, the embryo sac is derived from the megaspore mother cell either directly by mitotic division or by interrupting meiosis. In the mitotic diplospory, the megaspore mother cell divides mitotically thrice to form 8 nuclei. The embryosac is unreduced and have same number of chromosomes and genetic material.
• Apospory: In apospory, the nucellar cells give rise to the apomictic embryo sac. The initiation of the apospory embryo sac and the sexual one can occur simultaneously or it can displace or interrupt sexual embryo sac formation.
• Adventitious Embryony: It is a type of sporophytic apomixis, where embryos are produced directly from the nucellus or the integument of the ovule. The embryo develops by mitotic division and forms a bud-like structure.

Examples of Apomixis

Examples of apomixis can be found in the genera Crataegus (hawthorns), Amelanchier (shadbush), Sorbus (rowans and whitebeams), Rubus (brambles or blackberries), Poa (meadow grasses), Nardus stricta (Matgrass), Hieracium (hawkweeds) and Taraxacum (dandelions).

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By Team Learning Mantras