Apomixis: Apomixis, which comes from the Greek words "APO" (away from) and "mixed" (the act of mixing or mingling), refers to the formation of a plant from a seed without fertilisation or normal sexual reproduction. It is essentially an asexual process that results in a clone of the female parent plant.
In sexual reproduction, the ovule goes through developmental stages to produce the female gametophyte (embryo sac), which is then fertilized twice to produce the embryo and endosperm.
Apomixis is common in higher plants, with over 35 families known to exhibit it, including Gramineae, Compositae, and Rutaceae. Apomixis can also be seen in major cereals like maize and wheat. This article details apomixis, an important aspect of sexual reproduction in flowering plants for the NEET Exam, including its types, diagram, and function.
Flower – A Fascinating Organ of Angiosperms
Apomixis is the asexual development of seeds or embryos without fertilisation. Plantlets can also replace seeds and flowers with bulbils. Apomixis produces offspring genetically identical to the parent plant, except for nonrecurrent apomixis. The term is derived from the Greek words "away from" and "mixing."
Unlike normal asexual plant reproduction, which involves propagation from cuttings or leaves, apomixis produces viable seeds containing an asexual embryo. Apomixis refers specifically to agamospermy in flowering plants, which is clonal reproduction via seeds. While agamospermy could theoretically occur in gymnosperms, it does not appear to exist in that group.
Apogamy is a related term that has had different meanings over time. In plants with independent gametophytes, such as ferns, apogamy, and apomixis are used interchangeably to describe the formation of sporophytes via the parthenogenesis of gametophyte cells.
Male apomixis, also known as paternal apomixis, is the process by which pollen's genetic material replaces an egg's genetic material.
Pre-Fertilisation- Structures And Events in Flowering Plants
The following image shows the Apomictic Taraxacum officinale :
Plants can reproduce asexually through apomixis, which includes three primary types: adventitious embryony, apospory, and diplospory.
Definition: In diplospory, the embryo sac develops from the megaspore mother cell either through direct mitotic division or by interrupting meiosis.
Process:
Definition: Apospory involves the development of the apomictic embryo sac from nucellar cells and is the most common type of apomixis in higher plants.
Process:
Pollination, Types, Agents, Pollen Pistil Interaction
Definition: Adventitious embryony is a sporophytic form of apomixis where embryos develop directly from the nucellus or integument of the ovule.
Process:
Additional types of apomixis are based on occurrence and frequency, which are briefly discussed below.
Post Fertilisation – Structures and Events in Flowering Plants
Definition: Vegetative apomixis involves the production of vegetative bulbils or buds in the inflorescence instead of flowers.
Characteristics: Vegetative bulbils or buds are easily reproducible and contribute to the propagation of these plants.
Examples: This type of apomixis is observed in plants such as Fragaria, Agave, and Poa bulbosa.
Embryo, Development, Monocots And Dicots Plants, Embryogenesis
Apomixis is an asexual method of plant reproduction that occurs in many species, particularly fruit crops. Its key characteristics include:
Types of Seeds, Monocot and Dicot, Advantages, Seed Viability
Apomixis is a fascinating form of asexual plant reproduction, where seeds and embryos are produced without fertilisation. This phenomenon was initially discovered in Alchornea ilicifolia and has since been observed in over 400 flower plant species.
Apomixis is notably found in several genera, including:
These examples underscore the diversity and widespread occurrence of apomixis in nature, highlighting its importance in plant reproduction.
Sexual Reproduction in Flowering Plants MCQ
The following are the Advantages of Apomixis
Apomixis has practical applications in agriculture:
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