Development of the megaspore within the ovule (megasporangium) is known as megasporogenesis.
Topics
Reproduction in Lower and Higher Plants
- Reproduction
- Asexual Reproduction
- Asexual Reproduction in Unicellular Organisms > Binary Fission
- Binary Fission > Simple Binary Fission
- Binary Fission > Transverse Binary Fission
- Binary Fission > Longitudinal Binary Fission
- Asexual Reproduction in Unicellular Organisms > Multiple Fission
- Asexual Reproduction in Unicellular Organisms > Budding
- Asexual Reproduction in Multicellular Organisms > Fragmentation
- Asexual Reproduction in Multicellular Organisms > Spore Formation
- Vegetative Reproduction or Vegetative Propagation
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- Sexual Reproduction
- Flower
- Structure and Development of Anther
- Microsporogenesis
- Structure and Development of Male Gametophyte
- Structure and Development of Ovule
- Types of Ovules (Based on Orientation)
- Types of Ovules (Based on Integuments)
- Megasporogenesis
- Development of Female Gametophyte or Embryo Sac
- Pollination
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- Anemophily
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- Endosperm
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- Overview of Reproduction in Lower and Higher Plants
Reproduction in Lower and Higher Animals
- Reproduction
- Asexual Reproduction
- Asexual Reproduction in Animals > Gemmule Formation
- Asexual Reproduction in Multicellular Organisms > Budding
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Inheritance and Variation
- Heredity
- Gregor Johann Mendel – Father of Genetics
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Molecular Basis of Inheritance
- Deoxyribonucleic Acid (DNA)
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Origin and Evolution of Life
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Plant Water Relation
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- Mission Harit Maharashtra
- Overview of Biodiversity, Conservation and Environmental Issues
Estimated time: 10 minutes
CBSE: Class 12
CISCE: Class 12
CISCE: Class 12
Definition: Megasporogenesis
CBSE: Class 12
Maharashtra State Board: Class 12
CISCE: Class 12
Maharashtra State Board: Class 12
CISCE: Class 12
Megasporogenesis
Megasporogenesis is the process of formation of haploid (n) megaspores from a diploid (2n) Megaspore Mother Cell (MMC) by meiosis, within the nucellus of the ovule.
The Megaspore Mother Cell (MMC):
- A single hypodermal cell of the nucellus, at the micropylar region, differentiates into the archesporial cell.
- The archesporial cell may divide to produce an outer parietal cell and an inner sporogenous cell. The sporogenous cell functions as the Megaspore Mother Cell (MMC).
- Alternatively, the archesporial cell may directly function as the MMC.
Identifying features of the MMC:
| Feature | Description |
|---|---|
| Size | Large cell; conspicuously bigger than surrounding nucellus cells |
| Cytoplasm | Dense cytoplasm |
| Nucleus | Prominent nucleus |
| Ploidy | Diploid (2n) |
| Location | Micropylar region of the nucellus |
Meiotic Division of the MMC:
The MMC undergoes meiosis (reduction division), consisting of two successive divisions:
Meiosis I (Reductional Division)
The diploid MMC (2n) divides to produce two haploid (n) cells → called a dyad
Meiosis II (Equational Division)
Each cell of the dyad divides again
Result: Four haploid (n) megaspores arranged in a linear tetrad
(a) Parts of the ovule showing a large megaspore mother cell, a dyad and a tetrad of megaspores; (b) 2, 4, and 8-nucleate stages of embryo sac and a mature embryo sac; (c) A diagrammatic representation of the mature embryo sac
CBSE: Class 12
Maharashtra State Board: Class 12
Maharashtra State Board: Class 12
Key Points: Megasporogenesis
- Megasporogenesis is the process of formation of megaspores from a diploid megaspore mother cell (MMC) in the ovule.
- It occurs inside the nucellus of the ovule, usually near the micropylar region.
- The MMC undergoes meiosis to form four haploid megaspores arranged in a linear tetrad.
- Out of the four megaspores, three degenerate, and only one functional megaspore remains.
- The functional megaspore undergoes three mitotic divisions to form an 8-nucleate, 7-celled embryo sac (female gametophyte).
- The embryo sac contains one egg cell, two synergids, three antipodal cells, and one central cell with two polar nuclei.
