Megasporogenesis

1. Megasporogenesis
Dr R. K. Upadhyay

2. Definition
Megasporogenesis is the process of the formation of megaspores.
Site: Megasporangium (Ovule)
https://en.wikipedia.org/wiki/Ovule

3. OVULE
• The ovule is a flowering plant organ that produces
seeds.
• Ovule comprises
 Nucellus
 Integument
 Embryosac
• Ovule has micropylar end, Chalazal pole
• Eggs are located at the micropylar end.
• Antipodal cells are present at chalazal end

4. Process
Ovule
Megaspore mother cell
Megaspores
Meiosis
Four,
haploid

5. Monosporic Development
 one of the four megaspores is functional.
 The functional megaspore germinates into a female gametophyte
(embryo sac).
 This is known as monosporic development.
 The nucleus of the functional megaspore undergoes mitotic
divisions to produce a 7-celled, 8-nucleate embryo sac.

6. 7 celled 8 nucleate embryo sac
7 Cells
Egg ----------------01
Synergid----------02
Central cell-------01
Antipodal cell---03
8 Nucleus
Egg ----------------01
Synergid----------02
Polar Nuclei------02
Antipodal cell---03
Egg apparatus- egg + synergids
Egg + male gamete zygote embryo
Polar nuclei- fuse with male gamete during triple fusion and form triploid endosperm
Synergids- contain filiform apparatus, help in the entry of pollen tube, and facilitate fertilization (syngamy)