What is meant by monocarpic development of female gametophyte?
Answers
Answer:
The formation of the female gametophyte from a single functional megaspore is called as monosporic development.
The nucleus of functional megaspore divides mitotically to form two nuclei which move to opposite poles. This forms a two-nucleate embryo sac.
Two more sequential mitotic nuclear divisions result in the formation of four-nucleate and eight-nucleate stages of embryo sac.
These mitotic divisions are free nuclear type in which karyokinesis is not followed immediately by cytokinesis.
After the eight-nucleate stage, the walls are laid down leading to the organization of the typical female gametophyte. Six of eight nuclei are surrounded by cell walls and organized into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.
A typical angiosperm embryo sac at maturity is eight nucleate and seven cells. Three cells lie at micropylar end forming egg apparatus. Three ends at chalazal end called as antipodal cells. A single large central cell which has two polar nuclei.
Explanation:
When the female gametophyte (embryo sac) develops from a single megaspore, it is called monosporic development.
Usually, in most angiosperms, the megaspore mother cell divides by meiosis to form four haploid megaspores arranged in a linear fashion. The three haploid megaspores situated towards the micropyle degenerate, while one remains functional which develops into the female gametophyte.
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