Question

What is Megasporogenesis? Describe the development of a female gametophyte.

Hint:

The typical embryo sac in flowering plants is {8-nucleate and 7-celled}, formed from a single functional megaspore.

Answer 1

Concept: In flowering plants, the female gametophyte develops inside the ovule. The process begins with the formation of megaspores through meiosis, followed by their development into the embryo sac.
Step 1:Megasporogenesis Megasporogenesis is the process of formation of megaspores from a megaspore mother cell (MMC) inside the ovule.

• The megaspore mother cell undergoes meiotic division.
• This produces four haploid megaspores.
• Usually, three megaspores degenerate, and only one functional megaspore remains.

Step 2:Development of Female Gametophyte The functional megaspore undergoes mitotic divisions to form the female gametophyte or embryo sac.

• The nucleus of the functional megaspore divides three times.
• This produces eight nuclei.
• These nuclei organize themselves to form a seven-celled embryo sac.

Structure of the Embryo Sac:

• One egg cell
• Two synergids
• Three antipodal cells
• Two polar nuclei in the central cell

This structure forms the female gametophyte in flowering plants.