Question

Identify the correct statement.

• A. Only one megaspore present towards chalazal end remains functional.
• B. 3 megaspores present towards chalazal end degenerate gradually.
• C. Each megaspore mother cell directly develops into a megaspore.
• D. Each female gametophyte is 7-celled and 7-nucleated structure.

Hint:

Remember the "7-8 rule" for the embryo sac: 7 cells (3 antipodals, 2 synergids, 1 egg, 1 central cell) and 8 nuclei (3+2+1+2). The central cell is the largest and contains two nuclei!

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Megasporogenesis is the process of formation of megaspores from the Megaspore Mother Cell (MMC). In most flowering plants, this follows a specific pattern of division and degeneration known as monosporic development.
Step 2: Detailed Explanation:
1. Option (a) & (b): The MMC undergoes meiosis to produce a linear tetrad of 4 haploid megaspores. Usually, the three megaspores located towards the micropylar end degenerate, while the one at the chalazal end remains functional. Therefore, (a) is correct and (b) is incorrect. 2. Option (c): The MMC does not directly become a megaspore; it must undergo meiosis to produce four megaspores first. 3. Option (d): A typical mature female gametophyte (embryo sac) is a 7-celled but 8-nucleated structure (due to the central cell containing two polar nuclei).
Step 3: Final Answer
Statement (a) is the only correct statement.