Module: | Pollination & Outbreeding Devices
Q46: Consider the following statements regarding megasporogenesis and the megaspore tetrad:
1. During megasporogenesis, the diploid megaspore mother cell typically undergoes meiosis to form a linear tetrad of four haploid megaspores.
2. In the standard monosporic Polygonum type of development, the three megaspores located toward the micropylar end degenerate.
3. The single functional megaspore, which eventually develops into the embryo sac, is structurally located at the micropylar end of the ovule.
Which of the above statements is/are correct?
2. In the standard monosporic Polygonum type of development, the three megaspores located toward the micropylar end degenerate.
3. The single functional megaspore, which eventually develops into the embryo sac, is structurally located at the micropylar end of the ovule.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is incorrect.
The development of the female gametophyte relies on strict spatial dynamics.
The megaspore mother cell (MMC) differentiates at the micropylar region of the nucellus.
Following meiotic division, it forms four haploid cells.
Unlike the varied geometries of microspores, megaspores most frequently arrange themselves in a straight, linear tetrad.
Causally, to concentrate maternal resources into a single robust gametophyte, apoptosis (programmed cell death) eliminates three of the four spores.
Statement 3 features a highly tested spatial trap: it is always the three megaspores located near the micropyle that degenerate.
The single surviving, functional megaspore is strictly the one located at the chalazal end of the tetrad.
This chalazal megaspore then undergoes three mitotic divisions to form the 8-nucleate embryo sac.
The development of the female gametophyte relies on strict spatial dynamics.
The megaspore mother cell (MMC) differentiates at the micropylar region of the nucellus.
Following meiotic division, it forms four haploid cells.
Unlike the varied geometries of microspores, megaspores most frequently arrange themselves in a straight, linear tetrad.
Causally, to concentrate maternal resources into a single robust gametophyte, apoptosis (programmed cell death) eliminates three of the four spores.
Statement 3 features a highly tested spatial trap: it is always the three megaspores located near the micropyle that degenerate.
The single surviving, functional megaspore is strictly the one located at the chalazal end of the tetrad.
This chalazal megaspore then undergoes three mitotic divisions to form the 8-nucleate embryo sac.