Biology · Sexual Reproduction in Flowering Plants · NEET
Megasporogenesis is the formation of megaspores from the megaspore mother cell (MMC). One diploid MMC in the micropylar region of the nucellus undergoes ONE meiotic division and forms four haploid megaspores, usually in a linear row. Three of them degenerate and only one survives as the functional megaspore, which later becomes the embryo sac. Memory hook: "1 MMC, 1 meiosis, 4 megaspores, 3 die, 1 works" — the one that works is the functional megaspore.
One diploid MMC in the micropylar nucellus undergoes a single meiosis to form a linear tetrad of four haploid megaspores. Three (usually micropylar) degenerate; the one chalazal functional megaspore later divides by mitosis into the embryo sac.
Your doubts, answered
Is megasporogenesis meiosis or mitosis?
Megasporogenesis is MEIOSIS. The diploid megaspore mother cell (MMC) undergoes a single meiotic division to produce four haploid megaspores. Do not confuse this with the later mitotic (free-nuclear) divisions of the functional megaspore that build the embryo sac — those come under megagametogenesis, not megasporogenesis.
How many megaspores form from one megaspore mother cell?
One MMC forms exactly FOUR megaspores after one meiosis. They are usually arranged in a straight line, called a linear tetrad. This mirrors microsporogenesis, where one microspore mother cell also gives four microspores — but there all four survive, while here only one does.
Why do three megaspores degenerate and only one stay functional?
In a majority of flowering plants only one megaspore (usually the one at the chalazal end) remains alive and is called the functional megaspore; the other three degenerate. Because only this single megaspore forms the embryo sac, the development is called monosporic. NCERT states this as a simple fact — 'one of the megaspores is functional while the other three degenerate.'
Where exactly does the MMC form inside the ovule?
The ovule generally differentiates a single megaspore mother cell in the MICROPYLAR region of the nucellus. The nucellus is the diploid sporophytic tissue of the ovule, so the MMC is embedded inside it. This location detail is a common NEET fill-in-the-blank point.
What is the ploidy of the MMC, megaspore and functional megaspore?
The nucellus and the MMC are diploid (2n). After meiosis, each megaspore — including the functional megaspore — is haploid (n). The female gametophyte (embryo sac) that develops from the functional megaspore is therefore also haploid. This exact ploidy question is asked directly in NCERT.
Is the functional megaspore the same as the embryo sac?
No. The functional megaspore is a single haploid cell; it later DEVELOPS INTO the embryo sac by mitotic divisions. So the functional megaspore is the starting cell, and the embryo sac (female gametophyte) is the finished 7-celled, 8-nucleate structure it grows into.
⚠️ The NEET trap ✗ Megasporogenesis produces four megaspores and all four develop into the embryo sac. ✓ Megasporogenesis produces four megaspores, but only ONE (the functional megaspore) develops into the embryo sac; the other three degenerate. This single-megaspore route is called monosporic development. 🧠 NEET loves the parallel with microspores. All four microspores survive as pollen, but only one of four megaspores survives. Same meiosis, different survival — that asymmetry is the trap.
Real NEET questions
2017
Functional megaspore in an angiosperm develops into
A · Ovule
B · Endosperm
C · Embryo sac ✓
D · Embryo
Solution: Of the four megaspores, the single functional megaspore develops into the embryo sac (female gametophyte) by monosporic development. The ovule is the whole megasporangium that contains it, while endosperm and embryo are post-fertilisation products. NCERT Ch 1: 'Only the functional megaspore develops into the female gametophyte (embryo sac).'
2019
Which is the most common type of embryo sac in angiosperms?
A · Tetrasporic with one mitotic stage of divisions
B · Monosporic with three sequential mitotic divisions ✓
C · Monosporic with two sequential mitotic divisions
D · Bisporic with two sequential mitotic divisions
Solution: In most flowering plants only one megaspore is functional, so development is monosporic. The functional megaspore nucleus then undergoes three sequential free-nuclear mitotic divisions (2- then 4- then 8-nucleate). Hence monosporic with three sequential mitotic divisions.
2025
How many meiotic and mitotic divisions need to occur for the development of a mature female gametophyte from the megaspore mother cell in an angiosperm plant?
A · 1 Meiosis and 3 Mitosis ✓
B · No Meiosis and 2 Mitosis
C · 2 Meiosis and 3 Mitosis
D · 1 Meiosis and 2 Mitosis
Solution: The MMC divides by ONE meiosis to give four megaspores (megasporogenesis). The functional megaspore then undergoes THREE successive free-nuclear mitotic divisions (2- → 4- → 8-nucleate) to build the mature female gametophyte. Total: 1 meiosis and 3 mitoses.
Solved Sexual Reproduction in Flowering Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the process of formation of megaspores from the diploid megaspore mother cell by one meiotic division.
What is a functional megaspore?
It is the single surviving haploid megaspore (usually at the chalazal end) that develops into the embryo sac, while the other three megaspores degenerate.
What is a linear tetrad of megaspores?
After meiosis of the MMC, the four megaspores are commonly arranged in a straight row inside the nucellus; this row is called a linear tetrad.
How is megasporogenesis different from microsporogenesis?
Both involve meiosis. Microsporogenesis makes four microspores (all become pollen); megasporogenesis makes four megaspores but only one functional megaspore survives to form the embryo sac.
Which end of the ovule usually keeps the functional megaspore?
In most angiosperms the megaspore at the chalazal end remains functional, and the three towards the micropyle degenerate.
