Biology · Sexual Reproduction in Flowering Plants · NEET
A mature angiosperm embryo sac (female gametophyte) has 8 nuclei but only 7 cells. Six nuclei get their own cell walls (2 synergids + 1 egg + 3 antipodals = 6 cells), and the last two nuclei stay together as polar nuclei inside one big central cell. Memory hook: "8 nuclei, but 2 share a room" — so 8 nuclei live in only 7 cells.
The mature embryo sac has 7 cells holding 8 nuclei: 2 synergids + 1 egg (egg apparatus, micropylar end), 1 central cell with 2 polar nuclei, and 3 antipodals (chalazal end). The central cell carries the extra nucleus, so 8 nuclei fit in only 7 cells.
Your doubts, answered
Why is the embryo sac 8-nucleate but only 7-celled?
After the 8-nucleate free-nuclear stage, cell walls form around only six nuclei, giving six cells: 2 synergids, 1 egg cell, and 3 antipodals. The remaining two nuclei (the polar nuclei) do not get separate walls — they lie together in one large central cell. So 6 single-nucleus cells + 1 central cell (with 2 nuclei) = 7 cells, but 6 + 2 = 8 nuclei. That is why the count of nuclei (8) is more than the count of cells (7).
Which cell in the embryo sac has two nuclei?
The large central cell. It holds the two polar nuclei together. All other cells (the two synergids, the egg cell, and the three antipodals) have only one nucleus each. This is the single reason the numbers do not match: one cell carries two nuclei.
How are the 7 cells arranged inside the mature embryo sac?
Micropylar end (near the pollen tube entry): the egg apparatus = 2 synergids + 1 egg cell (3 cells). Centre: 1 large central cell with 2 polar nuclei. Chalazal end (opposite pole): 3 antipodal cells. That is 3 + 1 + 3 = 7 cells, holding 3 + 2 + 3 = 8 nuclei.
Do the polar nuclei count as one cell or two cells?
One cell. Both polar nuclei sit inside the same central cell, so they add 2 to the nucleus count but only 1 to the cell count. If you wrongly treated the central cell as two cells you would get 8-celled, which is a classic NEET mistake. It is 7-celled.
How many meiotic and mitotic divisions make the mature embryo sac?
From the megaspore mother cell: 1 meiosis (gives 4 megaspores, 3 degenerate) + 3 free-nuclear mitotic divisions of the functional megaspore (gives 2-, then 4-, then 8-nucleate stages). Then cell walls form to organise the 7-celled, 8-nucleate embryo sac. So the answer NEET asks is 1 meiosis and 3 mitoses.
⚠️ The NEET trap ✗ The mature embryo sac is 8-nucleate and 8-celled because each nucleus becomes its own cell. ✓ It is 8-nucleate but 7-celled. Two of the eight nuclei (the polar nuclei) stay together inside one central cell, so the cell count is one less than the nucleus count. 🧠 Nuclei and cells are NOT the same number here. Always remember: 2 polar nuclei share 1 central cell → 8 nuclei, 7 cells.
Real NEET questions
NEET 2021
A typical angiosperm embryo sac at maturity is
A · 7-nucleate and 7-celled
B · 8-nucleate and 8-celled
C · 8-nucleate and 7-celled ✓
D · 7-nucleate and 8-celled
Solution: After the 8-nucleate stage, cell walls are laid down so six nuclei form six cells (2 synergids + 1 egg + 3 antipodals) while the two polar nuclei stay together in one large central cell. So the mature embryo sac is 8-nucleate but only 7-celled.
NEET 2025
Assertion (A): A typical unfertilized angiosperm embryo sac at maturity is 8-nucleate and 7-celled. Reason (R): The egg apparatus has 2 polar nuclei. Choose the correct answer:
A · A is true but R is false ✓
B · A is false but R is true
C · Both A and R are true and R is the correct explanation of A
D · Both A and R are true but R is not the correct explanation of A
Solution: A is correct: 8-nucleate, 7-celled. R is false: the egg apparatus is 2 synergids + 1 egg cell only. The 2 polar nuclei lie in the large central cell, not in the egg apparatus. So A is true but R is false.
NEET 2023 Phase 2
In angiosperms the correct sequence of events in formation of female gametophyte in the ovule is: (A) 3 successive free nuclear divisions in functional megaspore (B) Degeneration of 3 megaspores (C) Meiotic division in megaspore mother cell (D) Migration of 3 nuclei towards each pole (E) Formation of wall resulting in seven celled embryo sac
A · (B),(C),(A),(D),(E)
B · (C),(B),(A),(D),(E) ✓
C · (A),(B),(C),(D),(E)
D · (C),(E),(A),(D),(B)
Solution: Order: (C) meiosis in MMC → (B) 3 megaspores degenerate → (A) 3 free-nuclear mitoses give 2/4/8-nucleate stages → (D) nuclei migrate to poles → (E) wall formation gives the 7-celled embryo sac. That is (C),(B),(A),(D),(E) = option 2.
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.
7-celled. It is 8-nucleate but 7-celled because the two polar nuclei share one central cell instead of forming two separate cells.
What are the 7 cells of the embryo sac?
2 synergids and 1 egg cell (the egg apparatus at the micropylar end), 3 antipodal cells (at the chalazal end), and 1 large central cell in the middle.
Where are the two polar nuclei located?
In the large central cell, situated just below the egg apparatus. They stay as free nuclei and are not surrounded by their own cell walls, which is why they do not form separate cells.
Is the embryo sac haploid or diploid?
The embryo sac cells are haploid (n) because the female gametophyte develops from a haploid functional megaspore by mitosis. The central cell has two haploid polar nuclei.
What is the difference between nucleate and celled here?
Nucleate counts the number of nuclei (8). Celled counts the number of cells (7). They differ because one cell, the central cell, carries two nuclei.
