Biology · Sexual Reproduction in Flowering Plants · NEET
After three free-nuclear mitotic divisions the functional megaspore has 8 nuclei. Cell walls then form around only 6 of them (2 synergids + 1 egg at the micropylar end, and 3 antipodals at the chalazal end). The remaining 2 nuclei do NOT get their own walls; they stay together as polar nuclei inside one large central cell. So there are 8 nuclei but only 7 cells (6 single-nucleus cells + 1 central cell holding 2 nuclei). This exact wording is a repeated NEET answer.
No. The egg apparatus is only the 2 synergids and 1 egg cell at the micropylar end. The 2 polar nuclei are located below the egg apparatus, inside the large central cell in the middle of the sac. NEET 2025 used exactly this trap: the reason 'egg apparatus has 2 polar nuclei' is FALSE.
There are usually 3 antipodal cells, placed at the chalazal end (the end opposite the micropyle, away from where the pollen tube enters). NCERT calls this a typical embryo sac. If a question says 'numerous antipodals', it is wrong for a typical angiosperm.
Everything in the unfertilised embryo sac is haploid (n) because the whole female gametophyte forms by mitosis from a haploid functional megaspore. So each polar nucleus is n, the central cell has two n nuclei, and each antipodal is n. Only after triple fusion does the central cell become the triploid (3n) primary endosperm cell.
It is the LARGEST cell of the embryo sac. It occupies most of the sac volume and contains the 2 polar nuclei. A NEET 2016 option said 'a small central cell is present' and that was wrong because the central cell is large, not small.
The central cell (with its 2 polar nuclei) fuses with the second male gamete in triple fusion to form the primary endosperm cell, which becomes the endosperm. The 3 antipodal cells are non-functional and usually degenerate; they do not take part in fertilisation.
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:
In majority of angiosperms:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
No. Before fertilisation the central cell is haploid; it just contains two haploid polar nuclei (n + n). It becomes triploid (3n) only after triple fusion, when it turns into the primary endosperm cell.
Two — the two polar nuclei. These two nuclei sometimes fuse before fertilisation to form a single diploid secondary nucleus, but NCERT usually shows them as two separate polar nuclei.
In a typical angiosperm the 3 antipodal cells are non-functional (vegetative) and usually degenerate. They do not fuse with any male gamete.
The central cell is the largest cell of the embryo sac and lies in the middle, carrying the two polar nuclei.
NEET repeatedly tests the exact structure of the mature embryo sac (8-nucleate, 7-celled) and the position and ploidy of the central cell, polar nuclei and antipodals in double fertilisation questions. One clear picture prevents easy trap losses.
