Question

A typical angiospermic embryo sac at maturity is eight nucleate and

• A. Single celled
• B. Four celled
• C. Seven celled
• D. Eight celled

Answer 1

The correct option is C Seven celled

Angiospermicfemale gametophyte is eight-celled embryo sac. The diploid cell of the embryo sac forms the mother cell and undergoes meiosis to form four haploid cell. Out of four, three degenerates and one forms the female megaspore. The megaspore undergoes three successive mitotic division which leads to formation of four nuclei each at both the ends i.e., at the micropylar and the chalazal end in the embryo sac. At the micropylar end, out of the four nuclei only three differentiate into two synergids and one egg cell. Together they are known as the egg apparatus. Similarly, at the chalazal end, three out of four nuclei differentiates as antipodal cells. The remaining two nuclei (of the micropylar and the chalazal end) move towards the centre and are known as the polar nuclei, which are situated in a large central cell. Hence, at maturity, the female gametophyte appears as a 7-celled structure, though it has 8 nucleate.

So, the correct answer is option C.