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With a Neat Diagram Explain the 7-celled, 8-nucleate Nature of the Female Gametophyte - CBSE (Science) Class 12 - Biology

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Question

With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.

Solution

The female gametophyte (embryo sac) develops from a single functional megaspore. This megaspore undergoes three successive mitotic divisions to form eight nucleate embryo sacs.

The first mitotic division in the megaspore forms two nuclei. One nucleus moves towards the micropylar end while the other nucleus moves towards the chalazal end. Then, these nuclei divide at their respective ends and re-divide to form eight nucleate stages. As a result, there are 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 cells (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.

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APPEARS IN

 NCERT Solution for Biology Textbook for Class 12 (2018 to Current)
Chapter 2: Sexual Reproduction in Flowering Plants
Q: 6 | Page no. 40
Solution With a Neat Diagram Explain the 7-celled, 8-nucleate Nature of the Female Gametophyte Concept: Pre-fertilisation - Structures and Events - The Pistil, Megasporangium (Ovule) and Embryo Sac.
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