Question

The embryo sac in most angiosperms is made up of

• A. 8 cells.
• B. 7 cells and 8 nuclei.
• C. many cells.
• D. 7 cells and 7 nuclei.

Answer 1

The correct option is B

7 cells and 8 nuclei.

The angiospermic embryo sac has four well-defined megaspores. One of which gives rise to the embryo sac. The functional megaspore enlarges. Its nucleus divides. A large vacuole is formed between the nuclei. Thus the daughter nuclei move to the micropylar and chalazal poles of the embryo sac. Each nucleus divides twice. Thus four nuclei are formed at each pole. One nucleus from each pole migrates to the center of the embryo sac. The two nuclei fuse to form a diploid secondary nucleus. Three nuclei at the micropylar end are surrounded by membranes. They form egg apparatus. The central cell enlarged arid become egg cell. The other two cells become synergids. Thus embryo sac is formed containing 8-nuclei and later 7-celled during its development.