AP BIOLOGY

Detailed explanation-1: -A mature embryo sac consists of two synergids, one egg cell and three antipodal cells with one nucleus each. Then there is one large central cell that has two nuclei. Hence, a mature embryo sac consists of 7 cells and 8 nuclei.

Detailed explanation-2: -Nucleus undergoes three mitotic divisions to form 8 nuclei. This type is also called Polygonum type. In the bisporic embryo sac, two megaspores take part in the formation of the embryo sac. The nucleus of two megaspores undergo two mitotic divisions and thus the resulting embryo sac is 8-nucleate.

Detailed explanation-3: -A mature female gametophyte (embryo sac/egg apparatus) of angiosperms is 7 celled with 8 nucleus .

Detailed explanation-4: -Monosporic embryo sac: In this type of embryo sac, out of the four megaspores, one megaspore at the chalazal side takes part in the formation of the embryo sac. Nucleus divides three times to form 8 nuclei. This type is called Polygonum type.

Detailed explanation-5: -Three cells present at the chalazal end of embryo sac are called as antipodals. The large central cell has two polar nuclei. This makes embryo sac 7 celled and 8 nucleate structure.