Question

8- nucleate embryo sac is

• A. Monosporic
• B. Bisporic
• C. Tetrasporic
• D. All the above

Answer 1

The correct option is D All the above

On the basis of megaspores contributing in the development of embryo sac, a number of mitotic divisions occurring in the functional megaspore and the organization of nuclei within the embryo sac, there are three types of embryo sacs:

1. 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.

2. Bisporic embryo sac: In this type of embryo sac, two megaspores take part in the formation of the embryo sac. The nucleus of two megaspores undergo two mitotic divisions and the resulting embryo sac is 8 nucleate.

3. Tetrasporic embryo sac: In this type of embryo sac, all the four megaspores take part in the formation of the embryo sac. The meiotic divisions in the megaspore mother cell are not followed by wall formation, so all the four haploid nuclei remain in a common cytoplasm and forming a coenomegaspore. The final organization of the embryo sac is 8-nucleate.

Hence, the 8-nucleate embryo sac can be monosporic, bisporic and tetrasporic.

So, the correct answer is D.