question_answer

Directions : (51 - 55)

Read the passage given below and answer the following questions.

In a majority of flowering plants, one of the megaspores is functional while the other three degenerates. Only the functional megaspore is the first cell of female gametophyte and develops into the female gametophyte or embryo sac. This method of embryo sac formation from a single megaspore is termed monosporic development. The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleated embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleated and later the 8-nucleated stages of the embryo sac. It is of interest to note that these mitotic divisions are strictly free nuclear, that is, nuclear divisions are not followed immediately by cell wall formation. After the 8-nucleated stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are surrounded by cell walls and organised into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.

Formation of embryo sac is called as

A) Megasporogenesis

B) Megagametogenesis

C) Microgametogenesis

D) Microsporogenesis