Question

In angiosperms, female gametophyte is called as embryo sac. Given figures represent different stages of embryo sac development in angiosperms. Arrange them in correct order and select the correct option.

• A. $\left(V\right)\to \left(I\right)\to \left(IV\right)\to \left(II\right)\to \left(III\right)\to \left(VII\right)\to \left(VI\right)\to \left(VIII\right)$
• B. $\left(VIII\right)\to \left(V\right)\to \left(II\right)\to \left(IV\right)\to \left(III\right)\to \left(VII\right)\to \left(VI\right)\to \left(I\right)$
• C. $\left(I\right)\to \left(II\right)\to \left(IV\right)\to \left(V\right)\to \left(VIII\right)\to \left(III\right)\to \left(VII\right)\to \left(VI\right)$
• D. $\left(VIII\right)\to \left(I\right)\to \left(V\right)\to \left(II\right)\to \left(IV\right)\to \left(III\right)\to \left(VI\right)\to \left(VII\right)$

Answer 1

Answer: (D)

The development of female gametophyte in angiosperms starts with differentiation of primary archesporial cell in the nucellus. In the hypodermal region of nucellus towards the micropylar end develops a primary archesporial cell which divides into outer primary parietal cell and inner primary sporogenous cell (megaspore mother cell) which divides by meiosis to form a row of four haploid megaspores and the megaspore at the chalazal end remains functional which forms 8 nucleate embryo sac. The functional megaspore is the first cell of female gametophyte. The cell enlarges and undergoes three free nuclear mitotic divisions. The first division produces two nucleate embryo sac. The two nuclei shift to the two ends and divide there twice forming four nucleate and then eight nucleate structure. One nucleus from each side moves to the middle. They are called polar nuclei. The remaining three nuclei form cells at the two ends, $3$ celled egg apparatus (two synergids and one egg cell) at the micropylar end and three antipodal cells at the chalazal end. The middle binudeate part organises itself into central cell.