The number of (i) meiotic and (ii) mitotic divisions required for the development of 7-celled, 8-nucleate monosporic embryo sac are
The number of (i) meiotic and (ii) mitotic divisions required for the development of 7-celled, 8-nucleate monosporic embryo sac are
The correct option is D (i) 1 & (ii) 7
In the ovule, megaspore mother cell divides meiotically and produces four megaspores. Out of these only one towards the chalazal end is functional. As the functional megaspore grows, its nucleus undergoes first mitotic division to form two nuclei separated by a central vacuole. As the vacuole enlarges one of the two daughter nuclei is pushed to the micropylar end and the other to the chalazal end to form a 2-nucleate structure. Both of these nuclei now undergo two more mitotic divisions each to form four nuclei at both the ends. At the micropylar end, three develop cell walls to form the egg apparatus while in the chalazal end the three nuclei develop cell wall to form the antipodals. The remaining one nuclei at each end migrates towards the center of the embryo sac forming the polar nuclei. Therefore, there is one meiotic and seven mitotic divisions.
(i) 1 & (ii) 7
In the ovule, megaspore mother cell divides meiotically and produces four megaspores. Out of these only one towards the chalazal end is functional. As the functional megaspore grows, its nucleus undergoes first mitotic division to form two nuclei separated by a central vacuole. As the vacuole enlarges one of the two daughter nuclei is pushed to the micropylar end and the other to the chalazal end to form a 2-nucleate structure. Both of these nuclei now undergo two more mitotic divisions each to form four nuclei at both the ends. At the micropylar end, three develop cell walls to form the egg apparatus while in the chalazal end the three nuclei develop cell wall to form the antipodals. The remaining one nuclei at each end migrates towards the center of the embryo sac forming the polar nuclei. Therefore, there is one meiotic and seven mitotic divisions.
