Hint: The female gametophyte is also called the megagametophyte or the embryo sac. Whereas the male gametophyte is also called the microgametophyte or the pollen grain.
Complete Answer: The female gametophyte’s formation from one single functional megaspore is known as Monosporic development. - The functional megaspore’s nucleus divides mitotically and forms two nuclei - which move to the opposite poles. Thus, forming a two-nucleate embryo sac. - Two more mitotic nuclear divisions occur, and form the four-nucleate and eight-nucleate stages of the embryo sac. - These are free nuclear type mitotic divisions, in which karyokinesis is not immediately followed by cytokinesis. - After the eight-nucleate stage, the walls are laid down, thus organising the typical female gametophyte. Six out of the eight nuclei are surrounded by cell walls and are organized into cells; the remaining two nuclei, called the polar nuclei are situated below the egg apparatus. - A typical angiosperm embryo sac at maturity is eight nucleate and seven cells. The mature embryo sac contains 3 synergid cells at the micropylar end, 3 antipodal cells at the chalazal end, an egg cell at the center, and a 2 polar nuclei, which fuse together to form the secondary nucleus.
Additional information: - In most of the flowering plants, a single megaspore mother cell is present at the micropylar end of the ovule’s nuclear region. It undergoes meiosis to form four haploid megaspores. - Later, out of these four megaspores, only one functional megaspore develops into the female gametophyte, while the remaining three degenerate.
Note: The female gametophytes form the female gametes and produce the physical and molecular basis for beginning of the seed development and fertilisation.
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What is meant by monosporic development of female gametophyte?
Sexual Reproduction in Flowering Plants Class12 NCERT EXERCISE1.5| Class 12 Chapter 1| Kanika Sharma