Question

With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.

Answer 1

Hint: The female gametophyte is also called the embryo sac, or megagametophyte. The female gametophyte develops within the ovule.

Complete Answer:
- A mature gametophyte represented by (e) in the given diagram contains three antipodal cells (AP), one central cell (CC), two synergid cells (SC) and one egg cell (EC). The female gametophyte develops from a single functional megaspore.
- The megaspore undergoes many mitotic divisions to form 7 celled 8 nucleate structures.
The central cell of the female gametophyte has two nuclei . Due to which female gametophytes become 8 nucleated.
- There are two ends of the female gametophyte – chalazal end and micropylar end. Antipodals are present at the chalazal end of the female gametophyte and synergids are present at the micropylar end of the female gametophyte.
- When male gametophyte fuses with the egg cell, it results in the diploid zygote. And when the male gamete fuses with central nuclei it results in the formation of triploid Primary Endosperm Nucleus which later develops into the endosperm.
- The process of fusion in which one male gamete fuses with an egg cell and one male gamete fuses with the central cell is called double fertilization.

Note: Endosperm is a tissue which is present inside the seeds of the plants. Endosperm provides nourishment to the growing embryo until it germinates. When the seed germinates it can make its own food with the help of leaves and green stem by the process called as photosynthesis. Endosperm contains many kinds of oils and proteins.