Chapter 23, Problem 35A

Summary Introduction

To write:

The reason female gametophyte of anthophyte produces many nuclei.

Introduction:

Anthophytes are widespread and diverse group of plants and are adapted to live in terrestrial as well as aquatic environments. They are unique as they have flowers. They have distinct life cycles and exhibit alternation of generations. The sporophyte generation is dominant and supports the gametophyte generation.

Explanation of Solution

In most flowering plants, the megaspore's nucleus undergoes mitosis three times, producing eight haploid nuclei. These eight nuclei make up the female gametophyte. Three of the nuclei moves to one end and develop into the antipodal cells which eventually degenerates. The nucleus nearest to the micropyle becomes the female gamete, or egg cell, and the two adjacent nuclei develop into synergid cells. The two remaining nuclei known as polar nuclei are enclosed in a single cell known as central cell. It is located in the centre of the gametophyte. The synergids help to guide the pollen tube during fertilization and eventually disintegrates. The central cell containing the polar nuclei fuses with a sperm to form the triploid nucleus that divide many times and eventually forms the endosperm. The endosperm stores food and supports the development of the growing embryo.

Conclusion

Thus, the nuclei produced by the female gametophyte allows the process of double fertilization.