Introduction

The creation of new progeny in plants, which can be achieved through sexual or asexual reproduction, is referred to as reproduction in plants. In order for plants to reproduce sexually, male and female gametes must fuse. A thin-walled sac that houses the egg nucleus and other nuclei that produce endosperm upon fertilisation makes up the female gametophyte of a seed plant. Angiosperm female gametophytes, also known as embryo sacs, are very small and have only a few nuclei, usually eight. Cell walls do not separate the cytoplasm that is more or less directly connected to these nuclei. The embryo sac is a female gametophyte that, when fertilised, generates endosperm. The mature organism is made up of seven cells and eight nuclei.

Embryo Sac

One female gamete (or egg) is present in each embryo sac. The two stages below describe how the embryo sac develops.

• First-stage megasporogenesis occurs when a single diploid mother cell undergoes meiosis, producing a haploid megaspore tetrad. One of these survives and later develops into the embryo sac, while the other three disintegrate.

• The second phase is called megagametogenesis. The functioning haploid megaspore undergoes mitosis at this stage, producing an 8-nucleate, 7-celled gametophyte and the embryo sac. Only the polar nuclei of the eight nuclei make their way to the centre, where they unite to form a single diploid cell (site). When this lone diploid cell fuses with the sperm, the triploid endosperm is created.

Conclusion

There is only one egg present in an embryo sac.