Female Gametophyte in Angiosperms

The female gametophyte in angiosperms is called the embryo sac. It is an important structure that plays a vital role in the reproduction of flowering plants. The embryo sac is located within the ovule, which is a part of the carpel or pistil, the female reproductive organ of the flower.

Formation of Embryo Sac

The formation of the embryo sac begins with the meiotic division of a diploid cell in the ovule. This cell, called the megaspore mother cell, undergoes meiosis and produces four haploid cells. Only one of these cells survives and develops into the embryo sac.

Structure of Embryo Sac

The mature embryo sac is a highly specialized structure that contains seven cells and eight nuclei. These cells and nuclei are arranged in a specific pattern that is important for successful fertilization. The structure of the embryo sac can be divided into three main parts:

1. The egg apparatus: This is the part of the embryo sac that contains the egg cell and two synergids. The synergids are important for guiding the pollen tube to the egg cell during fertilization.

2. The central cell: This is the largest cell in the embryo sac and contains two nuclei. These nuclei are important for the fusion of the male and female gametes during fertilization.

3. The antipodal cells: These are three small cells at the opposite end of the embryo sac from the egg apparatus. The function of these cells is not well understood, but they may play a role in nutrient storage.

Function of Embryo Sac

The embryo sac plays a vital role in the sexual reproduction of angiosperms. Its main function is to produce and protect the female gamete, the egg cell, and to provide a site for fertilization to occur. During pollination, the male gametes from the pollen grain travel down the pollen tube and enter the embryo sac. Fertilization occurs when one of the male gametes fuses with the egg cell, while the other fuses with the two nuclei in the central cell. This process results in the formation of a zygote and a triploid endosperm, which provides nutrients to the developing embryo.