Pseudo embryo sac is derived from Nucellus

The pseudo embryo sac is a structure that forms within the ovule of a flowering plant. It is responsible for the development of the female gametophyte, which ultimately gives rise to the embryo and endosperm after fertilization.

Development of the Pseudo Embryo Sac
- The development of the pseudo embryo sac begins with the differentiation of the nucellus, which is a part of the ovule.
- The nucellus is a central mass of tissue within the ovule that surrounds the megasporangium, where the female gametes are produced.
- As the megasporangium undergoes meiosis, it produces four megaspores.
- However, in most flowering plants, only one of these megaspores survives and develops into the embryo sac, while the other three degenerate.
- The surviving megaspore enlarges and undergoes three rounds of mitotic divisions to form the mature pseudo embryo sac.

Structure of the Pseudo Embryo Sac
- The mature pseudo embryo sac typically consists of seven cells.
- These cells are arranged in three different regions: the egg apparatus, the central cell, and the antipodal cells.
- The egg apparatus consists of two synergids and an egg cell.
- The central cell contains two polar nuclei, which will eventually unite with a sperm cell during fertilization to form the endosperm.
- The antipodal cells are typically located at the opposite end of the embryo sac and their function is not well understood.

Function of the Pseudo Embryo Sac
- The pseudo embryo sac plays a crucial role in sexual reproduction in flowering plants.
- The egg cell within the embryo sac is fertilized by a pollen grain, resulting in the formation of an embryo.
- The central cell of the embryo sac is also fertilized by a separate sperm cell, which leads to the formation of the endosperm.
- The endosperm provides nutrients to the developing embryo and is an important part of the seed.
- Therefore, the pseudo embryo sac is essential for the successful reproduction and propagation of flowering plants.

In conclusion, the pseudo embryo sac is derived from the nucellus, a part of the ovule. It is responsible for the development of the female gametophyte, including the formation of the embryo and endosperm after fertilization.