The female gametophyte in an angiosperm is also called the embryo sac. It is present inside the ovule or the megasporangium enclosed within the nucellus and integuments. Generally, there is only one embryo sac present in each ovule.
Female gametophyte in most of the angiosperms develops from a single megaspore. The formation of a megaspore is known as megasporogenesis. Typically a single megaspore mother cell (MMC) gets differentiated at the micropylar region of ovule or megasporangium unlike microsporangium, where each cell of sporogenous tissue can act as a pollen mother cell and gives rise to microspore tetrad.
The megaspore mother cell or MMC contains a dense cytoplasm and a large nucleus. The megaspore mother cell divides by meiotic division to give rise to 4 haploid megaspores. Generally, only one megaspore is functional and develops into the female gametophyte or the embryo sac. This is known as monosporic development. The rest three megaspores degenerate.
Monosporic Development of Female Gametophyte or Embryo Sac
The nucleus of the functional megaspore undergoes sequential mitosis division without the formation of a cell wall, i.e. free nuclear. It divides by mitosis to produce two nuclei, which move to the opposite poles of the embryo sac. Two more mitosis division leads to the formation of an embryo sac with 8 nuclei and then the cell wall formation takes place to form an embryo sac with 8 nuclei and 7 cells. The central cell possesses two polar nuclei.
Read in detail about Embryo Sac structure.
- Plant Growth and Development
- Sexual Reproduction in Flowering Plants
- Anatomy of Flowering Plants – Important Notes for NEET
- Morphology of Flowering Plants – Important Notes for NEET
- Difference Between Staminate and Pistillate Flowers
- Difference Between Parthenocarpy and parthenogenesis
Stay tuned to BYJU’S to learn similar questions and important points related to the Plant Kingdom.