Formation of Pollen and Embryonic Sac

Development of Pollen Grains and Embryo Sac

6.2

Development of Pollen Grains and Embryo Sac

Process of pollen grains formation:

An anther has four pollen sacs in which pollen grains will be produced in the pollen sacs
Each pollen sac contains many diploid (2n)
Each pollen mother cells (2n) undergoes meiosis to produce a tetrad which containing four haploid microspore (n)
The haploid cells in tetrad seperate to form pollen grains
Each haploid cell underdoes mitosis to form a generative nucleus (n) and a tube nucleus (n)

Process of embryo sac formation:

Ovule is formed in the ovum.
Each ovule contains one embryo sac (2n)
The embryo sac mother cells (2n) undergoes mitosis to form four haploid megaspore cells (n)
Three megaspores degenerated and remaining one
The remaining megaspore undergoes mitosis three times to form haploid embryo sac cells with eight nuclei

Three cells move to one and near to micropyle, forming two synergid cells and one egg cell
Three more cells move to another end to form three antipodal cells
One cell with two nuclei located at the center to form polar nuclei
The structure formed is known as embryo sac which is protected by integument