Extract from the CD-ROM – Convection within the Earth developed in partnership with the ENS.


Formation of the female gametophyte

Female sexual cells of flowers are in the carpel. In its inner part, the placenta carries the ovary, which contains the sexual mother cell: the megaspore that gives the embryo sac containing the mature female sex cells.

The first step is the meiosis of the mother cell of the megaspore. It produces four haploid cells. Three will degenerate, leaving only one: the megaspore. Its haploid nucleus will divide four times, producing eight nuclei. These divisions occur without cell separation (endo-reduplication). Two of the nuclei will stay in the central part of the cell. The other six migrates to the poles of the cell (three at each pole). The cell will then partition give the mature female gametophyte.