MMC ( megaspore mother cell ) is the female meiocyte that undergoes meiosis and produces 4 mega spores.Out of these four megaspores only one megaspore will remain functional and will undergo further development.
Meiosis is a reductional division which reduces the number of chromosomes in a parent cell to half in the daughter cell.MMC is diploid(2n) and after meiosis it forms four haploid(n) megaspores. So to maintain the ploidy of megaspore, meiosis is important.