During meiosis, the chromosome number doubles because the cells replicate their DNA and split into two cells in meiosis I and in meiosis II, they replicate DNA and split once again, to form four cells.
crossing over
mitosis and binary fission
Meiosis is important in the sexual reproduction of flowering plants because it produces haploid gametes (egg and sperm cells) with half the number of chromosomes. When these gametes fuse during fertilization, the resulting offspring will have a full set of chromosomes. This genetic diversity is essential for the adaptation and evolution of plant species.