One megaspore mother cell (megasporocyte) undergoes meiosis in each ovule.
At fertilization, one of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of an egg cell.įemale cones (ovulate cones) contain two ovules per scale. The pollen tube develops slowly as the generative cell in the pollen grain divides into two haploid sperm cells by mitosis. Pollination is defined as the initiation of pollen tube growth. Some gametophytes will land on a female cone. In the spring, large amounts of yellow pollen are released and carried by the wind. In the male cones (staminate cones), the microsporocytes give rise to pollen grains by meiosis. Like all gymnosperms, pines are heterosporous, generating two different types of spores: male microspores and female megaspores. Pine trees are conifers (cone bearing) and carry both male and female sporophylls on the same mature sporophyte.
