Formation of female gametes of gymnosperms

Question

Explain the formation of the female gametes of gymnosperms and also the relationship between this process and the concept of the alternation of generations?

Answer 1

In female strobiles (cones) there exist megasporophylls (fertile leaves of the strobile) which consist of megasporangia. In the megasporangium the spore mother cell go through the meiosis producing four haploid cells of which three regress and one provides birth to the functional megaspore. The functional megaspore through the several mitosis forms the female gametophyte which consists of the oospheres or female gametes of the plant. The female gametophyte is situated inside the megasporangium which has a small opening, the micropyle, through which pollen tube penetrates. The process is related to the diplobiontic life cycle (alternation of generations) as the functional megaspore produces the haploid stage of plant (the female gametophyte).