How does fertilization begin the sporophyte generation?

In the alternation of generations, the sporophyte generation begins at fertilization, which marks the transition from the haploid gametophyte phase.12

Fertilization occurs when a male gamete fuses with a female gamete (egg) to form a zygote. Because both gametes are haploid, this fusion results in a diploid zygote, which possesses a full complement of chromosomes. This zygote serves as the initial cell of the new sporophyte generation.123

Following fertilization, the zygote undergoes a series of mitotic divisions—a process known as embryogenesis—to develop into a multicellular embryo. This embryo eventually matures into the sporophyte plant body, which is the dominant phase in vascular plants. While fertilization is the standard trigger for this development, some organisms can initiate sporophyte growth through parthenogenesis, a process where the sporophyte arises without fertilization.3421