(botany) A phase in the life cycle of certain plants and algae that starts with the union of gametes up to the time that sporess are produced
In plants and certain algae (e.g. Archaeplastida and Heterokontophyta), their life cycle is comprised of two phases (or generations): the phase of gametophyte and the phase of sporophyte. This type of life cycle wherein there are two alternating phases is called alternation of generations. In particular, it is the alternation of diploid and haploid forms.
In plants, the sporophyte generation is that phase in their life cycle that begins with the union of two single-celled haploid gametes. This union of haploid (n) gametes results in the formation of a single-celled diploid (2n) zygote. The zygote germinates and grows by going through a series of mitotic divisions. Eventually, it develops into a multicellular sporophyte, i.e. a plant form that when mature produces spores. A mature sporophyte bears sporangium that produces sporocytes. Each sporocyte divides meiotically to produce four haploid spores. The single-celled haploid spore germinates to soon become a gametophyte (i.e. the plant form that bears gametangia that produces gametes), and this event marks the gametophyte generation.
In algae with alternation of generations, the sporophyte and the gametophyte are independent organisms.