<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (January 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (January 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> A sporophyte (/ spɔːroʊˌfaɪt /) is the diploid multicellular stage in the life cycle of a plant or alga . It develops from the zygote produced when a haploid egg cell is fertilized by a haploid sperm and each sporophyte cell therefore has a double set of chromosomes, one set from each parent . All land plants, and most multicellular algae, have life cycles in which a multicellular diploid sporophyte phase alternates with a multicellular haploid gametophyte phase . In the seed plants, the gymnosperms and flowering plants (angiosperms), the sporophyte phase is more prominent than the gametophyte, and is the familiar green plant with its roots, stem, leaves and cones or flowers . In flowering plants the gametophytes are very reduced in size, and are represented by the pollen and the embryo sac . </P> <P> The sporophyte produces spores (hence the name) by meiosis, a process also known as "reduction division" that reduces the number of chromosomes in each spore mother cell by half . The resulting meiospores develop into a gametophyte . Both the spores and the resulting gametophyte are haploid, meaning they only have one set of chromosomes . The mature gametophyte produces male or female gametes (or both) by mitosis . The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte . This cycle is known as alternation of generations or alternation of phases . </P>

What event starts the sporophyte stage of the life cycle
find me the text answering this question