Life Cycle
Sphagnum, like all other land plants, has an alternation of generations; like other bryophytes, the haploid gametophyte generation is dominant and persistent. Unlike other mosses, the gametophytes have no rhizoids to assist in water uptake.Sphagnum species can be unisexual (male or female, dioecious) or bisexual (male and female gametes produced from the same plant; monoecious); In North America, 80% of Sphagnum species are unisexual. Gametophytes have substantial asexual reproduction by fragmentation, producing much of the living material in sphagnum peatlands. Swimming sperm fertilize eggs contained in archegonia that remain attached to the female gametophyte. The sporophyte is relatively short-lived, and consists entirely of a shiny black, spherical spore capsule. Sporophytes are raised on stalks to facilitate spore dispersal, but unlike other mosses, Sphagnum stalks are produced by the maternal gametophyte. Tetrahedral haploid spores are produced in the sporophyte by meiosis, which are then dispersed when the capsule ruptures. The spores germinate to produce minute protonemae, which over time, develop the characteristic Sphagnum leaves.
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