Where Does Meiosis Take Place in Bryophytes?
Meiosis takes place in the tiny sprorophyte stage of bryophytes, which are attached to and dependent on the much larger gametophyte stage. The sporophytes create spores by meiosis, which disperse by wind and water to form new gametophytes. Fertilized eggs in gametophytes form sporophytes at the site of fertilization.
The sporophyte stage of bryophytes is diploid, with two versions of each chromosome in its DNA, while the gametophyte is haploid with only one. The spores the sporophyte forms are haploid, as are the gametes formed by the gametophytes. Because the gametophytes themselves are haploid, however, they produce gametes by mitosis rather than meiosis. Bryophytes require at least a thin film of standing water for their gametophytes to reproduce. This is because bryophyte sperm must be able to swim between plants in order to fertilize an egg.
Bryophytes include mosses, liverworts and hornworts. They are small, primitive plants without the advanced vascular systems of other types of plants. Their size is restricted by this lack of vascular tissue because they must rely on simple diffusion to spread water to all their cells. Despite this, mosses are relatively resistant to drying up and are the most abundant plants in the Arctic and Antarctic.