Endopolyploidy in Bryophytes: Widespread in Mosses and Absent in Liverworts

Endopolyploidy occurs when DNA replication is not followed by mitotic nuclear division, resulting in tissues or organisms with nuclei of varying ploidy levels. Endopolyploidy appears to be a common phenomenon in plants, though the prevalence of endopolyploidy has not been determined in bryophytes (including mosses and liverworts). Forty moss species and six liverwort species were analyzed for the degree of endopolyploidy using flow cytometry. Nuclei were extracted in LB01 buffer and stained with propidium iodide. Of the forty moss species, all exhibited endopolyploid nuclei (mean cycle value =0.65±0.038) except for the Sphagnum mosses (mean cycle value =0). None of the liverwort species had endopolyploid nuclei (mean cycle value = 0.04 ± 0.014). As bryophytes form a paraphyletic grade leading to the tracheophytes, understanding the prevalence and role of endopolyploidy in this group is important.