XVI International Botanical Congess

Pteridophytes are a pivotal group of plants, some of which have retained primitive features of cell division while others have evolved the more advanced type typical of seed plants. Monoplastidic cell division is seen as a plesiomorphic feature inherited from algal ancestors and modified through evolution. In monoplastidic cell division the plastid itself serves as the microtubule organizing center (MTOC) resulting in coordinated division of plastid, nucleus, and cytoplasm. In polyplastidic cell division, the MTOC is perinuclear. Monoplastidic mitosis is reported only in hornworts, Takakia, and Isoetales. Monoplastidic meiosis is more common, it occurs in all groups of bryophytes (although only a few hepatics), and in Isoetales, certain of the Lycopodiales and the Marratiales. It is not known to occur in Huperzia, leptosporangiate ferns, or seed plants.