Sporogenesis In Haploid Sporophytes Of Osmunda Japonica (Osmundaceae)

Three out of four haploid sporophytes of Osmunda japonica (2n = x = 22), produced artificially by induction of apogamy, developed fertile fronds and spores. The spores that germinated (up to 25% of the total green spores) were monoploid, determined by the nuclear DNA content and the somatic chromosome numbers of the gametophytes. The haploid 2 sporophyte produced more fertile spores than the two other haploids, providing an opportunity to observe the details of fertile spore development. In some spore mother cells of this plant, the random separation of 22 univalent chromosomes did not occur at the first meiotic division, but restitution nuclei were formed. The observation of chromosome behavior in the haploid 2 sporophyte showed that sporogenesis in haploid O. japonica resembles the Braithwaite scheme in apogamous ferns. Gametophytes, developed from spores of the three haploid sporophytes, produced a few sporophytes with diploid chromosome numbers. One of the new sporophytes was trisomic.