External Factors Inducing Germination of Fern Spores

Abstract

The dependence of spore germination on light in most species of ferns was established by nineteenth century biologists including Borodin, Schmidt, Kny, and Beck (see the excellent review of Sussman, 1965). However, there are conflicting reports on the ability of spores of certain species to germinate in the dark. For example, Borodin (1865), Schulz (1902), and Life (1907) were unable to demonstrate the germination of spores of Anemia phyllitidis in the dark, although Schelting (1875) claimed that it occurs. The light requirement for germination in various species has been found to be complex. Ability of spores to undergo dark germination may vary, for example, with age (Laage, 1907), with pretreatment at various temperatures (Heald, 1898; Schulz, 1902), or with exposure to various plant hormones. Reliable action spectra for light-induced promotion and inhibition of germination in species of Dryopteris and Osmunda (Biinning and Mohr, 1955; M\ohr, 1956; Mohr et al., 1964) show maxima at the absorption maxima of phytochrome. Gibberellic acid stimulation of dark germination, reported by Schraudolf (1962), was the first true case of a specific replacement of a light requirement in spore germination. Kato (1955) reported a gibberellin stimulation of germination in Dryopteris erythrosora and Cyathea sp., but this consisted merely of gibberellin promotion of rhizoid and protonemal growth in light. M'ore recently Naf (1966) has confirmed Schraudolf's observations and reported that dark germination is stimulated in Lygodium japonicum by gibberellic acid and in Anemia phyllitidis by an antheridogen-B preparation as well as by gibberellin. Naf also claimed a weak stimulation of germination of L. japonicum by antheridogen-B and by the medium upon which L. japonicum had been growing. However, these latter results seem to be based on counts of only