The effects of the herbicide asulam on the gametophytes of Pteridium aquilinum, Cryptogramma crispa and Dryopteris filix-mas

Abstract

Fern spores were germinated, grown and exposed to different concentrations of asulam (the active ingredient of Asulox) in liquid culture. Gametophytes of Pteridium aquilinum [L. (Kuhn)] (bracken) were exposed to 100 g l-1 for 24 h at the following three stages: germination; during filamentous growth; and after transition had occurred. This treatment severely inhibited germination and killed photosynthetic gametophytes outright. Gametophytes of all species tested [Pteridium aquilinum, Cryptogramma crispa (L.) Hook and Dryopteris filix-mas (L.) Schott] varied in their responses to lower concentrations. This variation was in terms of the response of the gametophytes and the numbers of gametophytes showing each response. Some gametophytes suffered 100% cell mortality, but in others some cells died and some survived, while the remainder of the gametophytes suffered no cell mortality. The cells affected varied from gametophyte to gametophyte at the same dose and the proportions of gametophytes showing each response changed with concentration, mortality increasing with increasing concentration. Pteridium showed lower levels of mortality at each concentration than either of the other species. The bioassay system described provides a rapid laboratory-based method to screen for Asulox susceptibility of fern gametophytes in comparison with Pteridium. (C) 2000 Annals of Botany Company.