Interpopulational comparison of dose-mediated antheridiogen response in Onoclea sensibilis

Intraspecific variation in antheridiogen response has been reported in seve ral fern species. Here, we characterized and compared dose-mediated antheri diogen response among six populations spanning the range of Onoclea sensibi lis, a species widely used for antheridiogen assays. A crude aqueous filtra te (CAF) of antheridiogen A(PT) was obtained from cultures of Pteridium aqu ilinum and introduced into mineral agar at six concentrations ranging from 0 (control) to 10(-1). Response was initially characterized for one populat ion using three criteria: percentage of male gametophytes, number of anther idia per gametophyte, and mean surface area of gametophytes. Percent male w as consistently the best descriptor of the response profile and was used to compare responses among populations. In all populations, gametophytes exhi bited little or no response at CAF concentrations 10(-5) and lower; a satur ated response, almost all gametophytes being male at 10(-3) and higher; and an intermediate response, usually between 50% and 80% males, at 10(-4). wi th few exceptions, response levels and profiles were very consistent among populations. Data and methodology provided herein indicate that use of the percent male criterion can provide a reliable quantitative assay using Onoc leo that can facilitate future comparative research in antheridiogens.