THE INDUCTION OF APOGAMY IN THE BRACKEN FERN

Abstract

A new method of inducing apogamy in normal fern gametophytes of Pteridium aquilinum has been demonstrated. Entire plants, apparently isolated sporophytic members, and structures of an intermediate nature between sporophyte and gametophyte were produced. The method involved growing gametophytes in sterile culture on a nutrient medium containing a suitable concentration of glucose. A series of experiments was carried out in which the concentration of glucose was varied from 0–8% and the optimum concentration was established to be 2.5%. Prothalli grown in the absence of glucose, which have only their photosynthate as an energy source, produced no apogamous structures. It was found that sucrose, maltose, or fructose could be substituted for the glucose in the induction of apogamy. Four other strains of Pteridium, and strains of Osmunda cinnamomea and Adiantum pedatum, also responded to the sugar treatment by producing apogamous plants. The osmotic pressure of the medium has been shown to have no effect on the induction of apogamy but it does appear to cause the decline in the response at the higher concentrations of sugar. The role of the sugar would therefore seem to be as a respiratory substrate, which in some way favors the induction of apogamy.