This mutation confers tolerance to the typical effects of abscisic acid (ABA) on gametophytes. Wild type gametophytes cultured in the presence of ABA exhibit multiple effects involving decreased growth rate and altered development. The number of antheridia on hermaphroditic wild type gametophytes is reduced and the number of rhizoids is increased. In some wild type hermaphrodites, the marginal notch meristem can become more centrally located in the presence of ABA. This results in an interesting pattern of growth that resembles a 'tube sock', with the tip of the toe representing the position of the meristem. The number of male gametophytes is also reduced. These effects, which can be induced in the wild type at a concentration of 5.0 - 50.0 mM ABA, are not evident in the mutant.

Hickok, L. G. l985. Abscisic acid-resistant mutants in the fern Ceratopteris: Characterization and genetic analysis. Can J. Bot. 63:1582- 1585

Warne, T. R. and L. G. Hickok. 1991. Control of sexual development of Ceratopteris richardii: antheridiogen and abscisic acid. Bot. Gaz. 152: 148- 153.