Effects of Auxins on Gametophyte Development and Sexual Differentiation in the Fern Ceratopteris thalictroides (L.) Brongn.

The auxins indole-3-butyric acid (IBA), α-napthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and indole-3-acetic acid (IAA) were tested for their effects on gametophyte development in the fern Ceratopteris thalictroides. Both 2,4-D and NAA affected gametophyte growth, cell size, antheridia number, and rhizoid development at concentrations of 10-6 M or greater. The effects of IAA were observed only at 10-4 M; growth of gametophytes was inhibited, and male/female differences were less pronounced. Normal development of male and female morphologies, which is mediated by an antheridiogen, was severely altered by IBA. While a sex ratio of 3 males to 1 female is normally evident in multispore cultures of gametophytes, all gametophytes were male at 10-4 M IBA. This effect was related to growth inhibition by IBA; IBA did not directly substitute for antheridiogen.