Abscisic acid blocks antheridiogen-induced antheridium formation in gametophytes of the fern Ceratopteris

Growth and differentiation of haploid gametophytes of the fern Ceratopteris are influenced by antheridiogen and abscisic acid. Antheridiogen induces the premature formation of male sex organs (antheridia), while abscisic acid, at a concentration of 10−4 M, completely blocks antheridia formation, even in the presence of antheridiogen. In addition, abscisic acid stimulates rhizoid production at concentrations of 10−6–10−5 M but becomes inhibitory at higher concentrations. Meristem development, which is normally at the margins of gametophytes, is often submarginal or central in the presence of abscisic acid and results in the formation of cup-shaped female gametophytes bearing archegonia.