Inhibitory Effect of Gibberellins on Archegonial Differentiation in Lygodium japonicum

Archegonial differentiation in light‐grown gametophytes of Lygodium japonicum was partially inhibited by exogenously applied gibberellin A3 (GA3) at a concentration of 10−6M, and fully prevented at 10−5M. The inhibitory effect was nullified by transferring the GA3‐treated samples onto fresh media omitting GA3, so that the archegonial formation became discernible 6 days after the transplantation. The application of 10−4M GA3 to younger gametophytes brought about a complete inhibition of archegonial differentiation, whereas the same concentration applied to older gametophytes did not influence the process at all, indicating the timing of archegonial differentiation during the ontogeny. Activity spectrum of authentic gibberellins on the basis of concentrations inducing 50% inhibition of archegonial formation was obtained as follows: GA4= GA9 > GA7 > GA3 > GA1= GA5= GA8.