Action of Purine and Pyrimidine Analogs on the Growth and Differentiation of the Gametophytes of the Fern Asplenium Nidus

The purine analogs, 8‐azaadenine, 8‐azaguanine, 8‐azaxanthine and 8‐azahypoxanthine, and the pyrimidine analogs, 2‐thiocytosine, 5‐fluorouracil, 2‐thiouracil and 6‐azauracil, inhibited the induction of 2‐dimensional growth in the gametophytes of the fern Asplenium nidus L. In contrast, thymine analogs such as 5‐fluorodeoxyuridine, 2‐thiothymine, 6‐azathymine and 5‐bromouracil caused non‐specific growth inhibitions without suppressing 2‐dimensional growth. Subinhibitory concentrations of 8‐azaxanthine, 8‐azahypoxanthine, and 2‐thiouracil promoted both 1‐dimensional and 2‐dimensional phases of growth of the gametophytes. Inhibitory effects of the analogs were observed on treatment of the spores or of gametophytes of different ages. Gametophytes growing in the analogs for different periods of time recovered from inhibition on transfer to the basal medium.