GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. I. EFFECTS ON PROTONEMAL AND RHIZOIDAL GROWTH AND INTERACTION WITH AUXIN

Three responses resulted from the treatment with ethylene of dark-grown gametophytes of Onoclea sensibilis. Elongation of the filament was increased, elongation of the rhizoid was decreased, and cell division was inhibited. The optimal ethylene concentrations were between 0.01 and 0.1 ppm. Filament elongation was very tolerant of high ethylene concentrations, since up to 1,000 ppm did not inhibit growth below control levels. Enclosing cultures of gametophytes in chambers of limited volumes produced all the effects of treatment with ethylene, but the responses to sealing were eliminated if plants were enclosed in a chamber which contained a solution of mercuric Perchlorate. This evidence that gametophytes produced ethylene was substantiated by a direct gas chromatographic demonstration of ethylene formation. The growth-regulating effects of ethylene and auxin appeared to be independent in filament and rhizoid growth. Inhibition of elongation by supra-optimal auxin concentrations could not be attributed to an auxin-stimulated production of ethylene.