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Spores of Onoclea sensibilis were investigated for inhibition of germination by ethylene. A curve of germination against ethylene concentration indicated a “threshold” type of response, but percentage of spore germination was not influenced either by the density of the inoculum or by the presence of 1 % sucrose in the culture medium. Ethylene totally inhibited dark germination, but in white light reversal of inhibition was possible in about 50% of the germinating spores. Time‐course studies revealed that in imbibed spores ethylene inhibited germination in the first 3 ± 1 hr of illumination. Dose‐response curves of light intensity vs. germination indicated that the response to light differed in the presence and absence of ethylene. Recovery from inhibition was possible once ethylene was allowed to escape, and the rate of recovery was accelerated by light.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.A B S T R A C T Spores of Onoclea sensibilis were investigated for inhibition of germination by ethylene. A curve of germination against ethylene concentration indicated a "threshold" type of response, but percentage of spore germination was not influenced either by the density of the inoculum or by the presence of 1 % sucrose in the culture medium. Ethylene totally inhibited dark germination, but in white light reversal of inhibition was possible in about 50% of the germinating spores. Time-course studies revealed that in imbibed spores ethylene inhibited germination in the first 3 + 1 hr of illumination. Dose-response curves of light intensity vs. germination indicated that the response to light differed in the presence and absence of ethylene. Recovery from inhibition was possible once ethylene was allowed to escape, and the rate of recovery was accelerated by light.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. AB ST RACT Ethylene, a natural product of sensitive fern (Onoclea sensibilis L.) gametophytes, has been demonstrated to inhibit cell division in light-grown prothallia. When plants were grown on Knop's solution plus 1 % sucrose under 300 ft-c or more of white light, all ethylene concentrations from 1-1000 pl/liter reduced the rate of increase of cell number by about one-half. The over-all rate of increase of cell number was regulated by various environmental and chemical factors, but regardless of the rate established in control cultures, ethylene treatment of 1-1000 ,ul/liter produced a relative 50% depression of cell number. Ethylene was specific for inhibition of cell division and was not a general inhibitor of growth. The ethylene inhibition did not result from a reduction of photosynthesis or energy supply. Further demonstration of ethylene as the active gaseous component resulted when cultures were grown in small enclosed containers with an ethylene absorbent, mercuric perchlorate, and consequently the cell number of gametophytes was restored to the level of unenclosed controls. ETHYLENE

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