Carbon Dioxide and Ethylene Control of Spore Germination in Onoclea sensibilis L 12

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RESUMO

Regulation of spore germination in the fern Onoclea sensibilis L. was investigated by applying CO2 alone and in combination with ethylene. Sterile spores were sown aseptically on Knops solution in loosely capped culture tubes, enclosed individually in 2-liter chambers, and grown under continuous white light. When maintained in enclosed containers with the ethylene-absorbent mercuric perchlorate and with atmospheres enriched up to 2% CO2 (v/v), spores germinated without any inhibition. Higher levels of applied CO2 were progressively inhibitory. Inhibition by CO2 was reversible. When CO2 was permitted to escape and spores were exposed subsequently to ambient laboratory air, recovery from inhibition occurred within 48 hours. Also, inhibition by CO2 was specific, since the same degree of inhibition resulted regardless of whether spores were treated with exogenous CO2 for 48, 72, or 96 hours. The effect on germination of 1 μl/l added ethylene depended upon the amount of applied CO2. When containers of KOH were enclosed and ambient CO2 was absorbed, inhibition of germination by 1 μl/l exogenous ethylene was 90%. When CO2 was applied in concentrations from 0.25 to 1.0% (v/v), CO2 increasingly antagonized the inhibitory action of 1 μl/l added ethylene. Thus, photoinduced germination of spores was regulated by competitively interacting levels of CO2 and ethylene.

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