Ethylene Inhibition of Phytochrome-Induced Germination in Potentilla norvegica L. Seeds.

Germination of Potentilla norvegica L. (rough cinquefoil) seeds stimulated by fluorescent irradiations of nearly 24 hours was inhibited by ethylene at <1 microliter per liter. Sensitivity to ethylene inhibition was highest during and immediately after the irradiation. By delaying ethylene treatment until about a day after the light potentiation, seeds escaped the inhibition. Ethylene inhibition may be readily reversed upon release of the gas and reirradiation of the seeds. Imbibition of seeds at 10 or 15 degrees C, or at high temperatures of 35 and 40 degrees C, partially prevented subsequent inhibition by ethylene. Alternating temperatures during germination nearly overcame the inhibition from 1 microliter per liter ethylene, but not higher doses. With brief red-irradiation and alternating temperatures, 0.1 microliter per liter ethylene promoted germination about 2-fold. These data suggest that ethylene may loosely associate on a site required for phytochrome action. The effect of temperature that opposed the inhibition may be to deny the association of ethylene with the site. Loose association is supported by the reversal of inhibition by gas release and increased temperature during germination. A blocking effect was shown by the failure of phytochrome to act when ethylene was present.