The relationship between ethylene and dormancy release in Echinacea seeds

Seed germination can be erratic in Echinacea species unless they receive chilling stratification to satisfy dormancy. E. tennesseensis and E. simulate seeds treated with 1-aminocyclopropane-1-carboxylic acid (ACC) were released from dormancy to a level equivalent to chilling stratification. Both treatments improved early and final germination in both species. Stratification and ACC treatments reduced the sensitivity of seeds to abscisic acid (ABA) as evidenced by their ability to germinate on ABA concentrations inhibitory to untreated seeds. The data suggests that both stratification and ACC act through a similar mode of action related to ABA sensitivity. However, treating seeds with the ethylene action inhibitor silver thiosulfate (STS) before or after stratification did not effect germination in either species. This suggests that the release from dormancy promoted by chilling stratification does not require ethylene.