Interaction of Oxygen and Ethylene in the Release of Ragweed Seeds from Dormancy

Ragweed (Ambrosia artemisiifolia L.) seeds were stratified at 5 C in air or nitrogen. Stratification in air led to a progressive increase in germination with time of treatment. The seeds stratified in nitrogen failed to germinate and required an additional stratification in air to induce germination. In a separate experiment, dormant seeds were treated with 10 ppm ethylene in air or in O2. After 2 wk of treatment, germination was 5.5% in air, 13.3% in O2, 41.3% in air plus ethylene, 71.4% in oxygen plus ethylene, and 31.3% in ethephon. Application of thiourea, serving to inhibit catalase activity, also stimulated germination.