Dormancy patterns in buried seeds of Datura ferox and D. stramonium

Seed burial at 20 cm accelerated after-ripening, and primary dormancy disappeared earlier than at 5 cm, but burial depths >10 cm prevented germination. Cyclic seasonal changes in dormancy were found in buried seeds of D. ferox but not in D. stramonium. In D. ferox, dormancy was alleviated during the winter and germinability was maximal in early spring; the increase in dormancy was preceded by high late spring-summer temperatures. In D. stramonium most seeds near the soil surface germinated in the field in a brief flush in early winter, at temperatures under which D. ferox did not germinate. -from Authors