Annual Seed Dormancy Cycles in Two Desert Winter Annuals

Freshly matured seeds of Eriogonum abertianum Torr. and Eriastrum diffusum (Gray) Mason and those of both species exhumed after various periods of burial in the Chihuahuan Desert in Arizona, USA, were tested for germination in light and darkness at five thermoperiods. Seeds of Eriogonum were nondormant (ND) at maturity in autumn 1988, and thus 87% of them germinated in light at 15/6 and at 20/10°C. Seeds entered conditional dormancy (CD) in winter, germination at 20/10°C decreased to 6% in light. However, a high percentage of the seeds were again ND by autumn 1990. Thus, like seeds of facultative winter annuals in humid, temperate regions, those of Eriogonum have an annual CD/ND cycle, which is characteristic of annuals in unpredictable habitats (...)