Habitat heterogeneity may influence the germination phenology of seed crops if the environments that seeds experience upon dispersal differ in their ability to induce secondary dormancy. We initiated germination trials for seeds from two populations of Silene latifolia in light (14 hr photoperiod) and dark conditions at 22 C in growth chambers (2 chambers per light treatment), and found significantly lower percent germination in the dark environment than the light treatment after 1 wk. When we subsequently exposed ungerminated seeds from the dark treatment to a 14 hr photoperiod, mean cumulative percent germination for these replicates after two wk (1wk dark, 1 wk light) was lower than the mean percent germination of seeds in the light treatment after 1 wk. Cumulative percent germination for seeds initially exposed to dark conditions plateaued after 2 wk in the light. At this time, cumulative percent germination of these seeds was significantly lower than that recorded for replicates that entered germination trials in the light at the same time the dark treated seeds were exposed to light. We conclude that our dark treatment initiated secondary physiological dormancy in a large percentage of seeds. Treatment with gibberellin (100 ppm) failed to break this dormancy. Stratification at 4 C for 1 mo broke dormancy for a fraction of the viable seeds that remained ungerminated. These results suggest that a large percentage of buried S. latifolia seeds may be unable to germinate immediately upon exhumation, although field investigations will be necessary to fully explore this potential effect of seed burial.

Key words: dark, germination, secondary dormancy, seeds, Silene latifolia