| Abstract: | Seeds of 40 populations of Bromus sterilis L. were collected in the southern and midland counties of England over a 2‐year period and grown outdoors in pots in two subsequent years. In the first year, seeds were tested in a 12‐h dark/12‐h light regime at 15 °C and in the second year the seeds were tested both in the dark/light regime and in the dark at 15 °C. There was a wide range in the degree of enforced dormancy given by the dark/light regime. Germination of freshly collected seeds in the dark/light regime after 21 days ranged from 44% to 97% in the populations tested in the first year and from 19% to 97% in populations tested in the second year. Induced dormancy was caused by light in two populations. Seeds had little innate dormancy apart from in two populations which gave 64% and 68% germination, respectively, in the dark after 21 days. A field trial in which seeds of a selected range of six populations were sown on the soil surface after harvest (August 8), showed that populations predicted to be inhibited by light in laboratory tests were also inhibited by light in the field and, depending upon the population, there was between 4% and 54% of the seeds remaining ungerminated by October 23 in the year of planting. By June of the following year, 36% of the seeds sown on the soil surface in one population still remained viable and ungerminated. The agricultural significance of the results is discussed. |
