Study of seasonal variation in dormancy of Spergula arvensis L. seeds in a condensed annual temperature cycle

Summary Changes in dormancy of Spergula arvensis seeds were studied during pre‐incubation at constant temperatures and under a temperature regime that condensed the annual temperature cycle into 73 days. Each day in the regime represented the mean day and night temperatures and day lengths of 5 successive days of an average year in The Netherlands. Incubation occurred in water or loamy sand, in darkness. Germination of the seeds was tested in water or KNO3 over a range of temperature. Seeds were irradiated with saturating doses of red light. In half of the treatments, pre‐incubated seeds were dehydrated at the transfer to the conditions of the germination test. Breaking of dormancy occurred under conditions of 'spring'. It did not depend on exposure to low‘winter’temperatures, but was induced by rising 'spring’temperatures. Seeds developed secondary dormancy in late‘autumn'. The expression of the changes in dormancy that were induced during pre‐incubation depended on the conditions of the germination test. Light, nitrate and dehydration stimulated germination. The experiments predicted that field emergence from nitrate‐poor soils that have not been dehydrated will be restricted to a short period in autumn, whereas disturbance of nitrate‐rich soils followed by a dry spell will stimulate germination of S. arvensis seeds from early spring to late autumn. The data presented good explanations for the cosmopolitan character and the serious weediness of this species. Its classification as a summer or winter annual is discussed.