The effect of environmental conditions on the annual dormancy pattern of seeds of Spergula arvensis

Abstract

The effect of environmental factors on the germination of exhumed seeds of Spergula arvensis L. after variable periods of burial in soil was investigated. Seeds were buried in the field and exhumed at regular intervals after which germination was tested over a range of conditions. These tests showed clear seasonal changes in dormancy during 3 successive years. Dormancy was broken in spring and reinduced in autumn at rising and falling temperatures, respectively. In experiments in incubators, greater loss of dormancy occurred at 10 and 15 °C than at 2 and 6 °C. As in the field, induction of dormancy occurred when the preincubation temperature was lowered. The expression of the dormancy pattern was strongly influenced by the germination tests conditions. At 15 °C, seeds germinated during a longer period of the year than at 2 or 30 °C. Irradiation with red light, addition of nitrate, and desiccation of the seeds prior to the germination test strongly stimulated germination. All three factors enabled germination of exhumed seeds during a longer period of the year. When light, nitrate, and desiccation were combined, exhumed seeds could germinate in all seasons. The seasonal germination pattern was modelled with a descriptive model based on the dual effect of temperature, which regulates dormancy and also affects germination. This model closely simulated germination at field temperatures. Germination of exhumed seeds in the field was restricted to the period of overlap between the germination temperature range computed with the model and field temperature. The features of the model supported the hypothesis that dormancy of S. arvensis is regulated by the actual changes in temperature rather than the combined effects of a cold and heat sum. Key words: Spergula arvensis, dormancy pattern, germination, regression model, weed seeds.