Article

Studies on the regulation of dormancy and germination may be valuable for rare plant population studies. Results of such studies on Spergula arvensis are described. Seeds were buried in the field and exhumed at regular intervals. Germination tests showed clear seasonal changes in dormancy, but test conditions strongly influenced the expression of the dormancy pattem. Seeds germinated during a longer period of the year at 15°C than at 2°C and 30°C. Irradiation with red light, addition of nitrate and desiccation of the seeds prior to the germination test stimulated germination and lengthened the germination periodo The seasonal germination pattem was modelled with a multiple linear regression model which was used to calculate the seasonai changes in the temperature range within which germination can proceed, and the effect of nitrate on this range. Similar calculations were made with models developed for Chenopodium album, Polygonum persicaria and Sisymbrium officinale. Graphs thus produced showed conspicuous differences in the ways in which dormancy in the four species is regulated and expressed. For rare plant population studies, knowledge of the temperature requirements for dormancy breaking and of the effect of temperature, light, nitrate and desiccation on germination may be valuable.