SEASONAL PERIODICITY IN GERMINATION OF SEEDS OF CHENOPODIUM-ALBUM L

Seeds of Chenopodium album L. were buried under field and controlled conditions. The germination capacity of these seeds was tested over a range of conditions at regular intervals. Seeds buried in the field only showed small seasonal changes in germination capacity when tested at constant temperatures in incubators. However, when germination was tested at field temperatures, seasonal changes in germination were more obvious. Nitrate and light always promoted germination. There was a strong positive interaction between the effects of the two factors. When nitrate and light were combined, exhumed seeds germinated over a much longer period of the year than in water with or without fight. Desiccation only stimulated germination under particular conditions, for example, when germination was tested in nitrate in darkness. A regression model was developed with the data from the germination tests in incubators. The model describes the changes in dormancy and germination and estimates germination at field temperatures accurately throughout the year. Despite the absence of clear seasonal changes in the temperatures suitable for germination (computed with the model), germination in the field showed seasonal periodicity, because the field temperature and the germination-temperature range only overlapped from spring to late summer. © 1993 Annals of Botany Company.