GERMINATION RESPONSE OF WEED SEEDS TO LIGHT, LIGHT OF SHORT-DURATION AND DARKNESS AFTER STRATIFICATION IN SOIL

Seeds of many species must be exposed to light before they can germina te. This dependence of germination on light could be exploited in agri culture to control weeds. The aim of our research was to determine the light requirements and light sensitivities of seeds of three populati ons each of 41 annual and one perennial weed species. Seeds were kept outdoors in moist soil during a cold-temperate winter. Germination was tested in light of long duration, in constant darkness and in darknes s after a short light exposure. Of the species with a low or moderate level of dormancy, 13 of 17 summer annuals, 11 of 17 winter annuals an d two of two unclassified annuals germinated to higher percentages aft er a 5-s light exposure than in constant darkness. In many of the spec ies, seeds from the three populations differed significantly in their response to light. A large potential exists for integrating light-less cultivation into weed control strategies. However, the large differen ces in germination percentage and light response between populations i mply that weed seed germination after a soil cultivation in darkness w ill be difficult to predict.