INFLUENCE OF ENVIRONMENTAL FACTORS ON SEED GERMINATION AND SEEDLING EMERGENCE OF YELLOWTOP (Flaveria bidentis)

Laboratory experiments were conducted in Beijing from 2008-2010 to determine the effects of light, temperature and planting depth on Flaveria bidentis germination and emergence. F. bidentis had positively photoblastic seeds which required light in germination. Seed germination had a wide temperature range, 15°C to 40°C, with the optimum temperatures from 22.5°C to 35°C The threshold temperature for germination was 14.7°C and the effective accumulated temperature required to reach 90% germination was 40.4°C. Germination was increased by 12% to 100% when the temperature was from 12.5°C to 20°C. Seedling emergence was the highest on the soil surface, and no seedlings emerged from a soil depth of 1 cm or deeper. The information gained from the study could help predict its potential distribution area and facilitate the development of effective weed control strategies.