Abstract:Bidens frondosa L. (Asteraceae), native to North America, is an annual invasive species with heteromorphic achenes. In order to understand its invasive mechanism, the achene morphology was observed, and the effects of light and temperature on germination of achene were studied. The results showed that central and peripheral achenes had significant difference in color, length, width and prick length. Under 12 h d-1 photoperiod, the achenes did not germinate at 15℃/10℃, and the germination rate of central achene was significantly higher than that of peripheral achene at 20℃/15℃ and 25℃/20℃, while that of the two achenes had no difference at 30℃/25℃, 35℃/30℃ and 40℃/35℃. Under full dark, the germination of central and peripheral achenes were all inhibited below 35℃/30℃ and 40℃. Both of light and achenes type had significant influences on the germination rate, germination index and germination speed. Therefore, Bidens frondosa could reduce competition among siblings and enhance the adaptability to different environments through differences in achene germination. It was advantageous to the achene germination under favorable environment and population preservation and expansion.
