为了解大狼耙草(Bidens frondosa)的入侵机理，对其中央瘦果和外围瘦果的形态特征和萌发特性进行了研究。结果表明，大狼耙草果序中的中央瘦果和外围瘦果在颜色、长度、宽度和芒刺长度等方面均存在明显差异。在周期性光照下，两种瘦果在15℃/10℃下不萌发；在20℃/15℃和25℃/20℃下中央瘦果的萌发率显著高于外围瘦果；而在30℃/25℃、35℃/30℃和40℃/35℃下两种瘦果的萌发率无显著差异。在全黑暗条件下，中央瘦果在低于35℃/30℃时萌发受到抑制，外围瘦果在低于40℃时萌发受到抑制。光照和瘦果类型除对大狼耙草的萌发率有显著影响外，对萌发指数和萌发速率也有明显影响。大狼耙草通过异形瘦果间的萌发差异减少同胞后代间的相互竞争，增强其对不同环境的适应性，使后代获得更多的生存机会，有利于瘦果在适宜的环境条件下萌发及入侵种群的存留与扩张。%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 signiifcant 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 signiifcantly 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 signiifcant inlfuences 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.
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