Bidens pilosa (Asteraceae), a noxious weed in many ecosystems worldwide, produces large amounts of heteromorphic (central and peripheral) achenes. The primary aims of the present study were to compare the morphological, dormancy/germination characteristics of dimorphic achenes. Temperatures simulating those in the natural habitat of B. pilosa were used to test for primary dormancy and germination behaviour of fresh central and peripheral achenes. The effects of cold stratification, gibberellic acid (GA3) and dry storage on breaking dormancy were tested and the germination percentage of dimorphic achenes in response to osmotic stress was measured. Cold stratification, GA3 and dry storage significantly increased the germination percentage, suggesting both types of achenes had non-deep physiological dormancy. Variously pretreated central achenes had significantly higher germination percentages than peripheral achenes. Central achenes were more osmotically tolerant than peripheral achenes with a high germination percentage in high polyethylene glycol concentrations. These above differences among dimorphic achenes of B. pilosa increased the species' fitness to adapt to heterogeneous habitats creating an ecological adaptive strategy that may allow B. pilosa to successfully thrive in stressful habitats.

中文翻译：

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Bidens pilosa（Asteraceae）的瘦果异质性：发芽差异和可能的适应性意义。

Bidens pilosa（菊科）是全世界许多生态系统中的一种有害杂草，可产生大量异形（中央和周边）瘦果。本研究的主要目的是比较双态瘦果的形态，休眠/萌发特性。模拟松毛虫自然栖息地中的温度的温度用于测试新鲜的中部和外围瘦果的主要休眠和萌发行为。测试了冷分层，赤霉素（GA3）和干燥储存对打破休眠的影响，并测量了响应渗透压的双态瘦果的发芽率。冷分层，GA3和干燥贮藏显着增加了发芽率，表明这两种瘦果都没有较深的生理休眠。经过各种预处理的中央瘦果的发芽率比周围瘦果的发芽率高得多。在高聚乙二醇浓度下，中央瘦果比周围瘦果具有更高的渗透耐受性，且发芽率较高。这些上述差异的B. pilosa双态瘦果提高了该物种适应异质生境的适应性，从而创造了一种生态适应策略，可以使B. pilosa在压力大的生境中成功繁殖。