The introduced meadow knapweed (Centaurea × moncktonii C.E. Britton), a hybrid of black (Centaurea nigra L.) and brown (Centaurea jacea L.) knapweeds, is increasingly common in pastures, meadows, and waste areas across many U.S. states, including New York. We evaluated the effects of temperature, light, seed stratification, scarification, and population on percent germination in four experiments over 2 yr. Percent germination ranged from 3% to 100% across treatment combinations. Higher temperatures (30:20, 25:15, and sometimes 20:10 C day:night regimes compared with 15:5 C) promoted germination, especially when combined with the stimulatory effect of light (14:10 h L:D compared with continuous darkness). Under the three lowest temperature treatments, light increased percent germination by 15% to 86%. Cold-wet seed stratification also increased germination rates, especially at lower germination temperatures, but was not a prerequisite for germination. Scarification did not increase percent germination. Differences between C. × moncktonii populations were generally less significant than differences between temperature, light, and stratification treatments. Taken together, these results indicate that C. × moncktonii is capable of germinating under a broad range of environments, which may have facilitated this species’ range expansion in recent decades. However, C. × moncktonii also shows evidence of germination polymorphism: some seeds will germinate under suboptimal conditions, while others may remain dormant until the abiotic environment improves. Subtle differences in dormancy mechanisms and their relative frequencies may affect phenological traits like the timing of seedling emergence and ultimately shape the sizes and ranges of C. × moncktonii populations.

中文翻译：

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美国纽约州草甸矢车菊 (Centaurea × moncktonii) 种群的种子萌发生态学

引进的草甸矢车菊（Centaurea × moncktoniiCE Britton），黑色（黑百合L.) 和棕色 (仙人掌L.) 矢车菊，在包括纽约在内的许多美国州的牧场、草地和荒地中越来越常见。我们在 2 年多的四个实验中评估了温度、光照、种子分层、划痕和种群对发芽率的影响。不同处理组合的发芽率从 3% 到 100% 不等。较高的温度（30:20、25:15，有时是 20:10 C 白天：夜间模式，与 15:5 C 相比）促进发芽，尤其是与光的刺激作用相结合时（与 14:10 h L:D 相比）持续的黑暗）。在三个最低温度处理下，光照增加了 15% 到 86% 的发芽率。冷湿种子分层也增加了发芽率，特别是在较低的发芽温度下，但不是发芽的先决条件。划痕没有增加发芽率。之间的差异C. × moncktonii种群的显着性通常低于温度、光照和分层处理之间的差异。综上所述，这些结果表明C. × moncktonii能够在广泛的环境下发芽，这可能有助于近几十年来该物种的范围扩大。然而，C. × moncktonii还显示出发芽多态性的证据：一些种子会在次优条件下发芽，而另一些种子可能会一直处于休眠状态，直到非生物环境改善。休眠机制及其相对频率的细微差异可能会影响物候性状，例如幼苗出苗的时间，并最终影响其大小和范围。C. × moncktonii人口。