Experiments were conducted to determine the effect of various environmental factors and burial depth on germination and seedling emergence of common beggar’s-tick [Bidens alba (L.) DC.] seeds at two different stages of afterripening. Mature B. alba seeds were stored at 4 C for 3 to 5 mo (new seed lot) and 13 to 15 mo (old seed lot) until experiment initiation. Germination exponentially decreased with increasing moisture stress. Germination rate decreased from 87 ± 2.9% to 13 ± 6.1% as osmotic potential decreased from 0 to −0.5 MPa and was completely inhibited at osmotic potentials below −0.83 MPa. A large portion of the new seeds tested positively photoblastic, but seeds that had afterripened for 1 additional year were partially desensitized to the light requirement. New and old seeds still germinated to a greater percentage in the presence of light than under continuous dark at temperatures ranging from 15 to 35 C. Both new and old seeds germinated over a range of temperatures from 5 to 35 C, but the optimum temperatures for germination was 15 to 30 C in the presence of light. Regardless of seed lot, seedling emergence was the greatest when seeds were sown at the soil surface. Seedling emergence was abruptly reduced when burial depth was 1 cm or greater. Based on these results, we conclude that shallow cultivation could effectively suppress this population of B. alba from emerging when incorporated into an integrated control strategy. The information obtained in this research identifies some important factors that facilitate the widespread presence of B. alba in Florida and may contribute to weed management programs.

中文翻译：

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受环境因素影响的后熟两个不同阶段的普通乞丐 (Bidens alba) 种子的发芽和出苗

通过试验确定了各种环境因素和埋藏深度对普通叫花蜱发芽和出苗的影响[白鬼针草(L.) DC.] 后熟两个不同阶段的种子。成熟B. alba种子在 4°C 下储存 3 至 5 个月（新种子批次）和 13 至 15 个月（旧种子批次），直到实验开始。随着水分胁迫的增加，发芽率呈指数下降。当渗透压从 0 降至 -0.5 MPa 时，发芽率从 87 ± 2.9% 降至 13 ± 6.1%，并且在低于 -0.83 MPa 的渗透压下被完全抑制。大部分新种子的光胚性测试呈阳性，但再成熟一年的种子对光照要求部分脱敏。在 15 至 35 摄氏度的温度下，新老种子在光照条件下的发芽率仍高于在持续黑暗条件下的发芽率。新老种子均在 5 至 35 摄氏度的温度范围内发芽，但最适温度为在光照条件下，发芽温度为 15 至 30 摄氏度。无论种子批次如何，在土壤表面播种时出苗量最大。当埋深为1厘米或更大时，出苗率突然降低。基于这些结果，我们得出结论，浅耕可以有效抑制该种群B. alba当纳入综合控制策略时，就会出现。在这项研究中获得的信息确定了一些促进广泛存在的重要因素B. alba在佛罗里达州，可能有助于杂草管理计划。