Temperature may regulate seed dormancy and germination and determine the geographical distribution of species. The present study investigated the thermal limits for seed germination of Polygonum ferrugineum (Polygonaceae), an aquatic emergent herb distributed throughout tropical and subtropical America. Seed germination responses to light and temperature were evaluated both before (control) and after stratification at 10, 15 and 20°C for 7, 14 and 28 d. Germination of control seeds was ~50% at 10 and 15°C, and they did not germinate from 20 to 30°C. The best stratification treatment was 7 d at 10°C, where seed germination was >76% in the dark for all temperatures, except at 30°C, and < 60% in light conditions. A thermal time approach was applied to the seed germination results. Base temperature (Tb) was 6.3°C for non-dormant seeds and optimal temperature (To) was 20.6°C, ceiling temperature (Tc (<50)) was 32.8°C, and thermal time requirement for 50% germination was 44.4°Cd. We concluded that a fraction of P. ferrugineum seeds is dormant, has a narrow thermal niche to germinate (10 and 15°C) and that cold stratification (10°C) alleviated dormancy and amplified the thermal range permissive for germination of the species. Consequently, P. ferrugineum is expected to occur in colder environments, for example, at high altitudes. Higher temperatures decrease the probabilities of alleviate dormancy and the ability of their seeds to germinate.

中文翻译：

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黄蓼 Wedd 的热需求和萌发生态位宽度。来自巴西东南部

温度可以调节种子的休眠和发芽，并决定物种的地理分布。本研究调查了种子萌发的热极限黄蓼蓼科（Polygonaceae），一种水生草本植物，分布于热带和亚热带美洲。在 10、15 和 20°C 分层 7、14 和 28 天之前（对照）和分层之后评估种子发芽对光和温度的反应。对照种子在 10 和 15°C 的发芽率约为 50%，它们在 20 至 30°C 不发芽。最好的分层处理是在 10°C 下 7 天，在所有温度下，除 30°C 外，所有温度下种子发芽率 > 76%，光照条件下发芽率 < 60%。将热时间方法应用于种子发芽结果。基础温度（吨b) 为非休眠种子的 6.3°C 和最佳温度 (吨○) 为 20.6°C，天花板温度 (吨c (<50)) 为 32.8°C，50% 发芽所需的热时间为 44.4°Cd。我们得出结论，一小部分P. ferrugineum种子处于休眠状态，具有狭窄的发芽热生态位（10 和 15°C），冷分层（10°C）减轻了休眠并扩大了物种发芽的热范围。所以，P. ferrugineum预计将发生在较冷的环境中，例如在高海拔地区。较高的温度会降低缓解休眠的可能性和种子发芽的能力。