• Large amounts of heavy metals have been released into the environment. Thus, the allelopathic effects of invasive alien species on the germination performance of co-occurring indigenous species may be altered or even heightened with the rapid growth in heavy metal pollution.
• This study evaluated the impacts of Canada goldenrod (Solidago canadensis L.) leaf extracts at concentrations of 0, 10 or 20 gl 1 on the germination of lettuce under different forms of heavy metal pollution (Cu²⁺, Pb²⁺ or a combination of Cu²⁺ and Pb²⁺; 35 mgl 1) during incubation in Petri dishes for 10 days.
• Goldenrod leaf extracts (high concentration) reduced growth of aboveground and belowground parts of lettuce as well as competition for light and soil nutrients. However, low concentrations of goldenrod leaf extracts dramatically improved growth of lettuce roots, competition for light, soil nutrient availability, leaf photosynthetic area and growth competitiveness. The combination of goldenrod leaf extracts and heavy metal pollution was synergistic on most lettuce germination parameters, probably because high concentrations of goldenrod leaf extracts together with heavy metal pollution had a synergistic negative impact on lettuce germination.
• Consequently, increased levels of heavy metal pollution may favour invasion of invasive alien species while largely suppressing germination of indigenous species.

中文翻译：

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重金属污染可改善加拿大菊科植物对生菜发芽的化感作用。

• 大量重金属已释放到环境中。因此，随着重金属污染的迅速增长，外来入侵物种对共生本土物种发芽性能的化感作用可能会改变甚至增强。
• 这项研究评估了0、10或20 gl 1浓度的加拿大金毛（（Solidago canadensis L.）叶片提取物在不同形式的重金属污染（Cu 2 ⁺，Pb ²⁺或多种形式的重金属污染）下对生菜萌发的影响。 Cu ²⁺和Pb ²⁺； 35 mgl 1）在培养皿中孵育10天。
• 菊科植物的叶提取物（高浓度）减少了莴苣地上和地下部分的生长，以及对光和土壤养分的竞争。然而，低浓度的菊科植物叶提取物显着改善了莴苣根的生长，对光的竞争，土壤养分的利用率，叶片的光合面积和生长竞争力。菊科植物叶提取物与重金属污染的组合在大多数莴苣萌发参数上具有协同作用，这可能是因为高浓度菊科植物叶提取物与重金属污染对莴苣的发芽具有协同负面影响。
• 因此，重金属污染水平的增加可能有利于入侵外来物种的入侵，同时在很大程度上抑制了土著物种的发芽。