The success of invasive plants can be better understood by comparing their traits with closely related native species. This study compared germination ecology and seedling growth of invasive Ageratum houstonianum and Ageratum conyzoides with co-occurring and allied native Adenostemma lavenia. Seeds were germinated under a different light (12 h photoperiod/complete dark), temperatures (low: 25°C/15°C day/night, and high: 30°C/20°C), and different levels of water stress (−0.1, −0.25, −0.5, −0.75, and −1 MPa). Seedlings were grown to determine biomass allocation, relative growth rate (RGR), plant height, and number of leaves. The seed mass and size of native A. lavenia were higher than those of invasive species. Seeds of all species were positively photoblastic. At low temperature and in all levels of water stress, all measured parameters except mean germination time were the highest in A. houstonianum. However, at high temperature, there was no significant difference in germination percentage between A. houstonianum and A. lavenia. No germination of A. conyzoides and A. lavenia was recorded beyond −0.5 MPa water potential, but seeds of A. houstonianum germinated up to −0.75 MPa. A. houstonianum had higher root mass fraction, root-to-shoot ratio, and number of leaves than the other two species. Stem mass fraction and the height of seedling were highest in A. conyzoides. The RGR was 1.6 times higher in invasive Ageratum species than the native species; it was slightly higher in A. houstonianum than in A. conyzoides. Overall, the results suggest that germination traits and seedling growth performance can be used as predictors of a species' invasiveness.

中文翻译：

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入侵性Ageratum物种和近缘本地Adenostemma lavenia的发芽生态学和幼苗生长

通过将入侵植物的性状与密切相关的本地物种进行比较，可以更好地了解入侵植物的成功。本研究比较了入侵性Ageratum houstonianum和Ageratum conyzoides与共存和相关的本地Adenostemma lavenia的发芽生态和幼苗生长。种子在不同的光照（12小时光周期/完全黑暗）、温度（低：25°C/15°C白天/夜间，高：30°C/20°C）和不同水平的水分胁迫下发芽（ -0.1、-0.25、-0.5、-0.75 和 -1 MPa）。培育幼苗以确定生物量分配、相对生长率（RGR）、植物高度和叶子数量。本地A. lavenia的种子质量和大小均高于入侵物种。所有物种的种子均具有阳性光能性。在低温和各级水分胁迫下，除平均发芽时间外的所有测量参数均以休斯敦蘑菇最高。但在高温下， A. houstonianum和A. lavenia的发芽率没有显着差异。在水势超过-0.5 MPa 的情况下，A. conyzoides和A. lavenia没有发芽，但A. houstonianum的种子在水势高达-0.75 MPa 时发芽。A. houstonianum 的根质量分数、根冠比和叶片数量均高于其他两个物种。茎质量分数和苗高以A. conyzoides最高。入侵Ageratum物种的RGR比本地物种高1.6倍；A. houstonianum的含量略高于A. conyzoides。总体而言，结果表明发芽性状和幼苗生长性能可以用作物种入侵性的预测因子。