Myriophyllum spicatum L. is a widely distributed submerged aquatic plant species, which became a model species for different test systems using either unrooted or sediment-rooted plants. Here, we tested the response of unrooted and sediment-rooted M. spicatum to different combinations of temperature, light and CO₂ conditions, respectively. Overall, the relative growth rates of rooted plants were higher than for unrooted plants, with sediment-rooted plants showing a stronger growth response to varying growth conditions. Relative growth rates based on dry mass and fresh mass strongly differed due to differences in dry matter contents. M. spicatum showed increased branching under elevated CO₂ and high light conditions. Sediment-rooting caused higher biomass allocation to roots, but lower allocation to stems and leaves. The dry matter contents were higher in unrooted than in rooted plants and increased with increasing CO₂ and light availability, while temperature had only a minor effect. Chlorophyll contents decreased with increasing dry matter contents, and were reduced under both high CO₂ and high light conditions. We conclude that the responses to varying growth conditions should be considered in test systems using M. spicatum. Moreover, the selection of the analyzed growth parameters can strongly influence the outcome of studies. We further recommend that the growth conditions must be controlled, particularly the pH, which often change due to the photosynthetic carbon uptake of the plants.

Myriophyllum spicatum L.是一种广泛分布的淹没水生植物物种，已成为使用无根或有根的植物的不同测试系统的模型物种。在这里，我们测试了无根和沉积物层次的响应M.藻到的温度，光照和CO的不同组合₂分别条件。总体而言，有根植物的相对生长速率高于无根植物，其中以沉积物为根的植物对不同的生长条件表现出较强的生长响应。由于干物质含量的差异，基于干物质和新鲜物质的相对增长率存在很大差异。在升高的CO ₂下，M。spicatum显示出增加的分支和强光条件下。泥沙生根导致较高的生物量分配给根，但较低的分配给茎和叶。无根植物的干物质含量高于无根植物，并且随着CO ₂和光利用率的增加而增加，而温度的影响很小。叶绿素含量随着干物质含量的增加而降低，并且在高CO ₂和高光照条件下均降低。我们得出的结论是，在使用sp。sp.atum的测试系统中应考虑对变化的生长条件的响应。此外，分析生长参数的选择会强烈影响研究结果。我们进一步建议必须控制生长条件，特别是pH，由于植物吸收光合作用的碳经常会改变pH。