Root competition is a key factor determining plant performance, community structure and ecosystem productivity. To adequately estimate the extent of root proliferation of plants in response to neighbours independently of nutrient availability, one should use a set-up that can simultaneously control for both nutrient concentration and soil volume at plant individual level. With a mesh-divider design, which was suggested as a promising solution for this problem, we conducted two intraspecific root competition experiments: one with soybean (Glycine max) and the other with sunflower (Helianthus annuus). We found no response of root growth or biomass allocation to intraspecific neighbours, i.e. an ‘ideal free distribution’ (IFD) norm, in soybean; and even a reduced growth as a negative response in sunflower. These responses are all inconsistent with the hypothesis that plants should produce more roots even at the expense of reduced fitness in response to neighbours, i.e. root over-proliferation. Our results suggest that neighbour-induced root over-proliferation is not a ubiquitous feature in plants. By integrating the findings with results from other soybean studies, we conclude that for some species this response could be a genotype-dependent response as a result of natural or artificial selection, or a context-dependent response so that plants can switch from root over-proliferation to IFD depending on the environment of competition. We also critically discuss whether the mesh-divider design is an ideal solution for root competition experiments.

中文翻译：

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在控制养分浓度和土壤体积后，在网状分隔器实验中没有邻居诱导的大豆和向日葵根系生长增加

根系竞争是决定植物性能、群落结构和生态系统生产力的关键因素。为了充分估计植物根系增殖的程度，以独立于养分可用性，应使用一种可以同时控制植物个体水平的养分浓度和土壤体积的设置。使用网状分隔器设计（被认为是解决该问题的一种有希望的解决方案），我们进行了两个种内根竞争实验：一个与大豆（Glycine max），另一个与向日葵（Helianthus annuus）。我们发现在大豆中，根系生长或生物量分配对种内邻居没有反应，即“理想的自由分布”（IFD）规范；甚至减少生长作为向日葵的负面反应。这些反应都与植物应该产生更多根的假设不一致，即使以降低响应邻居的适应性为代价，即根过度增殖。我们的研究结果表明，邻居诱导的根过度增殖并不是植物中普遍存在的特征。通过将这些发现与其他大豆研究的结果相结合，我们得出结论，对于某些物种，这种反应可能是由于自然或人工选择而产生的基因型依赖性反应，或者是环境依赖性反应，因此植物可以从根部过度转换。根据竞争环境向 IFD 扩散。我们还批判性地讨论了网格分隔器设计是否是根竞争实验的理想解决方案。