Chen Bin J W, Huang Li, During Heinjo J, Wang Xinyu, Wei Jiahe, Anten Niels P R
College of Biology and the Environment, Nanjing Forestry University, Longpan Road 159, Xuanwu District, Nanjing 210037, China.
Section of Ecology and Biodiversity, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584CH Utrecht, The Netherlands.
AoB Plants. 2021 Apr 14;13(3):plab020. doi: 10.1093/aobpla/plab020. eCollection 2021 Jun.
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 () and the other with sunflower (). 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.
根系竞争是决定植物生长表现、群落结构和生态系统生产力的关键因素。为了在不考虑养分有效性的情况下充分估计植物根系对邻体响应的增殖程度，应该采用一种能够在植物个体水平上同时控制养分浓度和土壤体积的设置。采用网室分隔设计（这被认为是解决该问题的一个有前景的方案），我们进行了两项种内根系竞争实验：一项以大豆（）为对象，另一项以向日葵（）为对象。我们发现，大豆的根系生长或生物量分配对种内邻体没有响应，即不符合“理想自由分布”（IFD）范式；而向日葵甚至出现了生长减少的负响应。这些响应均与植物应通过牺牲自身适合度来产生更多根系以响应邻体的假设（即根系过度增殖）不一致。我们的结果表明，邻体诱导的根系过度增殖并非植物普遍存在的特征。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，这种响应可能是自然或人工选择导致的基因型依赖响应，或者是一种环境依赖响应，即植物可以根据竞争环境从根系过度增殖转变为理想自由分布。我们还批判性地讨论了网室分隔设计是否是根系竞争实验的理想解决方案。
