Jia Xuan, Huangfu Chaohe, Hui Dafeng
Anhui Province Key Laboratory of Wetland Ecosystem Protection and Restoration, School of Resources and Environmental Engineering, Anhui University, Hefei, China.
Department of Biological Sciences, Tennessee State University, Nashville, TN, United States.
Front Plant Sci. 2020 Dec 10;11:584370. doi: 10.3389/fpls.2020.584370. eCollection 2020.
Plant species may acquire different forms of nitrogen (N) to reduce competition for the same resource, but how plants respond to neighbors with different densities in their N uptake is still poorly understood. We investigated the effects of competition regime on the uptake of different N forms by two hygrophytes, and , by conducting a hydroponic test of excised roots and an experiment in a subtropical wetland ecosystem. The two species were grown either in monocultures or mixtures with various neighbor densities. Root functional traits and N uptake rates of different N forms were measured. Our results showed that N uptake was mainly determined by N form, rather than species identity. Both species were able to use organic N sources, but they took up relatively more N supplied as NO than as NH or glycine, irrespective of competition treatments. Both species preferred NO when grown in monoculture, but in the presence of competitors, the preference of fast-growing persisted while acquired more NH and glycine, with stronger responses being observed at the highest neighbor density. The hydroponic test suggested that these divergences in N acquisition between two species might be partially explained by different root functional traits. To be specific, N uptake rates were significantly positively correlated with root N concentration and specific root length, but negatively correlated with root dry matter content. Our results implicated that has a competitive advantage with relatively more stable N acquisition strategy despite a lower N recovery than , whereas could avoid competition with via a better access to organic N sources, partly mediated by competition regimes.
植物物种可能会获取不同形态的氮（N）以减少对同一资源的竞争，但植物在氮吸收方面如何应对不同密度的邻居仍知之甚少。我们通过对离体根进行水培试验以及在亚热带湿地生态系统中进行田间试验，研究了竞争格局对两种水生植物（[植物名称1]和[植物名称2]）吸收不同形态氮的影响。这两个物种分别以单作或与不同邻居密度混合种植的方式生长。测量了根功能性状和不同形态氮的吸收速率。我们的结果表明，氮吸收主要由氮形态决定，而非物种身份。两个物种都能够利用有机氮源，但无论竞争处理如何，它们吸收以NO₃⁻形式供应的氮相对多于以NH₄⁺或甘氨酸形式供应的氮。两个物种在单作时都偏好NO₃⁻，但在有竞争者存在的情况下，生长迅速的[植物名称1]的偏好持续存在，而[植物名称2]则吸收更多的NH₄⁺和甘氨酸，在最高邻居密度下观察到更强的响应。水培试验表明，两个物种在氮获取方面的这些差异可能部分由不同的根功能性状来解释。具体而言，氮吸收速率与根氮浓度和比根长显著正相关，但与根干物质含量负相关。我们的结果表明，尽管[植物名称1]的氮回收率低于[植物名称2]，但其具有相对更稳定的氮获取策略，具有竞争优势，而[植物名称2]可以通过更好地获取有机氮源来避免与[植物名称1]竞争，这部分是由竞争格局介导的。
