Yu Qing, Wang Haijun, Wang Hongzhu, Xu Chao, Liu Miao, Ma Yu, Li Yan, Ma Shuonan, Hamilton David P, Jeppesen Erik
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.
School of Life Sciences, Institute of Ecology and Biodiversity, Shandong University, Qingdao, China.
Front Plant Sci. 2022 Jul 14;13:939589. doi: 10.3389/fpls.2022.939589. eCollection 2022.
Ammonium (NH-N) produces a paradoxical effect on submersed macrophytes because it is not only the preferred nitrogen source for the growth of plants but also threatens the growth of plants at high concentration. Whether short-term and small-scale physiological toxicity experiments at an individual level can reflect the effects of high ammonium on populations of submersed macrophytes in natural conditions is still unclear. In this study, an 18-month experiment was conducted in six 600 m ponds subjected to different levels of ammonium loading. The effects of high ammonium on populations of canopy-forming and rosette-forming were explored. The results showed that and populations can develop high cover and height at high ammonium concentration (7 mg/L) at short-term exposures, and may be tolerant to 18 mg/L ammonium concentration. However, the cover of and the height of both species were inhibited at 2.4 mg/L at long-term exposures. The height of was two to six times higher than that of across all treatments and control by the end of the experiment, and the cover of was 7-11 times higher than that of in most NH-N loading treatments, except the cover of in the highest NH-N loading treatment with 18 mg/L NH-N. The rosette-forming resists ammonium stress by slow growth (shoot elongation) to reduce consumption, while canopy-forming species resist ammonium stress by shoot elongation and canopy development to capture light. Although increasing ammonium concentration may induce severe stress on , the morphological characteristics of this species may, to some extent, release the plants from this stress. Our present study indicates that the negative effects of ammonium stress on the development of populations increased with exposure duration, and the submersed macrophyte community with stronger ability for light capture and dispersal may resist high ammonium stress. Nevertheless, in strongly ammonium-enriched systems, competition and succession cannot be neglected.
铵（NH-N）对沉水大型植物产生了一种矛盾的影响，因为它不仅是植物生长的首选氮源，而且在高浓度时会威胁植物的生长。在个体水平上进行的短期和小规模生理毒性实验是否能反映高铵对自然条件下沉水大型植物种群的影响仍不清楚。在本研究中，在六个600立方米的池塘中进行了为期18个月的实验，这些池塘受到不同水平的铵负荷影响。探究了高铵对冠层形成型和莲座丛形成型种群的影响。结果表明，在短期暴露于高铵浓度（7毫克/升）时，[具体物种1]和[具体物种2]种群能够形成高覆盖度和高度，[具体物种2]可能耐受18毫克/升的铵浓度。然而，在长期暴露于2.4毫克/升时，[具体物种1]的覆盖度和两个物种的高度均受到抑制。到实验结束时，在所有处理和对照中，[具体物种1]的高度比[具体物种2]高两到六倍，并且在大多数NH-N负荷处理中，[具体物种1]的覆盖度比[具体物种2]高7至11倍，但在最高NH-N负荷处理（18毫克/升NH-N）中[具体物种2]的覆盖度除外。莲座丛形成型的[具体物种2]通过缓慢生长（茎伸长）来抵抗铵胁迫以减少消耗，而冠层形成型物种通过茎伸长和冠层发育来抵抗铵胁迫以捕获光照。尽管铵浓度增加可能会对[具体物种1]诱导严重胁迫，但该物种的形态特征在一定程度上可能使植物从这种胁迫中解脱出来。我们目前的研究表明，铵胁迫对种群发育的负面影响随着暴露持续时间的增加而增加，并且具有更强光捕获和扩散能力的沉水大型植物群落可能抵抗高铵胁迫。然而，在铵强烈富集的系统中，竞争和演替不可忽视。
