固氮菌缓解氮限制环境中丛枝菌根真菌对加拿大一枝黄花的营养竞争

丛枝菌根真菌(AMF)能与大多数陆生植物的根系形成共生体, 有助于宿主植物吸收养分。但营养胁迫下, 根系微生物对AMF与宿主植物间关系的影响少见报道。该研究假设: 在营养极度匮乏(如氮胁迫)环境下, AMF与宿主植物可能产生营养竞争, 而固氮菌的介入能够缓解两者对营养的竞争关系。为了验证这一假设, 该文探究了加拿大一枝黄花(Solidago canadensis)生长受限的氮浓度, 并在氮受限条件下检验了AMF、加拿大一枝黄花及固氮菌三者间的关系。结果表明: 低氮处理明显抑制了加拿大一枝黄花的地上生物量和总生物量, 尤其以0.025 mmol·L^-1 N的氨态氮对加拿大一枝黄花的负影响更甚。在此氮浓度下, 单独添加AMF总体上都进一步抑制了加拿大一枝黄花的生长, 而固氮菌的添加在一定程度上提高了氮受限条件下AMF对宿主的根部侵染率及宿主植物生物量。这表明固氮菌能够缓和氮受限条件下AMF和加拿大一枝黄花间的营养竞争关系。研究结果加深了对外来植物在极度营养胁迫环境下与多种微生物互作的入侵机制的理解。

Nitrogen-fixing bacteria alleviates competition between arbuscular mycorrhizal fungi and Solidago canadensis for nutrients under nitrogen limitation

Aims Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with most terrestrial plants, contributing to the nutrient uptake of host plants. While little is known on how rhizospheric microorganisms affect the relationships between AMF and host plants under nutritional stress. We hypothesize that AMF may compete for nutrients with host plants in extremely nutrient-limited environments, such as nitrogen deficient habitats, and nitrogen-fixing bacteria will alleviate the competition.Methods In order to test our hypotheses, we grew Solidago canadensis plants under nitrogen deficient treatments. We inoculated plants with AMF and a nitrogen-fixing bacterium to test the relationships among the host plant and microorganisms.Important findings Under the lowest nitrogen level (0.025 mmol·L^-1 N of ammonium nitrogen), the growth of S. canadensis was more restricted with AMF colonization, suggesting competition between AMF and the host. However, with the inoculation of nitrogen-fixing bacterium, AMF colonization was promoted and plant growth was increased. These results indicate that nitrogen-fixing bacteria could moderate the competition for nutrients between AMF and their host under nitrogen deficiency. This study improves our understanding of the invasion mechanisms of alien plants, where they interact with different microorganisms under extreme nutrient stress.