AMF对大气CO2升高与土壤Cd污染耦合的响应及对树木幼苗调节机制

Arbuscular mycorrhizal fungi (AMF) can be symbiotically associated with 70 - 90% terrestrial vascular plant species, which can enhance the resistance of host plants to heavy metal stress. The response of AMF to both elevated atmospheric CO2 and heavy metal-contaminated soils would affect the adaptation of its host plants to their surroundings, which would affect the healthy and the function of ecosystem. Since forest plantation is important for regional and global climate change mitigation and C balance and the seedlings stage is important for future development of trees, the response of AMF to the combination of elevated atmospheric CO2 and Cd-contaminated soils and the regulation mechanism of AMF on seedlings physiology will be studied by employing both OTCs (Open top chambers) and artificially contaminated soil in this study. Photosynthesis of tree seedlings, as a key problem, will be used to explore the response mechanism of AMF to elevated CO2 combined with Cd-contaminated soils. The regulation mechanism of AMF on seedlings physiology under the combination of elevated CO2 and Cd-contaminated soils will be clarified by analyzing effects and contributions of AMF on the fate of Cd and changes in antioxidantsystem and osmoregulation of seedlings, P and Cd uptake by seedlings, and molecular biology mechanism of seedlings in Cd resistance. Overall, the result of this study will help to evaluate ecological service function of AMF for forest plantation and to scientifically manage plantation ecosystem in heavy metal stress under global environmental change scenarios.

丛枝菌根真菌(AMF)能与70-90%的陆生植物形成菌根共生体，增强宿主植物抵抗逆境如重金属胁迫等的能力。大气CO2浓度升高和土壤重金属污染共存时，AMF的响应及其对宿主植物的调控能力关系生态系统健康和功能。鉴于人工林在减缓区域和全球气候变化、碳平衡方面的重要作用及树木幼苗期对未来生长发育的关键性，本项目拟采用CO2开顶箱和人工污染土壤结合法探讨AMF对大气CO2浓度升高与土壤Cd污染耦合的响应及对树木幼苗调节机制。从幼苗光合作用角度分析AMF对大气CO2浓度升高与土壤Cd污染耦合的响应特征及机理；通过分析CO2浓度升高下AMF的变化对土壤Cd归趋的影响及贡献，结合幼苗抗氧化系统、渗透调节性、P和Cd吸收能力、Cd抗性分子生物学水平变化等方面，阐明AMF在耦合条件下对树木幼苗的调节机制。结果可为评估全球变化与土壤重金属污染共存下人工林AMF生态服务功能和合理管理人工林生态系统提供科学支持。

丛枝菌根真菌(AMF)能与70~90%的陆生植物形成菌根共生体，增强宿主植物抵抗逆境如重金属胁迫等的能力。大气CO2升高和土壤重金属污染共存时，AMF的响应及其对宿主植物的调控能力关系生态系统健康和功能。鉴于人工林在减缓区域和全球气候变化、碳平衡方面的重要作用及树木幼苗期对未来生长发育的关键性，本项目采用了CO2开顶箱和人工污染土壤结合法探讨AMF对大气CO2升高与土壤Cd污染耦合的响应及对刺槐幼苗调节机制。研究表明：① 大气CO2浓度升高显著提高了土壤Cd污染下刺槐幼苗根际土壤AMF基因丰度，但降低了根系 AMF 基因丰度和群落多样性。② 摩西斗管囊霉属（Funneliformis mosseae）是根际土壤和根系中相对丰度最高的优势属，CO2浓度升高显著增加了Cd处理下根系摩西斗管囊霉属（Funneliformis mosseae）相对丰度；摩西斗管囊霉属、近明球囊霉属（Claroideoglomus）、原囊霉属（Archaeospora）和类球囊霉属（Paraglomus）在根系定殖存在明显竞争性。③土壤 C 和 pH 值及根系生物量、N 和 C/N 比显著影响根际土壤 AMF 群落特征，而土壤DTPA-Cd 和根系 C、N、Cd 含量及 Cd 积累量显著影响根系 AMF 群落组成。④大气CO2浓度升高提高了Cd污染下幼苗的光合能力，根系 AMF 群落显著影响抗氧化酶活性，且根系AMF 基因丰度、OTUs 和双型囊霉属（Ambispora）是影响抗氧化酶活性的显著影响因子，而摩西斗管囊霉属显著影响Cu/Zn-SOD、POD 和 CAT 基因相对表达。⑤大气CO2浓度升高可通过促进黄酮的合成改善Cd污染下刺槐幼苗非酶防御系统。⑥根系AMF群落显著影响叶片黄酮的合成，且摩西斗管囊霉属是黄酮含量变化解释率最高的显著因子，其在根系定殖通过抑制黄酮合成关键酶的基因表达水平和活性显著降低了黄酮的合成；⑦摩西斗管囊霉定殖显著降低了根系甘露糖、半乳糖、槲皮素、没食子酸、绿原酸和对羟基苯甲酸的合成量。结果可为评估全球变化与土壤重金属污染共存下人工林AMF生态服务功能和合理管理人工林生态系统提供科学支持。