稻田土壤氧环境对水稻根系与AMF“碳磷交易”的调控机制研究

The condition of soil oxygen nutrition in paddy field are of great importance to the growth, development and grain production of rice (Oryza sativa L.), but the study concerning the soil oxygen nutrition in rice cultivation system is still limited. The “carbon-phosphorus (C-P) trade” between arbuscular mycorrhizal fungi (AMF) and the roots of terrestrial plant is of great significance to the nutrition uptake and utilization for most plants. However, the research on the “C-P trade” in wetland environment is rare. Our previous study found that the “C-P trade” between AMF and rice plants occurred even under soil waterlogging conditions, and its efficiency is strongly regulated by the oxygen condition in soil. In this study, we aim to further clarify the mechanisms involved in this regulatory effects of soil oxygen condition on the “C-P trade” under wetland environments. We will evaluate in detail the effects of soil oxygen condition on the (i) diversity and community structure of root colonizing AMF, and (ii) the AMF compatibility of rice plant, including the plant carbon nutrition level, root aerenchyma development and AMF resistance. The typical rice varieties with high and low root radial oxygen loss levels, respectively, will be used in the pot culture, pond culture and field experiments with or without AMF inoculation; and the techniques of stable isotope tracer, high-throughput sequencing and aerobic irrigation, etc. will be applied. The results from this study would provide helpful references on how to improve the soil oxygen nutrition by appropriate agricultural managements, and therefore making use of the beneficial effect of AMF and exploring the production potential of rice. This research project would also clarify the roles played by AMF in the C and P cycling in paddy wetland, and therefore increasing our understanding on its ecological function and application potential in paddy and other wetland systems.

稻田土壤氧营养状况是决定水稻生长发育和产量的重要因素，但是相关研究还较为薄弱。丛枝菌根真菌（AMF）与大部分陆生植物根系的“碳磷交易”对宿主的养分吸收和利用具有重大意义，但是在湿地环境中的相关研究还极为缺乏。课题组前期证实在湿地环境中AMF与水稻根系同样存在“碳磷交易”，且交易水平强烈受到土壤氧环境的调控。本项目拟利用前期筛选的根系泌氧能力差异明显的典型水稻品种，综合运用稳定同位素示踪、高通量测序、增氧灌溉等技术，通过模拟稻田湿地的盆栽、池栽及大田试验，探究土壤氧环境通过影响AMF群落特征以及与水稻AMF相容性密切相关的植株碳营养水平、皮层细胞发育及根系AMF抗性，进而调控两者“碳磷交易”的过程和机理。研究结果将为通过适宜的农艺措施改善稻田氧营养、挖掘AMF养分效应及水稻生产潜力提供参考；也能解析丛枝菌根在稻田系统的碳、磷流动中的作用，揭示湿地环境中AMF的生态功能及应用前景。

丛枝菌根真菌（AMF）在稻田等湿地系统中广泛存在，但它们在湿地环境下的生态功能还所知甚少。课题组前期研究证实，湿地土壤氧环境对湿地宿主根际AMF群落组成具有重要影响。在此基础上，本项目结合运用13C稳定同位素示踪、高通量测序等研究手段，通过模拟稻田湿地的盆栽、池栽及大田实验，系统研究了稻田土壤氧环境（通过不同淹水处理以及不同根系泌氧水平水稻品种实现）对AMF与水稻 “碳磷交易”的影响及其作用机制。我们的研究结果表明：（1）在不同淹水环境下AMF与水稻之间均存在明显的“碳-磷养分交易”；“碳磷交易”的效率不仅受到土壤缺氧环境的强烈抑制，而且受到水稻生长发育时期的影响：在水稻有较强养分需求的生理时期其与AMF“碳磷交易”的效率更高；（2）AMF对水稻生长、发育的促生效应强烈受到土壤氧环境和水稻碳水平（通过不同遮荫处理实现）的影响：土壤低氧以及水稻低碳环境均明显降低AMF对水稻的促生效应，甚至导致AMF抑制水稻生长；（3）土壤低氧环境下水稻通过增强基础防御、减少对AMF碳源供应降低了AMF在其根内的定殖水平；与此同时，土壤低氧环境也降低了AMF从土壤获取P并转运给水稻的能力。本研究最主要的创新包括两方面：（a）在国际上首次确切证实在淹水环境下AMF与水稻之间存在明显的“碳-磷养分交易”，揭示了AMF在湿地生态系统养分循环过程中的重要作用；（b）阐释了土壤氧环境通过影响水稻、AMF的生理、生化特征调控两者“碳磷交易”，进而影响菌根效益的过程和机制。总体上，该项目的开展显著提高了我们对AMF在稻田（及其他湿地）系统中碳、磷流动及循环的理解，也为通过适宜的农艺措施（包括氧运筹、水稻品种选育等）改善稻田氧营养、挖掘AMF养分效应及水稻生产潜力提供了重要参考。在本项目的资助下，项目负责人作为第一或通讯作者在Soil Biol. Biochem、Sci Total Environ.、Front. Microbiol、Mycorrhiza等本领域的主流学术刊物发表SCI论文6篇，在国内核心刊物《微生物学报》和《植物生态学报》发表论文2篇（8篇论文全部标注本项目资助），授权国家发明专利1项、培养博士研究生1名、硕士研究生4名；项目负责人王宇涛博士在项目执行期内入选 “广东省扬帆计划引进创新创业团队”和 广州市“珠江科技新星”人才项目。