丛枝菌根共生对宿主植物适应低磷土壤的影响

Adaptation to local habitat is of important for plants to suivial and develop population in the environment. Except abiotic factors, biotic interactions (e.g. competition, predation, parasitism and mutualism) also contribute to plant adaptation to environment. Although experiments have showed that negative intraction between plant and other species (e.g. plant competition, herbivory and parasitism) play important role in plant adaptation to local environment, whether and how mutualism between species play a role in plant adaptation is poorly understood. The overall goal of this grant project is to examine whether and how symbiosis between plant and arbuscular mycorrhizal fungi (AMF) affect host plant adaptation to low soil phosphors (P) .The central hypotheses of this project are that AMF may reduce root mophorlogical phenotypic plasticity and maitain fitness of host plant under low P soil through enhancing functions of root system. Specific objectives of this project are: (1) to examine whether and how AMF affect host plant root mophorlogical phenotypic plasticity and fittness of growth and reproduction in host plant; (2) to test whether transgenerational plasticity and plant adaptation occur under low P soil and lack of AMF; (3) to characterize what are machnisms that AMF affect plant adaptation to low P soil. Model plant Medicago truncatula L. symbiosis with AMF are used as model symbiotic system in this study. Common garden experiment and reciprocal transplant experiment are conducted to test whether transgenerational plasticity and plant adaptation occur under low P soil and lack of AMF. Isotope tracing (13C, 15N and 32 P) is employed to test how AMF mediate nutrient uptake and allocation. Our project will reveal, for the first time, that how AMF affect host plants in adaptation to low P soil. The significance of this project is to enhance our understanding what strategy the plants may take under stress environment, and that the mutual symbioses between species can play important roles in plant adaptation to stress envrioment.

生物种间相互作用对植物适应环境的影响一直受到关注。研究已表明种间负相互作用（如竞争、捕食和寄生）对植物适应环境有重要影响，而植物之间的互惠以及共生对植物适应胁迫环境的影响机理有待揭示。本项目拟研究"植物-丛枝菌根共生是否和如何通过影响宿主植物的适合度从而影响植物对低磷土壤的适应"。项目以模式植物蒺藜苜蓿（Medicago truncatula L.）与丛枝菌根真菌共生为研究体系，研究：（1）低磷土壤下丛枝菌根对根系形态表型变异及植物生长和繁殖适合度的影响；（2）通过同质园实验和交互种植实验，研究低磷土壤下根系形态和丛枝菌根的变化是否具有跨世代传递性、植物对低磷土壤的适应性反应；（3）通过同位素示踪实验，研究丛枝菌根在宿主植物适应低磷土壤的作用机理。结果将揭示丛枝菌根对植物适应低磷土壤的影响及机理，有助于加深认识植物适应胁迫环境的策略及生物种间相互作用在植物适应胁迫环境中的作用。

生物种间相互作用对植物适应环境的影响一直受到关注。研究已表明种间负相互作用（如竞争、捕食和寄生）对植物适应环境有重要影响，而植物之间的互惠以及共生对植物适应胁迫环境的影响机理有待揭示。本项目拟研究“植物-丛枝菌根共生是否和如何通过影响宿主植物的适合度从而影响植物对低磷土壤的适应”。项目以模式植物蒺藜苜蓿（Medicago truncatula L.）与丛枝菌根真菌共生为研究体系，研究：（1）低磷土壤下丛枝菌根对根系形态表型变异及植物生长和繁殖适合度的影响；（2）通过同质园实验和交互种植实验，研究低磷土壤下根系形态和丛枝菌根的变化是否具有跨世代传递性、植物对低磷土壤的适应性反应；（3）通过同位素示踪实验，研究丛枝菌根在宿主植物适应低磷土壤的作用机理。经4年研究，完成了项目计划的研究内容和目标, 重要研究进展如下：（1）丛枝菌根真菌（AMF）影响宿主植物根的生长和形态。 低磷水平下AMF显著增加宿主植物根系生物量、根长和根系分支数量，胁迫越强丛枝菌根真菌对宿主植物根形态的影响越大。（2）AMF影响宿主植物的生活史和生物量的分配格局。低磷胁迫下，AMF提早宿主植物的开花时间15-30天（与AMF缺失的宿主相比），使其开花时间和生活史与土壤正常磷下水平下得宿主植物一致。从生物量的分配看，早期AMF促进宿主植物地下根系的生长（提高根冠比），随着世代的推移（第三代），与AM共生的宿主植物根冠比下降，种子和果实的生物量比重提高。（3）AMF对宿主植物根系的影响具有跨世代效应。同质园实验经历低磷胁迫且与AMF共生的宿主植物，其后代（子三代）在低磷环境下具有更高的生物量和更长的侧根长（与与AMF缺失宿主的后代相比）。（4）AMF影响有机物分解和植物光合碳化物的在宿主植物-AMF菌丝分配。稳定性同位素（13C/15N）示踪实验表明，AMF促进有机物分解并从中吸收15N传递养分给宿主植物；低磷土壤环境，宿主植物将更多光合产物13C分配到根外菌丝。上述研究结果有助于理解生物之间相互作用在生物在适应胁迫环境的作用。