荒漠先锋植物羽毛针禾适应环境的特殊方式之一是由根分泌物与多种微生物及沙粒构成的根鞘。研究显示羽毛针禾的根鞘几乎完全包裹根须,则其与环境的营养交换大都需通过根鞘;对根鞘微生物的分离鉴定证实其中有自生固氮菌存在。氮缺乏是荒漠环境缺水之后的第二限制因素,无固氮能力的羽毛针禾在先锋定植中如何有效获得氮素营养，特别是根鞘微生物在氮素供给或转运中的作用与机制都仍未知。为了解羽毛针禾的氮素营养策略,本项目以高通量测序法分析根鞘的微生物组成和固氮酶多样性;检测盆栽苗添加可利用氮时的根鞘发育,并以前述测序获得的主要微生物、固氮酶类群设计特异引物,以定量PCR检测其对外源氮的响应;分析根鞘中有机质与氮获得方式间的关系;以15N标记示踪法探查根鞘与羽毛针禾的氮素营养通道,揭示其氮素转运机制。研究目标是在了解羽毛针禾氮素营养途径的基础上揭示其环境适应机制。创新性为利用分子探查和15N示踪探索羽毛针禾的氮素营养机制

A sand born drought-resistant plant, Stipagrostis pennata（Trin.) de Winter, could colonize pioneerly in desert during revegetation. One strategy for their environment adaptation was the rhizosheath formatted by root-hair, mucilaginous exudates, microbial components, and soil particles. Previous reports has confirmed that rhizosheath of the S. pennata surrounded almost all of the root hairs. So the rhizosheath must be as a transit depot for nutrient exchange between plant and environment. Studies have also shown that nitrogen-fixing bacteria were included in the microorganisms isolated from rhizosheath. Nitrogen deficiency was the second limiting factor except water in desert. Plants that could colonize pioneerly in there but has no nitrogen-fixing ability should have its own strategy for nitrogen. For the purpose to understand its strategy for nitrogen utilization, the microorganisms and nitrogenase diversity of rhizosheath would be analyzed by high-throughput sequencing with unique primers. Then, the plant would be cultured in laboratory and nitrogen fertilizers with gradient concentrations would be added. The diversity responses of main microorganism population and nifH gene to the fertilizer addition would be estimated by Quantitative PCR with unique primers that selected from the previous analyzes above. The pathway of nitrogen transmission between rhizosheath and the plant would be traced by isotope-labelling method with 15N. The objective of the project was to reveal the environment adaptive mechanism of the S. pennata based on its nitrogen nutrient strategy. And this would be helpful for the desert ecology restoration. The innovation of the project was that the mechanism of the nitrogen strategy of the plant was explored by molecular detection and 15N tracing.