蓝藻诱导凤眼莲根系氮素高效跨膜转运的机理

Nitrogen loading reduction with Eichhornia crassipes has increasingly become a measure and received widespread attention. Nitrogen absorption ability of plants may exert a great influence on N-reducing in waters. Previous studies have confirmed that the nitrogen absorption and transport ability of E. crassipes can be improved with existence of cyanobacteria, but the intrinsic mechanisms behind this phenomenon are still unclear. In this proposal, we will focus on finding the mechanisms of efficient nitrogen trans-membrane transport in E. crassipes roots with different approaches. First, from morphology level, various techniques such as root scanning, electron microscopy, stereo microscope will be used to exam the root micro-structure. Second, from physiology and biochemistry levels, the enzyme activities, intracellular nitrogen activities and biological functions of amino acid will be monitored by using isotope dual-labeling approach, ion-selective microelectrode technology and related biochemical analysis methods. Finally, from genetic level, the RT-PCR technique will be used to investigate the differences in ammonium transporter (AMT). The results of this study will provide theoretical basis for nitrogen loading reduction using E. crassipes in algae dominant eutrophic waters, and broaden the research area in dynamics of nitrogen cycle, as well as have huge realistic and scientific impacts on solving problems related to eutrophication.

采用凤眼莲削减水体氮负荷已日益成为广为关注的举措，氮素吸收能力是影响植物氮素削减效果的重要因素。前期研究发现，蓝藻提高了凤眼莲对氮素的吸收与转运能力，但其发生机理尚不清楚。本项目重点关注凤眼莲根系的相关生物学变化特征，首先拟凭借根系扫描、体视显微镜和电子显微镜等技术，从形态结构方面寻找根系高效吸收与转运氮素的证据；其次，综合同位素双标记技术、离子选择性微电极技术及相关生化分析手段，对根系酶活、胞内氮素活度、氨基酸生物学功能等进行系统分析，从生理生化层面探究氮素高效跨膜转运的可能机理；最后，运用RT-PCR等分子生物学技术，探讨根系氨转运蛋白的表达差异性，从分子与基因水平揭示根系对氮素高效跨膜转运的内在机理。本研究可丰富水体氮素循环动力学的研究内容，为今后选用凤眼莲削减藻型富营养化水体氮负荷提供数据支撑和理论支持，对改善水体富营养化有重要意义。

采用凤眼莲削减水体氮负荷已日益成为广为关注的举措，氮素吸收能力是影响植物氮素削减效果的重要因素。前期研究发现，蓝藻提高了凤眼莲对氮素的吸收与转运能力，但其发生机理尚不清楚。本项目重点关注凤眼莲根系的相关生物学变化特征，首先凭借根系扫描、体视显微镜和电子显微镜等技术，从形态结构方面寻找根系高效吸收与转运氮素的证据；其次，综合同位素双标记技术、非损伤微测技术及相关生化分析手段，对根系活力、表面积、酶活等进行系统分析，从生理生化层面探究氮素高效跨膜转运的可能机理；最后，运用RT-PCR等分子生物学技术，探讨根系氨转运蛋白的表达差异性，从分子与基因水平揭示根系对氮素高效跨膜转运的内在机理。本项目通过比较生理化学方法与根系分析仪根系研究方法，对凤眼莲根系面积等指标的测定方法进行优化与校准；简化了无菌凤眼莲制备流程，在较短时间内获得较大群体数量的无菌苗，为实验开展提供良好的材料。结果表明：与蓝藻互作下凤眼莲根系氮素吸收速率显著提高至89.37 pmol•cm-2•s-1，凤眼莲根系胞间连丝密度显著升高，氨转运蛋白表达有明显升高，推测与氮素高效吸收有关；溶解氧的波动不仅影响水体中氮素赋存形态，而且适度增氧促进与蓝藻互作下凤眼莲根系对氮素吸收与富集；与蓝藻共存下，凤眼莲硝酸还原酶活性、根系表面积有显著升高，而根系谷氨酰胺合成酶活力有显著降低；通过CN双标记，估算凤眼莲通过根系吸收的氮素速率（12.25～25.69μg/g鲜重/d），且存在一定的碳氮协同作用；高浓度氮素水体中，凤眼莲通过吸收削减氮素达53.06%；通过原位实验明确了在蓝藻死亡过程中，凤眼莲可高效削减了水体亚硝态氮和氨氮等有害氮素浓度，确保水产品安全。本研究可丰富水体氮素循环动力学的研究内容，为今后选用凤眼莲削减藻型富营养化水体氮负荷提供数据支撑和理论支持，对改善水体富营养化有重要意义。