The Significance of Plant Nitrogen Uptake and Metabolism for the Competition for Nitrogen in the Rhizosphere

该项目的目的是描述和量化植被成分(老山毛榉、自然更新、其他林下植物)在以山毛榉为主的森林中植物和微生物之间争夺N的重要性。为此，将在空间和时间上研究竞争模式以及分子和生理背景。这些研究包括测定山毛榉对NH4+、NO3-、氨基酸和氨基糖的吸收速率和吸收动力学，以及对常见田间地点山毛榉N转运蛋白基因和N代谢酶的表达进行分析。在田间试验和控制条件下(温室和人工气候室)，将分析供水、氮肥、碳素供应、竞争林下和菌根化对氮素吸收、代谢和分配的影响以及氮素营养状况。将确定叶和根凋落物作为山毛榉再生氮源的意义。在实验室实验中，将研究根际气相中NO和CO2浓度变化对N吸收和代谢的影响。所取得的成果将有助于对系统的了解，并将部分用作在不断变化的环境中以过程为导向的N竞争模型的输入参数。

This project is aimed to characterize and quantify the significance of vegetation components (old growth beech, natural regeneration, other understorey) in the competition for N between plants and microorganisms in beech-dominated forests. For this purpose, competition pattern as well as the molecular and physiological background will be studied in space and time. These studies include the determination of uptake rates and uptake kinetics of NH4+, NO3-, amino acids, and amino sugars, combined with expression analyses of genes of N-transporters and enzymes of N metabolism in beech at the common field sites. In experiments in the field and under controlled conditions (greenhouses and phytotrons) the effects of water supply, N-fertilisation, C-supply, competing understorey, and mycorrhization on N-uptake, -metabolism, and -partitioning as well as the N-nutritional status will be analysed. The significance of leaf vs. root litter as N source for beech regeneration will be determined. In laboratory experiments, the consequences of changing NO and CO2 concentrations in the gaseous phase of the rhizosphere on N-uptake and ¿metabolism will be studied. The results achieved will contribute to system understanding and will partially be used as input parameters for process-oriented modelling of competition for N in a changing environment.