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

该项目旨在描述和量化植被成分（老生长山毛榉、自然更新、其他林下植被）在山毛榉为主的森林中植物和微生物对N的竞争中的重要性。为此，我们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，并结合对常见田间地点N转运蛋白基因和N代谢酶的表达分析。在田间和受控条件下（温室和植物栽培室）的试验中，将分析供水、施氮、供碳、竞争林下和菌根化对氮素吸收、代谢和分配以及氮素营养状况的影响。将确定叶片凋落物与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NO和CO2浓度变化对氮吸收和氮代谢的影响。所取得的结果将有助于系统理解，并将部分用作在不断变化的环境中竞争N的面向过程建模的输入参数。

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.