Spatio-temporal pattern of root exudation and enzyme activities in the rhizosphere

根系分泌物是根际生物化学时空自组织的主要驱动力。我们假设根系与土壤微生物的相互作用是克服局部营养缺乏的有效策略-在根际-通过联合（根和微生物）生产互补和有效的酶系统来动员植物的营养。酶在根际分布的梯度将被指定为最佳和缺乏营养供应。根分泌物对动力学参数和酶效率的影响将在普通田间试验（CFE）中进行酶谱分析。根毛对微生物功能的影响将基于微生物分配理论进行探讨，我们以氮(N)为例进行了代表性测试，假设缺氮刺激了具有高底物亲和力的N获取酶的产生。有根毛和无根毛的根际产生酶的效率将根据Km的变化来确定，并将与玉米植株对15N的吸收进行比较。为了量化和定位土壤有机质中矿化氮和硼(B)的酶，将在两个玉米品种：有根毛和没有根毛的土壤中测定参与C、N和B循环的酶的动力学。根系沉积和酶活性的时空格局将通过14C成像与酶活性的酶谱定位相结合来分析，根据根毛的存在和土壤质地来创建根周围根际自组织的图像。将二维酶谱与微计算机断层扫描相结合，揭示土壤孔隙的分布和连通性，开发三维酶谱新方法。该方法将为sp2阶段的其他项目提供支持。基于酶谱分析、放射性同位素成像和生长根周围热点酶动力学的结合，我们将得出根-微生物相互作用对N和B的局部动员的基本结论，以及对根际自组织时空格局的影响。

Root exudates are the main driver for biochemical spatio-temporal self-organization of the rhizosphere. We hypothesize that the interactions of roots with soil microorganisms is an efficient strategy to overcome nutrient deficiency locally - in the rhizosphere - by joint (roots and microbial) production of complementary and efficient enzyme systems for mobilization of nutrients for plants. The gradients of enzyme distribution in the rhizosphere will be specified at optimal and deficient nutrient supply. The effects of root exudates on kinetic parameters and enzyme efficiencies will be investigated by zymography in the common field experiment (CFE).Effect of root hairs on microbial functions will be explored based on the microbial allocation theory, which we representatively test at the example of nitrogen (N), hypothesizing that N deficiencies stimulate the production of N acquiring enzymes with high substrate affinity. The efficiency of enzymes produced in the rhizosphere with/without root hairs will be determined based on the Km changes and will be compared with the 15N uptake by maize plants from 15N labeled litter. To quantify and localize the enzymes mineralizing N and boron (B) from soil organic matter, kinetics of enzymes involved in C, N and B cycles will be determined in soil under two maize varieties: with and without root hairs. The spatio-temporal pattern of rhizodeposition and enzyme activities will be analyzed by coupling 14C imaging with localization of enzyme activities by zymography, depending on root hair presence and soil texture to create a picture of rhizosphere self-organization around the growing root. Combining the 2D zymography with micro computed tomography to unravel the distribution and connectivity of pores in soil, we will develop the new approach of 3D zymography. This approach will be offered for other projects in the 2nd phase of the SPP.Based on combination of zymography with radioisotope imaging and enzyme kinetics in hotspots around the growing roots, we will draw fundamental conclusions about root-microbial interactions with respect to the localized mobilization of N and B, and consequences for spatio-temporal pattern of rhizosphere self-organization.