This title appears in the Scientific Report :
2023
Please use the identifier:
http://dx.doi.org/10.18154/RWTH-2023-11292 in citations.
Rhizosphere models and their application to resource uptake efficiency
Rhizosphere models and their application to resource uptake efficiency
The efficient acquisition of finite and plant growth-limiting resources becomes increasingly important in sustainable agriculture and crop production. The rhizosphere as root-soil interface and its traits are critical for plant nutrition. Thus, I aim at discovering traits and mechanisms for efficien...
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Personal Name(s): | Kuppe, Christian W. (Corresponding author) |
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Contributing Institute: |
Bioinformatik; IBG-4 Biotechnologie; IBG-1 Pflanzenwissenschaften; IBG-2 |
Imprint: |
RWTH Aachen University
2023
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Physical Description: |
1 Online-Ressource : Illustrationen |
Dissertation Note: |
Dissertation, RWTH Aachen, 2023 |
DOI: |
10.18154/RWTH-2023-11292 |
Document Type: |
Dissertation / PhD Thesis |
Research Program: |
Biological and environmental resources for sustainable use |
Subject (ZB): | |
Publikationsportal JuSER |
The efficient acquisition of finite and plant growth-limiting resources becomes increasingly important in sustainable agriculture and crop production. The rhizosphere as root-soil interface and its traits are critical for plant nutrition. Thus, I aim at discovering traits and mechanisms for efficient nutrient uptake via rhizosphere modeling. Rhizosphere models are interdisciplinary. They build on soil models and encompass a collective equation system of biological, physical, and chemical concepts. Such concepts and underlying assumptions are fundamental to simulation results and their interpretation. Hence, in the first part of the thesis, I comprehensively analyze how the rhizosphere has been modeled so far. Nutrient uptake calculated from rhizosphere models affects the entire plant. I compared numerical methods for calculating uptake, since for root architecture models with a large number of root segments, each with its own soil conditions with a priori unknown concentration profiles, such methods need to be reliable, fast, and accurate. The hitherto de facto standard methods for single ion transport in radial rhizosphere models, Crank-Nicolson and explicit Euler, are not universally applicable for the wide range of parameter values. I recommend adaptive stiff or Runge-Kutta methods with higher-order spatial discretizations. In the second part of the thesis, I develop two novel models to simulate the uptake of the essential nutrients, phosphorus (P) and nitrogen (N). This mechanistic modeling addresses how plant traits influence uptake efficiency. I explain how upland rice can efficiently grow on strongly sorbing soils with low plant-available P and how root-exudation of biological nitrification inhibitors (BNIs) can facilitate N uptake efficiency and reduce N loss to the environment. The mechanisms behind efficient P uptake on strongly sorbing soils, and the role of different root classes, were not well understood. Fine lateral roots are metabolically low-cost and make up a large proportion of the root system, but their sole uptake strength is low. Models typically underestimated P uptake, which restrained targeted trait selection. However, the new P-pH model agrees with the observed plant P-uptake. The model allows for fast- and slowly reacting P depending on root-induced pH change, different root classes, and root morphology. The pH value (in the initially acidic soil) increases throughout the rhizosphere by acid-base diffusion, forming a P solubilization zone around the root. However, this solubilized P diffuses to the root too slowly. The results of the data-driven modeling convey to breeders the importance of solubilization and fine hairy lateral roots as integrative phenotype, i.e. in combination with other traits, because fine roots are most beneficial for P uptake in the vicinity of thicker roots due to their greater solubilization of P. BNIs have been suggested as strategy for improving N uptake and reducing environmental N pollution. Not all plants exude BNIs, and their importance to plants is questionable. With the new N-BNI model, I investigate the efficacy of BNIs and explain under which conditions BNIs are beneficial. The benefit of nitrification inhibition for uptake strongly depends on the availability of soil N-forms. BNIs are only beneficial for plant-N uptake when it is not impaired by lower nitrate production over the growth period. If nitrate availability is low, nitrification would be beneficial for uptake. The model indicates that the same N uptake can be achieved with reduced fertilizer application due to reduced nitrification and, therefore, reduced N loss. As mode of action, the sensitivity analysis suggests bactericidal exudates rather than bacteriostatic ones. Selection for BNI exudation should be accompanied by improved ammonium uptake. In conclusion, the rhizosphere models in this thesis enabled the identification of traits for P- and N-efficient plants. The results of the P-pH modeling are already used by a plant breeder developing new rice lines. Future studies on BNIs are required to consider rhizosphere conditions since the ecological and plant-physiological benefits of BNIs are distinct. |