Multiscale Modelling of Soil-Plant Interactions

Mathematical techniques and simulation have become widely used in many disciplines of engineering and science. It is the goal of this project to apply these techniques in order to contribute to a better understanding of the impact of microscale soil-plant interactions on a whole plant basis. In prarticular, we focus on the role of mycorrhizal fungi in plant solute uptake. Applications range from plant mineral nutrition to the potential use of plants for phytoremediation. Mycorrhizas are mutualistic symbiotic associations between plant roots and soil fungi, formed by more than 80 % of all terrestrial plants. The external hyphae spreading into the soil provide mycorrhizal plants with an additional pathway for nutrients and other solutes into the root. This may result in improved plant mineral nutrition, for example of phosphorus. It is the goal of this project to develop detailed mechanistic and hierarchical models for soil-plant interactions based on literature data and the expertise of co-operating experimentalists. We consider three spatial scales: the scale of one single hypha in the soil, the scale of a single cylindrical root and the scale of a whole plant. On the scale of a single hypha, we describe solute removal from soil as well as the fate of the solute inside the fungus. Most available data and thus our model development, focus on the uptake and translocation of phosphorus by arbuscular mycorrhizal fungi and transfer of phosphorus into the plant root cells. This transfer is believed to occur at the arbuscular interface. On the single root scale we model microscopic phenomena of solutes in the soil- plant system including root exudation, carbon flow and microbial dynamics. Furthermore, uptake by the fungal mycelium surrounding a mycorrhizal root will be calculated. On the scale of the whole plant, we consider competition between mycorrhizal roots and the contribution of the fungus to overall plant uptake. Furthermore, we pursue the question whether there is a trade off between exuding solubilizing agents and sustaining a mycorrhizal network. Through homogenisation techniques, information will be transferred from smaller to higher scales. Screening for literature data, data preparation and analysis will provide the basis for quantifying model processes and parameters as well as model validation. Numerical computations are performed in MATLAB 7.1.0 and numerical solutions of partial differential equations sought with the solver package FEMLAB 3.2. Results of this project will contribute to more efficient crop management or phytoremediation strategies and plant breeding as well as the design of new experiments.