Simulating rhizodeposition patterns around growing and exuding root systems

Abstract

In this study, we developed a novel model approach to compute the spatio-temporal distribution patterns of rhizodeposits around growing root systems in three dimensions. Root systems were generated using the root architecture model CPlantBox. The concentration of rhizodeposits at a given location in the soil domain was computed analytically. To simulate the spread of rhizodeposits in the soil, we considered rhizodeposit release from the roots, rhizodeposit diffusion into the soil, rhizodeposit sorption to soil particles, and rhizodeposit degradation by microorganisms. To demonstrate the capabilities of our new model approach, we performed simulations for the two example rhizodeposits mucilage and citrate and the two example root systems Vicia faba and Zea mays. The rhizodeposition model was parameterized using values from the literature. Our simulations showed that the rhizosphere soil volume with rhizodeposit concentrations above a defined threshold value (i.e., the rhizodeposit hotspot volume), exhibited a maximum at intermediate root growth rates. Root branching allowed the rhizospheres of individual roots to overlap, resulting in a greater volume of rhizodeposit hotspots. This was particularly important in the case of citrate, where overlap of rhizodeposition zones accounted for more than half of the total rhizodeposit hotspot volumes. The rhizodeposit hotspot volume around the tap root system Vicia faba was shown to be much larger than around the fibrous root system Zea mays. Coupling a root architecture model with a rhizodeposition model allowed us to get a better understanding of the influence of root architecture as well as rhizodeposit properties on the evolution of the spatio-temporal distribution patterns of rhizodeposits around growing root systems.

A snapshot of the root phenotyping landscape in 2021

“…Mathematical modelling is a powerful tool to better understand roots and rhizosphere processes and to help us identify optimal root phenotypes in contrasting environments (Roose et al, 2016;Postma et al, 2017;Pascut et al, 2021). Functional-structural root architecture models are particularly well suited for such endeavour (Dunbabin et al, 2013;Landl et al, 2021). However, despite the high degree of complementarity between modelling and experimental approaches, only 21% of the survey participants reported using root modelling in their research.…”

“…root respiration, water conductivity, nutrient uptake, root exudation rate, etc.) of different root types (Postma et al, 2017;Schnepf et al, 2018;Couvreur et al, 2018;Heymans et al, 2020;Landl et al, 2021).…”

Linking rhizosphere processes across scales: Opinion

“…All computations were performed on the Linux cluster of IBG-3 at Forschungszentrum Jülich, which facilitated parallelisation. Details can be found in Landl et al (2021).…”