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. This model approach allows us to study the evolution of rhizodeposition patterns around complex three-dimensional root systems. 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 example root system Vicia faba. 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. 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.

Linking rhizosphere processes across scales: Opinion

“…The mathematical model behind this example is explained in Landl et al (2021). Briefly, the 3D root architecture model CPlantBox (Schnepf et al 2018) was coupled with a rhizodeposition model to investigate the spatio-temporal distribution patterns of rhizodeposits in the soil as affected by root architecture development and rhizodeposit properties.…”

“…Simulations were performed for two rhizodeposits, mucilage and citrate, and the example root system Vicia faba. Details can be found in Landl et al (2021). Parameterisation of the root architecture model For the simulation of root architectures, CPlantBox requires a set of appropriate model input parameters.…”

“…The diffusion coefficients in water for mucilage and citrate were taken from (Watt et al 2006), the impedance factor from Olesen et al (2001), the soil buffer power for citrate from Oburger et al (2011) and the decomposition rate constants for mucilage and citrate from Kirk et al (1999) and Nguyen et al (2008). All values can be found in Table 1 of Landl et al (2021).…”

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.…”

Combining Models of Root-Zone Hydrology and Geoelectrical Measurements: Recent Advances and Future Prospects

“…The former derives from the direct rootcurrent iteration and depends on the large surface area and capacitance of roots, which, in turns, has been linked to root physiology and suberization (Weigand, 2017;Peruzzo et al, 2021;Tsukanov and Schwartz, 2021). The latter, indirect impact, is a combination of the root-induced changes in the physical, chemical, and biological properties of the rhizosphere, e.g., RWU, root exudation, solute uptake and rhizosphere microbiome changes (Landl et al, 2021).…”