P21 - Dynamics & Structure
Relevance of root growth and related soil structure formation for spatiotemporal patterns of chemical and biological properties and emergent system functions
The first project phase we identified root diameter as trait with high plasticity. Sand induced larger root diameters than loam. In the second phase we conduct pot experiments with controlled bulk density and controlled pore size distributions in order to identify the role of mechanical impendance and root-soil contact in modulating root diameter (WP1). Ethylene measurements in the rhizosphere will be done in order to identify its important role as a signalling hormone. Another striking finding from phase 1 wasere the very different root decomposition rates in sand and loam. In phase 2 we conduct tailored incubation experiments to identify the mechanisms that control root decomposition (WP2). Furthermore, long-term observations of emergent system properties like biopore recycling and infiltration capacity will be continued in phase 2 (WP3). Finally, the protocols for correlative imaging of the rhizosphere that were developed in phase 1, will be applied to pot experiments to better understand the patchy patterns of element and isotope concentrations in the rhizosphere (WP4).
Plants are assumed to form their root growth as well as uptake and release patterns according to their genetic predisposition and environmental factors. This will be explored jointly by the entire SPP by means of two different maize genotypes (wildtype vs. root hairless mutant) and two different soil textures (sand vs. loam). The identification of these spatio-temporal patterns in the rhizosphere at the scale of entire plants and at scale of individual roots calls for a combination of various imaging techniques
We use X-ray tomography to measure the three-dimensional root system architecture of different maize genotypes grown in different soil textures and compare them quantitatively through different image-derived parameters such as total root length, root diameter and root distances. The samples will be scanned repeatedly to measure root development over time. In addition, we investigate at the scale of individual roots how root growth changes soil structure in the rhizosphere as well as radial element concentrations through uptake and release.
We plan to conduct pot experiments under well-defined conditions in a climate chamber as well as undisturbed soil sampling in the field during a growing to circumvent the restrictions of limited space for root growing in a pot.
We are not only interested in whether and how different genotypes and soil textures induce different root system architecture and modifications of the rhizosphere but also as to how this changes the functioning of the soil-plant system at larger scales. Therefore, the image-derived root system properties will be compared with the functional behaviour such as plant growth, plant nutrition and water transport and storage.
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