Role of root mucilage in water and phosphorus uptake in semi-arid environment: Bridging the gap from theories on the pore scale to emergent behaviour at the plant scale (RootMucilage)

• Applicants: Professor Dr. Mutez Ali Ahmed; Professorin Dr. Michaela Dippold; Dr. Mathilde Knott; Professorin Dr. Andrea Schnepf
• Subject Area: Soil Sciences ; Plant Cultivation, Plant Nutrition, Agricultural Technology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567033511

Mucilage, a polymeric gel released at the root tip and capable of absorbing large volumes of water, has been hypothesised to facilitate water and nutrient uptake, especially under dry soil conditions. To date, this hypothesis has been tested only through artificial experiments and numerical simulations. However, the impact of mucilage on water and phosphorus (P) at the plant scale remains speculative. Thus, this proposal gathers the expertise of four complementary teams and a unique set of 150 maize lines to address the long-standing questions: i) how mucilage secretion influences water and P uptake, and ii) how its impact is affected by soil type and mucilage physico-chemical properties. This goal requires a multidisciplinary approach combining expertise in plant physiology, biogeo- and physico-chemistry and modelling, the synergy between the partners and their complementary skills and facilities. The project is structured into four closely interrelated work packages (WP). In WP1, we will characterise the root secretion of mucilage, the physico-chemical properties of the secreted mucilage and their response to soil conditions. We will screen the 150 lines for mucilage production and key physical (WP1a) and basic chemical and polymeric properties (WP1b). In WP1c, we will compare the mucilage properties of ten contrasting maize lines (identified in WP1a,b) in field-like conditions in lysimeters under contrasting soil texture (sand vs. loam) and water availability. In WP2, we will investigate the effect of mucilage traits on root water uptake under controlled lab conditions. The impact of three contrasting mucilage traits (identified in WP1) on transpiration and leaf water potential during soil and atmospheric drought will be investigated in WP2a. In WP2b, we will leverage neutron imaging to measure root architecture, water fluxes and water dynamics in the rhizosphere for the same lines. The information from WP2a,b will be integrated into a functional-structural root architecture model to disentangle the impacts of root architecture, dynamic soil conditions, and mucilage on root water uptake (WP2c). In WP3, we will investigate the effect of mucilage traits on soil processes controlling P mobilisation and uptake. In WP3a,b, the relation between mucilage physico-chemical properties and its impact on P diffusion (WP3a) and the activation of microbially supported P mobilisation (WP3b) will be studied. The objective of WP3c is to add a phosphate module to the model of WP2c computing phosphate uptake by growing maize to evaluate the combined impact of root architecture, dynamic soil conditions, and mucilage on root water and P uptake. In WP4, the impact of mucilage on combined water stress and P deficiency will be studied in the field simulating different environmental conditions. This project will generate a profound mechanistic understanding of the role of mucilage in the strongly interrelated process of water and P uptake at the plant scale.

• DFG Programme: Research Grants