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Repeated drought cycles and boron uptake in the rhizosphere
Project
Project code: DFG-403626025
Contract period: 01.01.2018
- 31.12.2020
Purpose of research: Experimental development
Root exudates interact with nutrients under deficient conditions. It is so far unknown (i) whether this is relevant under sufficient nutrient supply, (ii) whether interactions are affected by drought/rewetting cycles, and (iii) in which spatio-temporal pattern roots respond to local drought stress. Among all nutrients, boron (B) is unique in forming complexes with cis-diols. It is intriguing that B complexers are present in high amounts in root exudates. B uptake occurs via passive diffusion, facilitated or active transport, and complexation in the rhizosphere likely reduces B uptake via all pathways.Moderate droughts occur throughout the growing season. During drought, exudate production is increased to facilitate root growth into the drying soil. This may result in B complexation, reduced B uptake, and induced B deficiency upon re-watering and plant re-growth. Repeated droughts lead to metabolic changes, which likely alter exudate composition in a spatio-temporal sequence, depending on stress level, re-watering conditions and root age. Self-organization of the plants may result in re-distribution of resources within the plant.This project addresses four hypotheses: (1) increased formation of B-complexes in the rhizosphere reduces B uptake; (2) this process is enhanced under mild drought stress; (3) upon re-watering, reduced B uptake contributes to occurrence of B deficiency; (4) repeated droughts alter primary metabolism, change the composition of exudates and B uptake rates; plants in turn respond with metabolic adaptation.In this project, mucilage is collected and analysed for potential B binding molecules and B-containing complexes using column affinity chromatography with B-specific resins, and 11B NMR spectroscopy. Formation of B complexes is tested in vitro and correlated with B uptake rates of plants grown under conditions of reduced or normal mucilage production. In small scale pot and rhizobox experiments, B uptake rates are assessed by applying small volumes of 10B or 11B enriched isotopes to different root parts for 24 hours, and isotope measurements by LC-ICP-MS. Exudates are collected exactly at the position of local B application for metabolic and proteomic analyses. Different drought stress/re-watering scenarios are applied, and tissue samples are additionally taken at defined root positions and analysed using a metabolomics and proteomics approach. Induction of B deficiency is monitored via expression of B responsive genes. The pot experiments are complemented by large rhizobox experiments and non-destructive collection of mucilage from brace roots of field grown plants.The outcomes of these studies will provide information on the spatio-temporal pattern of “crosstalk” between stressed and non-stressed root parts, and help to elucidate the mechanisms underlying a possible systemic responses of the system root/shoot which may lead to re-distribution of resources within the plant under conditions of repeated drought events.
Section overview
Subjects
- Crop Production
- Plant Nutrition
- Climate Change
