Correlative Visualization of Root Mucilage Degradation Using X-ray CT and MRI

• Published in: Frontiers in environmental science Vol. 6
• Main Authors: van Veelen, Arjen, Tourell, Monique C., Koebernick, Nicolai, Pileio, Giuseppe, Roose, Tiina
• Format: Journal Article
• Language: English
• Published: Lausanne Frontiers Research Foundation 25-05-2018; Frontiers Media S.A
• Subjects: 1H-MRI; Beads; Binding sites; Biological activity; Carbon; Cations; chia; Computed tomography; Corn; Correlation; Drought; Environmental science; Exudates; Exudation; Hydration; Immobilization; Magnetic resonance imaging; Medical imaging; Microbial activity; Microorganisms; Molecular weight; Mucilage; NMR; Nuclear magnetic resonance; Nutrient availability; Organic chemistry; Organic compounds; Plant roots; Polysaccharides; Porous materials; Porous media; Rhizosphere; root-exudate; Saccharides; Salvia columbariae; Sandy soils; Seeds; Soil water; Soils; Visualization; X-ray CT; United Kingdom > UK
• ISSN: 2296-665X; 2296-665X
• DOI: 10.3389/fenvs.2018.00032

Root exudates are a crucial component of the rhizosphere. Often, they take a form of a gel exuded by the plant roots and are thought to influence the soil aggregation, root penetration into soil, soil nutrient availability, immobilization of toxic cations and microbial activity amongst other things. In addition, the capacity of exudates to store water makes the plants potentially less susceptive to drought. Major components of root exudates are high molecular weight organic compounds consisting of predominantly polysaccharides and proteins, which makes it challenging to visualize using current rhizosphere visualization techniques, such as X-ray computed tomography (CT). In this contribution, we use correlative X-ray CT (resolution ~20 m) in combination with Magnetic Resonance Imaging (MRI, resolution ~120 m) to set up groundwork to enable in situ visualization of mucilage in soil. This multimodal approach is necessary because mucilage density closely matches that of water. We use chia seeds as mucilage analogue, because it has been found to have a similar consistency to root mucilage. Moreover, to understand mucilage development in time, a series of samples made by chia seeds placed in different porous media were prepared. Structurally and chemically, mucilage breaks down towards a water-like substance over a course of two weeks. Depending on its relative concentration, these changes were found to be less dominant when seeds were mixed in porous media. Having set up the groundwork for correlative imaging of chia seeds in water and an artificial soil (Nafion and sand/beads) this enables us to expand this imaging to deal with plant root exudates under natural conditions.