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  • 1
    Book
    Book
    Universitäts- und Landesbibliothek Sachsen-Anhalt
    Language: English
    Description: Die Wasseraufnahme von Pflanzenwurzeln wird durch die Wurzelarchitektur, dieVerteilung von Wurzeln im Boden, bestimmt. Die vorliegende Arbeit präsentiert neue Erkenntnisse über die Quantifizierung der Wurzelarchitektur mit Hilfe von Röntgen-Computertomographie(CT). Die Kombination von klassischen Gefäßexperimenten, CT Bildgebung und numerischer Modellierung ermöglicht die Untersuchung der räumlichen und zeitlichen Dynamik des Wasserhaushalts von Boden und Pflanze. Numerische Simulationen der Wasseraufnahme virtueller Wurzelsysteme, die auf CT Daten basieren, können die experimentell gemessene Dynamik des Bodenmatrixpotentials erfolgreich wiedergeben. Die Wurzelwasseraufnahme kann dabei nicht mit der gemessenen Veränderung des lokalen Wassergehalts gleichgesetzt werden, da es signifikante hydraulische Umverteilung im Boden gibt. Es wird gezeigt, dass die Heterogenität der Bodenfeuchte einen erheblichen Einfluss auf die Entwicklung des simulierten Pflanzenwasserpotentials hat. Eine bedeutende Folge von Trockenstress ist die Schrumpfung der Wurzeln und die Abnahme des Kontaktes zwischen Boden und Wurzel.... ; Water uptake by plant roots is determined by root system architecture, the distribution of roots in soil. This thesis presents novel insights into the quantification of root system architecture with X-ray computed tomography (CT). The combination of classic pot experiments, CT imaging and numerical modelling enables the investigation of the spatial and temporal hydrodynamics of soil and plants. Numerical simulations of water uptake by virtual root systems based on CT data can successfully reproduce the experimentally measured dynamics of soil matric potential. Root water uptake must not be equated with the measured change of local water content because there is significant hydraulic redistribution within the soil. It is shown that the heterogeneity of soil moisture content has a strong impact on the development of the simulated plant water potential. An important consequence of drought stress is the shrinkage of roots and the reduction of contact between roots and soil....
    Keywords: Wurzelarchitektur; Rhizosphäre; Röntgen-Computertomographie; Wurzelwasseraufnahme; Viciafaba; Wurzelwachstum; Wurzel-Boden-Interaktionen ; Root System Architecture; Rhizosphere; X-Ray Ct; Root Water Uptake; Viciafaba; Root Growth; Root-Soil Interactions ; Ddc::600 Technik, Medizin, Angewandte Wissenschaften::630 Landwirtschaft::630 Landwirtschaft Und Verwandte Bereiche
    Source: DataCite
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  • 2
    Language: English
    In: Plant and Soil, 2018, Vol.431(1), pp.417-431
    Description: Aims Root shrinkage in drying soil has been shown repeatedly. The aim of this study was to investigate the dynamics of root-soil contact and its relationship with plant water status during soil drying. Methods The development of root-soil contact of Vicia faba L. during a drying period was studied. Plants (N = 4) were grown in cylinders filled with a sandy soil. Samples were repeatedly scanned with an X-ray CT scanner to visualize root-soil contact. Soil matric potential, transpiration rate, and stomatal conductance were measured daily. Results Root-soil contact was lower in taproots than in lateral roots at any time. Transpiration rate and stomatal conductance decreased before roots started to shrink. Root-soil contact decreased significantly over the course of the drying period, starting at soil matric potentials below -20 kPa. Root shrinkage did not differ significantly between taproots and laterals. Conclusions This study confirms previous findings with Lupinus albus roots in that roots shrink after transpiration rate decreases. The dynamics of root shrinkage are governed by soil water availability and transpirational demand.
    Keywords: Root-soil contact ; X-ray CT ; Rhizosphere ; Drought stress ; Root shrinkage
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    Language: English
    In: Frontiers in Environmental Science, May 25, 2018
    Description: 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 μm) in combination with Magnetic Resonance Imaging (MRI, resolution ~120 μm) 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 analog, 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 toward a water-like substance over a course of 2 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.
    Keywords: Soil Structure ; Magnetic Resonance Imaging ; Cat Scans
    ISSN: 2296-665X
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  • 4
    In: New Phytologist, October 2017, Vol.216(1), pp.124-135
    Description: In this paper, we provide direct evidence of the importance of root hairs on pore structure development at the root–soil interface during the early stage of crop establishment. This was achieved by use of high‐resolution (c. 5 μm) synchrotron radiation computed tomography (SRCT) to visualise both the structure of root hairs and the soil pore structure in plant–soil microcosms. Two contrasting genotypes of barley (Hordeum vulgare), with and without root hairs, were grown for 8 d in microcosms packed with sandy loam soil at 1.2 g cm−3 dry bulk density. Root hairs were visualised within air‐filled pore spaces, but not in the fine‐textured soil regions. We found that the genotype with root hairs significantly altered the porosity and connectivity of the detectable pore space (〉 5 μm) in the rhizosphere, as compared with the no‐hair mutants. Both genotypes showed decreasing pore space between 0.8 and 0.1 mm from the root surface. Interestingly the root‐hair‐bearing genotype had a significantly greater soil pore volume‐fraction at the root–soil interface. Effects of pore structure on diffusion and permeability were estimated to be functionally insignificant under saturated conditions when simulated using image‐based modelling.
    Keywords: Hordeum Vulgare ; Image‐Based Modelling ; Noninvasive Imaging ; Rhizosphere ; Root Hairs ; Soil Structure ; Synchrotron
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 5
    Language: English
    In: Frontiers in plant science, 2015, Vol.6, pp.370
    Description: Split root experiments have the potential to disentangle water transport in roots and soil, enabling the investigation of the water uptake pattern of a root system. Interpretation of the experimental data assumes that water flow between the split soil compartments does not occur. Another approach to investigate root water uptake is by numerical simulations combining soil and root water flow depending on the parameterization and description of the root system. Our aim is to demonstrate the synergisms that emerge from combining split root experiments with simulations. We show how growing root architectures derived from temporally repeated X-ray CT scanning can be implemented in numerical soil-plant models. Faba beans were grown with and without split layers and exposed to a single drought period during which plant and soil water status were measured. Root architectures were reconstructed from CT scans and used in the model R-SWMS (root-soil water movement and solute transport) to simulate water potentials in soil and roots in 3D as well as water uptake by growing roots in different depths. CT scans revealed that root development was considerably lower with split layers compared to without. This coincided with a reduction of transpiration, stomatal conductance and shoot growth. Simulated predawn water potentials were lower in the presence of split layers. Simulations showed that this was related to an increased resistance to vertical water flow in the soil by the split layers. Comparison between measured and simulated soil water potentials proved that the split layers were not perfectly isolating and that redistribution of water from the lower, wetter compartments to the drier upper compartments took place, thus water losses were not equal to the root water uptake from those compartments. Still, the layers increased the resistance to vertical flow which resulted in lower simulated collar water potentials that led to reduced stomatal conductance and growth.
    Keywords: R-Swms ; Vicia Faba ; Plant Root Growth ; Root Water Uptake ; Split-Root
    ISSN: 1664-462X
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  • 6
    Language: English
    In: Vadose Zone Journal, 2014, Vol.13(8), p.0
    Description: Root system architecture and associated root–soil interactions exhibit large changes over time. Nondestructive methods for the quantification of root systems and their temporal development are needed to improve our understanding of root activity in natural soils. X-ray computed tomography (X-ray CT) was used to visualize and quantify growth of a single Vicia faba L. root system during a drying period. The plant was grown under controlled conditions in a sandy soil mixture and imaged every second day. Minkowski functionals and Euclidean distance transform were used to quantify root architectural traits. We were able to image the root system with water content decreasing from 29.6 to 6.75%. Root length was slightly underestimated compared with destructive measurements. Based on repeated measurements over time it was possible to quantify the dynamics of root growth and the demography of roots along soil depth. Measurement of Euclidean distances from any point within the soil to the nearest root surface yielded a frequency distribution of travel distances for water and nutrients towards roots. Our results demonstrate that a meaningful quantitative characterization of root systems and their temporal dynamics is possible.
    Keywords: Agriculture;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
    Source: CrossRef
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  • 7
    Description: These are 3D synchrotron X-ray computed tomography data, showing plant roots ingressing different soils. There are three compressed folders, with the contents representing individual image steps of the different samples. Each sample was imaged 8 times across time, at 6-minute intervals, producing a time-lapse sequence.Data is available on request via http://library.soton.ac.uk/datarequest...
    Source: DataCite
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  • 8
    Description: Data set for The effect of root exudates on rhizosphere water dynamics, published in the Proceedings of the Royal Society A in 2018....
    Source: DataCite
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  • 9
    Language: English
    Description: copy abstract from ePrints including any note on access restriction Dataset supports: Koebernick, N.et al (2017). High-resolution synchrotron imaging shows that root hairs influence rhizosphere soil structure formation. New Phytologist....
    Keywords: Bioengineering Group
    Source: DataCite
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  • 10
    In: New Phytologist, March 2019, Vol.221(4), pp.1878-1889
    Description: Soil adjacent to roots has distinct structural and physical properties from bulk soil, affecting water and solute acquisition by plants. Detailed knowledge on how root activity and traits such as root hairs affect the three‐dimensional pore structure at a fine scale is scarce and often contradictory. Roots of hairless barley (Hordeum vulgare L. cv Optic) mutant (NRH) and its wildtype (WT) parent were grown in tubes of sieved (〈250 μm) sandy loam soil under two different water regimes. The tubes were scanned by synchrotron‐based X‐ray computed tomography to visualise pore structure at the soil–root interface. Pore volume fraction and pore size distribution were analysed vs distance within 1 mm of the root surface. Less dense packing of particles at the root surface was hypothesised to cause the observed increased pore volume fraction immediately next to the epidermis. The pore size distribution was narrower due to a decreased fraction of larger pores. There were no statistically significant differences in pore structure between genotypes or moisture conditions. A model is proposed that describes the variation in porosity near roots taking into account soil compaction and the surface effect at the root surface.
    Keywords: Hordeum Vulgare ; Noninvasive Imaging ; Particle Packing ; Rhizosphere ; Root Hairs ; Soil Structure ; Synchrotron
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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