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Intact plant MRI for the study of cell water relations, membrane permeability, cell-to-cell and long distance water transport. J Exp Bot

Laboratory of Biophysics and Wageningen NMR Centre, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
Journal of Experimental Botany (Impact Factor: 5.79). 02/2007; 58(4):743-56. DOI: 10.1093/jxb/erl157
Source: PubMed

ABSTRACT Water content and hydraulic conductivity, including transport within cells, over membranes, cell-to-cell, and long-distance xylem and phloem transport, are strongly affected by plant water stress. By being able to measure these transport processes non-invasely in the intact plant situation in relation to the plant (cell) water balance, it will be possible explicitly or implicitly to examine many aspects of plant function, plant performance, and stress responses. Nuclear magnetic resonance imaging (MRI) techniques are now available that allow studying plant hydraulics on different length scales within intact plants. The information within MRI images can be manipulated in such a way that cell compartment size, water membrane permeability, water cell-to-cell transport, and xylem and phloem flow hydraulics are obtained in addition to anatomical information. These techniques are non-destructive and non-invasive and can be used to study the dynamics of plant water relations and water transport, for example, as a function of environmental (stress) conditions. An overview of NMR and MRI methods to measure such information is presented and hardware solutions for minimal invasive intact plant MRI are discussed.

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    • "Several research works on molecular transport have been carried out at the stem and root plants levels [9] [10]. To our knowledge, few publications have been devoted to investigate the water transport and distribution within the fruit [11] [12] [13]. The purpose of the present study was the implementation of a methodology for quantitative measurements using NMR imaging combined with efficient and biocompatible CA dedicated to study the physiological changes related to water movement within the fruit. "
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    ABSTRACT: Non destructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a non-invasive technique providing physiological and morphological information on biological tissues. The aim of this study was to design a robust and accurate quantitative measurement method based on NMR imaging combined with contrast agent (CA) for mapping and quantifying water transport in growing cherry tomato fruits. A multiple flip-angle Spoiled Gradient Echo (SGE) imaging sequence was used to evaluate the intrinsic parameters maps M0 and T1 of the fruit tissues. Water transport and paths flow were monitored using Gd3 +/[Fe(CN)6]3 −/D − mannitol nanoparticles as a tracer. This dynamic study was carried out using a compartmental modeling. The CA was preferentially accumulated in the surrounding tissues of columella and in the seed envelopes. The total quantities and the average volumeflow of water estimated are : 198 mg, 1.76 mm3/h for the columella and 326 mg, 2.91 mm3/h for the seed envelopes. We demonstrate in this paper that the NMR imaging technique coupled with efficient and biocompatible CA in physiological medium has the potential to become a major tool in plant physiology research.
    Journal of Magnetic Resonance Imaging 08/2014; 32(10):1418-1427. DOI:10.1016/j.mri.2014.08.005 · 2.79 Impact Factor
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    • "Scheenen et al . 2001 ; Van As 2007 ) was obtained for every pixel in an image . From these single pixel propagators , the following flow character - istics were extracted for each volume element in the image , as described by Scheenen et al . "
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    ABSTRACT: Anoxic conditions should hamper the transport of sugar in the phloem, since this is an active process. The canopy is a carbohydrate source and the roots are carbohydrate sinks. By fumigating the shoot with N2 or flooding the rhizosphere, anoxic conditions in the source or sink, respectively, were induced. Volume flow, velocity, conducting area and stationary water of the phloem were assessed by non-invasive MRI-flowmetry. Carbohydrates and δ13C in leaves, roots and in phloem saps were determined.Following flooding, volume flow and conducting area of the phloem declined and sugar concentrations in leaves and in phloem saps slightly increased. Oligosaccharides appeared in phloem saps and after three days carbon transport was reduced to 77%. Additionally, the xylem flow declined and showed finally no daily rhythm. Anoxia of the shoot resulted within minutes in a reduction of volume flow, conductive area and sucrose in the phloem sap decreased. Sugar transport dropped to below 40% by the end of the N2-treatment. However, volume flow and phloem sap sugar tended to recover during the N2-treatment.Both anoxia treatments hampered sugar transport. The flow velocity remained about constant, although phloem sap sugar concentration changed during treatments. Apparently, stored starch was remobilized under anoxia.
    Plant Cell and Environment 07/2014; DOI:10.1111/pce.12399 · 5.91 Impact Factor
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    • "Conventionally, to examine xylem sap transport and functional water flow pathways, an aqueous dye such as fuchsin or safranin was injected into xylem vessels and the dyed vessels were traced at the height above the dye injection as the water-conducting pathway (Harris 1961, Sano et al. 2005, Umebayashi et al. 2007). As a non-destructive imaging method, nuclear magnetic resonance (NMR) can be employed to visualize xylem in intact samples with a spatial resolution of around 20 mm (Wistuba et al. 2000, Holbrook et al. 2001, Scheenen et al. 2007, Van As 2007). However, because the relatively low spatial resolution of these methods precludes visualization of water flow in individual xylem vessels (Kim et al. 2014), a more realistic view of the hydraulic map that takes the spatial arrangement of individual vessels in the xylem network into account (Holbrook and Zwieniecki 2005) is essential for understanding water transport. "
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    ABSTRACT: In vascular plants, the xylem network constitutes a complex microfluidic system. The relationship between vascular network architecture and functional hydraulic regulation during actual water flow remains unexplored. Here, we developed a method to visualize individual xylem vessels of the three-dimensional xylem network of Arabidopsis thaliana, and to analyze the functional activities of these vessels using synchrotron X-ray computed tomography with hydrophilic gold nanoparticles as flow tracers. We show how the organization of the xylem network changes dynamically throughout the plant, and reveal how the elementary units of this transport system are organized to ensure both long-distance axial water transport and local lateral water transport. Xylem vessels form distinct clusters that operate as functional units and the activity of these units, which determines water flow pathways, is modulated by varying not only the number and size of xylem vessels, but also by altering their interconnectivity and spatial arrangement. Based on these findings, we propose a regulatory model of water transport that ensures hydraulic efficiency and safety. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
    Plant and Cell Physiology 03/2014; 56(3). DOI:10.1093/pcp/pcu198 · 4.98 Impact Factor
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