Three-dimensional pore space quantification of apple tissue using X-ray computed microtomography

BIOSYST, MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, W. de Croylaan 42, 3001 Leuven, Belgium.
Planta (Impact Factor: 3.26). 08/2007; 226(3):559-70. DOI: 10.1007/s00425-007-0504-4
Source: PubMed


The microstructure and the connectivity of the pore space are important variables for better understanding of the complex gas transport phenomena that occur in plant tissues. In this study, we present an experimental procedure for image acquisition and image processing to quantitatively characterize in 3D the pore space of apple tissues (Malus domestica Borkh.) for two cultivars (Jonagold and Braeburn) taken from the fleshy part of the cortex using X-ray computer microtomography. Preliminary sensitivity analyses were performed to determine the effect of the resolution and the volume size (REV, representative elementary volume analysis) on the computed porosity of apple samples. For comparison among cultivars, geometrical properties such as porosity, specific surface area, number of disconnected pore volumes and their distribution parameters were extracted and analyzed in triplicate based on the 3D skeletonization of the pore space (medial axis analysis). The results showed that microtomography provides a resolution at the micrometer level to quantitatively analyze and characterize the 3D topology of the pore space in apple tissue. The computed porosity was confirmed to be highly dependent of the resolution used, and the minimum REV of the cortical flesh of apple fruit was estimated to be 1.3 mm(3). Comparisons among the two cultivars using a resolution of 8.5 mum with a minimum REV cube showed that in spite of the complexity and variability of the pore space network observed in Jonagold and Braeburn apples, the extracted parameters from the medial axis were significantly different (P-value < 0.05). Medial axis parameters showed potential to differentiate the microstructure between the two evaluated apple cultivars.

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Available from: Fernando A Mendoza, Sep 09, 2014
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    • "New tomographic imaging methods enable a thorough update of the blueprints of these long known transport pathways and how they develop during fruit growth. X-ray micro-Computed Tomography (µCT) has been employed to visualize and characterize voids in a variety of fleshy fruit tissue samples such as cucumber (Kuroki et al., 2004), pome fruit (Mendoza et al., 2007; Verboven et al., 2008), mango (Cantre et al., 2014b), and kiwi (Cantre et al., 2014a). X-ray µCT is likely the most appropriate technique to study voids in 3D as it provides a relatively large contrast between air and cells even for high resolutions (as low as 1 µm and beyond). "
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    ABSTRACT: The void network and vascular system are important pathways for the transport of gases, water and solutes in apple fruit (Malus × domestica Borkh). Here we used X-ray micro-tomography at various spatial resolutions to investigate the growth of these transport structures in 3D during fruit development of "Jonagold" apple. The size of the void space and porosity in the cortex tissue increased considerably. In the core tissue, the porosity was consistently lower, and seemed to decrease toward the end of the maturation period. The voids in the core were more narrow and fragmented than the voids in the cortex. Both the void network in the core and in the cortex changed significantly in terms of void morphology. An automated segmentation protocol underestimated the total vasculature length by 9-12% in comparison to manually processed images. Vascular networks increased in length from a total of 5 m at 9 weeks after full bloom, to more than 20 m corresponding to 5 cm of vascular tissue per cubic centimeter of apple tissue. A high degree of branching in both the void network and vascular system and a complex three-dimensional pattern was observed across the whole fruit. The 3D visualizations of the transport structures may be useful for numerical modeling of organ growth and transport processes in fruit.
    Frontiers in Plant Science 09/2015; 6:679. DOI:10.3389/fpls.2015.00679 · 3.95 Impact Factor
    • "The measurement method is another factor: X-Ray microtomography values depend on the measurement protocol. The microporosity varied between 19% and 29% in parenchyma tissue of Jonagold apples depending on the image resolution and representative elementary volume used for the analysis [39]. Similar variations can be expected for MRI since the apparent microporosity depends on the main magnetic field strength [18]. "
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    ABSTRACT: Water status and distribution at subcellular level in whole apple fruit were evaluated by Magnetic Resonance Imaging (MRI) measurement of the multi-exponential transverse (T2) relaxation of water protons. Apparent microporosity, also estimated by MRI, provided mapping of gas distribution in fruit tissues. Measuring for the first time the multi-exponential relaxation of water and apparent tissue microporosity in whole fruit and combining these with histological measurements provided a more reliable interpretation of the origins of variations in the transverse relaxation time (T2) and better characterization of the fruit tissue. Measurements were performed on 54 fruit from 3 different cultivars. Fruit of different sizes were selected for each cultivar to provide tissues with cells of different dimensions. Macrovision measurements were carried out on parenchymal tissue from all fruit to investigate the impact of cell morphology and cell size of all samples on T2 value. The results showed that the MRI transverse relaxation signal is well fitted by a tri-exponential decay curve that reflects cell compartmentalization. Variations in cell size partially explained the different T2 observed. This study highlighted the heterogeneity of apple tissues in terms of relaxation parameters, apparent microporosity and cell morphology and in relation to specific variations between fruit of different cultivars. Copyright © 2015 Elsevier Inc. All rights reserved.
    Magnetic Resonance Imaging 02/2015; 33(5). DOI:10.1016/j.mri.2015.02.014 · 2.09 Impact Factor
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    • "Biol. (2014), cated software now available for the tomographic reconstructions and interpretations (Mendoza et al., 2007; Verboven et al., 2012, 2013). "
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    ABSTRACT: Floods can completely submerge terrestrial plants but some wetland species can sustain O2 and CO2 exchange with the environment via gas films forming on superhydrophobic leaf surfaces. We used high resolution synchrotron X-ray phase contrast micro-tomography in a novel approach to visualise gas films on submerged leaves of common cordgrass (Spartina anglica). 3D tomograms enabled a hitherto unmatched level of detail regarding the micro-topography of leaf gas films. Gas films formed only on the superhydrophobic adaxial leaf side (water droplet contact angle, Φ = 162°) but not on the abaxial side (Φ = 135°). The adaxial side of the leaves of common cordgrass is plicate with a longitudinal system of parallel grooves and ridges and the vast majority of the gas film volume was found in large ∼180 μm deep elongated triangular volumes in the grooves and these volumes were connected to each neighbouring groove via a fine network of gas tubules (∼1.7 μm diameter) across the ridges. In addition to the gas film retained on the leaf exterior, the X-ray phase contrast micro-tomography also successfully distinguished gas spaces internally in the leaf tissues, and the tissue porosity (gas volume per unit tissue volume) ranged from 6.3 to 20.3% in tip and base leaf segments, respectively. We conclude that X-ray phase contrast micro-tomography is a powerful tool to obtain quantitative data of exterior gas features on biological samples because of the significant difference in electron density between air, biological tissues and water.
    Journal of Structural Biology 10/2014; 188(1). DOI:10.1016/j.jsb.2014.08.003 · 3.23 Impact Factor
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