title: Void space inside the developing seed of Brassica napus and the modelling of its function.
abstract: The developing seed essentially relies on external oxygen to fuel aerobic respiration, but it is currently unknown how oxygen diffuses into and within the seed, which structural pathways are used and what finally limits gas exchange. By applying synchrotron X-ray computed tomography to developing oilseed rape seeds we uncovered void spaces, and analysed their three-dimensional assembly. Both the testa and the hypocotyl are well endowed with void space, but in the cotyledons, spaces were small and poorly inter-connected. In silico modelling revealed a three orders of magnitude range in oxygen diffusivity from tissue to tissue, and identified major barriers to gas exchange. The oxygen pool stored in the voids is consumed about once per minute. The function of the void space was related to the tissue-specific distribution of storage oils, storage protein and starch, as well as oxygen, water, sugars, amino acids and the level of respiratory activity, analysed using a combination of magnetic resonance imaging, specific oxygen sensors, laser micro-dissection, biochemical and histological methods. We conclude that the size and inter-connectivity of void spaces are major determinants of gas exchange potential, and locally affect the respiratory activity of a developing seed.
authors.affiliation: BIOSYST- MeBioS, Faculty of Bioscience Engineering, University of Leuven, W. de Croylaan 42, 3001, Leuven, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Verboven
authors.affiliation: BIOSYST- MeBioS, Faculty of Bioscience Engineering, University of Leuven, W. de Croylaan 42, 3001, Leuven, Belgium.
authors.forename: Els
authors.initials: E
authors.lastname: Herremans
authors.affiliation: Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466, Gatersleben, Germany.
authors.forename: Ljudmilla
authors.initials: L
authors.lastname: Borisjuk
authors.affiliation: IPS/ANKA, Karlsruhe Institute of Technology, PO Box 3640, 76021, Karlsruhe, Germany.|ESRF, 6 rue Jules Horowitz, BP220, 38043, Grenoble Cedex, France.
authors.forename: Lukas
authors.initials: L
authors.lastname: Helfen
authors.affiliation: BIOSYST- MeBioS, Faculty of Bioscience Engineering, University of Leuven, W. de Croylaan 42, 3001, Leuven, Belgium.
authors.forename: Quang Tri
authors.initials: QT
authors.lastname: Ho
authors.affiliation: Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466, Gatersleben, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Tschiersch
authors.affiliation: Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466, Gatersleben, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Fuchs
authors.affiliation: BIOSYST- MeBioS, Faculty of Bioscience Engineering, University of Leuven, W. de Croylaan 42, 3001, Leuven, Belgium.
authors.forename: Bart M
authors.initials: BM
authors.lastname: Nicolaï
authors.affiliation: Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466, Gatersleben, Germany.
authors.forename: Hardy
authors.initials: H
authors.lastname: Rolletschek
mesh_terms: D029688:Brassica napus / Q000196:embryology* / Q000648:ultrastructure; D002451:Cell Compartmentation; D019069:Cell Respiration; D003198:Computer Simulation; D004058:Diffusion; D005740:Gases / Q000378:metabolism; D018546:Hypocotyl / Q000648:ultrastructure; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism; D010938:Plant Oils / Q000378:metabolism; D016062:Porosity; D015203:Reproducibility of Results; D012639:Seeds / Q000196:embryology* / Q000648:ultrastructure; D055114:X-Ray Microtomography
chemical_list: D005740:Gases; D010938:Plant Oils; D010100:Oxygen
keywords: Brassica napus; gas exchange; mitochondrial respiration; oxygen diffusivity; synchrotron X-ray computed tomography