title: Phloem flow and sugar transport in Ricinus communis L. is inhibited under anoxic conditions of shoot or roots.
abstract: Anoxic conditions should hamper the transport of sugar in the phloem, as 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 magnetic resonance imaging (MRI) flowmetry. Carbohydrates and δ(13) C in leaves, roots and 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 3 d, 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.
authors.affiliation: ADP International Plant Science Consulting, Talstraße 8, Gundelfingen, D-79194, Germany; Institute for Landscape Biogeochemistry, Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V., Eberswalderstr. 84, Müncheberg, 15374, Germany.
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Peuke
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.forename: Susan
authors.initials: S
authors.lastname: Trumbore
authors.forename: Carel W
authors.initials: CW
authors.lastname: Windt
authors.forename: Natalia
authors.initials: N
authors.lastname: Homan
authors.forename: Edo
authors.initials: E
authors.lastname: Gerkema
authors.forename: Henk
authors.initials: H
authors.lastname: VAN As
mesh_terms: D001692:Biological Transport; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D002367:Ricinus communis / Q000187:drug effects / Q000378:metabolism*; D009584:Nitrogen / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D052585:Phloem / Q000187:drug effects / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D013213:Starch / Q000378:metabolism; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000187:drug effects / Q000378:metabolism
chemical_list: D014867:Water; D002244:Carbon; D013213:Starch; D009584:Nitrogen; D010100:Oxygen
keywords: Ricinus; carbohydrates; flooding; isotopic signature; phloem; xylem