title: Testing the Münch hypothesis of long distance phloem transport in plants.
abstract: Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, United States.
authors.forename: Michael
authors.identifier: 0000-0003-0391-9891
authors.initials: M
authors.lastname: Knoblauch
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, United States.|Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.
authors.forename: Jan
authors.initials: J
authors.lastname: Knoblauch
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, United States.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Mullendore
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.|Arnold Arboretum of Harvard University, Boston, United States.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Savage
authors.affiliation: Department of Biosciences, Brookhaven National Laboratory, Upton, New York.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Babst
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, United States.
authors.forename: Sierra D
authors.initials: SD
authors.lastname: Beecher
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, United States.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Dodgen
authors.affiliation: Department of Physics, Technical University of Denmark, Lyngby, Denmark.
authors.forename: Kaare H
authors.initials: KH
authors.lastname: Jensen
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.
authors.forename: N Michele
authors.initials: NM
authors.lastname: Holbrook
mesh_terms: D001692:Biological Transport; D049915:Ipomoea nil / Q000254:growth & development / Q000378:metabolism*; D009997:Osmotic Pressure; D052585:Phloem / Q000378:metabolism*
keywords: Münch; long distance transport; morning glory; phloem; plant biology; pressure flow hypothesis; sieve element