title: Plant pneumatics: stem air flow is related to embolism - new perspectives on methods in plant hydraulics.
abstract: Wood contains a large amount of air, even in functional xylem. Air embolisms in the xylem affect water transport and can determine plant growth and survival. Embolisms are usually estimated with laborious hydraulic methods, which can be prone to several artefacts. Here, we describe a new method for estimating embolisms that is based on air flow measurements of entire branches. To calculate the amount of air flowing out of the branch, a vacuum was applied to the cut bases of branches under different water potentials. We first investigated the source of air by determining whether it came from inside or outside the branch. Second, we compared embolism curves according to air flow or hydraulic measurements in 15 vessel- and tracheid-bearing species to test the hypothesis that the air flow is related to embolism. Air flow came almost exclusively from air inside the branch during the 2.5-min measurements and was strongly related to embolism. We propose a new embolism measurement method that is simple, effective, rapid and inexpensive, and that allows several measurements on the same branch, thus opening up new possibilities for studying plant hydraulics.
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Luciano
authors.initials: L
authors.lastname: Pereira
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Paulo R L
authors.initials: PR
authors.lastname: Bittencourt
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Rafael S
authors.initials: RS
authors.lastname: Oliveira
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Mauro B M
authors.initials: MB
authors.lastname: Junior
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Fernanda V
authors.initials: FV
authors.lastname: Barros
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Rafael V
authors.initials: RV
authors.lastname: Ribeiro
authors.affiliation: Department of Plant Biology, Institute of Biology, PO Box 6109, University of Campinas - UNICAMP, 13083-970, Campinas, SP, Brazil.
authors.forename: Paulo
authors.initials: P
authors.lastname: Mazzafera
mesh_terms: D000388:Air / Q000032:analysis*; D001703:Biophysics / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D018547:Plant Stems / Q000737:chemistry / Q000502:physiology*; D014867:Water; D052584:Xylem / Q000502:physiology
chemical_list: D014867:Water
keywords: cavitation; drought; plant hydraulics; water transport; xylem