title: Diurnal patterns in Scots pine stem oleoresin pressure in a boreal forest.
abstract: Coniferous tree stems contain large amounts of oleoresin under positive pressure in the resin ducts. Studies in North-American pines indicated that the stem oleoresin exudation pressure (OEP) correlates negatively with transpiration rate and soil water content. However, it is not known how the OEP changes affect the emissions of volatile vapours from the trees. We measured the OEP, xylem diameter changes indicating changes in xylem water potential and monoterpene emissions under field conditions in mature Scots pine (Pinus sylvestris L.) trees in southern Finland. Contrary to earlier reports, the diurnal OEP changes were positively correlated with temperature and transpiration rate. OEP was lowest at the top part of the stem, where water potentials were also more negative, and often closely linked to ambient temperature and stem monoterpene emissions. However, occasionally OEP was affected by sudden changes in vapour pressure deficit (VPD), indicating the importance of xylem water potential on OEP as well. We conclude that the oleoresin storage pools in tree stems are in a dynamic relationship with ambient temperature and xylem water potential, and that the canopy monoterpene emission rates may therefore be also regulated by whole tree processes and not only by the conditions prevailing in the upper canopy.
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Rissanen
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Hölttä
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Vanhatalo
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Aalto
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Nikinmaa
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Rita
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Bäck
mesh_terms: D002940:Circadian Rhythm; D002980:Climate; D008954:Models, Biological; D041605:Pinus sylvestris / Q000033:anatomy & histology / Q000502:physiology*; D010936:Plant Extracts / Q000378:metabolism*; D018547:Plant Stems / Q000502:physiology*; D011312:Pressure; D066188:Taiga; D013696:Temperature; D013729:Terpenes / Q000032:analysis; D055548:Vapor Pressure; D052584:Xylem / Q000033:anatomy & histology
chemical_list: D010936:Plant Extracts; D013729:Terpenes; C018620:oleoresins
keywords: Pinus sylvestris; monoterpene emissions; resin storage; temperature; water balance