Journal Article

PreJuSER-58851

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Evidence for discontinuous water columns in the xylem conduit of tall birch trees

Westhoff, M. ; Zimmermann, D. ; Schneider, H.FZJ* ; Wegner, L. H. ; Geßner, P. ; Jakob, P. ; Bamberg, E. ; Shirley, S. ; Bentrup, F.-W. ; Zimmermann, U.

2009
Wiley-Blackwell - STM Oxford [u.a.] :Wiley- Blackwell

This record in other databases:      

Please use a persistent id in citations: doi:10.1111/j.1438-8677.2008.00124.x

Abstract: The continuity of the xylem water columns was studied on 17- to 23-m tall birch trees (trunk diameter about 23 cm; first branching above 10 m) all year round. Fifty-one trees were felled, and 5-cm thick slices or 2-m long boles were taken at regular, relatively short intervals over the entire height of the trees. The filling status of the vessels was determined by (i) xylem sap extraction from trunk and branch pieces (using the gas bubble-based jet-discharge method and centrifugation) and from trunk boles (using gravity discharge); (ii) (1)H nuclear magnetic resonance imaging of slice pieces; (iii) infusion experiments (dye, (86)Rb(+), D(2)O) on intact trees and cut branches; and (iv) xylem pressure measurements. This broad array of techniques disclosed no evidence for continuous water-filled columns, as postulated by the Cohesion-Tension theory, for root to apex directed mass transport. Except in early spring (during the xylem refilling phase) and after extremely heavy rainfall during the vegetation period, cohesive/mobile water was found predominantly at intermediate heights of the trunks but not at the base or towards the top of the tree. Similar results were obtained for branches. Furthermore, upper branches generally contained more cohesive/mobile water than lower branches. The results suggest that water lifting occurs by short-distance (capillary, osmotic and/or transpiration-bound) tension gradients as well as by mobilisation of water in the parenchymatic tissues and the heartwood, and by moisture uptake through lenticels.

Keyword(s): Betula: physiology (MeSH) ; Biological Transport: physiology (MeSH) ; Plant Roots: physiology (MeSH) ; Plant Stems: physiology (MeSH) ; Plant Transpiration: physiology (MeSH) ; Trees: physiology (MeSH) ; Water: physiology (MeSH) ; Xylem: physiology (MeSH) ; Water ; J ; Betula pendula (birch) (auto) ; Cohesion-Tension theory (auto) ; cohesive water (auto) ; H-1 NMR imaging (auto) ; mobile water (auto) ; pressure probe (auto) ; xylem sap extraction (auto) ; xylem water (auto)

Note: The authors are extremely grateful to the second mayor of the town of Rimpar, U. Haase and to the forester W. Pospichal for giving permission to fell a large number of tall birches in the forest of Rimpar. We would also like to thank very much our tree climbers P. Berecry and G. Fleischmann for professional tree felling, sample collection and rope-assisted lowering of the trees. Special thanks go to our numerous helpers in the field: W. Bauer, M. Behringer, A. Biegner, J. Endter, A. Gessner, F. Groeber, B. Hofmann, M. Kiesel, M. Kullik, C. Low, K. Muller, S. Nieft, L. Plie ss, K. Pfeffer, R. Reuss, M. Tarantola and G. Zimmermann. Sincere thanks are also given to K. Schwuchow and S. Nieft for excellent performance of some of the microscopic investigations and to A. Liebrich, O. Reichert and N. Spindler for their great help in evaluating the enormous bulk of data. This work was supported by grants from the BMBF to E.B. and U.Z. (0313369B).

---

Contributing Institute(s):

1. Phytosphäre (ICG-3)

Research Program(s):

1. Terrestrische Umwelt (P24)

Appears in the scientific report 2009

---