Document Detail


Frost drought in conifers at the alpine timberline: xylem dysfunction and adaptations.
MedLine Citation:
PMID:  17249241     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Drought stress can cause xylem embolism in trees when the water potential (psi) in the xylem falls below specific vulnerability thresholds. At the alpine timberline, frost drought is known to cause excessive winter embolism unless xylem vulnerability or transpiration is sufficiently reduced to avoid critical psi. We compared annual courses of psi and embolism in Picea abies, Pinus cembra, Pinus mugo, Larix decidua, and Juniperus communis growing at the timberline vs. low altitude. In addition, vulnerability properties and related anatomical parameters as well as wood density (D(t)) and wall reinforcement (wall thickness related to conduit diameter) were studied. This allowed an estimate of stress intensities as well as a detection of adaptations that reduce embolism formation. At the alpine timberline, psi was lowest during winter with corresponding embolism rates of up to 100% in three of the conifers studied. Only Pinus cembra and Larix decidua avoided winter embolism due to moderate psi. Minor embolism was observed at low altitude where the water potentials of all species remained within a narrow range throughout the year. Within species, differences in psi50 (psi at 50% loss of conductivity) at high vs. low altitude were less than 1 MPa. In Picea abies and Pinus cembra, psi50 was more negative at the timberline while, in the other conifer species, psi50 was more negative at low altitude. Juniperus communis exhibited the lowest (-6.4 +/- 0.04 MPa; mean +/- SE) and Pinus mugo the highest psi50 (-3.34 +/- 0.03 MPa). In some cases, D(t) and tracheid wall reinforcement were higher than in previously established relationships of these parameters with psi50, possibly because of mechanical demands associated with the specific growing conditions. Conifers growing at the alpine timberline were exposed to higher drought stress intensities than individuals at low altitude. Frost drought during winter caused high embolism rates which were probably amplified by freeze-thaw stress. Although frost drought had a large effect on plant water transport, adaptations in hydraulic safety and related anatomical parameters were observed in only a few of the conifer species studied.
Authors:
Stefan Mayr; Uwe Hacke; Peter Schmid; Franziska Schwienbacher; Andreas Gruber
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Ecology     Volume:  87     ISSN:  0012-9658     ISO Abbreviation:  Ecology     Publication Date:  2006 Dec 
Date Detail:
Created Date:  2007-01-25     Completed Date:  2007-02-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0043541     Medline TA:  Ecology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3175-85     Citation Subset:  IM    
Affiliation:
Institut für Botank, University Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria. stefan.mayr@uibk.ac.at
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological
Altitude*
Freezing
Juniperus / physiology*
Pinaceae / physiology*
Seasons
Water / physiology*
Xylem / physiology*
Chemical
Reg. No./Substance:
7732-18-5/Water

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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