Document Detail

Photosynthesis, chlorophyll fluorescence and spectral reflectance in Sphagnum moss at varying water contents.
MedLine Citation:
PMID:  17406904     Owner:  NLM     Status:  MEDLINE    
Moss samples from the Fluxnet-Canada western peatland flux station in the Boreal Region of Alberta were measured in the laboratory to obtain the net photosynthesis rate and chlorophyll fluorescence of the moss under controlled environmental conditions, including the regulation of moss water content, simultaneously with measurements of moss spectral reflectance. One objective was to test whether the photochemical reflectance index (PRI) detected changes in moss photosynthetic light-use efficiency that were consistent with short-term (minutes to hours) changes in xanthophyll cycle pigments and associated changes in non-photochemical quenching (NPQ), as recorded by chlorophyll fluorescence. The rate of net photosynthesis was strongly inhibited by water content at values exceeding approximately 9 (fresh weight/dry weight) and declined as the water content fell below values of approximately 8. Chlorophyll fluorescence measurements of maximum photosystem II efficiency generally remained high until the water content was reduced from the maximum of about 20 to values of approximately 10-11, and then declined with further reductions in moss water content. A significant linear decline in NPQ was observed as moss water content was reduced from maximum to low water content values. There was a strong negative correlation between changes in NPQ and PRI. These data suggest that PRI measurements are a good proxy for short-term shifts in photosynthetic activity in Sphagnum moss. A second objective was to test how accurately the water band index (WBI, ratio of reflectance at 900 and 970 nm) recorded changes in moss water content during controlled laboratory studies. Strong linear relationships occurred between changes in moss water content and the WBI, although the slopes of the linear relationships were significantly different among sample replicates. Therefore, WBI appeared to be a useful tool to determine sample-specific water content without destructive measurements.
K Eric Van Gaalen; Lawrence B Flanagan; Derek R Peddle
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-04-04
Journal Detail:
Title:  Oecologia     Volume:  153     ISSN:  0029-8549     ISO Abbreviation:  Oecologia     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-07-19     Completed Date:  2007-09-05     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  19-28     Citation Subset:  IM    
Department of Biological Sciences, University of Lethbridge, 4401 University Drive West, Lethbridge, AB, Canada T1K 3M4.
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MeSH Terms
Chlorophyll / metabolism*
Photosynthesis / physiology*
Sphagnopsida / metabolism*
Water / metabolism*
Reg. No./Substance:
1406-65-1/Chlorophyll; 7732-18-5/Water

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

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