Document Detail

The light environment and cellular optics of the snow alga Chlamydomonas nivalis (Bauer) Wille.
MedLine Citation:
PMID:  11421066     Owner:  NLM     Status:  MEDLINE    
The alga Chlamydomonas nivalis lives in a high-light, cold environment: persistent alpine snowfields. Since the algae in snow receive light from all angles, the photon fluence rate is the critical parameter for photosynthesis, but it is rarely measured. We measured photon irradiance and photon fluence rate in the snow that contained blooms of C. nivalis. On a cloudless day the photon fluence rate at the snow surface was nearly twice the photon irradiance, and it can be many times greater than the photon irradiance when the solar angle is low or the light is diffuse. Beneath the surface the photon fluence rate can be five times the photon irradiance. Photon irradiance and photon fluence rate declined exponentially with depth, approximating the Bouguer-Lambert relationship. We used an integrating sphere to measure the spectral characteristics of a monolayer of cells and microscopic techniques to examine the spectral characteristics of individual cells. Astaxanthin blocked blue light and unknown absorbers blocked UV radiation; the penetration of these wavelengths through whole cells was negligible. We extracted astaxanthin, measured absorbance on a per-cell basis and estimated that the layer of astaxanthin within cells would allow only a small percentage of the blue light to reach the chloroplast, potentially protecting the chloroplast from excessive light.
H L Gorton; W E Williams; T C Vogelmann
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Photochemistry and photobiology     Volume:  73     ISSN:  0031-8655     ISO Abbreviation:  Photochem. Photobiol.     Publication Date:  2001 Jun 
Date Detail:
Created Date:  2001-06-25     Completed Date:  2001-07-26     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0376425     Medline TA:  Photochem Photobiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  611-20     Citation Subset:  IM    
Department of Biology, St. Mary's College of Maryland, 18952 E. Fisher Road, St. Mary's City, MD 20686-3001, USA.
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MeSH Terms
Chlamydomonas / metabolism,  radiation effects*
Chloroplasts / metabolism,  radiation effects
Optics and Photonics
beta Carotene / analogs & derivatives*,  metabolism,  radiation effects
Reg. No./Substance:
0/Xanthophylls; 472-61-7/astaxanthine; 7235-40-7/beta Carotene

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

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