Comparative Algal and Byrophyte Physiology
Gray, Dennis W. , Lewis, Louise A. , Cardon, Zoe G. .
Comparative physiology of desert crust algae and their aquatic relatives: exploring desiccation tolerance and photoprotection.
Recent molecular data suggest that desert green algae have evolved from freshwater ancestors at least 14 times in three major algal classes (Chlorophyceae, Trebouxiophyceae, and Charophyceae). These multiple independent origins offer a unique opportunity to study the adaptation of photosynthetic organisms to life on land in a comparative phylogenetic framework. We investigated the photorecovery of phylognetically matched desert and aquatic algae following desiccation in darkness and under illumination, and investigated differences in photoprotection exhibited by these same algae. Desert algae survived extended periods of desiccation (at least 4 weeks) when dried in darkness, and rapidly recovered high levels of photosynthetic quantum yield when rehydrated in the dark. However, when 4 weeks of desiccation was accompanied by illumination, half of the desert taxa lost their ability to recover quantum yield during rehydration in the dark. Aquatic algae, in contrast, recovered very little during dark rehydration following even just 24 hours of desiccation. Re-illuminating algae after they had been rehydrated produced a nearly complete recovery of quantum yield in all desert and two of five aquatic taxa. Examining the induction of non-photochemical quenching (a photoprotection mechanism) revealed marked differences in the ability of fully hydrated desert and aquatic algae to respond to short term changes in illumination and to acclimate to long term changes in illumination of the growth environment. These contrasts provide physiological evidence that desert green algae possess means of desiccation tolerance and photoprotection that are distinct from those in aquatic relatives, corroborating molecular evidence that they are not happenstance, short-term visitors from aquatic environments.
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1 - Utah State University, Plants, Soil, and Biometeorology, Crop physiology Laboratory, Logan, UT, 84322-4820, USA
2 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
3 - University of Connecticut, Ecology & Evolutionary Biology, Ecology and Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 4/Hilton
Date: Tuesday, July 10th, 2007
Time: 9:30 AM