Cyclic environmental factors only partially explain the seasonal variability of photoprotection and physiology in two mosses from an unforested headwater stream
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Universidad de La Rioja
info
ISSN: 0007-2745
Año de publicación: 2010
Volumen: 113
Número: 2
Páginas: 277-291
Tipo: Artículo
Otras publicaciones en: Bryologist
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Resumen
We studied the relationships between environmental variables and the physiology of two (semi-)aquatic mosses (Bryum pseudotriquetrum and Fontinalis antipyretica) in an unforested headwater stream over a three year period. Neither environmental or physiological variables showed significant interannual variations. Most environmental variables (water temperature, stratospheric ozone, and photosynthetic, UV-A and UV-B radiation) showed distinct seasonal variations, but only a few physiological ones did. In both species, photoprotection variables (the activity of the xanthophyll cycle and the bulk UV absorbance of the methanol-extractable UV-absorbing compounds, MEUVAC) varied more seasonally than variables related to physiological activity, such as the sclerophylly index and chlorophyll fluorescence parameters (Fv/F m and ΦPSII). Changes in physiological activity would be attenuated by the buffering capacity of water with respect to the influence of environmental factors, and dynamic variables like Fv/Fm and ΦPSII would be little determined by cyclic environmental factors. In B. pseudotriquetrum, both MEUVAC and kaempferol 3,7-O-diglycoside (a potentially UV-protective flavonoid) were positively associated with radiation levels, whereas in F. antipyretica photoprotection mechanisms were not correlated with any environmental variable. In addition, MEUVAC was 3-4 fold higher in B. pseudotriquetrum than in F. antipyretica. Thus, different photoprotection mechanisms, with a different environmental regulation, can be suggested for these two species. DNA damage was not found in any sample, probably because both species displayed efficient DNA repair mechanisms. © 2010 The American Bryological and Lichenological Society, Inc.