DNA damage and photosynthesis in Prasiola crispa ssp antarctica and Sanionia uncinata in response to manipulated UV-B radiation

The terrestrial vegetation in the Antarctic Peninsula region has a higher diversity than elsewhere in Antarctica. However, the vegetation in this region is regularly under the influence of strong seasonal ozone depletion during spring and early summer. We investigated DNA damage and photosynthesis in response to short-term fluctuations of UV-B radiation in two cryptogam species. Samples of the terrestrial alga P. crispa ssp. antarctica and the moss Sanionia uncinata were exposed outdoors to reduced, ambient and enhanced levels of UV-B radiation at Rothera Research Station in January 1999 and 2000. PSII efficiency, net photosynthesis (NP) and dark respiration (DR) remained largely unaffected by UV-treatment. DNA damage measured as cyclobutane pyrimidine dimer, CPD, formation increased significantly due to UV-B exposure whereas no effect on photosynthesis could be established. We conclude that DNA damage is more sensitive to UV-B radiation than photosynthesis. There was no clear linear relationship between DNA damage levels and cumulative weighted UV-B dose in the species investigated. Together with the considerable variation in DNA damage levels this indicated that the CPD levels measured resulted from a combination of damage and repair processes.