Differential Photosynthetic Inhibition by UltraViolet Radiation in Species from the Arctic-Alpine Life Zone

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Abstract
Inhibition of photosynthesis and epidermal damage resulting from UV irradiation were assessed for arctic and alpine plant species. These species were taken from a latitudinal gradient of the arctic-alpine life zone from the Andes to northern Alaska [USA], which spans a steep change in solar UV-B irradiation (280-320 nm). Ecotypes and species from the Arctic, where solar UV-B flux is very low, were consistently more sensitive to UV radiation than their counterparts from lower latitude alpine regions, where solar UV-B flux is high. Most of the species did not display a change in UV-radiation sensitivity following a 2-wk pretreatment at elevated UV-B irradiance. The difference in photosynthetic inhibition caused by UV irradiation of arctic and alpine ecotypes of Oxyria digyna could not be attributed solely to differences in UV flux penetrating to mesophyll tissues. Further, arctic ecotypes exhibited short-term fluorescence transients indicating damage to the oxidizing side of Photosystem II in the photosynthetic light reaction, whereas there was no indication of this for alpine ecotypes. Thus, there apparently are inherent qualitative and quantitative differences in the UV-radiation sensitivity of photosynthetic systems in arctic and alpine ecotypes.