TY - JOUR
T1 - Improved UV-B screening capacity does not prevent negative effects of ambient UV irradiance on PSII performance in High Arctic plants. Results from a six year UV exclusion study
AU - Albert, Kristian R
AU - Mikkelsen, Teis N.
AU - Ro-Poulsen, Helge
AU - Michelsen, Anders
AU - Arndal, Marie F
AU - Bredahl, Linda
AU - Håkansson, Kirsten Birch
AU - Boesgaard, Kristine
AU - Schmidt, Niels Martin
N1 - Copyright © 2010 Elsevier GmbH. All rights reserved.
PY - 2010/12/15
Y1 - 2010/12/15
N2 - Long-term responses of ambient solar ultraviolet (UV) radiation were investigated on Salix arctica and Vaccinium uliginosum in a High Arctic heath ecosystem in Zackenberg, northeast Greenland. Over a period of six years, UV exclusion was conducted in the growing season by means of filters: 60% UV-B reduction, 90% UV-B+UV-A reduction, UV transparent filter control, and an open control without filter. Plant responses were evaluated using specific leaf area, leaf content of UV-B absorbing compounds and PSII performance parameters derived from chlorophyll-a fluorescence induction curves. Based on the JIP-test, we calculated the total performance index PI(total), which includes the integrating antennae, the PSII reaction center, intersystem electron transport and reduction of PSI end acceptors-dependent parameters. In both species, UV exclusion significantly decreased the content of UV-B-absorbing compounds. Salix increased its specific leaf area, while Vaccinium decreased it. UV exclusion increased the PI(total) in both species during all six years of experimentation. This response was governed by a significantly decreased RC/ABS, a marginally non-significant increased ET(o)/TR(o) and a significantly increased TR(o)/ABS=F(V)/F(M) and RE(o)/ET(o). These results demonstrate the current level of ambient UV-B to decrease PSII performance significantly in these High Arctic plants. It appears that the two plant species both have improved their UV-screening capacity, but through different strategies, although this did not sufficiently prevent negative effects of the ambient UV radiation. We argue the decreased PSII performance to be part of a response decreasing plant carbon uptake. We speculate the negative effects on PSII performance mediated by ambient UV irradiance to be present in years where warming induces early snowmelt, exposing the vegetation to high spring UV-B, and to be present in the future to the degree the ozone layer is not fully recovered.
AB - Long-term responses of ambient solar ultraviolet (UV) radiation were investigated on Salix arctica and Vaccinium uliginosum in a High Arctic heath ecosystem in Zackenberg, northeast Greenland. Over a period of six years, UV exclusion was conducted in the growing season by means of filters: 60% UV-B reduction, 90% UV-B+UV-A reduction, UV transparent filter control, and an open control without filter. Plant responses were evaluated using specific leaf area, leaf content of UV-B absorbing compounds and PSII performance parameters derived from chlorophyll-a fluorescence induction curves. Based on the JIP-test, we calculated the total performance index PI(total), which includes the integrating antennae, the PSII reaction center, intersystem electron transport and reduction of PSI end acceptors-dependent parameters. In both species, UV exclusion significantly decreased the content of UV-B-absorbing compounds. Salix increased its specific leaf area, while Vaccinium decreased it. UV exclusion increased the PI(total) in both species during all six years of experimentation. This response was governed by a significantly decreased RC/ABS, a marginally non-significant increased ET(o)/TR(o) and a significantly increased TR(o)/ABS=F(V)/F(M) and RE(o)/ET(o). These results demonstrate the current level of ambient UV-B to decrease PSII performance significantly in these High Arctic plants. It appears that the two plant species both have improved their UV-screening capacity, but through different strategies, although this did not sufficiently prevent negative effects of the ambient UV radiation. We argue the decreased PSII performance to be part of a response decreasing plant carbon uptake. We speculate the negative effects on PSII performance mediated by ambient UV irradiance to be present in years where warming induces early snowmelt, exposing the vegetation to high spring UV-B, and to be present in the future to the degree the ozone layer is not fully recovered.
KW - Arctic Regions
KW - Photosystem II Protein Complex
KW - Salix
KW - Ultraviolet Rays
KW - Vaccinium
U2 - 10.1016/j.jplph.2010.05.023
DO - 10.1016/j.jplph.2010.05.023
M3 - Journal article
C2 - 20688417
SN - 0176-1617
VL - 167
SP - 1542
EP - 1549
JO - Journal of Plant Physiology
JF - Journal of Plant Physiology
IS - 18
ER -
