Long-term effects of elevated UV-B radiation on photosynthesis and ultrastructure of Eriophorum russeolum and Warnstorfia exannulata.
The depletion of stratospheric ozone above the Arctic regions may increase the amount of UV-B radiation to which the northern ecosystems are exposed. In this paper, we examine the hypothesis that supplemental UV-B radiation may affect the growth rate and photosynthesis of boreal peatland plants and could thereby affect the carbon uptake of these ecosystems. In this study, we report the effects of 3-year exposure to elevated UV-B radiation (46% above ambient) on the photosynthetic performance and ultrastructure of a boreal sedge Eriophorum russeolum and a moss Warnstorfia exannulata. The experiment was conducted on a natural fen ecosystem at Sodankylä in northern Finland. The effects of UV-B radiation on the light response of E. russeolum CO(2) assimilation and the maximal photochemical efficiency of photosystem II in a dark-adapted state (F(v)/F(m)) were measured in the field. In addition, the effect of supplemental UV-B radiation on organelles of photosynthetic cells was studied by electron microscopy. The UV-B treatment had no effect on the CO(2) assimilation rate of either species, nor did it affect the structure of the cell organelles. On chlorophyll fluorescence, the UV-B exposure had only a temporary effect during the third exposure year. Our results suggested that in a natural ecosystem, even long-term exposure to reasonably elevated UV-B radiation levels does not affect the photosynthesis of peatland plants.
Department of Biology, University of Eastern Finland, Joensuu Campus, P.O. Box 111, FI-80101 Joensuu, Finland. jaana.haapala@uef.fi
Jaana K
JK
Haapala
Sami K
SK
Mörsky
Sanna
S
Saarnio
Hanne
H
Suokanerva
Esko
E
Kyrö
Jouko
J
Silvola
Toini
T
Holopainen
D019068:Bryopsida / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D019069:Cell Respiration / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D029785:Cyperaceae / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D048788:Growth and Development / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects*; D014466:Ultraviolet Rays
D002734:Chlorophyll