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Action of UV‐B radiation on photosynthetic primary reactions in spinach chloroplasts
Author(s) -
Iwanzik W.,
Tevini M.,
Dohnt G.,
Voss M.,
Weiss W.,
Gräber P.,
Renger G.
Publication year - 1983
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1983.tb04201.x
Subject(s) - spinacia , photosynthesis , photosystem ii , photochemistry , chloroplast , action spectrum , photosystem i , oxygen evolution , spinach , chemistry , chlorophyll fluorescence , dcmu , electron transport chain , absorption (acoustics) , photoinhibition , fluorescence , biophysics , p680 , biology , biochemistry , materials science , physics , electrochemistry , optics , electrode , composite material , gene
Spinach ( Spinacia oleracea L. cv. Matador) chloroplasts were irradiated with several levels of UV‐B radiation. Measurements which reflect characteristic steps of photosynthetic electron transport were made to localize the site of impairment of photosynthesis by UV‐B radiation. Variable fluorescence, the μs‐kinetics of the 320 nm absorption changes and also oxygen evolution were substantially reduced in chloroplasts irradiated with UV‐B. It was not possible to restore the amplitude of the 320 nm absorption changes nor the signal of the transmembrane electric field measured at 520 nm by adding the photo‐system II donor couple hydroquinone/ascorbate to UV‐B treated chloroplast samples. This indicates that impairment of photosystem II activity is not caused by selective inhibition of the water‐splitting enzyme system Y, but rather is due to blockage of photosystem II reaction centers. Photosystem 1 is inferred to be highly resistant to UV‐B radiation. These results suggest that the reaction centers of photosystem II are transformed into dissipative sinks for excitation energy by action of UV‐B radiation.