Electronic Resource
Oxford, UK
:
Blackwell Publishing Ltd
Physiologia plantarum
58 (1983), S. 0
ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1983.tb04201.x
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