Effects of ultraviolet irradiation on photosynthetic pigments in some filamentous cyanobacteria

Abstract

The effects of ultraviolet-B irradiation on the cyanobacteria Anabaena variabilis, Oscillatoria tenuis, Nodularia baltica, N. harveyana and Phormidium uncinatum (Baikal and Tübingen strain) indicated that pigmentation and energy transfer to the photosynthetic reaction centers were impaired. Absorption and fluorescence spectra showed photobleaching of photosynthetic pigments, especially in the accessory antenna pigments, with prolonged irradiation. Fluorescence emission and excitation spectra indicated an initial disturbance of energy transfer and subsequent photobleaching of these pigments. Exposure to solar and artificial UV-B irradiation resulted in a very rapid inhibition of photosynthetic oxygen exchange, as compared to photobleaching, including structural changes in the photosynthetic apparatus.