EFFECT OF UV-A AND UV-B RADIATION ON PIGMENTS, FREE AMINO-ACIDS AND ADENYLATE CONTENT OF DUNALIELLA-TERTIOLECTA BUTCHER (CHLOROPHYTA)

The marine chlorophycean Dunaliella tertiolecta Butcher grown under co ntrolled laboratory conditions was exposed to UV-A (10.2 W m(-2)), UV- B (1.6 W m(-2)) or UV-A plus UV-B (10 W m(-2)/1.5 W m(-2)) in connecti on with white light (100 W m(-2)) radiation for up to 5 h at 20 degree s C. Uptake of N-15-ammonium (5 or 100 mu M) was more affected by UV-B and UV-A plus UV-B radiation than by UV-A. Pattern of pigments varied in dependence on the exposure time (2 or 5 h) and the waveband of the applied UV as well as of the used ammonium concentration. The xanthop hyll cycle was more affected by UV-A plus UV-B radiation than by UV-B or UV-A. UV-A and UV-B irradiance resulted in an increase of main amin o acid biosynthesis and an enhancement of the main free amino acid poo ls. Changes in the pattern of the free amino acid pools were found in dependence on the applied ammonium concentration (5 or 100 mu M). Cont ents of AMP, ADP and ATP were also differently affected by UV radiatio n in dependence on the ammonium concentration(1). Results are discusse d in relation to the UV effects on photosynthetic pigments, energy sup ply and the key enzymes of the carbon and nitrogen metabolism. (C) 199 7 Published by Elsevier Science S.A.