Changes in the pattern of pigments and free amino acids of the macroalga Laminaria saccharina (L.) Lamour exposed to UV-A and UV-B after Addition of 15N-ammonium

Main pigments of Laminaria saccharina from the North Sea were enhanced after 5 h UV-A irradiation (WG 320) in all parts of the thalli. UV-B plus UV-A (WG 295) caused a decrease of all major pigments at the top and the middle of the thallus. Uptake of N-15-ammonium was differently affected by UV radiation in dependence on the age of the thalli pieces. Changes in the pattern of free amino acid pools and of N-15-labelling were observed after 5 h UV-A or UV-B plus UV-A radiation of the whole Laminaria thalli. A significant reduction of the pool sizes in the middle part of the thalli was found after 5 h UV exposure. Variations in the N-15-incorporation into the free amino acids mere nor identical with pattern of the pools. The damaging effect of UV-B plus UV-A radiation was more pronounced than that of UV-A using a similar fluence rare. The results were discussed with reference to the different response of the exposed thalli and the impact on the key enzymes of nitrogen metabolism.