Impact of UV-A and UV-B radiation on pattern of pigments of the Antarctic macroalga Leptosomia simplex L. was studied during the Polarstern cruise (ANT XII/2) 1994/95 under controlled laboratory conditions. An 8 h exposure to UV-A of 17.6 W m-2 led usually to an increase of carotenoid contents, but to a decrease in contents of chlorophyllide (Chlide) a and chlorophyll (Chl) a. UV-B irradiation (300-320 nm) caused a decrease in contents of Chlide a, lutein, and zeaxanthin, but an increase in contents of Chl a and carotenes. Enhancement of carotenoid contents was attributed to a protection of the photosynthetic apparatus. UV effects on the 15N-ammonium uptake were correlated with the changes in pigment contents.
Wolffia arrhiza (L.) Wimm. plants precultivated under different radiation conditions were exposed to UV-B at low or strong "white" irradiance. Photosynthetíc electron transport (Hill actívity) was more damaged by UV-B under 6 W m"^ than at 15 W m‘2 supplemental "white light" (WR). The inhibitory effect was more pronounced using red radiation (RR) precultivated plants compared to precultívatíon at blue radiation (BR) or WR. Hill reaction in RR grown W. arrhiza with a high growth rate was more affected by UV-B - in comiection with DCMU and 1,5- diphenyl carbazide - than of plants with a low growth rate. No effect was observed using plants precultivated at BR or WR.