PHOTOSYSTEM-2 PHOTOINACTIVATION AND REPAIR IN THE SCENEDESMUS CELLS TREATED WITH HERBICIDES DCMU AND BNT AND EXPOSED TO HIGH IRRADIANCE

Changes in fluorescence parameters observed during irradiation of the Scenedesmus cells showed that photosystem 2 (PS2) photoinactivation in cells treated with phenolic PS2 inhibitor 2-bromo-3-methyl-6-isopropy l-4-nitrophen (BNT) was significantly accelerated in comparison with c ontrol and DCMU-treated cells. Moreover, a negligible difference in th e rate of PS2 photoinactivation in the absence and presence of chloram phenicol indicated that both DCMU and BNT blocked the PS2 repair proce ss.