EVIDENCE OF SINGLET OXYGEN EVOLUTION BY WHOLE LIVING CELLS OF CHLAMYDOMONAS-REINHARDTII

The oxygen evolved by Chlamydomonas reinhardtii in the light is measur ed simultaneously with a Clark electrode and with the nitrosodimethyla niline-imidazole colorimetric method which is specific for singlet oxy gen. Experiments with wild-type and FuD7 mutant cells (unable to synth esize the D1 protein of Photosystem II), with dichlorophenyldimethylur ea (which blocks electron transfer from Photosystem II to Photosystem I) and with dibromothymoquinone (which diverts electrons from their no rmal path between the two photosystems), as well as with hydroxylamine (an inactivator of the water-splitting part of Photosystem II and a c ompetitor of water for electron donation to it), all point to the depe ndence of detected singlet oxygen on photolysis of water by Photosyste m II.