Comparative studies on electron transfer in Photosystem II of herbicide-resistant mutants from different organisms

We have studied the electron transfer properties of Photosystem II using several techniques (fluorescence, oxygen emission and thermoluminescence measurements) in a series of herbicide-resistant mutants from widely different organisms. Five mutants of Synechocystis 6714, of which we have determined the D1 sequence, one mutant of Synechococcus 7942, one mutant of Chlamydomonas reinhardtii, a triazine-resistant biotype of Chenopodium album and their herbicide-susceptible controls were analyzed. Two mutants have an almost unimpaired Photosystem II electron transfer. For five mutants of the different organisms, the initial phase of the electron transfer Q − A to Q B is unaltered but the electron transfer equilibrium between these two acceptors is displaced. In the Chlamydomonas-resistant mutant, the electron transfer from Q − A to Q B is slowed down.