Toxic effects of antimony on photosystem II of Synechocystis sp as probed by in vivo chlorophyll fluorescence

It has been demonstrated that antimony (Sb) at concentrations ranging from 1.0 to 10.0 mg L-1 inhibits O-2 evolution. Deeper insight into the influence of Sb on PSII was obtained with measurements of in vivo chlorophyll fluorescence. The donor and the acceptor sides of PSII were shown to be the target of Sb. Sb treatment induces inhibition of electron transport from Q (A) (-) to Q(B)/Q (B) (-) and accumulation of P (680) (+) . S-2(Q(A)Q(B))(-) charge recombination and oxidation by PQ9 molecules became more important in Q (A) (-) reoxidation as the electron transfer in PSII was inhibited. Sb exposure caused a steady increase in the proportion of PSIIX and PSII beta. These changes resulted in increased fluxes of dissipated energy and decreased index of photosynthesis performance, of maximum quantum yield, and of the overall photosynthetic driving force of PSII.