Inhibition of photosystem II in the presence of copper (Cu2+) ions

The study explores the inhibitory effects of copper ions (Cu2+) on the photochemical activity of photosystem II (PSII), revealing a significant suppression of oxygen evolution in thylakoid membranes. A clear correlation was observed between increasing Cu2+ (CuSO4) concentrations and a decline in PSII activity, emphasizing the metal's disruptive influence on photosynthetic function. Notably, the inhibition of O2 evolution exhibited a time-dependent pattern, with an initial rapid decrease of 40-60% immediately after Cu2+ exposure, followed by a gradual and sustained decline. These findings suggest the presence of at least one high-affinity copper binding site within PSII, which may play a key role in mediating the complex inhibitory effects of Cu2+ on electron transport and overall photosynthetic efficiency. Keywords: Photosynthesis, photosystem II, copper, oxygen evolution, delayed light emission