Effect of the insecticide clothianidin on the photosynthetic electron transport chain in pea

Clothianidin (CL) is a neonicotinoid insecticide widely used in crop protection against insect pests. However, its effects on photosynthesis remain largely unknown. Here, by investigating the influence of CL at the concentrations of 22 and 110 μg/L on the primary processes of photosynthesis, membrane fluidity and structural changes of pea chloroplasts, we located several primary binding sites of this pesticide. Similar dynamics were observed for both concentrations. However, statistically significant differences were only found at 110 μg/L for all methods used. The light saturated rate of linear electron flow decreased mainly due to the disturbance of electron flow on the acceptor side of photosystem II (PSII) associated with the appearance of Q_B-nonreducing centers and empty Q_B binding sites of PSII. The functioning of the donor side of PSII, the activity of photosystem I (PSI) and the maximum quantum yield of PSII photochemistry (Fv/Fm) were not found to be significantly altered. Increased membrane fluidity and structural alterations of the thylakoid membrane led to a decrease in the development of the proton gradient ΔрН and membrane energization processes.