Inhibition of photosynthesis in cucumber leaves by oxybenzone

Oxybenzone (OBZ), a widely used sunscreen additive, has damaging effects on corals and plants. This study demonstrated that OBZ significantly inhibited photosynthesis and growth of cucumber (Cucumis sativus L.) seedlings. Combined analyses of chlorophyll fluorescence and 820-nm reflection suggested that OBZ severely inhibited photosynthetic electron transport (PET) from Q(A) to cytochrome b(6)f (Cyt b(6)f) complex, restricting the reduction of the reaction center in PSI. Separate measurements of PSI and PSII PET in chloroplasts indicated that OBZ inhibited the PET of neither PSII nor PSI, but it severely inhibited the whole linear PET. We thus confirmed that the inhibition of PET by OBZ was due to the inhibition of plastoquinones (PQs) and/or the Cyt b(6)f complex between PSI and PSII. PET is essential for producing ATP and NADPH used in CO2 assimilation. Therefore, limiting the use of sunscreens containing OBZ is significant in protection of aquatic and terrestrial ecosystems and ensuring the safety of agricultural production.