| Summary: | In this study, for a first time (according to our knowledge), we couple the methodologies of chlorophyll fluorescence imaging analysis (CF-IA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), in order to investigate the effects of cadmium (Cd) accumulation on photosystem II (PSII) photochemistry. We used as plant material <i>Salvia sclarea</i> that grew hydroponically with or without (control) 100 μM Cd for five days. The spatial heterogeneity of a decreased effective quantum yield of electron transport (Φ<i><sub>PSΙΙ</sub></i>) that was observed after exposure to Cd was linked to the spatial pattern of high Cd accumulation. However, the high increase of non-photochemical quenching (NPQ), at the leaf part with the high Cd accumulation, resulted in the decrease of the quantum yield of non-regulated energy loss (Φ<i><sub>NO</sub></i>) even more than that of control leaves. Thus, <i>S. sclarea</i> leaves exposed to 100 μM Cd exhibited lower reactive oxygen species (ROS) production as singlet oxygen (<sup>1</sup>O<sub>2</sub>). In addition, the increased photoprotective heat dissipation (NPQ) in the whole leaf under Cd exposure was sufficient enough to retain the same fraction of open reaction centers (<i>q</i><sub><span style="font-variant: small-caps;">p</span></sub><span style="font-variant: small-caps;">) </span>with control leaves. Our results demonstrated that CF-IA and LA-ICP-MS could be successfully combined to monitor heavy metal effects and plant tolerance mechanisms.
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