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Open AccessArticle

Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure

1
Department of Botany, Faculty of Biology, National and Kapodistrian University of Athens, 15784 Athens, Greece
2
Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization—Demeter, Thermi, 57001 Thessaloniki, Greece
3
Department of Trace Analysis, Faculty of Chemistry, Adam Mickiewicz University, 61-614 Poznań, Poland
4
Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
5
Department of Botany, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2021, 22(1), 41; https://doi.org/10.3390/ijms22010041
Received: 8 November 2020 / Revised: 15 December 2020 / Accepted: 17 December 2020 / Published: 22 December 2020
(This article belongs to the Special Issue Molecular Mechanisms of Responses to Low-Intensity Exposures)
Five-day exposure of clary sage (Salvia sclarea L.) to 100 μM cadmium (Cd) in hydroponics was sufficient to increase Cd concentrations significantly in roots and aboveground parts and affect negatively whole plant levels of calcium (Ca) and magnesium (Mg), since Cd competes for Ca channels, while reduced Mg concentrations are associated with increased Cd tolerance. Total zinc (Zn), copper (Cu), and iron (Fe) uptake increased but their translocation to the aboveground parts decreased. Despite the substantial levels of Cd in leaves, without any observed defects on chloroplast ultrastructure, an enhanced photosystem II (PSII) efficiency was observed, with a higher fraction of absorbed light energy to be directed to photochemistry (ΦPSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in an important decrease in the dissipated non-regulated energy (ΦNO), modifying the homeostasis of reactive oxygen species (ROS), through a decreased singlet oxygen (1O2) formation. A basal ROS level was detected in control plant leaves for optimal growth, while a low increased level of ROS under 5 days Cd exposure seemed to be beneficial for triggering defense responses, and a high level of ROS out of the boundaries (8 days Cd exposure), was harmful to plants. Thus, when clary sage was exposed to Cd for a short period, tolerance mechanisms were triggered. However, exposure to a combination of Cd and high light or to Cd alone (8 days) resulted in an inhibition of PSII functionality, indicating Cd toxicity. Thus, the rapid activation of PSII functionality at short time exposure and the inhibition at longer duration suggests a hormetic response and describes these effects in terms of “adaptive response” and “toxicity”, respectively. View Full-Text
Keywords: Salvia sclarea; chlorophyll fluorescence imaging; non-photochemical quenching; tolerance mechanism; photoprotective mechanism; oxidative stress; reactive oxygen species; toxicity; adaptive response; photochemical efficiency Salvia sclarea; chlorophyll fluorescence imaging; non-photochemical quenching; tolerance mechanism; photoprotective mechanism; oxidative stress; reactive oxygen species; toxicity; adaptive response; photochemical efficiency
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MDPI and ACS Style

Adamakis, I.-D.S.; Sperdouli, I.; Hanć, A.; Dobrikova, A.; Apostolova, E.; Moustakas, M. Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure. Int. J. Mol. Sci. 2021, 22, 41. https://doi.org/10.3390/ijms22010041

AMA Style

Adamakis I-DS, Sperdouli I, Hanć A, Dobrikova A, Apostolova E, Moustakas M. Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure. International Journal of Molecular Sciences. 2021; 22(1):41. https://doi.org/10.3390/ijms22010041

Chicago/Turabian Style

Adamakis, Ioannis-Dimosthenis S.; Sperdouli, Ilektra; Hanć, Anetta; Dobrikova, Anelia; Apostolova, Emilia; Moustakas, Michael. 2021. "Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure" Int. J. Mol. Sci. 22, no. 1: 41. https://doi.org/10.3390/ijms22010041

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