Leaf Age-Dependent Effects of Foliar-Sprayed CuZn Nanoparticles on Photosynthetic Efficiency and ROS Generation in Arabidopsis thaliana

Ilektra Sperdouli; Julietta Moustaka; Orestis Antonoglou; Ioannis-Dimosthenis S Adamakis; Catherine Dendrinou-Samara; Michael Moustakas

doi:10.3390/ma12152498

Leaf Age-Dependent Effects of Foliar-Sprayed CuZn Nanoparticles on Photosynthetic Efficiency and ROS Generation in Arabidopsis thaliana

Materials (Basel). 2019 Aug 6;12(15):2498. doi: 10.3390/ma12152498.

Authors

Ilektra Sperdouli^{1

2}, Julietta Moustaka^{1

3}, Orestis Antonoglou⁴, Ioannis-Dimosthenis S Adamakis^{1

5}, Catherine Dendrinou-Samara⁴, Michael Moustakas⁶

Affiliations

¹ Department of Botany, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
² Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organisation-Demeter, Thermi, GR-57001 Thessaloniki, Greece.
³ Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
⁴ Laboratory of Inorganic Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
⁵ Department of Botany, Faculty of Biology, National and Kapodistrian University of Athens, Athens 157 72, Greece.
⁶ Department of Botany, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece. moustak@bio.auth.gr.

Abstract

Young and mature leaves of Arabidopsis thaliana were exposed by foliar spray to 30 mg L^-¹ of CuZn nanoparticles (NPs). The NPs were synthesized by a microwave-assisted polyol process and characterized by dynamic light scattering (DLS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). CuZn NPs effects in Arabidopsis leaves were evaluated by chlorophyll fluorescence imaging analysis that revealed spatiotemporal heterogeneity of the quantum efficiency of PSII photochemistry (Φ_PSΙΙ) and the redox state of the plastoquinone (PQ) pool (q_p), measured 30 min, 90 min, 180 min, and 240 min after spraying. Photosystem II (PSII) function in young leaves was observed to be negatively influenced, especially 30 min after spraying, at which point increased H₂O₂ generation was correlated to the lower oxidized state of the PQ pool.. Recovery of young leaves photosynthetic efficiency appeared only after 240 min of NPs spray when also the level of ROS accumulation was similar to control leaves. On the contrary, a beneficial effect on PSII function in mature leaves after 30 min of the CuZn NPs spray was observed, with increased Φ_PSΙΙ, an increased electron transport rate (ETR), decreased singlet oxygen (¹O₂) formation, and H₂O₂ production at the same level of control leaves.An explanation for this differential response is suggested.

Keywords: bimetallic nanoparticles; hydrogen peroxide; mature leaves; non-photochemical quenching; photoprotective mechanism; photosynthetic heterogeneity; plastoquinone pool; redox state; spatiotemporal heterogeneity; young leaves.