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 (ΦPSΙΙ) and the redox state of the plastoquinone (PQ) pool (qp), 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 ΦPSΙΙ, 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.
Highlights
Both zinc (Zn) and copper (Cu) are essential elements for plant growth [1]
We have previously evaluated the phytotoxicity of 15 mg L−1 and 30 mg L−1 of CuZn NPs sprayed on tomato plants by determining their effects on the light reactions of photosynthesis [38]
The2019, crystal of the NPs was investigated through X-ray diffraction (XRD) (Figure4 1a)
Summary
Both zinc (Zn) and copper (Cu) are essential elements for plant growth [1]. Zn deficiency results in a rapid inhibition of plant growth and development, while several physiological processes are impaired [1,2,3]. Zinc scarcity in arable soils [4] is a major problem worldwide [2], which is mainly due to the low Zn soil solubility resulting in Zn unavailability to plant roots [5]. Adequate Zn supply is suggested to improve productivity and nutrients in crops [6]. Low Zn concentrations in soils can be improved by adding Zn fertilizers, but this is a costly and ineffective policy [7]. To Materials 2019, 12, 2498; doi:10.3390/ma12152498 www.mdpi.com/journal/materials
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