Effect of a Zinc Phosphate Shell on the Uptake and Translocation of Foliarly Applied ZnO Nanoparticles in Pepper Plants (Capsicum annuum) Article Swipe
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· 2024
· Open Access
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· DOI: https://doi.org/10.1021/acs.est.3c08723
· OA: W4391716647
Here, isotopically labeled <sup>68</sup>ZnO NPs (ZnO NPs) and <sup>68</sup>ZnO NPs with a thin <sup>68</sup>Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> shell (ZnO_Ph NPs) were foliarly applied (40 μg Zn) to pepper plants (<i>Capsicum annuum</i>) to determine the effect of surface chemistry of ZnO NPs on the Zn uptake and systemic translocation to plant organs over 6 weeks. Despite similar dissolution of both Zn-based NPs after 3 weeks, the Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> shell on ZnO_Ph NPs (48 ± 12 nm; -18.1 ± 0.6 mV) enabled a leaf uptake of 2.31 ± 0.34 μg of Zn, which is 2.7 times higher than the 0.86 ± 0.18 μg of Zn observed for ZnO NPs (26 ± 8 nm; 14.6 ± 0.4 mV). Further, ZnO_Ph NPs led to higher Zn mobility and phloem loading, while Zn from ZnO NPs was stored in the epidermal tissues, possibly through cell wall immobilization as a storage strategy. These differences led to higher translocation of Zn from the ZnO_Ph NPs within all plant compartments. ZnO_Ph NPs were also more persistent as NPs in the exposed leaf and in the plant stem over time. As a result, the treatment of ZnO_Ph NPs induced significantly higher Zn transport to the fruit than ZnO NPs. As determined by spICP-TOFMS, Zn in the fruit was not in the NP form. These results suggest that the Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> shell on ZnO NPs can help promote the transport of Zn to pepper fruits when foliarly applied. This work provides insight into the role of Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> on the surface of ZnO NPs in foliar uptake and <i>in planta</i> biodistribution for improving Zn delivery to edible plant parts and ultimately improving the Zn content in food for human consumption.