Changes of the antioxidant system in pear (Pyrus communis L.) fruits by foliar application of copper, selenium, iron, and zinc nanoparticles

Abstract

Innovations in agricultural nanotechnology are a viable option for improving the antioxidant system in the pear crop helping to mitigate the different types of abiotic and biotic stresses whose effects have increased due to the advance of climate change. Therefore, foliar applications were made with nanoparticles (NPs) of copper (Cu), iron (Fe), and zinc (Zn) at 250 ppm, as well as applications with selenium (Se) at 50 ppm, and control with water in a commercial pear orchard (Bartlett variety), to evaluate its effect on the behavior of the enzymatic antioxidant system, the concentration of bioactive compounds, and the evaluation of damage by lipid peroxidation, hydrogen peroxide concentration, and activity of polyphenol oxidases (PPO) in the fruits. The results indicate that the Cu and Se NPs stimulated in the fruits a greater synthesis of total phenols, flavonoids, and ascorbic acid, achieving higher concentrations than the control fruits, and also exhibited greater antioxidant activity in vitro. An opposite effect was observed in the fruits of the treatment with Zn NPs, since the concentration of phenols and flavonoids was reduced by 33.14 and 34.24 %, respectively, as well as a decrease in antioxidant activity. On the other hand, the Cu and Fe NPs improved the activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase, additionally, the integrity of the membranes was maintained, thus avoiding enzymatic browning due to the activity of the PPOs in the fruits. The highest concentration of malondialdehyde and PPOs activity was observed in the fruits of the treatment with Se and Zn NPs. The results indicate that the application of Cu NPs at 250 ppm can improve the enzymatic and non-enzymatic antioxidant system in Bartlett cultivar pear fruits.