Leveraging Nanotechnology for Safer Herbicide Use: Insights from Maize Tolerance to Nanoencapsulated Atrazine

Previous work has shown that nanoencapsulation of atrazine enhances the herbicidal action of this active ingredient. This increased activity is expected to control weeds and not compromise the tolerance of maize plants to the herbicide. This study aimed to evaluate the tolerance of maize plants to atrazine in postemergence application with different nanoformulations. Parameters of photosystem II (PSII) activity and growth of the maize plants in a greenhouse were evaluated after application of the formulations: conventional atrazine (ATZ), atrazine encapsulated in nanocapsules (NCs) of poly-(ε-caprolactone) (PCL + ATZ), PCL coated with chitosan (PCL/CS + ATZ), and zein (ZN + ATZ), at doses of 1000 and 2000 g active ingredient (a.i.) ha^-1, in addition to the three NCs formulations without a.i. Oxidative stress markers and the activity of antioxidant and detoxification enzymes were quantified only in plants applied with atrazine, PCL + ATZ, PCL/CS + ATZ, and ZN + ATZ at a dose of 2000 g a.i. ha^-1. All NC nanoformulations without a.i. were nontoxic to the physiology and growth of maize plants. Plants treated with ATZ developed up to 39% higher glutathione S-transferase activity and lower inhibition of PSII (on average 12%) compared to the nanoencapsulated herbicide. In contrast, PCL + ATZ, PCL/CS + ATZ, and ZN + ATZ induced higher antioxidant enzymatic activity in comparison to ATZ, like increases in ascorbate peroxidase (26%), catalase (95%), peroxidase (120%), and superoxide dismutase (41%). The effect on photosynthetic activity was transient for all formulations tested, with total recovery observed 14 days after application. Furthermore, ATZ, PCL + ATZ, PCL/CS + ATZ, and ZN + ATZ did not compromise maize plant growth. These results indicate that, under the evaluated conditions, maize plants remained tolerant to the active ingredient applied in a nanoencapsulated formulation.