Abstract
Poly(epsilon-caprolactone) (PCL) nanocapsules have been used as a carrier system for the herbicide atrazine, which is commonly applied to maize. We demonstrated previously that these atrazine containing polymeric nanocapsules were 10-fold more effective in the control of mustard plants (a target species), as compared to a commercial atrazine formulation. Since atrazine can have adverse effects on non-target crops, here we analyzed the effect of encapsulated atrazine on growth, physiological and oxidative stress parameters of soil-grown maize plants (Zea mays L.). One day after the post-emergence treatment with PCL nanocapsules containing atrazine (1 mg mL−1), maize plants presented 15 and 21% decreases in maximum quantum yield of photosystem II (PSII) and in net CO2 assimilation rate, respectively, as compared to water-sprayed plants. The same treatment led to a 1.8-fold increase in leaf lipid peroxidation in comparison with control plants. However, all of these parameters were unaffected 4 and 8 days after the application of encapsulated atrazine. These results suggested that the negative effects of atrazine were transient, probably due to the ability of maize plants to detoxify the herbicide. When encapsulated atrazine was applied at a 10-fold lower concentration (0.1 mg mL−1), a dosage that is still effective for weed control, no effects were detected even shortly after application. Regardless of the herbicide concentration, neither pre- nor post-emergence treatment with the PCL nanocapsules carrying atrazine resulted in the development of any macroscopic symptoms in maize leaves, and there were no impacts on shoot growth. Additionally, no effects were observed when plants were sprayed with PCL nanocapsules without atrazine. Overall, these results suggested that the use of PCL nanocapsules containing atrazine did not lead to persistent side effects in maize plants, and that the technique could offer a safe tool for weed control without affecting crop growth.
Highlights
Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4diamine) is a triazine herbicide that is applied for the preand post-emergence control of broadleaf and grassy weeds in cultivations of crops such as maize and sugarcane (Rodrigues and Almeida, 2011)
We evaluated the effects of pre- and post-emergence treatments with PCL nanocapsules containing atrazine on growth, physiological and oxidative stress parameters of maize (Zea mays L.) plants, as compared to those induced by a commercial atrazine formulation
The effects of the two formulations were transient, because the Fv/Fm ratios for plants treated with ATZ or nanocapsules without atrazine (NC)+ATZ recovered to the same values obtained for control plants 2 or 4 days after treatment, respectively
Summary
Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4diamine) is a triazine herbicide that is applied for the preand post-emergence control of broadleaf and grassy weeds in cultivations of crops such as maize and sugarcane (Rodrigues and Almeida, 2011). Even in non-target tolerant plant species, atrazine accumulation has been shown to cause toxic responses, inducing oxidative stress and negatively affecting crop growth and productivity (Alla and Hassan, 2006; Li et al, 2012). In this scenario, research into technologies that minimize the deleterious impacts of atrazine without hindering its biological activity toward target weeds is of great relevance
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