Atrazine is an herbicide that is widely applied in corn and sugarcane cultures in Brazil, in spite of the negative effects of this compound to the environment and human health. Poly(?-caprolactone) nanocapsules have been developed as carrier systems for atrazine that allow a controlled release of the herbicide, thereby reducing its genotoxicity. In the present study, the post-emergence herbicide activity of these atrazine-containing nanocapsules was evaluated and compared with a commercial formulation of atrazine. In these assays, mustard (Brassica juncea) was used as a model of plant species sensitive to atrazine. The treatment of mustard plants with nanocapsules containing atrazine at 1 mg mL-1 initially induced leaf clorosis that evolved to intense necrosis and ultimately to plant death, the same symptoms observed in plants treated with the commercial herbicide. Consequently, dry weight of aerial organs was reduced by 70 % after both treatments. Gas exchange analysis demonstrated that photosynthetic CO2 assimilation rate was drastically inhibited by application of encapsulated or commercial atrazine, leading to an increase in intercellular CO2 concentration and a decrease in stomatal conductance of mustard leaves. The use of ten-fold diluted formulations of atrazine-containing nanocapsules resulted in the same effects on the analyzed morphological and physiological parameters in comparison with the undiluted formulation. Differently, the same dilution of the commercial atrazine compromised its herbicide activity. No effects were observed when plants were treated with empty nanocapsules. Overall, these results with mustard plants demonstrate that atrazine-containing poly(?-caprolactone) nanocapsules present a very effective post-emergence herbicide activity. More importantly, the use of encapsulated atrazine would allow the application of lower dosages of the herbicide, what might reduce its environmental impacts. Acknowledgments: S�o Paulo Research Foundation, CNPq, CAPES and Fundunesp.

Evaluation of the nanoherbicide activity against mustard plants

248th National Meeting (2014)

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