Evaluation of the side effects of poly(epsilon-caprolactone) nanocapsules containing atrazine toward maize plants

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.

Nanocapsules Containing Neem (Azadirachta Indica) Oil: Development, Characterization, And Toxicity Evaluation

“…Additionally, no effects were observed after treatment with NC, compared to the control (Fig. 5), in agreement with previous studies that showed that unloaded PCL nanocapsules did not affect the physiological parameters of maize and mustard plants 45, 46 . The absence of an effect of the nanoformulations without neem oil, used as negative controls, indicates that the inert materials used in the encapsulation process did not cause adverse effects 47 .

Figure 5Net photosynthesis and stomatal conductance of maize plants 1 and 8 days after treatment with the NC_20, NC_15, NC_10, and NC formulations, or with water (control).

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Post-Emergence Herbicidal Activity of Nanoatrazine Against Susceptible Weeds

“…The use of nanoencapsulated atrazine would, therefore, enable the application of lower doses of the herbicide; this could result in reduced release of atrazine into the environment and, in this way, decreased effects on non-target organisms. Oliveira et al (2015b) demonstrated that atrazine-containing PCL nanocapsules had no persistent toxic effects on maize plants, a crop where atrazine is widely applied for weed control. Despite small effects on oxidative stress and photosynthetic parameters that were detected in maize leaves after treatment with the nanoherbicide, these effects were transient and shoot growth remained unaffected.…”

Atrazine nanoencapsulation improves pre‐emergence herbicidal activity against Bidens pilosa without enhancing long‐term residual effect on Glycine max

“…Moreover, this nanoformulation showed reduced toxicity toward some non‐target organisms, such as the human cells, the algae Pseudokirchneriella subcapitata and the fish Prochilodus lineatus , compared with non‐nanoherbicide . The nanoencapsulation improved the post‐emergence herbicidal activity of atrazine against target species ( Brassica juncea , Bidens pilosa and Amaranthus viridis ), whereas the growth of maize plants was not affected . Therefore, in comparison with the non‐nanoherbicide, a tenfold reduction in atrazine dosage was enabled when atrazine‐containing PCL nanocapsules were applied for the post‐emergence control of target plants .…”

“…14,18,19 The nanoencapsulation improved the post-emergence herbicidal activity of atrazine against target species (Brassica juncea, Bidens pilosa and Amaranthus viridis), whereas the growth of maize plants was not affected. [20][21][22] Therefore, in comparison with the non-nanoherbicide, a tenfold reduction in atrazine dosage was enabled when atrazine-containing PCL nanocapsules were applied for the post-emergence control of target plants. 20,22 This would result in an enormous decrease in atrazine input to the environment without compromising weed control.…”