The
chirality of pesticides has emerged as an important issue in
pesticide design and applications because enantiomers can differ greatly
in their environmental fate and risk. Despite the increasing concern
over the unintended effects of inactive or less effective enantiomers,
massive amounts of chiral pesticides are applied as racemic mixtures.
As a potential substitute for glyphosate, the market of glufosinate
is expected to grow rapidly. However, very little information is available
on its enantioselective efficacy-risk assessment, especially at the
environmentally relevant concentration. The overall aim of this study
is to determine if the switch from glufosinate racemic mixture to l-glufosinate was favored regarding environmental health. Thus,
we examined (i) the herbicidal activity of Rac- and l-glufosinate
to the weed, Echinochloa crus-galli, and (ii) adverse
effects on nontarget zebrafish (Danio rerio). Significant
higher herbicidal activities were achieved by l-glufosinate
at both 1 and 5 mg/L. Embryotoxicity and teratogenicity are significantly
different: Rac-glufosinate induced a significantly higher lethality
(LC50 = 17.29 mg/L) and malformations. The oxidative stress
markers, including superoxide dismutase (SOD), catalase (CAT), and
malondialdehyde (MDA), were preferably induced by Rac-glufosinate
at mRNA and enzymatic activity levels. In summary, we suggest that l-glufosinate should be applied preferably over Rac-glufosinate.
Glufosinate is a non-selective chiral herbicide, which has been used extensively around the world. However, limited information on the enantioselectivity of Racand L-glufosinate against crops. In this study, the enantioselective effects on the growth, antioxidant, and targeted enzyme activities of maize seedlings of chiral glufosinate were investigated. The results showed the enantioselective growth inhibitions were observed at both 1 and 5 mg/L concentration levels. L-Glufosinate induced more growth rate reduction in shoot height and weight compared to Rac-glufosinate. All of the antioxidant enzyme activities increased obviously in the leaves of maize seedlings treated by 1 mg/L of glufosinate. Superoxide dismutase (SOD) activity, catalase (CAT) activity, peroxidase (POD) activity, glutathione reductase (GR) activity, and malondialdehyde (MDA) content induced by L-glufosinate were 1.36, 1.16, 1.51, 1.65, and 1.65 times higher than those by Rac-glufosinate, respectively Notably, the glutamine synthetase (GS) activity was significantly reduced to 80% and 57% in the control group at 1 mg/L treated with Racand L-glufosinate, respectively. Our results indicated that Racand L-glufosinate showed the obvious enantioselectivity in the growth of maize seedlings, which has shed light on the potential enantioselective phytotoxicity of glufosinate. Data provided here will be helpful to develop the environmentally friendly herbicides.
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