Glutathione S-transferase (GST, EC 2.5.1.18) plays an important role in the response to stress caused by herbicides in plants; it is considered to be a detoxifying enzyme since it metabolizes a great variety of xenobiotic compounds, by combining them with reduced glutathione, forming substances of low toxicity. Maize (Zea mays) was chosen in this work for showing injury problems when submitted to weed chemical control. This research aimed to determine the alterations in the activity of this enzyme in glyphosate-treated maize plants. The experimental design was completely randomized, in a 4 x 4 factorial arrangement, with four treatments (glyphosate at concentrations of 1,000, 2,500 and 5,000 ppm and control plant treated with water) and four developmental stages (9, 16, 23 and 30 days after emergence), with five replicates. The herbicide was applied on the maize plant shoots, which were collected at 24, 48 and 72 hours after herbicide application and utilized for determining the GST activity and lipoperoxide content. It was verified that glyphosate does not change the lipoperoxide content, but increases GST activity for most treatments utilized, indicating its action in the degradation of glyphosate in maize plants.
metabolization of xenobiotics; detoxification; inhibitor of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)
