In order to investigate physiological and biochemical changes of wheat under stress residue of Imazethapyr herbicide (Imazethapyr), an experiment was conducted in a completely randomized design with four replications in greenhouse conditions at university of Mohaghegh Ardebili. The treatments consisted of five dose levels of herbicide Imazethapyr (0, 0.011, 0.022, 0.033 and 0.044 micrograms of herbicide) per kilogram of soil. The analysis of variance showed that the content of the main and auxiliary pigments of leaf, proline, sugar content, protein, activity of catalase enzymes, peroxidase, polyphenol oxidase, root and shoot dry weight were significantly affected by herbicide. The results showed the Imazethapyr herbicide stopped the production of valine leucine and isoleucine amino acids. As a result, the rapid reduction in the volume of these amino acids led to a reduction in protein synthesis in wheat plant. Therefore, the application of doses of 0.011, 0.022, 0.033 and 0.044 micrograms of herbicides decreased 14, 26, 44 and 47 percent of leaf protein content, respectively, compared with control treatment. Further, theapplication of these doses resulted in the reduction of 2.8, 5, 27 and 64% of activity of catalase enzyme, 3.5, 39, 49 and 52% peroxidase enzyme activity and 13, 24, 35 and 46% activity of polyphenol oxidase enzyme, compared with control treatment. The results revealed that Imazethapyr herbicide activates wheat antioxidant enzymes to reduce plant tolerance from damage caused by herbicide residues; therefore, it can be used as a marker or index of herbicide damage rate in physiological research.
