Blackwell Publishing Journal Backfiles 1879-2005
2,4-dichlorophenoxyacetic acid (2,4-D) is an analogue compound to the plant hormone indole-3-acetic acid (IAA), which is used either as a growth-promoting substance or as a herbicide, depending on its concentration. In this work, the effect of 2,4-D on the growth and ROS metabolism of pea (Pisum sativum L.) leaves is reported. The herbicide considerably reduced the plant growth and negatively influenced several physiological parameters in a dose-dependent manner. At structural level, damage of the mesophyll cells and the enlargement and dilation of thylakoids were observed in 2,4-D-treated plants. 2,4-D notably affected xanthine oxidase and superoxide dismutase activities, as well as the activity and transcript levels of the ascorbate–glutathione cycle enzymes, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase. Furthermore, in herbicide-treated plants, an increase in the H2O2 production, levels of lipid peroxidation, endopeptidase activity and oxidatively modified proteins took place. Results obtained showed that an overproduction of superoxide radicals (O2−) and hydrogen peroxide (H2O2) could take place in plants treated with 2,4-D, thus contributing to the generation of oxidative stress, with the concomitant degradation of proteins. A model of the role of ROS-mediated enzymatic systems in the oxidative mode of action of 2,4-D and other auxinic herbicides is proposed.
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