ABSTRACT
Herbicides adversely affect both the target plant and its environment. In this study, Helianthus annuus L. cv. “Oliva CL” was treated post-emergence with 0.3 to 3.1 mM quizalofop-p-ethyl. The peroxidase activity (POD), ascorbate peroxidase activity (APX), lipid peroxidation, pigment sys tem and total phenolic content were then determined on the 1st, 5th, 10th and 15th days following treatment. The POD activity increased on all application days, and the APX activity increased on the 5th day and decreased on the 10th and 15th days. In addition, the malondialdehyde (MDA) content was increased on the 1st, 5th, 10th and 15th days, except for the in H. annuus plants treated with 1.6 to 3.1 mM quizalofop-p-ethyl. The total chlorophyll, carotenoid and total phenolic content were important and changed in a time dependent manner. In the present study, we also investigated the possible role of salicylic acid (SA) in protecting H. annuus seedlings from herbicide toxicity. The plants were first treated with 0.5 mM SA pre-emergence and then treated with 0.3 to 3.1 mM quizalofop-p-ethyl herbicide post-emergence. In general, increases in the POD activity and MDA content were observed in the treatment groups on all application days. In the treated groups, the APX activity increased until the 15th day. In the SA pre-treated plants, the total phenollic, total chlorophyll and carotenoid content were also important in a time dependent manner.