No 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 system 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.

Glyphosate is an herbicide that is applied after non-selective germination and affects plant growth. In this study, glyphosate was applied to Zea mays L. after germination, at a concentration range from 0.017 to 0.145 M in a growth chamber. The effects of this herbicide on some antioxidant enzymes, lipid peroxidation, total chlorophyll and total carbohydrate content were investigated on days 1, 5 and 10 following the application. Results showed that peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) were increased in the groups treated with glyphosate on days 5 and 10, but the activities of reduced glutathione (GSH) and glutathione reductase (GR) were decreased on day 10. Malondialdehyde (MDA) content indicating lipid peroxidation was increased on days 1, 5 and 10. Changes in total chlorophyll and total carbohydrate contents were found to be time-dependent. These increases and decreases in the antioxidant activities, MDA content, total chlorophyll and total carbohydrate content in Zea mays L. were determined as a symptom of cytotoxicity caused due to glyphosate.