Effects of Herbicides on the Antioxidant System in Wheat and Ryegrass Plants

Maria Luiza De Grandi, journalist, Ciência Rural, Santa Maria, RS, Brazil.

Camila Peligrinotti Tarouco, PhD in Fitossanidade, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brazil.

Herbicides are widely used to control weeds in agriculture. The application of herbicides promotes physiological and biochemical changes even in tolerant species.

In order to evaluate the interference of the herbicides clodinafop-propargyl and 2,4-D in the antioxidant system of wheat, and iodosulfuron-methyl in wheat and ryegrass, researchers from the Federal University of Santa Maria (UFSM) in partnership with the Federal University of Pelotas (UFPel), Instituto Federal Catarinense (IFC) and Oklahoma State University, developed the article entitled Antioxidant detoxification system of wheat and ryegrass plants subjected to various herbicides. The study was published in Ciência Rural (vol. 54, no. 7, 2024).

The research investigated the effects of herbicides used to control weeds, specifically those with different mechanisms of action, such as ACCase inhibitors, auxin mimics and ALS enzyme inhibitors, which can affect the metabolism of wheat and ryegrass plants. The scientific development of the article encompassed two studies, divided into three experiments, conducted in a completely randomized design in a greenhouse and phytotron.

“The motivation for the research arose from the need to understand how weeds, such as ryegrass, compete with wheat crops for resources such as water, nutrients and light, and how this competition can affect wheat growth and productivity,” explained Camila Peligrinotti Tarouco.

Image: photographed by the author

According to the researcher, understanding how herbicides act on plant signaling is a key element in determining the plants’ tolerance capacity and in mitigating the adverse effects of herbicides. “Understanding this action helps identify how plants respond to herbicide treatment, which is essential for developing strategies that increase the effectiveness of weed control and, at the same time, minimize negative impacts on the target crop,” she highlights.

The use of herbicides caused significant changes in the physiological and biochemical processes of plants. The herbicides iodosulfuron-methyl, clodinafop-propargyl and 2,4-D increased oxidative stress in plants, as evidenced by increased levels of hydrogen peroxide, TBARS and cell leakage. In addition, there was a reduction in the levels of chlorophylls and carotenoids in wheat plants, indicating damage to the photosynthetic capacity of the plants.

The increase in the dose of iodosulfuron-methyl led to a reduction in the activity of the antioxidant enzymes SOD (superoxide dismutase), CAT (catalase) and APX (ascorbate peroxidase), in both wheat and ryegrass plants. This decrease in enzyme activity suggests that the plants’ ability to cope with the oxidative stress caused by the herbicide was compromised, contributing to impaired plant growth and development.

Although herbicides are recommended for weed control in wheat crops, they can cause physiological and biochemical changes that can result in phytotoxicity and reduce the selectivity of the product in the crop. Therefore, it is essential to investigate these side effects to ensure that herbicides are used effectively and safely, minimizing negative impacts on the crop.

To read the article, access

TAROUCO, P.C. et al. Antioxidant detoxification system of wheat and ryegrass plants subjected to various herbicides. Ciência Rural [online]. 2024, vol. 54, no. 7, e20230132 [viewed 12 February 2025]. https://doi.org/10.1590/0103-8478cr20230132. Available from: https://www.scielo.br/j/cr/a/kpq7GWdPnTrTVJvPXxZn6Wy/

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