The effect of salicylic acid treatment on the antioxidant enzyme activities in Thymus vulgaris seedlings

Thymus Garden (Thymus vulgaris L.) is one of the economically important plants which is extremely sensitive to oxidative stress and drought stress during germination time. Salicylic acid, as an herbal hormone, plays an important role in increasing plant tolerance to biotic and abiotic stresses. The current study was conducted aiming to increase the plant resistance to environmental stress by increasing its enzymatic and non-enzymatic antioxidant capacity by salicylic acid treatment. In this experimental study, the plant seeds were soaked in 2mM salicylic acid solution a randomized complete block design with three replicates for 16 hours, and they were then planted in pots. Pots were transferred to growth chamber with constant and controlled conditions for 16 hours of light: 8 hours of dark at a temperature of 25°C for 14 days. At the end of the experiment, the growth parameters of plants, germination percentage, phenol content, and the activity of the important antioxidant enzymes, such as superoxide dismutase, catalase, polyphenol oxidase and peroxidase, were measured and compared with the control group. Although salicylic acid did not have a significant impact on plant growth, it has led to an effective of antioxidant enzymes in the plant. Moreover, this treatment has increased the antioxidant content of the plant. Treatment with salicylic acid could result in an increase in Garden Thyme tolerance to stress conditions.