The plants can absorb nutrients and reduce water in face to drought stress. These conditions reduce plant growth rate and change physiological traits. In this study, the effect of drought stress on morphological and physiological characteristics of Thymus vulgaris L. was investigated under water deficit condition. A field experiment was conducted using three irrigation levels as 90% Field Capacity (90%FC), 50% FC and 25% FC based on a Randomized Complete Block Design (RCBD) in four replications. The seedlings of T. vulgaris were moved to the field and planted in early spring. The field was irrigated for each treatment for 3 months (June to August 2019). The soil moisture for each treatment was determined by the pressure plate method. At the end of the experiment, three plants in each plot were taken with their roots. The results of ANOVA showed significant differences between treatments for all the traits (P<0.05). For shoot length, the highest and lowest values of 43.2 and 19.9 cm were obtained in 90% FC and 25% FC, respectively. The highest shoot weight (13.66 g) and the lowest root weight (7.33 g) were obtained in 90% FC treatment. The highest and lowest values of both (total nitrogen and potassium) were obtained in 90% FC and 25% FC, respectively. The highest and lowest proline contents with values of 4.2 and 2.3 μmol/g FW were obtained in 25% FC and 90% FC, respectively. The highest values of soluble carbohydrates, Catalase (CAT) and Peroxidase (POD) activity were obtained in 25% FC compared to other treatment. Based on the results of present study, T. vulgaris L. is a suitable plant species for cultivation under drought stress conditions.
