This experiment was conducted to investigate the effect of drought stress and vermicompost biofertilizer on some morphological, physiological and biochemical characteristics of Thymus vulgaris in greenhouse of Khorramabad Agricultural and Natural Resources Research and Training Center in a completely randomized design with three replications. The pot experiment was performed. Factors included vermicompost fertilizer levels at 0, 30, 50 and 70% of pot volume and water stress including post-discharge irrigation (85 (control), 70 (moderate stress), and 55 (severe stress). The moisture content was the field capacity. The results showed that with increasing drought stress, the amount of photosynthetic pigments (chlorophyll a and chlorophyll b), antioxidant enzyme catalase, protein, secondary metabolites of alpha-terpinene, thymol and carvacrol and morphological traits of plant height, number of sub-branches, fresh weight and dry weight of plants decreased significantly, but drought stress of antioxidant enzymes and hydrogen peroxidase significantly increased the amount of unstructured soluble sugars and amino acid proline. Increased consumption of vermicompost significantly increased chlorophyll b, hydrogen peroxidase, alphaterpinene, thymol, carvacrol, essential oil percentage, plant height, number of sub-branches, fresh weight and dry weight of plant, but chlorophyll a and unstructured soluble sugars reduced. According to the results of this experiment, with increasing the severity of drought stress, despite the plant's antioxidant defense and osmotic regulation, the production of most secondary metabolites and the growth of the thyme stress-sensitive plant decreased significantly; However, consumption of vermicompost increased secondary metabolites, growth and fresh and dry weight of the plant.

Keywords: antioxidant enzymes, Osmotic regulation, photosynthetic pigments, secondary metabolites

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