Two pot experiments were conducted on the 17th and 11th of march during 2015 and 2016 growth seasons respectively at the greenhouse, Dept. Agric. Botany, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Egypt to investigate the impact of drought stress on some growth, biochemical and anatomical parameters of Thymus vulgaris L. Plants were exposed to two different irrigation levels: 70-80 and 30-40 of water holding capacity (WHC) as well-irrigated and drought stressed plants respectively. The results indicated that all investigated growth parameters and leaf photosynthetic pigments were decreased significantly by exposing to drought stress. There were significant increase in the concentration of reactive oxygen species (ROS) as indicated by measuring of H2O2 and malondialdehyde (MDA). A similar trend was observed in respect to osmolytes including proline, total soluble sugars and free amino acids. Also, drought stress increased significantly total soluble phenols and the specific activity of Phenylalanine ammonia-lyase (PAL) and Polyphenol oxidase (PPO), whereas, no significant differences were detected in peroxidase (POD). The anatomical examination showed that there were several significant changes associated with water limited supply in the stem and leaf of plants.
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