Introduction: Basil (Ocimum basilicum) is an annual plant which belongs to the Lamiaceae family. It used as a drug, spice and fresh vegetable. Drought stress is one of the important limiting factors of plant growth. Water stress has significant effects on morphological and biochemical characteristics of purple Basil. As the soil water content decreases, the plant height, stem diameter, number and area of leaves, leaf area index (LAI), herb yield and leaf chlorophyll contents (a, b and total chlorophyll) decrease, as well. However, the amounts of anthocyanin and proline increase….