Effect of Drought Stress on Some Morphological Characteristics and Essential Oil Production Levels of Ocimum basilicum in Different Stages of Growth and Development

Ocimum basilicum L.from Lamiaceae is used as a herb, spice and fresh vegetable. Since medicinal plants have different reactions to drought stress in the production of effective compounds, Diagnosis of medicinal plants growth under different irrigation conditions and drought stress can be a guide for growing plants in dry and low water conditions. Therefore, in order to evaluate the effect of drought stress on morphological characteristics and essential oil content, especially linalool, in different stages of plant growth of Basil plant, a completely randomized factorial design was carried out in 3 replications. The experimental treatments included three levels of dryness (no stress, mild stress and severe stress) in potted conditions, in vegetative, pre-flowering, flowering and fruit-growing stages. The results showed that drought stress had a significant effect on evaluated characteristics. So, with decreasing of soil moisture content, plant height, number and leaf area, decreased in all stages of growth and Stem diameter increased at all stages, especially in severe stress and root length, increased during flowering stage. In reproductive stages, drought stress caused a significant reduction in the number of flowers than the control. Extreme stress in flowering and fruiting stages has had decrease in the amount of essential oil production, especially linalool. However, mild stress showed increase in the production of these compounds in both steps. The highest percentage of essential oil was related to mild drought stress at flowering stage and the highest amount of linalool was due to mild drought stress in the fruiting stage.