Effects of drought stress on the quantity and quality of essential oil and water use efficiency in Eucalyptus (Eucalyptus camaldulensis Dehnh.)

Drought stress has different effects on morphological, physiological and biochemical processes of plants. Moreover, the quantity and quality of essential oil are affected by drought stress. Eucalyptus species including Eucalyptus camaldulensis Dehnh. are considered as rich sources of essential oils especially 1,8-cineol. In order to study the effect of drought stress on essential oil yield, the type of chemical compounds and also water use efficiency in E. camaldulensis, this research was conducted in a completely randomized design with three treatments including 100, 70, and 40% field capacity and three replications. The experiment was carried out in combat desertification research station of Shahid Sadoughi under lisymetry conditions. Results showed that increasing of soil moisture led to the increased production of essential oil. However, mild drought stress resulted in increased essential oil yield and improved water use efficiency. Mild drought stress compared to other treatments (p < 0.001), improved the production of 1, 8-cineol, however it was observed that it decreased or stopped the production of many other compounds. The percentage of 1, 8 - cineol in the treatments of 100, 70 and 40% field capacity, were, 69.33, 78.13 and 51.87, respectively. The production of α-pinene, as another important compound was also affected by enough moisture (without stress) so that It's value showed significant difference with other treatments (p <0.001). The percentage of α-pinene in the treatments of 100, 70 and 40% field capacity, were, 14.0, 7.03 and 4.06, respectively. The moisture treatments including 100% FC (without stress), 70% FC (mild stress) and 40% FC (severe stress) were studied with three replicates and completely randomize design.