Evaluation the effects of cycocel and salicylic acid on some physiological characteristic and essential oil under normal and drought conditions in medical plant Dragonhed (Dracocephalum moldavica L.)

Drought is one of the most important environmental stresses which impact on morphological, physiological and biochemical process of plant and have major effects on agricultural productions. Application of plant growth regulators like salicylic acid as growth stimulator and cycocel as growth inhibitor effect on different growth process and influence on increases of drought tolerance. In order to study the effect of growth regulators, cycocel and salicylic acid on physiological changes and essential oil at dragonhead in drought stress condition in the research field of Zanjan University.
Material and A split plot experiment with two factors irrigation (normal and water stress) and growth regulators treatment (control, 600 and 1200 µm cycocel and 800 and 1600 µm salicylic acid) was conducted in based of completely randomized block design with four replications. Two moisture regimes (normal and drought stress) were main factors. In drought stress, plants were irrigated before flowering stage and after that irrigation was stopped in drought stress treatment until end of experiment. Different levels of salicylic acid (800 and 1600 µm) and cycocel (600 and 1200 µm) and control were sub factors which was applied once, two days before drought treatment.
Findings: Interaction of moisture in growth regulators in year for treats transpiration, stomatal conduct, photosynthesis, mesophyll conduct and photosynthesis water use efficiency was significant, but treats of relative water content, essential oil percent, essential oil yield and sub-stomatal CO2 concentration was not significant. Mean compression of interaction of growth regulators in moisture for essential oil yield indicated that there is no significant differences between growth regulators treatment in drought stress, but in normal condition it had significant impact, so that the highest essential oil yield obtained at 1600 µm salicylic acid. A negative and significant correlation between essential oil percent with transpiration, stomatal conduct and photosynthesis rate and also exist a positive and significant correlation with photosynthesis water use efficiency.
Results of this experiment showed that drought stress reduced physiological traits include, chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate and also it significantly changed plant water status and decreased relative water content. Drought stress decreased essential oil present and essential oil yield. So that even the use of growth regulators that used in this experiment were unable to compensate for this decrease. So it can be concluded that in drought stress conditions due to decreased chlorophyll and greenness plant and also reduced leaf area in dragonhead the essential oil is reduced