Effect of Water Deficit Stress on Growth, Yield and Essential Oil Content of Dracocephalum moldavica

Moldavian balm (Dracocephalum moldavica) is an annual herb plant belonging to the Lamiaceae family. Moldavian balm is considered stomachic and sedative. Essential oil of this plant are used in pharmaceutical and food industries and possesses antimicrobial feature. To study the effects of different levels of water stress on growth, yield and essential oil content of Moldavian balm, a pot experiment in randomized complete block design with four treatments and four replications was conducted. Water stress treatments were: 100% of field capacity (non-stress), 85% of field capacity (mild water stress), 70% of field capacity (moderate water stress) and 55% of field capacity (severe water stress). According to the results of statistical analysis, water stress had significant effect on growth parameters, herb yield and essential oil yield. As the soil water content decreased, plant height, stem diameter, number and length of auxiliary shoots, fresh and dry herb yield in pot and essential oil yield decreased. There was no significant difference between water stress treatments for essential oil content. The highest amounts of essential oil content (0.35 ml/100gr dry weight) and essential oil yield (0.115 ml/pot) were observed in 70% and 100% of field capacity, respectively.