The effect of water deficit on quantitative and qualitative characters of balm (Melissa officinalis L.)

In order to study drought stress effect on quantitative and qualitative features of balm (Melissa officinalis L.) a research was conducted under field condition in Karaj, Iran in 2005. Experiment was conducted using Randomized Complete Block Design with 4 replications. Treatment included T1 (non stress), T2 (80%FC), T3 (60%FC), T4 (40%FC) and T5 (20%FC). Effect of drought stress on shoot yield, essential oil yield, percentage of essential oil, leaf and stem yield, height, tiller number, length and width of leaf, stem diameter and internodes was significant (α=0.001). Effect of drought stress on number of lateral stem was not significant. Comparison of treatment means showed that highest shoot yield was related to T1 (non Stress) (6469kg/ha), highest essential oil (12.970 kg/ha) and highest essential oil percentage (0.3012%) was related to T4 (40%FC) and T5 (20%FC), respectively. Highest height (65.32 cm), leaf length (6.27 cm) and width (4.58 cm) were related to T1 (non stress). Highest stem diameter was related to T5 (20%FC). It could be concluded that moderate drought stress is beneficial for balm essential oil.