The effect of drought stress on proline contents, soluble sugars, chlorophyll and relative water contents of balm (Melissa officinalis L.)

In this research effect of drought stress on physiological characteristics of balm (Melissa officinalis L.) was performed 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 chlorophyll a, chlorophyll b, proline, soluble sugars, relative water contents, percentage and yield of essential oil were significant (α=0.001). Effect of drought stress on total chlorophyll was significant (α=0.005). Comparison of treatment means showed that highest chlorophyll a (1.921mg/l), chlorophyll b (1.197mg/l), total chlorophyll (2/283mg/l) were related to T1 (control), T5 (20%FC) and T1 (control), respectively. Highest accumulation of proline with 2.545 mg/l mean was related to T3 (60%FC). Maximum relative water content with 93.369 mean percentage related to T1 (control). It could be concluded that plant accumulation of proline and solublesugars increased tolerance and showed that moderate drought stress is beneficial for balm production.