The effect of drought stress on growth indices of Balm (Melissa officinalis L.)

The effect of drought stress on growth indices of Balm (Melissa officinalis L.) wasconducted in Alborz Research Station-Karaj Iran. This research was performed under aCompletely Randomized Block Design with 4 replications in 2006. In this research theeffect of stress treatments T1 (control=100%FC), T2 (80%FC), T3 (60%FC), T4 (40%FC) and T5 (20%FC) were studied on some growth indices of Balm such as LAI, TDW, CGR, and RGR according to the Growing Degree days. Results showed that the maximum LAI and TDW were 2.5 and 650 gr/m2 in control (100%FC) treatment respectively. So minimum LAI and TDW related to hard stress treatment (20%FC). The control treatment had high CGR in the first and end of growth periods but RGR was low in the late in this treatment. The maximum RGR were observed in medium stress and specially 60%FC. It had distinguished that the best indices were belonged to non stress condition. But, attention to closely of 60%FC indices to control and highest percentage and yield of essential oil of this treatment was accepted as a suitable drought stress in production of this plant.