Melissa officinalis is a perennial herbaceous plant from Lamiaceae family, widely used in food and pharmaceutical
industries to add aroma. Drought stress in plants may happen due to the increase in water loss, insufficient water
absorption or both. Salicylic acid (SA) is an important secondary metabolite in plants with hormone-like action in
some biochemical pathways. Adding it during water-deficit stress, may alter a number of physiological processes,
increasing the resistance of plant against possible damage by water loss. The aim of this study was to examine the
effect of drought stress (DRU) on secondary metabolites of Melissa officinalis and also the efficacy of salicylic acid
treatment to minimize the damages. According to the results, treatment of plant with 0.7 mM salicylic acid had
considerable alteration in the quantity of important secondary metabolites. Protein concentration increased in all
stages; Chlorophyll a reached to the highest amount; the amount of the MDA increased at the first and second
stages in 1/3 fc drought treatment as well as at the third stage in 2/3 fc. Besides, total phenol content increased at
stage I in 1/3 fc drought and the flavonoid content increased in 1/3 fc drought at all stages. Finally, content of
anthocyanin was increased at first and third stages 1/3 fc drought, as well as at second stage in 1/3 fc drought. In
conclusion, application of salicylic acid (0.7 mM) was useful for improving quality of lemon balm subjected to
stress due to water deficit