Effect of Salicylic Acid Foliar Application on Yield and Essential Oil in Moldavian Balm Under Salinity Stress Conditions

Moldavian balm (Dracocephalum moldavica) is a valuable medicinal plant adaptable to different climatic regions found in the North and North West of Iran. Soil salinity is known as a limiting factor for plants growth in arid and semi-arid regions of the world, including Iran. This study was carried out as a factorial experiment based on a completely randomized design in order to investigate the effect of four levels of salicylic acid solution (0, 0.5, 1 and 5.1 mM) and three levels of salinity with sodium chloride (0, 2.5 and 5 mmohs/cm) with three replicates on some morphological traits, yield and essential oil of Moldavian balm at greenhouse. Number of lateral flowering stems was reduced by 9.3 and 28.4% under 2.5 and 5 mmohs/cm salinity, respectively compared to non-stress condition. Also, 0.5, 1 and 1.5 mM salicylic acid increased number of lateral flowering stems by an average of 32.5 % compared to the control. Results of mean comparison showed that in 2.5 mmohs/cm salinity, application of all three concentrations of salicylic acid, and in 5 mmohs/cm salinity, application of 1 and 1.5 mM salicylic acid, shoot dry weight of plant, essential oil percentage, essential oils yield and harvest index of essential oil had better performance than the control. Concentrations of 0, 1 and 1.5 mM of salicylic acid increased root dry weight of plant in 2.5 and 5 mmohs/cm salinity compared to the control. Chlorophyll content was significantly decreased in 5 mmohs/cm salinity level, but the application of all three levels of salicylic acid increased Chlorophyll content as much as 15 percent compared to the control.