Improving essential oil content and yield of ajowan organs under water stress by application of salicylic acid and abscisic acid

This research was carried out in 2014 and 2015 to assess the effects of salicylic acid (SA) (0 and 1 mM) and abscisic acid (ABA) (0 and 50 µM) on essential oil content and yield of ajowan (Carum copticum L.) organs under different irrigation intervals (I1, I2, I3, I4: irrigation after 70, 100, 130 and 160 mm evaporation, respectively). Plants were sprayed by SA and ABA at vegetative and reproductive stages. In both years, the biomass of vegetative organs (leaves and stem), flower production and seed yield per unit area of ajowan decreased with decreasing water availability. All organs mass improved by application of ABA and particularly SA. Essential oil percentage of all organs increased, but essence yield decreased as a result of water limitation. Reduction in essential oil yield of ajowan organs due to water stress strongly related with the reduction of individual organ mass under stress. Foliar spray of ABA and especially SA improved the medicinal and commercial value of ajowan under different irrigation intervals by enhancing plant organs biomass and accumulation of more essential oil.