Evaluation of the foliar application effect of salicylic acid on the morpho-physiological and phytochemical traits of the essential oil from Satureja bachtiarica Bunge. under deficit irrigation conditions

Cultivation of Satureja bachtiarica Bunge. in dry conditions requires the use of novel methods to obtain the highest yield of the effective medicinal substances. This investigation was done to investigate the effect of foliar application of salicylic acid (SA) at 1 mM on the morpho-physiological and phytochemical traits of S. bachtiarica under water deficit conditions during two experimental years (2017-2018 and 2018-2019) in Shahrekord, Iran. The experiment was performed as a factorial in a CRBD with three replications, which irrigation treatment in two levels [normal irrigation (irrigation after draining 30% F.C.) and deficit irrigation (irrigation after draining 50% F.C.)], and the foliar application at two levels (control and SA) were considered. The essential oil from the aerial parts of the herb was extracted by water distillation and analyzed by GC/MS. The content of chlorophyll a, b and total at 663 and 645 nm, carotenoids at 470 nm and the content of proline at 520 nm were determined using a spectrophotometer. According to the results, water deficit stress caused the physiological and phytochemical changes in S. bachtiarica. As the amount of proline (139%), chlorophyll a (57%), b (46%) and total (55%), the essential oil content (7%) and carvacrol as the major compound (7%) increased under water deficit stress. The highest values of the essential oil content (1.67% v/w), the concentrations of carvacrol (45.7%) and p-cymene (18.6%) were obtained under deficit irrigation under SA. The maximum levels of thymol and β-caryophyllene were achieved from the herbs under deficit irrigation as well as SA foliar application. Totally, SA as a defense factor reduced the negative effects of deficit irrigation conditions on most of the evaluated traits. In conclusion, the foliar-spraying of salicylic acid is recommended for stabilize of the quantity and quality of the active substance yield of S. bachtiarica under water deficit stress.