Effect of salicylic acid application on some physiological characteristics and essential oil production of lemon verbena (Lippia citrodora L.) under salinity stress

The aim of this research was to study the effect of salicylic acid (SA) usage on some physiological characteristics and essential oil production of lemon verbena (Lippia citrodora L.) under salinity stress. For this purpose, a pot factorial experiment was performed based on a completely randomized design with 4 salinity levels (0, 50, 100 and 150 mM NaCl), 4 SA levels (0, 150, 300 and 450 mg/L) and three replications. The measured traits included total soluble protein, malondialdehyde (MDA), hydrogen peroxide, glycine betaine, some antioxidant enzyme activities, and essential oil production. The interaction effect of the treatments on all of the studied traits were significant at 1% P value. The results showed that the highest amount of total soluble protein, MDA, hydrogen peroxide, glycine betaine, ascorbate peroxidase and superoxide dismutase activities were observed at 150 mM salinity level and application of SA at 300 mg/L causes to decrease total soluble protein and glycine betaine, and 150 mg/L of SA causes to decrease MDA. But application of this plant growth regulator had no significant effect on hydrogen peroxide. Also, the results showed that catalase enzyme activity and essential oil content at the highest salinity level (150 mM) reached to the lowest amounts. In total, the results of this study indicated that the SA application especially at 300 mg/L causes to improve the studied traits in this experiment and its usage under stress conditions is recommended.