Phytochemical changes essential oil and growth performance of Thymus daenensis Celak. under the influence of light and salicylic acid

In this study, to investigate the phytochemical changes of essential oil and growth performance of Thymus daenensis Celak. affected by light and salicylic acid, an experiment was conducted as a split plot in a completely randomized block design with three replications. The tested factors included salicylic acid foliar spraying at three levels (0-0.2 M) and two light levels (50-100%). Special nets were used to create 50% shading. The amount of light reduction compared to the control treatment was measured by a lux meter. Foliar spraying was done before flowering. Plant essential oil was obtained from flowering aerial branches by Clevenger apparatus and analyzed by GC-MS. The highest yield of flowering branches and height were from 0.1 M salicylic acid (33.35 kg/ha and 24.33 cm, respectively) and full light treatments (32.50 kg/ha and 22.47cm respectively). The highest amount of chlorophyll a (5.2 mg/g), chlorophyll b (1.98 mg/g) and the number of lateral branches (180/35) due to the application of 0.1 M salicylic acid × 50% light treatment significantly increased compared to the control treatment. The amount of essential oil decreased with increasing light intensity and the use of salicylic acid improved this attribute. So that with full light intensity it reached the lowest level of 1.95% and the application of 0.1 M salicylic acid increased the percentage of essential oil (3.1) compared to the control treatment. The most components of thyme essential oil with the use of 0.1 M salicylic acid× 50% light treatment include carvacrol (4.4%), paracetamol (14.6%), beta-caryophylline (5.95%). Also, the highest amount of thymol was related to 0.1 M salicylic acid treatment (59.66%) and full light (57.8%). In general, the results showed that the use of salicylic acid has a positive effect on improving the qualitative and quantitative characteristics of the essential oil components of thyme. (5.95%). Also, the highest amount of thymol was related to 0.1 M salicylic acid (59.66%) and full light (57.8%). In general, the results showed that the application of salicylic acid had a positive effect on improving the qualitative and quantitative characteristics of the essential oil components of thyme.