Introduction
Artemisia dracunculus L. is a perennial fragrant plant which is commonly used as a flavoring vegetable in many countries. The plant is widely used in the food, pharmaceutical, cosmetic, and health industries. The medicinal value of tarragon is due to the presence of essential oil, phenolics and flavonoids, phenolic acids, coumarins, and alkaloids. In the last decade, due to climatic changes, salinity stress has become one of the most important biological problems, which causes a decrease in plant productivity. Salinity stress, by creating water and ionic imbalance, induces drought stress and increases the concentration of vacuolar sap. Moreover, the ionic toxicity and ionic competition in the cell membranes as a result of salt stress leads to programmed cell death. Therefore, it is important to find solutions to overcome or reduce the effects of salinity stress on plants. Biochar is an organic carbonic compound that can affect the physicochemical structure of the soil. Biochar, by increasing the absorption of nutrients, enhances the cation exchange capacity, and water holding capacity in the soil, improves the soil structure, and increases the plant access to the soil nutrients, and in this way helps to enhance the yield of the plant.
Materials and Methods
To investigate the effects of soil-based biochar (zero, 7, and 14% v) application and, NaCl salinity stress (zero, 75, and 150 mM) on the growth and some physiological traits of Artemisia dracunculus L.; a factorial experiment was conducted based on the completely randomized design with three replications during 2022 in Research Greenhouse of Azarbaijan Shahid Madani University. After adding biochar to the soil mixture, tarragon rhizomes were plantd in the pots. One month later, after complete stablishment of plants, salinity levels were imposed. The plants were maintained in the growing medium for 3 month. Later the plant parts were sampled for the traits measurement.
 Results and Discussion
Plant height, aerial parts dry weight, chlorophyll a, hydrogen peroxide, malondialdehyde, proline, sodium, and potassium content were influenced by the interaction effects of experimental treatments. The treatments without salinity and 75 mM NaCl salinity stress + the application of 14% (v) biochar caused an increase in the plant height and aerial part dry weight of the plant. The highest content of chlorophyll a was obtained in the treatment without salinity stress + both levels of biochar and 75 mM NaCl salinity stress + application of 14% (v) of biochar. The salinity stress )150 mM( in the condition of not using biochar increased the content of hydrogen peroxide, malondialdehyde, and sodium content (35 mg g^-1 DW) of the plant. The highest proline content was observed in 150 mM salinity stress with both levels of biochar application and non-application. The highest potassium content was obtained in the treatment without salinity stress with the application of 14% (v) of biochar, which showed a 71% increase compared to the control. The potassium-to-sodium ratio was affected by the main effect of biochar, and the use of 7 and 14% biochar increased the potassium-to-sodium ratio of the plant. The independent effects of salinity stress and biochar affected leaf relative water content, essential oil, chlorophyll b, and carotenoid content. Seven and 14% biochar treatments increased the chlorophyll b content compared to the control. The application of 14% biochar raised the relative water content of leaves (17% increase compared to the control), and carotenoids. By increasing the salinity stress to 150 mM, the leaf-relative water content decreased by 22% compared to the control, and the highest leaf-relative water content was observed in the control. Both 75 and 150 mM salinity stress treatments increased carotenoid content. The top essential oil content was observed in 14% (v) of biochar, which showed a 76% increase compared to the control. 75 mM salinity stress increased the essential oil content as well. 18 components were identified in Artemisia dracunculus essential oil.Estragole (84.3-90.8%) was the dominant component of the essential oil, and the highest content of this compound was obtained in 150 mM NaCl salinity stress + 14% biochar application.The second component in terms of abundance was d-limonene (1.05-3.02%), and the highest content of this compound was observed in the 75 mM salinity stress + 7% (v) of biochar application.
 Conclusion
The overall results showed that 150 mM salinity stress hurts the growth and physiological characteristics of A. dracunculus, but the use of biochar at the rate of 14% improved the growth and physiological characteristics and even enhanced the dominant components content of essential oil under salt stress.
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