Role of Salicylic Acid in Promoting Salt Stress Tolerance and Enhanced Artemisinin Production in Artemisia annua L.

In the present investigation, the role of salicylic acid (SA) in inducing salinity tolerance was studied in Artemisia annua L., which is a major source of the antimalarial drug artemisinin. SA, when applied at 1.00 mM, provided considerable protection against salt stress imposed by adding 50, 100, or 200 mM NaCl to soil. Salt stress negatively affected plant growth as assessed by length and dry weight of shoots and roots. Salinity also reduced the values of photosynthetic attributes and total chlorophyll content and inhibited the activities of nitrate reductase and carbonic anhydrase. Furthermore, salt stress significantly increased electrolyte leakage and proline content. Salt stress also induced oxidative stress as indicated by the elevated levels of lipid peroxidation compared to the control. A foliar spray of SA at 1.00 mM promoted the growth of plants, independent of salinity level. The activity of antioxidant enzymes, namely, catalase, peroxidase, and superoxide dismutase, was upregulated by salt stress and was further enhanced by SA treatment. Artemisinin content increased at 50 and 100 mM NaCl but decreased at 200 mM NaCl. The application of SA further enhanced artemisinin content when applied with 50 and 100 mM NaCl by 18.3 and 52.4%, respectively. These results indicate that moderate saline conditions can be exploited to obtain higher artemisinin content in A. annua plants, whereas the application of SA can be used to protect plant growth and induce its antioxidant defense system under salt stress.