Although there is a plethora of traditional plants with great therapeutic potential, the majority of medicinal plants have yet to be utilized on a large scale. One of the main reasons for this is the chemical variability inherent in plant-derived therapeutics. Many of the medically useful secondary metabolites produced by plants are the result of the latter's response to stress. When medicinal plants taken from the wild are cultivated under “optimal” growing conditions, the natural stressors on the plant are removed and, therefore, the content of secondary metabolites and, consequently, the therapeutic activity of the plants are greatly reduced. A possible aid in overcoming these difficulties is elicitation, the use of biotic and abiotic elicitors to stimulate the stress response in plants and increase the content of biologically active compounds. Elicitation has already been utilized in the study of disease resistance in plants, as well as in metabolic studies in cell culture. Elicitation can also be a powerful aid in the characterization and development of many potentially beneficial medicinal plants. This review summarizes the current state of knowledge concerning the utilization of biotic and abiotic elicitors in plants.

Elicitation: An Underutilized Tool in the Development of Medicinal Plants as a Source of Therapeutic Secondary Metabolites

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.

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

Modulation of salt stress effects on the growth, physio-chemical attributes and yields of Phaseolus vulgaris L. plants by the combined application of salicylic acid and Moringa oleifera leaf extract

Salicylic acid in relation to other phytohormones in plant: A study towards physiology and signal transduction under challenging environment

Salicylic acid (SA) is a common, plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was therefore conducted to test whether the application of SA at various concentrations (0, 0.10, 0.50, or 1.00 mM) as a foliar spray would protect pistachio (Pistacia vera L.) seedlings subjected to salt stress (0, 30, 60, or 90 mM NaCl). SA improved growth rate of pistachio seedlings under salt stress and increased relative leaf chlorophyll content, relative water content, chlorophyll fluorescence ratio, and photosynthetic capacity as compared with the control at the end of salt stress. SA ameliorated the salt stress injuries by inhibiting increases in proline content and leaf electrolyte leakage. It appeared the best ameliorative remedies of SA obtained when pistachio seedlings were sprayed at 0.50 and 1.00 mM.

Improving salt tolerance by exogenous application of salicylic acid in seedlings of pistachio

Plant secondary metabolites constitute the most important class of natural products with diverse and valuable chemical properties and biological activities Artemisinin, isolated from Artemisia annua L, is potentially a drug that could be effective against multidrug-resistant strains of the malarial parasite, Plasmodium Salicylic acid (SA) acts as a potential plant growth regulator and plays an important role in regulating a number of plant physiological and biochemical processes The present study was conducted to assess the alterations in plant growth, photosynthetic capacity, enzyme activities, and content and yield of artemisinin in Artemisia annua L in response to foliar application of SA Four levels of SA (000, 025, 050, and 100 mM SA) were applied on the aboveground plant parts Plant height and dry weight were altered significantly as the level of SA increased Besides, application of SA positively improved chlorophyll and carotenoid contents Furthermore, significant enhancement in net photosynthetic rate (317%) and the activity of nitrate reductase (172%) and carbonic anhydrase (109%) was noticed as the level of SA was increased from 000 to 100 mM SA Most importantly, the content and yield of artemisinin was positively regulated by the SA In comparison to no SA application (control), SA at 100 mM increased the content and yield of artemisinin by 258 and 500%, respectively

A. Khan

Papers

Salicylic acid acts as potent enhancer of growth, photosynthesis and artemisinin production in Artemisia annua L.