عنوان مقاله [English]
Background and objectives: The production of metabolites in medicinal plants farming is very important. Therefore, the application of some materials for increasing growth and production of secondary metabolites has driven attention. Elicitors are efficiently applied for increasing secondary metabolites production in medicinal plants. Elicitors can induce physiological changes in plant. Exogenous application of the compounds like jasmonic acid and salicylic acid causes induction of virtual stress in plant and triggers defensive responses. In response to created oxidative stress, plant increases the expression of antioxidant genes followed by an increase in activity of enzymatic and non-enzymatic antioxidants (mostly have medicinal properties). Accordingly, this experiment was aimed at studying the jasmonic acid and salicylic acid effects on induction of oxidative stress and increasing resistance and yield of Echinacea.
Materials and methods: The present experiment was conducted as randomized complete blocks design with 12 treatments and three replications in Agriculture Faculty of Shahrood University of Technology in 2015-2016. Experimental treatments were spraying the jasmonic acid with 4 concentrations (0, 5, 20 and 50 micromolar), the salicylic acid with 3 concentrations (0, 5.0 and 1 milimolar) and spraying both of them [(5ja-0.5 sa, 20 ja-0.5 sa and 50 ja- 0.5 sa) and (5ja-1 sa, 20 ja-1 sa and 50 ja- 1sa)] three times with ten-day intervals, starting from reproductive stage initiation. The induced oxidative stress was presented by measuring NADPH oxidase activity and oxygen peroxide concentration, increasing resistance measured by antioxidant enzymes activity including catalase, guaiacol peroxidase, poly phenol oxidase, ascorbate peroxidase, and non-enzymatic antioxidant activity including total phenol and petal ascorbic acid; finally, the reaction of leaf soluble protein, chlorophyll a and b, leaf dry weight and dry flower yield to spraying was measured.
Results: The analysis of variance results indicated that spraying affected significantly all studied traits. The highest amount of NADPH oxidase was observed for treatment 20ja-1sa which was 1.6 times of control. The highest concentration of oxygen peroxide was seen for treatments 5 micromolar jasmonic acid and 0.5 milimolar salicylic acid. The top amount of catalase enzyme activity was found for 20 micromolar jasmonic acid treatment with an average of 0.021 micromole per minute per gram fresh tissue. The highest and the lowest activity of leaf guaiacol peroxidase were observed for 20 micromolar jasmonic acid-1 milimolar salicylic acid and control treatments, with average of 0.205, and 0.038 micromole per minute per gram tissue, respectively. The top value of ascorbate peroxidase activity was found for 20 micromolar jasmonic acid-1 milimolar salicylic acid treatment with an average of 0.29 micromole per minute per gram fresh leaf tissue, which was almost twofold of control. The greatest amount of total phenol was obtained for 0.5 milimolar salicylic acid which appeared to be 3.68 times of control. The greatest amount of ascorbic acid was observed for five micromolar jasmonic acid-0.5 milimolar salicylic acid treatment which appeared to be 4.68 times of control.
Conclusion: Elicitors induce the transduction signal network. Following that, cytoplasm acidification and increase in amount of extra cellular pH take place. The NADPH oxidase activity, responsible for production of reactive oxygen species, increased and production of H2O2, one of the reactive oxygen species, got enhanced. The activity of enzymatic and non-enzymatic antioxidants such as phenols and acid ascorbic concentrations promoted. Increasing the activity of defense systems in plant causes the creation of favorable conditions for construction activities such as enhancing the amount of chlorophyll a and b, and soaring soluble protein content and finally increasing the weight of leaf and flower of plant.