Time and Concentration Dependent Changes in Antioxidant and Photosynthetic Capacity of Origanum vulgare L. (Lamiaceae) in Response to Exogenous Methyl Jasmonate

Oregano (Origanum L.) is a medicinal plant from the Lamiaceae family that its role in the treatment of various diseases is known since ancient time. This research was conducted with the aim of evaluating the effects of elicitation with methyl jasmonate (MeJA) on some physiological and biochemical properties of the oregano (Origanum vulgare L.) medicinal plant. An experiment in the form of a two-factor factorial completely randomized design were performed. The elicitor concentration at 4 levels (zero, 0.1, 0.5 and 2.5 mM) and the exposure time after applying the MeJA treatment at 4 levels (zero, 24, 48 and 96 h) were considered as the main factors. The highest contents of Chlorophyll a (Chl a) were seen in two treatment combinations of 0.0 mM MeJA, 48 h and 0.5 mM MeJA, 24 h. While, the highest level of Peroxidase (POX) activity was obtained in two treatments of 2.5 mM and 0.5 mM MeJA. The 2.5 mM concentration resulted in higher concentration of antioxidant enzymes up to 96 h after the treatment. Generally, the foliar spraying of MeJA caused an increased amount of Chl a, proline, antioxidant enzymes including ascorbate peroxidase (APX), catalase (CAT), polyphenol oxidase (PPO) and peroxidase (POX). But the MeJA concentration and post-treatment time showed no significant effect on the content of total soluble protein (TSP), chlorophyll b (Chl b) and carotenoids (CAR). The results of this research can be useful in botanical, biological, agricultural biotechnology and medicinal studies on Origanum and other medicinal plants.