Effects of Methyl Jasmonate on Some Physiological and Biochemical Responses of Licorice (Glycyrrhiza glabra L.) at Different Salinity Levels

Salinity is a major environmental factor limiting plant growth in natural ecosystems. Glycyrrhiza glabra is an important Fabaceae (perennial plant) that its root and rhizome extracts are used in food, health, medical and pharmaceutical industries. To assess the effect of methyl jasmonate (MeJA) and salinity on licorice, an experiment was conducted as factorial based on completely randomized design with three replications. Accordingly, plants were exposed to the concentrations of 0, 100, 200 and 300 mM NaCl for five weeks, 24 h after foliar application of 0, 50 and 100 µM MeJA. In our experimental condition, a significant decrease in shoot dry weight, shoot and root fresh weights, plant height, leaf relative water content (RWC), Ca concentration of shoot and root and root Mg concentration were observed at 300 mM NaCl, while total chlorophyll, chl a and chl b concentrations and carotenoids were not affected significantly by salinity. Also, NaCl at 300 mM caused a significant increase in proline and total soluble sugar contents, Na+/K+ ratio and dry weight of roots. Results showed that exogenous application of MeJA at 50 µM level improved plant tolerance to salinity up to 200 mM NaCl and increased growth parameters, photosynthetic pigments, soluble sugar and proline content of shoot and root in comparison with control. Moreover, the application of MeJA caused a significant increase in Mg concentration of the shoot and root of control plants.