Effects of Methyl Jasmonate and Salicylic Acid on Increasing Cold Tolerance of Bell Pepper (cv.Emily) Seedlings

Among the chemicals that their effects on reducing chilling injury has recently been studied are salicylates and jasmonates. Therefore، in this study the effects of salicylic acid and methyl jasmonate on increasing the cold tolerance of bell pepper cv. Emily was examined. Experiment was done as a 7×2 factorial in the completely randomized design (CRD) with four replications. The first factor contained salicylic acid in three concentrations of 0. 1، 0. 5 and 1 mM and methyl jasmonate at the rates of 0. 001، 0. 01 and 0. 1 mM plus control (distilled water) and the second factor involved application of hormone، spraying whole plant and soil drenching. Treatments were applied at 7-9 leaves stage. After application of hormones، plants moved to 0º C for 3 days and then returned back to greenhouse temperature. Three days later different attributes were measured. Results showed that except for soluble sugars and leaf proline، there was no significant differences between two methods of hormone application. For all traits، application of hormone showed significant effects but due to significant interactions between hormone and application method، the effect of hormone treatment depended on the method of application. Drenching 0. 5 mM salicylic acid reduced chilling injury (necrotic lesions) and increased quantum efficiency of PSII (Fv/Fm)، chlorophyll content، soluble sugars and leaf proline، compared to untreated plants، thus improved cold tolerance. Methyl jasmonate in the rate of 0. 01 mM reduced chilling injury and increased Fv/Fm in comparison with control، but only when it was used as drench it increased concentrations of chlorophyll a and b and soluble sugars and cold tolerance compared to other two concentrations.