The effect of methyl jasmonate on antioxidant enzymes and improving the resistance of Cucurbita pepo in low temperature

Early sowing in spring season is important for the use of mild conditions as well as proper vegetative growth, but the occurrence of low temperatures at the beginning of the growing season may cause the problem for plant establishment. In order to investigate the effect of methyl jasmonate (MeJA) on antioxidant enzymes and improving the resistance of pumpkin (Cucurbita pepo) to low temperature stress, a factorial experiment include six concentrations of methyl jasmonate (0, 1, 5, 50, 100 and 150 μM) and three temperature levels (8, 11 and 14 °C) was conducted in a completely randomized design. The results showed that no seeds were germinated at 8 °C. At 11 °C and lack of methyl jsmonate, no seeds were germinated, but the application of methyl jasmonate increased germination to 76.66%. At 14 °C and lack of methyl jasmonate, only 26% of the seeds are germinated. However, the application of methyl jasmonate increased germination to 100%. The highest germination rate was recorded at 1 and 50 μM methyl jasmonate, which that at 14 °C. The activities of superoxide dismutase and guaiacol peroxidase were very high at both concentrations of MeJA, but at 11 ° C the highest activity of these enzymes were observed at a concentration of 1 and 100 μM of methyl jasmonate. At 14 °C, the catalase activity was higher in methyl jasmonate treatments than the control but at 11 °C it was more in the control than the methyl jasmonate treatments. Therefore, the valuable effect of methyl jasmonate to creating resistance to   relatively cool air (above 10 °C) has been proven. According to results of this experiment, it can be said that the application of methyl jasmonate increases the resistance of the seeds of pumpkin seeds to low temperature stress, and the earlier sowing of this plant can increase its production potential.