Effects of the role of salicylic acid, drought stress, ethylene and interaction of three factors on seed germination of Brassica napus

Salicylic acid (SA) or orthohydroxybenzoic acid and other compounds which are belong to this group are plant phenolics that play a major role in regulation of many physiological processes e.g. growth, development, ion absorption and germination. In this study, the effects of salicylic acid (0.1, 1, 1.5, 2, 2.5 and 5mM) on seed germination of Brassica napus were investigated. 20 seeds were transferred on whattman paper inside of each Petri dish. All Petri dishes were incubated to germinator. The condition of germinator was: 16h day light and 8h dark period with 230C and 160C respectively and the humidity condition inside germinator was 58%. Germination percentage and the rate of germination were measured up to 5 days. Triton X-100 was used as surfactant for either control or treated plants. For drought treatment, solutions of polyethylene glycol 6000 were prepared with water potential 0, -0.4, -0.6, -0.9and -1.1 Mpa. 6 levels of ethylene treatment were applied (0, 10, 30, 50, 70, 90 ppm). For interaction effects of salicylic acid on drought stress, 4 levels of salicylic acid (0, 1, 1.5, 2 mM) and 3 levels water potential of (0, -0.4, -0.6 Mpa) were investigated. The seeds were treated for 2 days in salicylic acid and therefore 3 days in polyethylene glycol 6000. For observation of interaction effects of ethylene on salicylic acid and ethylene on drought stress, 4 levels of salicylic acid treatment (0, 0.5, 1, 1.5 mM), 3 levels of ethylene in (0, 10, 50 ppm) and 3 levels of water potential (0, -0.4, 1.1 Mpa) were applied. Results showed that the percentage of seed germination was reduced significantly in treated seeds with salicylate when compared with control. However, osmotic stress did not effect on germination percentage but seed germination rate reduced significantly. Interaction effect of salicylic acid and ethylene on seed germination was significant as well as drought stress. Mean of the required for day germination isnt sometimes applied for calculation of germination rate. Therefore, we suggest that the sum of instantaneous velocity used germination rate calculation. Priming with salicylic acid is advisable to be done in low temperature. Treatment with ethylene reduced negative effects of salicylic acid and drought stress on seeds germination, thus we suggest ethylene can be used for better germination.