Improving drought tolerance of germinating seeds by exogenous application of gibberellic acid (GA(3)) in rapeseed (Brassica napus L.)

In this study, the application of gibberellic acid-3 (GA(3)) during priming to improve drought tolerance in rapeseed (Brassica napus L.) was evaluated. Seeds of rapeseed (c.v. Zhongshuang No.10) were primed in 0, 100, 200, 300, 400 and 500 mg.1(-1) aerated solution of GA(3) for 8 h. The primed seeds were set to germinate for 7 days under simulated drought stress by applying 15% PEG6000 solution. GA3 significantly improved seed germination characteristics under drought stress. Compared with no-GA(3) priming treatment, seeds with 300 mg.1(-1) GA(3) showed a significantly increased drought tolerance index (88% increase), seedling fresh weight (42.9%) and hypocotyl length (72.7%). GA(3) treatment also significantly increased soluble sugars (47.2% increase), soluble proteins (35.6%) and free proline (62.9%). The level of electrolyte leakage from seedling cotyledons was significantly reduced after priming and the malondialdehyde (MDA) content of the cotyledons decreased by 36.6%, possibly due to the enhanced levels of superoxide dismutase (increased by 13%), catalase (increased by 45.6%) and peroxidase (increased by 46.6%). The result of this research showed that use of GA(3) during priming enhances seed germination of rapeseed and improves seedling tolerance to drought stress.