Objective  Effects of pre-soaking seeds in isosteviol solution on germination and seedling growth of Brassica napus under salt stress were studied.

  Method  Seeds of Qinyou No. 2, a variety of B. napus , were pre-soaked in isosteviol solutions of different concentrations to determine the rate, index, and vigor of the seeds, as well as the height, chlorophyll content, root length and activity, malonaldehyde (MDA) content, and antioxidant enzyme activity of the seedlings under salt stress.

  Result  Salt stress inhibited the germination of B. napus seeds with a threshold concentration at NaCl 140 mmol ·L⁻¹. By pre-soaking the seeds in a 1×10⁻⁸ mol·L⁻¹ isosteviol solution, the root activity, chlorophyll content, and SOD activity in cotyledons of the seedlings were significantly increased. Compared to CK₂ (seeds pre-soaked in deionized water prior to germination in a NaCl 140 mmol ·L⁻¹ medium), the isosteviol treatment increased 27.33% on root activity, 36.94% on chlorophyll content, and 83.31% on SOD activity, while significantly reduced MDA content by 32.11% in the cotyledons. When a 1×10⁻⁹ mol·L⁻¹ isosteviol solution was used for the pre-soaking, the POD and CAT activities were significantly increased by 140.80% and 47.25%, respectively, over those under CK₂. The pre-soaking treatment also significantly improved the germination rate, index, and vigor of the seeds, and significantly increased the height and root length of the seedlings.

  Conclusion  Pre-soaking the seeds with an isosteviol solution of appropriate concentration (i.e., 1×10⁻⁹−1×10⁻⁸ mol·L⁻¹) enhanced the salt resistance of B. napus reducing the adverse effects on the seed germination and seedling growth caused by the salt stress.