Objective  Roles of iron (Fe), manganese (Mg), boron (B), and molybdenum (Mo) played in the seed germination and seedling physiological activities of Polygala tenuifolia were studied.

  Methods  P. tenuifolia seeds were soaked in solutions containing the trace elements in 5 concentration gradients. Seed germination was evaluated according to the germination rate, germination index, and seedling vigor index. Measurements on root length, fresh weight, and contents of proline, soluble total sugar, superoxide dismutase (SOD), peroxidase (POD), and superoxide dismutase (POD) of the seedlings were also obtained for the analysis.

  Result  The Fe treatments of 0-40 mg·L⁻¹ increased the indices except proline content with statistically significant differences. But beyond that level the indices declined rapidly. Under the Mg treatments in the range of 0-150 mg·L⁻¹, all indices excluding proline content increased to levels higher than those of control except for catalase activity. As did with Fe, when the Mg concentration became higher, the indices declined. The proline content increased in the seeds being treated with either Fe or Mg within the concentration ranges tested. The seed germination rate and index as well as the seedling vigor index, root length, and fresh weight increased with increasing B concentration from 0 to 1.5 mg·L⁻¹ with a peak observed at 1.0 mg·L⁻¹, which was higher than that of control. At 1.5 mg B·L⁻¹, the contents of proline and total soluble sugar and the activities of SOD, POD, and CAT reached their maximal levels, which, beside proline, were higher than those of control. In the concentrations of 0-40 mg·L⁻¹, Mo induced increases on the indices higher than those of control, but not on proline content and SOD activity. At higher concentrations, Mo caused declines on the indices.

  Conclusion   The selected trace elements could promote the germination of P. tenuifolia seeds at low concentrations but inhibit it at high concentration. The treatments of 40 mg Fe·L⁻¹, 150 mg·L⁻¹ Mg, 1.0-1.5 mg·L⁻¹ B, or 40 mg·L⁻¹ Mo appeared best for the seed germination as well as seedling growth.