Objective  Effects of magnesium (Mg) application on the endogenous hormones, medicinal material yield, and active componentl-borneol accumulation of Blumea balsamifera (L.) DC. during growth periods were studied.

  Method  One-year-old seedlings of B. balsamifera were treated with MgSO₄·7H₂O to provide the plants with Mg at levels of 0.0, 1.5, 15.0 or 150.0 mg·mL⁻¹. Spanning across the growth periods of the plants, contents of gibberellic acid (GA₃), auxin (IAA), abscisic acid (ABA), and zeatin (ZR) in leaf were determined by the enzyme linked immunosorbent assay; yield of medicinal material on an electronic scale; and, contents of l-borneol by GC. The combined total l-borneol in life cycle was calculated as the per plant yield of the active component.

  Result  On the 30th, 60th, and 90th day after the treatments, the 4 endogenous hormones and medicinal material yield of the treated plants significantly increased. The greatest effects were observed at the application levels of 1.5 or 15.0 mg·mL⁻¹. Sampled on the 60th and 90th day, the l-borneol contents in leaf significantly differed by the varied treatments the plants received (P<0.01). The lowest content showed up in the leaves tested on the 60th day after the 0.0 mg·mL⁻¹ control treatment, while 1.5 mg·mL⁻¹ had 34.37%, 15.0 mg·mL⁻¹ applications rendered 35.48%, and 150.0 mg·mL⁻¹ resulted in 25.00% on l-borneol. At the end of 90d, the l-borneol in leaf under 1.5 mg·mL⁻¹ treatment was significantly higher than those under other treatments, but no statistically significant differences found among the treatments on the 30th or the 120th day (P>0.05). All Mg applications significantly increased the per plant yields on l-borneol (P<0.05).

  Conclusion  The Mg applications significantly boosted the endogenous hormones, medicinal material yield, and l-borneol production of the individual B. balsamifera plant in 30 d. On the 60th, 90th, and 120th day, the applications at the rates of 1.5 and 15.0 mg·mL⁻¹ seemed more apparent in promoting the yield of the medicinal material and the content of l-borneol than either control or the highest dosage.