Objective: To investigate effect of exogenous magnesium(Mg) on biomass and contents of effective constituents of Blumea balsamifera in slow growth period of winter. Method: One-year-old B. balsamifera seedlings were applied with MgSO4 · 7H2O which supplied Mg in slow growth period of winter three times.Height

ground diameter

length of leaf

width of leaf and biomass were measured.UV was adopted to determine the content of total flavonoids in different parts of B. balsamifera with detection wavelength of 500 nm.The content of l-bornel in leaves of B. balsamifera were determined by GC

initial temperature was 80 ℃ for 2 min

then warmed to 100 ℃ by 5 ℃ · min-1 at 4 min

and warmed to 200 ℃ by 10 ℃ · min-1 at 10 min.Temperature of injection port was 220 ℃ and FID detector temperature was 240 ℃

injection volume was 0.6 μL and split ratio was 9: 1. Result: Exogenous Mg significantly enhanced growth indexes of this plant

especially of ground diameter

length and width of leaf.As a result

exogenous Mg increased significantly biomasses of leaves

stems and roots

respectively.Biomasses of leaves and stems under 10 g · L-1 Mg treatment were 226.47 g and 140.40 g

which were 10.09 and 5.28 times compared with the control black treatment(CK)

respectively.Biomasses of leaves and stems under 15 g · L-1 Mg treatment were 244.88 g and 146.02 g.However

exogenous Mg could not enhance or affect indistinctively the mass fraction of total flavonoids and l-borneol

but it increased qualities of total flavonoids and l-borneol significantly.Qualities of l-borneol under 10

15 g · L-1 Mg treatments were 8.5 and 10.0 times by comparing with CK

respectively. Conclusion: Exogenous Mg can promote plant growth and biomass accumulation

significantly increase qualities of total flavonoids and l-borneol in B. balsamifera in slow growth period of winter.