Effect of light intensity and nitrogen level on growth and biomass of Rauvolfia vomitoria

A potted experiment was conducted to study the growth and biomass of Rauvolfia vomitoria plant under different light intensities (15%, 40% and 70% of full sunlight) and nitrogen levels (15 g, 30 g and 60 g per plant). The results show that the growth, individual biomass and biomass allocation are significantly influenced by light intensity and nitrogen level (P<0.05). The plant height, ground diameter, relative growth rate of height and ground diameter (RGR_H, RGR_D) and individual biomass under 70% light intensity are higher than those under 15% and 40% light intensity, and more biomass is allocated to underground plant part. The height, ground diameter, RGR_H, RGR_D and individual biomass decrease with increasing nitrogen level under 15% and 40% light intensity. Under 70% light intensity, R. vomitoria plant grows best and individual biomass reaches the highest value of 559.6 g at 30 g nitrogen per plant. At the same light intensity, root mass ratio (RMR) and root to shoot ratio (R/S) decrease with increasing nitrogen level. On the other hand, specific leaf area (SLA) and leaf mass ratio (LMR) are highest at 15% light intensity and 60 g nitrogen per plant. Analysis on individual biomass, RMR, R/S and growth characteristics including height, ground diameter, RGR_H, RGR_D reveals that 70% light intensity and 30 g nitrogen per plant combination yields the optimum condition for R. vomitoria plants.