Ammonium-nitrogen Supply Induces Growth, Physiological and Secondary Metabolites Changes in Centella asiatica L. Urban

Background: Centella [Centella asiatica (L.) Urban], as a herb, is well known for its nutritional and pharmaceutical value. Nitrogen fertilizer plays a significant role in yield and quality of the herb. The present study was aimed to evaluate the effect of mineral nitrogen on the centella plant yield, total chlorophyll, total flavonoid content, antioxidant activities and C/N ratio. Methods: The experiment was conducted under greenhouse conditions. Mineral nitrogen fertilizer ammonium nitrate (33% N) was applied with 30, 60, 90 and 120 kg N ha-1, with no N (0 kg ha-1) as the control. The dosage was split into three times application at 7, 14 and 21 days after transplanting. All plants were watered 10-days intervals with the nutrient solution. Result: The results showed that the increasing doses of nitrogen improved growth rate and overall biomass of centella. Among nitrogen treatments, the 60 kg N ha-1 were found to yield maximum growth and the maximum values of leaf number, leaf area, rosette diameter and petiole length. The application of nitrogen (30-60 kg N ha-1) increased the total chlorophyll and reduced total flavonoid content, antioxidant activity and the C:N ratio. The application of 60 kg N ha-1 of nitrogen should be considered as the optimal amount for reconciling limited yield loss and maintaining the quality of centella.