Effects of Shading and Nitrogen Fertilizer on Growth and Physiology of Gandarusa (Justicia gendarussa Burm. F.)

Abstract

Gandarusa (Justicia gendarussa Burm. F.) is a shrub used in herbal medicine, but knowledge of optimal cultivation methods for enhancing plant growth and metabolite yield is limited. This research aimed to evaluate the effect of shading and nitrogen fertilizer on the growth, photosynthetic parameters, and total sugar content of gandarusa. A split-plot experimental design was used with shading (S) (0% (S0), 25% (S25), and 50% (S50)) as the main plots and nitrogen fertilizer (N) (0 (N0), 90 (N90), 180 (N180), and 270 (N270) kg ha-1) as the subplots. The results showed that the combination of S0 and N270 was the most effective treatment for plant growth, indicated by the highest values of plant height and the number of leaves and branches. It also yielded high sugar content, with a value range of 72-76 mg g-1 leaves wet weight. The combination of S0 and N0 produced the highest photosynthetic rate (Pn) in the plant at 23.91 mol CO2 m-2 s-1, and total chlorophyll content was highest with S25 and N270. Based on the results, shading decreased Pn, sugar production, and growth of gandarusa, while nitrogen fertilizer enhanced them. However, there was no interaction between shading and fertilizer on sugar production and growth of gandarusa, except for Pn.