Conservation and domestication of young tongkat ali (Eurycoma longifolia Jack) via evaluating root and shoot traits by combining different light intensities and water levels

The effects of three light intensities (represented by different shade levels) and three water levels on plant growth parameters, including root mass ratio, root/shoot ratio, height ratio, plant height, stem diameter, and total biomass of young tongkat ali ( Eurycoma longifolia Jack) plants, were investigated. The two-factor experiment was laid out in a split-plot design based on a randomized complete block design (RCBD) with three replications. The factors were organized as follows: main plot, irradiance intensity; subplot, water treatments – used to determine the interactions among water availability, various proportions of irradiance, different durations of shading on the root system, and tongkat ali root growth performance. Results showed that plant growth parameters, including plant height, stem diameter, and total biomass, were reduced by only the light scarcity condition (25% FC) by 22%, 25%, and 20%, respectively, compared to the non-shaded condition after 4 1 2 months of treatment. Meanwhile, lower values were recorded for root mass ratio (10%–12.5%) and root/shoot ratio (24%–29%), while height ratio (8%–11%) was higher in 70% shading compared to 50% shading and the control, thus exhibiting lower ability for tongkat ali seedlings to compete for water and light.