<div>Background:&nbsp;Indigofera tinctoria plays the role of a natural dye source that produces indigo color and contains the secondary metabolite indican which is highly responsive to light intensity. This study aims to examine the critical period for the formation of the secondary metabolite indican on light intensity. 
 
Methods: The method used was a completely randomized block design with a split-plot design. The study consisted of 2 treatment factors, namely: length of shade (main plot) and light intensity (subplot). The length of shade included 5 levels, namely early growth phase (up to 1 month after planting), mid-growth phase (up to 2 months after planting), maximum growth phase (up to 3 months after planting), 1 month before harvest and 2 months before harvest. Light intensity had 3 levels, namely 50% light intensity (38,464.3 lux), 25% (19,232.15 lux) and 10% (7,692.86 lux). 
 
Result: The combination of duration of shade and light intensity affected the growth, yield and content of secondary metabolites (indican) in Indigofera tinctoria. The highest number of leaves, plant fresh weight and biomass was found in the combination of shade in the early growth phase (up to 1 month after planting) with 50% light intensity. The highest indican production was found in the mid-growth shading (up to 2 months after planting) with 10% light intensity, which was 843.33 ppm. The critical period of shade to increase indican production along with the number of leaves was the mid-growth phase (up to 2 months after planting).</div>

The Critical Period of Production of the Secondary Metabolite Indican in (Indigofera tinctoria L.) on Light Intensity