Research in Plant Metabolites

Research in Plant Metabolites

Optimization of Planting Date and Plant Density for Maximizing Indigocarmine Content and Improving Photosynthetic Traits of Medicinal-Industrial Indigo (Indigofera tinctoria L.) under Khuzestan Climatic Conditions

Document Type : Original Article

Authors
Mohammad Reza Zargaran Khouzani 1
Mohammad Hossein Gharineh 2
ahmad koochek zadeh 2
,Amin lotfi jalal abadi 2
1 Department of Plant Production Engineering and Genetics, Khuzestan University of Agricultural Sciences and Natural Resources
2 Faculty member, Department of Plant Production Engineering and Genetics, Khuzestan University of Agricultural Sciences and Natural Resources
10.22034/jrpsm.2025.528664.1075
Abstract
Indigofera tinctoria L. is one of the most important medicinal-industrial plants, valued for its indigo carmine pigments and valuable phenolic compounds, which have extensive applications in the pharmaceutical and dyeing industries. As a natural source of plant-based dyes, it holds high economic value & exhibits moderate tolerance to environmental stresses such as drought and heat. This study was conducted in Shahid Bahonar Agricultural High School, Shushtar with the aim of evaluating the effects of planting date and plant density on photosynthetic traits and indigo carmine content of Indigo plant, using a split-plot design based on a randomized complete block design with three replications over two consecutive growing seasons (2022–2023). Treatments in the first year included six planting dates (April 29, May 19, June 8, June 28, July 17 and August 6) and four plant densities (30, 40, 50 and 60 plants per square meter). In the second year, two planting dates (July 17 and August 6) were excluded, and only four planting dates (April 29, May 19, June 8 and June 28) along with the same four plant densities were tested. Analysis of variance revealed that planting date, plant density, and their interaction significantly affected all qualitative traits at the 1% probability level. Mean comparison results showed that early planting in spring (April 29) yielded the highest values for chlorophyll a, chlorophyll b and total chlorophyll (1.82, 0.73 and 2.55 mg/g, respectively), as well as indigo carmine content (5.91 g/m²). Delaying planting, especially during the hotter months, significantly reduced all qualitative traits. A plant density of 40 plants per square meter was identified as the optimal level, at which the highest photosynthetic indices and indigocarmine content were observed. A significant positive correlation between chlorophyll content and indigocarmine concentration indicated a direct relationship between photosynthetic activity and secondary metabolite production in this plant. Overall, early planting in April and a plant density of 40 plants/m² are recommended as the best treatments for maximizing both the quality and quantity of indigo carmine in the indigo plant.
Keywords
Agronomic practices, Chlorophyll content, Cultivation management, Natural dyes "> and Secondary metabolites
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