Research in Plant Metabolites

Research in Plant Metabolites

valuation of Nitrogen Levels and Planting Density Management on Physiological Traits and Secondary Metabolites in the Medicinal-Industrial Plant Indigo (Indigofera tinctoria L.)

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.2025.528531.1076
Abstract
Indigofera tinctoria L. is one of the most important dye-yielding plants worldwide, with numerous industrial and medicinal applications. Considering the significant role of agronomic factors in improving both quantitative and qualitative yield of this plant species, the present study was conducted during the 2023 cropping season in Shushhtar County, northern Khuzestan Province, Iran, using a split-plot experimental design based on a randomized complete block design with three replications. The objective was to evaluate the effects of different nitrogen fertilizer rates (25,50,75&100 kg.ha⁻¹) and plant densities (30,40,50 & 60 plants m⁻²) on photosynthetic traits (chlorophyll a ,b ,total chlorophyll & carotenoids) and indigocarmine pigment content.The results indicated that increasing nitrogen application significantly enhanced all photosynthetic traits as well as the secondary metabolite indigocarmine. The highest values of chlorophyll a (1.85 mg g⁻¹), chlorophyll b (0.73 mg.g⁻¹), total chlorophyll (2.58 mg.g⁻¹), and indigocarmine percentage (0.81%) were observed under the treatment of 75 kg N ha⁻¹ and a density of 30 plants m⁻². Moreover, the treatment of 75 kg N ha⁻¹ combined with a planting density of 40 plants m⁻² provided the highest indigocarmine content (5.75 g m⁻²), which was identified as optimal in terms of quantitative performance.Analysis of variance revealed that all main effects were statistically significant at the 1% probability level, while the interaction effect of nitrogen and density was significant at the 5% probability level for all studied traits. The relatively low coefficient of variation (ranging from 3.8% to 7.2%) indicated high accuracy in conducting the experiment. A strong positive and significant correlation (r=0.91) between photosynthetic indices and indigocarmine content suggests a direct role of the photosynthetic system in the synthesis of secondary metabolites.Ultimately, applying 75 kg ha⁻¹ of nitrogen along with a planting density range of 30–40 plants m⁻² was identified as the best treatment in terms of balancing product quality and quantity. These treatments can be proposed as an optimal cultivation model for Indigofera tinctoria L. in similar climatic regions.
Keywords
Agricultural management
Environmental stress
Photosynthesis
Plant pigments and Protective mechanisms