Diversity in agro-morphological and phytochemical traits with comparative leaf trichome observations among Iranian common nettle (Urtica dioica L.) populations

Phenotypic diversity within medicinal plants is crucial for identifying elite genotypes and supporting sustainable cultivation and breeding strategies. Urtica dioica L. (common nettle) is a widely distributed perennial species with high concentrations of bioactive compounds, making it an important target for pharmaceutical, nutraceutical, and cosmetic industries. In this study, eight Iranian U. dioica populations ( UDP1 – UDP8 ), cultivated under controlled greenhouse conditions, were assessed for their agro-morphological characteristics, phytochemical profiles, antioxidant power, and trichome micromorphology. Significant variability was observed across UDPs in plant height, shoot and root biomass, and biomass allocation patterns. UDP7 demonstrated the highest shoot biomass, whereas UDP4 and UDP2 outperformed in root development. Phytochemical analysis revealed considerable differences in specialized metabolites content among UDPs. UDP4 exhibited the highest levels of total phenolics (4.93 mg gallic acid equivalent/g DW), flavonoids (46.50 mg rutin equivalent/g DW), and antioxidant power (22.60 μmol Fe 2+ /g DW). HPLC profiling identified chlorogenic acid, caffeoylmalic acid, and rutin as key compounds, with UDP5 containing the highest chlorogenic acid and rutin levels, and UDP8 the highest caffeoylmalic acid content. Scanning electron microscopy revealed notable diversity in trichome density, length, and distribution patterns. These findings highlight the rich agro-morphological and phytochemical diversity among native Iranian UDPs and suggest that UDP7 , followed by UDP1 , is particularly promising for biomass production, whereas UDP4 showed superior overall phytochemical and antioxidant potential, and UDP5 and UDP8 represent valuable sources of specific phenolic compounds for future domestication, breeding, and phytopharmaceutical applications.