Anatomical Study of Three Species of the Asteraceae Family from the Anbar Governorate, Iraq

This study explores the stem and leaf anatomy of three Asteraceae species Lactuca serriola L., Sonchus asper (L.) Hill, and Sonchus oleraceus L., collected from Anbar Governorate in Iraq, to identify diagnostic traits relevant to taxonomy. Fresh specimens were identified at the University of Anbar and handmade transverse sections were prepared, stained with safranin, and examined under a light microscope. Both qualitative and quantitative features of the dermal, ground, and vascular tissue systems were analyzed, including stomatal density, epidermal cell dimensions, and tissue thickness. A stripped epidermis technique was used for detailed leaf surface analysis. Anatomical differences were evident among the species. S. oleraceus exhibited a biseriate epidermis and showed greatest thickness in epidermal (67.5 µm), cortical (320 µm), and pith (1920 µm) tissues along with the highest stomatal density (131.5/mm² adaxial). Trichomes appeared only in S. asper, which also had the longest epidermal cells. L. serriola had the thickest mesophyll (154 µm) and main vascular bundles (738 µm). All species displayed anomocytic stomata but stomatal size and density varied across adaxial and abaxial surfaces. These anatomical traits provide valuable taxonomic markers for species differentiation within Asteraceae and offer insights into their structural adaptations and evolutionary significance.