Taxonomic significance of stem and leaf anatomy and pollen and seed micromorphological characters in the Papaver (Poppy) sect. Rhoeadium from Türkiye

The poppy (Papaver) has beautiful flowers that attract the attention of not only taxonomists but also the public. However, it also presents several taxonomic problems. This study examines 13 taxa of Papaver sect. Rhoeadium, including the following species native to Türkiye: P. purpureomarginatum, P. dubium subsp. dubium, P. dubium subsp. laevigatum, P. arachnoideum, P. arenarium, P. commutatum subsp. euxinum, P. guerlekense, P. rhopalothece, P. stylatum, P. clavatum, P. syriacum, P. rhoeas, and P. postii. Plant specimens were collected from natural populations, and anatomical investigations were carried out on stem and leaf cross-sections. Pollen and seed features were examined using both light microscopy and scanning electron microscopy. The anatomical analysis revealed several taxonomically informative features, including the presence and number of chlorenchyma and collenchyma layers, and the arrangement of vascular bundles. Pollen characteristics (including size, shape, polar axis length to equatorial axis length ratio, and exine ornamentation) and seed morphology traits (such as shape, color, anticlinal and periclinal wall structures, and surface sculpturing patterns) proved to be diagnostic for species delimitation. A comprehensive assessment of morphological, anatomical, palynological, and seed micromorphological characters led to the reevaluation of P. postii, P. syriacum, and P. rhopalothece, which are here considered distinct species. This study highlights the systematic value of anatomical and micromorphological traits in Papaver sect. Rhoeadium, demonstrating their relevance for taxonomic delimitation at both species and sectional levels, and providing a robust framework for future phylogenetic studies.