The taxonomic relevance of floral morphology in Teucrium species from Türkiye

Abstract

Teucrium, the second largest genus in the subfamily Ajugoideae, is known for its complexity. The aim of this study was to investigate the floral morphology of some Teucrium taxa naturally grown in Türkiye. For this purpose, macro- and micromorphological characters of 25 taxa of Teucrium were examined in detail by scanning electron microscopy. Additionally, hierarchical cluster analysis (HCA) was carried out to identify closely related taxa and principal component analysis (PCA) was performed to determine the potential distinctive floral characters. Statistical analyses were performed using PAST software. A total of seven types of glandular and nonglandular trichomes were detected in the calyx, corolla, stamen, pedicel, and bract of the taxa. Glandular trichomes were defined as peltate or capitate, while nonglandular trichomes were classified as simple unicellular or uniseriate. Calyx morphology and the presence of long-stalked capitate trichomes on the corolla resulted the most significant variables for the PCA. Overall, the study revealed that floral macro- and micromorphological characters are distinctive within the genus. Some differences were observed between two different dendrograms created using micromorphological or macro and micromorphological characters. The systematic value of trichome micromorphology is indisputable, but the use of both floral macro- and micromorphological characters is more meaningful.