Petiole anatomical study in some taxa of the genus Alcea (Malvaceae) from Iran

Different species of the genus Alcea, due to the presence of mucilaginous compounds, are considered valuable medicinal plants in traditional medicine and pharmaceutical industries. In recent years, numerous biosystematics studies have been conducted to help resolve classification and identification issues of species. In this study, the anatomical characteristics of petioles in 15 taxa of Alcea in Iran were investigated. Middle parts of leaf petioles in the lower inflorescence were sectioned, double stained, and photographed under microscope. The most important traits examined in this study included the number of layers of collenchyma, parenchyma and the chlorenchyma cells in the cortex, the thickness and number of layers of sclerenchyma fibres in the phloem and the structure of vascular bundles. Based on the anatomical traits of the petioles, cluster analysis was carried out based on Euclidean distance using the Ward method. The results of the cluster analysis showed that some closely related taxa were grouped together, while the placement of others did not align with taxonomic proximity. The findings of this research indicate that certain anatomical characters of petioles, observed in closely related species, can only be used for species identification, but less so for taxonomic grouping.