Petiole anatomy of selected species in family Lamiaceae and its systematic relevance

Abstract

Microanatomical traits are one of the reliable features that are exploited for accurate species identification. The petiole anatomy of selected species Lamiaceous species is well explained in depth and linked to their systematic relevance. This study aimed to provide the taxonomic value of petiole micromorphology of 15 species of Lamiaceae. The petiole was sectioned with Microtome to visualize under a light microscope to measure micromorphological qualitative and quantitative attributes. The qualitative including petiole shape, vascular bundles (VBs), the shape of the epidermis, and collenchymatous and parenchymatous cells showed diversified traits. The quantitative traits such as the number of VBs, vessel elements, outlines, parenchyma, collenchyma, and upper and lower epidermis cells were measured. The highest mean length of VB (7.7 µm) was noticed in Stellaria linearis Benth. The highest VBs nine in number (3 central and 6 subsidiary) was examined in Salvia argentea L. The maximum vessel element (95 in number) were present in Thymus linearis Benth. Winged petiole was observed in nine taxa covered by uniseriate trichome hairs to be a valuable aspect in the taxonomy of Lamiaceae. The petiolar features-based statistical analysis was performed using dendrogram clustering and principal component analysis (PCA) accounting for the delineated of Lamiaceous species. This study describes the morpho-anatomy of petiole in the Lamiaceae can be further elaborated for correct identification using a phylogenetic-based micromorphological taxonomic approach.