Comparative anatomical and micromorphological studies on Teucrium creticum and Teucrium orientale var. orientale (T. sect. Teucrium, Lamiaceae)

Abstract

Teucrium creticum L. and T. orientale L. var. orientale are two related taxa in Teucrium sect. Teucrium. In this study, the value of anatomical and micromorphological characters for distinguishing between these two taxa is analysed. Transverse sections of the stem, as well as both transverse and surface sections of the leaves were examined anatomically. According to the data obtained, collenchyma and sclerenchyma do grow more in T. creticum than in T. orientale var. orientale. The leaves of T. creticum are hypostomatic and have a characteristic hypodermis, which is under the upper epidermis, as well as abundant spherocrystals in the upper epidermis. The leaves of T. orientale var. orientale are amphistomatic, yet no spherocristals exists in epidermal cells and the hypodermis is absent. The results obtained from studies carried out under scanning electron microscope (SEM) shows that the nutlet micromorphology varies between the two taxa. In both taxa, the nutlet surfaces are reticulate and glandular. Eglandular hairs do occur. However, in T. orientale var. orientale, 20–60 μm long eglandular hairs with scabrid surface occur only along the margins of the nutlets, whereas the ¾ dorsal sides of the nutlets in T. creticum are all covered with 90–500 μm long, smooth‐surfaced hairs. Additionally, while the glandular hairs on the nutlets of T. creticum are subsessile, those on the nutlets of T. orientale var. orientale are capitate and distinctly stalked.