Ultrastructure of leaf epidermis in some species of Achillea (Asteraceae).

Introduction: Achillea millefolium L. is used in official medicine of many countries. One of important diagnostic features of A. millefolium raw material is the ultrastructure of the leaf epidermis, which can be used for distinguishing A. millefolium from closely related species. Objective: The purpose of this article is to present the results of an original study of the leaf surface ultrastructure of six related species of Achillea and to identify additional diagnostic features. Methods: From each taxon, 20 samples of middle cauline leaves were taken and analysed with light (LM) or scanning electron (SEM) microscopy. Results: The studied species differ in the degree of sinuosity of anticlinal walls of basic epidermal cells and their projections, the type and presence of epicuticular wax, the type of relief of the leaf surface and the type of cuticle. On both surfaces of the leaf lamina, there is a complex pubescence formed by uniseriate non-glandular and biseriate glandular trichomes; their structure is similar, but the size and localization are sometimes different. Conclusion: It is possible to clearly distinguish the raw materials of any of the studied Achillea species from other taxa only with the help of the whole complex of the analysed species-specific micromorphological features of the leaf epidermis. This study is aimed at facilitating the identification of yarrow raw materials and can be used in the future for the development of regulatory documents for this herbal medicinal material, at least within the limits of the territory of Ukraine and adjacent territories. [ABSTRACT FROM AUTHOR]