Foliar morphoanatomical characterization of medicinal plant Youngia japonica (L.) D.C. (Asteraceae)

Youngia japonica (L.) D.C. (Asteraceae) is a synanthropic herb native to Southeastern Asia, commonly known as asiatic or oriental [false] hawk's beard. It's a cosmopolitan weed with medicinal and edible uses and reported antioxidant, antiallergenic, antiviral and antitumor properties. In Brazil, this plant was recently introduced and is in frank spreading. The study aims to perform the contribution to morphoanatomical characterization of the species. For the characterization of morphology, anatomy and leaf venation pattern, fully expanded leaves from plants collected on the campus of the UFRJ, in Ilha do Fundão, RJ, Brazil were subjected to standard plant histology procedures. Conical uniseriate tector trichomes are present along the foliar blade and petiole epidermis. Petiole shows uniseriate epidermis whose cells have isodiametric to elliptic cross section and thickened periclinal walls. In the proximal region of the petiole it's observed a discontinuous layer of subepidermal lacunar collenchyma. Vascular system is composed of a flattened crescent of collateral bundles. In the central bundle are observed one or more layers of cells with angle-thickened walls, facing the abaxial side. Bordering the abaxial face of the bundles occur laticifers. Leaves are amphistomatic, with anomocytic stomata. Mesophyll is homogeneous formed by cells of variated sizes, with a slight tendecy to bilaterallity in some portions. In the margin of leaves there are projections associated with the leaf venation. This study is the first fully addressing Y. japonica foliar morphoanatomy, which is required, in Brazil, for registration as a plant drug.