Anatomy of vegetative organs of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. (Araliaceae)

Abstract

Eleutherococcus senticosus (Araliaceae) is widely used as adaptogen in herbal medicine. Since comprehensive anatomical analysis of its vegetative organs was not available, the present study aimed at providing the reference data on the structure of leaves and roots, under- and aboveground stems of 1–4 year-old plants by means of conventional light microscopy. In the primary structure, roots were di- or triarch, with secretory canals facing protoxylem. Concurrently with cambium initiation, additional pericyclic secretory canals differentiated close to the existing ones. In the root secondary structure, secretory canals were formed in the conductive secondary phloem and maintained in the nonconductive one. Stem primary structure encompassed uniseriate epidermis with scant prickles, primary cortex and stele. Primary cortex was composed of collenchyma, chlorenchyma, ground parenchyma with secretory canals and ca. triseriate starch sheath. In outer stele (pericycle) strands of sclerenchyma fibers (stereids) differentiated, alternated with parenchyma. In the ring of open collateral bundles, cambium became continuous concurrently with (sub)epidermal initiation of phellogen. In the wide pith, ground parenchyma occurred, with a few secretory canals close to protoxylem. Secondary structure stems retained the cortical tissues in the 4th year; new secretory canals appeared in the conductive secondary phloem. The epithelial cells/sheath cells complexes were maintained even in the oldest nonconductive phloem (and in the cortex) in stems of 4 year-old plants, while the successively formed sieve tube-companion cell complexes functioned till the end of the vegetation periods only. The bifacial leaves exhibited shade adaptation in chlorenchyma structure; secretory canals were formed mainly in veins’ phloem.