Comparative anatomy of stems and leaves of plectranthus L. (Lamiaceae) in Saudi Arabia and systematic implications.

A comparative anatomical study of the Plectranthus species growing in Saudi Arabia by using light microscopy method in order to evaluate their diagnostic value for systematic studies. Macro- and micromorphological characters, including stem, leaf, petiole anatomical, and trichome structures are presented. Descriptions of stem shape in cross-section, epidermal cell shape, cortex, pith, vascular bundles, leaf shape in cross-section, mesophyll, types and distribution of trichomes are presented. Taxonomic phylogenetic implications of stem, leaf, and trichomes anatomical micromorphology are also discussed in comparison with the available gross morphological and molecular data. Results of the present study offer useful data for evaluating the taxonomy of Plectranthus both at subgeneric and sectional levels. Moreover, our results indicate some degree of similarity among the species of subgenus Germanea and support the monophyly of this subgenus. A remarkable result from this study was identifying P. arabicus with distinctive characters and suggesting that it should be treated as a separate subgenus. Likewise, distinguishing differences between closely related endemic species P. asirensis and P. hijazensis are offered, and should be conserved as a different subgenus. A key for the identification of the investigated taxa based on studied characters is provided. Microsc. Res. Tech. 79:583-594, 2016. © 2016 Wiley Periodicals, Inc.

Stem and leaf anatomy of Plectranthus neochilus Schltr., Lamiaceae

Plectranthus neochilus Schltr. is an aromatic herb named " boldo" or " boldo-gambá" and employed for treating hepatic insufficiency and dyspepsia in folk medicine. This paper has investigated its stem and leaf anatomy, in order to contribute for the medicinal plant identification. The botanical material was prepared according to standard microtechniques. The stem has quadrangular transection and, in secondary growth at the level analyzed, shows uniseriate epidermis and numerous trichomes. The glandular ones are capitate and peltate. The former has short unicellular or long multicellular stalk and uni- or bicellular head. The latter presents short stalk and eight-celled ovoid head. The non-glandular trichomes are multicellular, uniseriate and coated with granular cuticle. It is observed angular collenchyma, cambia forming phloem outward and xylem inward, and perivascular fiber caps next to the phloem. The blade has uniseriate epidermis coated with striate cuticle, diacytic stomata on both surfaces, numerous trichomes similar to the stem ones, and homogeneous mesophyll. The midrib shows one or two collateral bundles and the petiole has many of them distributed as an open arc.

Plectranthus neochilus Schltr. é uma erva aromática denominada boldo ou " boldo-gambá" e empregada no tratamento de insuficiência hepática e dispepsia na medicina popular. Este trabalho investigou a anatomia caulinar e foliar, com a finalidade de contribuir na identificação dessa planta medicinal. O material botânico foi preparado de acordo com microtécnicas usuais. O caule tem secção transversal quadrangular e, em crescimento secundário no nível analisado, exibe epiderme unisseriada e numerosos tricomas. Os tricomas glandulares são capitados e peltados. Os primeiros têm pedicelo curto e unicelular ou longo e pluricelular e cabeça uni ou bicelular. Os peltados apresentam pedicelo curto e cabeça ovóide com oito células. Os tricomas tectores são pluricelulares, unisseriados e recobertos com cutícula granulosa. Observam-se colênquima angular, câmbio vascular formando floema em direção centrífuga e xilema para o centro, e calotas de fibras perivasculares apostas ao floema. A lâmina foliar tem epiderme uniestratificada revestida por cutícula estriada, estômatos diacíticos em ambas as superfícies, numerosos tricomas similares aos do caule e mesofilo homogêneo. A nervura central possui um ou dois feixes vasculares colaterais e o pecíolo apresenta vários feixes colaterais em arco aberto.