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Herbal medicines are gaining popularity worldwide for human healthcare because of their therapeutic potential. However, adulteration and use of unauthentic raw herbals as substitutes have become a major issue for the local communities and industry for reasons of safety and efficacy. Therefore, the authentication of medicinal plants before their use in herbal medicines is a need of time. Hence, the present study was designed with an aim, to authenticate the therapeutic Lamiaceous taxa by using pollen traits observed under scanning electron microscopy. Pollen micro-morphological studies solve the problem through discrimination and correct identification of the Lamiaceae species from the adulterants. Based on pollen features, Lamiaceae were further divided into two sub-families Lamioideae (tricolpate) and Nepetoideae (hexa-colpate). The pollen grains of Lamioideae were found as small to medium-sized, tricolpate, radially/bilateral symmetrical, sub-spheroidal and oblate shape. Besides, exine patterns bireticulate, reticulate and micro-reticulate, colpus surface sculpturing as psilate, gemmate, scabrate, and verrucate have also been reported. A significant variation was found in the pattern of the reticulum, thickness, and the number of secondary lumina per primary lumen. Similarly, Nepetoideae has a hexa zono-colpate pollen but tri and tetra zono-colpate pollen have also been observed. Hence, this study contributes to the authentication and correct identification of medicinally important Lamiaceae taxa by using scanning electron microscopic techniques and can help to solve the adulteration problem. Highlights Authentication of medicinally important Lamiceous taxa was carried out through scanning electron microscopic techniques. Chemotaxonomic characterization was used for the accurate identification of the therapeutic taxa. The medicinal, palynological and phytochemical significance of Lamiaceae taxa were evaluated. A significant variation was seen in the palynological traits that help in the determination and authentication of the therapeutic Lamiaceous species. Based on the chemotaxonomic characterization, our study can help to solve the adulteration problem for the reason of safety and efficacy., (© 2022 Wiley Periodicals LLC.)

Lamioideae comprised the second-largest subfamily in Lamiaceae. Although considerable progress has recently been made in the taxonomic study of Lamioideae, the subfamily remains one of the most poorly investigated subfamily in Lamiaceae. Therefore, the present study was designed with the aim to document the pollen micromorphology of some selected Lamioideae taxa and its taxonomic significance from Pakistan. Pollen micromorphological features were observed using scanning electron microscopy. The pollen grains are monad, tricolpate, radially/bilateral symmetrical. The pollen grains were small to medium-sized having oblate, oblate/subspheroidal, and subspheroidal shape. Exine sculpturing was observed as reticulate, microreticulate, and bireticulate. The colpus surface ornamentation was found as verrucate, gemmate, scabrate, and psilate. There was a considerable variation between the species in the micromorphology, that is, the coarseness of the reticulum, thickness of the muri comprising the reticulum and the number of secondary lumina per primary lumen. Hence, this study documented the pollen morphology of some selected taxa of the subfamily Lamioideae from Pakistan and strengthens the taxonomic identification of subfamily based on pollen characters, which helps in the correct identification, discrimination of the species of Lamioideae at generic and species level., (© 2020 Wiley Periodicals LLC.)

Foliar micromorphological features are useful to elucidate the taxonomy and systematics of the Lamiaceae species. Leaf epidermal morphology using scanning electron microscopy and light microscopy of 22 Lamiaceae species from 15 genera have been investigated with an aim to solve its taxonomic problem in the correct identification. Various foliar micromorphological features were observed to explain their importance in resolving the correct identification of Lamiaceae taxa. Two main types of trichomes were observed; glandular trichomes (GTs) and nonglandular trichomes (NGTs). GTs were further divided into seven subtypes including the capitate, subsessile capitate, sessile capitate, sunken, barrel, peltate, and clavate. Similarly, NGTs were also divided into simple unicellular and multicellular including conical, falcate, cylindrical, dendrite, papillose, and short hook shape. Quantitative measurement includes the length and width of the trichomes, stomatal complex, epidermal cells, stomata, and trichomes index. Based on the foliar micromorphological characters, a taxonomic key was developed to delimit and correctly identify studied taxa. Further molecular, other anatomical and phylogenetic studies are recommended to strengthen the systematics of Lamiaceae., (© 2019 Wiley Periodicals, Inc.)

The present study is insight into pollen morphology for characterizing species and their utility in the taxonomic separation of certain taxa of subfamily Nepetoideae (Lamiaceae) from Pakistan. The pollen micromorphology of 11 species of the Nepetoideae was analyzed and documented using light microscopy and scanning electron microscopy (SEM) for both qualitative and quantitative characteristics. Most species have hexazonocolpate pollen grains but trizonocolpate and tetrazonocolpate pollen with circular and oval amb were also rarely observed in Mentha spicata. The basic pollen shape in most of the studied species was subspheroidal but prolate grains were also observed in M. spicata, S. coccinea, and S. plebeia. The exine sculpturing of Nepetoideae pollen was taxonomically very informative particularly at subfamily level. Observations of exine sculpturing with SEM revealed various types of pollen grains: reticulate, bireticulate, microreticulate, perforate, aerolate, and gammate. The bireticulate type further subdivided into three subtypes based on the number of secondary lumina in each primary lumen and is characterized by varying characteristics of the secondary reticulum and primary muri. A significant variation was observed in colpus surface ornamentation. The maximum polar diameter was found in O. americanum (58 ± 5.8 μm) and the maximum equatorial diameter observed in O. basilicum (50.25 ± 1.37 μm). Pollen features of the studied species were discussed and compared based on the current taxonomical concepts. The results showed that pollen traits of the subfamily Nepetoideae was found significant to classify the taxa. Furthermore, pollen features provide additional evidence to distinguish macromorphologically similar taxa from each other., (© 2019 Wiley Periodicals, Inc.)

Foliar epidermal features were based on the micromorphology of trichomes types, epidermal cells and stomatal complex. Even though each feature has its own limited taxonomic value but collectively these characteristics may be systematically important especially for the discrimination and identification of complex and problematic taxa. The systematics significance of nonglandular (NGTs) and glandular trichomes (GTs), stomatal complex and epidermal cells of Lamiaceous flora were analyzed by using the light microscopy (LM) and scanning electron microscopy (SEM). Variations on the observed epidermal appendages were divided into two basic types: glandular and nonglandular. GTs can be divided into subtypes: sessile capitate, subsessile capitate, and barrel and sunken. NGTs were also divided into subtypes: dendritic, stellate, conical, falcate, simple and 1-6 cells long having granulate and smooth surface ornamentation. NGTs were the most dominant features of both adaxial and abaxial surfaces of all observed taxa. Vitex negundo, Isodon rugosus, Colebrookea oppositifolia, and Marrubium vulgare could be demarked because of their twisted like appearance of NGTs at the abaxial surface. The Lamiaceae had both hypostomatic and amphistomatic leaf. Stomata were observed as diacytic, anisocytic, and anomocytic. Epidermal cells were found to be irregular, isodiametric, and rectangular. Based on these characters a taxonomic key was developed to delimit the closely related taxa. Distribution and morphology of the foliar epidermal trichomes through SEM highlight an important taxonomic tool used by the taxonomists as an aid to the correct identification of problematic Lamiaceae taxa., (© 2019 Wiley Periodicals, Inc.)