Flos Lamii albi has a high biological activity and is widely used in herbal medicine. The aim of the study was to characterize the secretory structures present in Lamium album subsp. album corolla and the location of phenolic compounds. Additionally, we carried out qualitative phytochemical analyses of flavonoids and phenolic acids. Light, fluorescence, and scanning electron microscopy were used to analyze the structure of the floral organs. The main classes of phenolic compounds and their localization were determined histochemically. Phytochemical analyses were performed with high-performance thin-layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). Six types of glandular trichomes were found which contained flavonoids, phenolic acids, and tannins. The phytochemical studies demonstrated the presence of caffeic, chlorogenic, ferulic, gallic, p-coumaric, protocatechuic, syringic, gentisic, and vanillic phenolic acids as well as rutoside, isoquercetin, and quercetin flavonoids. The corolla in L. album subsp. album has antioxidant properties due to the presence of various polyphenols, as shown by the histo- and phytochemical analyses. The distribution and morphology of trichomes and the content of phenolic compounds in the corolla have taxonomic, pharmacognostic, and practical importance, facilitating the identification of the raw material.

The centuries-old experience of folk medicine, nutritional traditions, and the results of numerous research studies show that plants of the genus Plantago can be used for medicinal, cosmetic, dietetic, and ritual purposes. In the phytochemical composition of Plantago, there is an abundance of biologically active substances (among others, glycosides, flavonoids, polysaccharides, and vitamins) exhibiting beneficial effects and, simultaneously, there is a low content of compounds that may exert a toxic effect. Scientific research has confirmed that Plantago plants have antioxidative, apoptosis-inhibiting, protective, healing-enhancing, spasmolytic, anthelmintic, and antimicrobial properties; they inhibit the development of some tumours, reduce the level of lipids in blood and inhibit tissue glycation. In phytotherapy, leaves, stems, and/or seeds of different plantain species are used. Plantago leaves and seeds are also used to manufacture creams, lotions, and face masks. Different parts of these plants (fresh plant material, extracts, or isolated substances) are also used in human and animal nutrition. Plantain leaves can be eaten like lettuce or added to salads, fried in pastry, used to prepare a tea, juice, or wine. Its seeds are added to cakes, bread, breakfast cereals, ice cream, and drinks, or they are cooked like groats. Animals fed with plantain can live longer and are healthier, while meat derived from such animals is tastier and healthier to humans. Plantago seeds are readily eaten by cage birds. Plantain pollen, produced in large amounts (up to 20,000 pollen grains per 1 stamen of P. lancolata), can cause allergies in sensitive people. Due to a long flowering period of plants of the genus Plantago, the effect of the allergenic factor persists for many weeks. In Poland days with the maximum concentration of airborne plantain pollen most often occur in July.

The intensely fragrant flowers of the Rosa rugosa Thunb. have been applied in medicine, and food and cosmetic industries. The species is cultivated for production of rose essential oil (Oleum Rosae) from its flowers. R. rugosa petals secrete the largest quantities of essential oil. The aim of the study was to identify the characteristics of the epidermis of both sides of the petal and to observe whether adaxial and abaxial epidermal cells can secrete essential oil. The investigations were conducted using light and scanning electron microscopy. The analyses were focused on petal thickness and characteristics of the mesophyll. The study has demon- strated that only adaxial epidermal cells form conical papillae covered by massive cuticular striae. The surface of the papillae displayed remnants of a secretory substance. In turn, the inner walls of the abaxial epidermal cells were flat and covered by a striated cuticle, which exhibited various striation patterns. Frarant substances stored under the cuticle caused local stretching thereof and disappearance of striation. The results of our observations allow a statement that the cells of the adaxial and abaxial epidermis of R. rugosa petals differ in terms of the structure and they secrete fragrant substances.

Dracocephalum moldavica L. is an aromatic plant emitting intense lemon scent. The aboveground parts of the plants constitute raw material for medicine and food industry. In contrast to the comprehensively investigated trichomes, there are only few studies of the histochemical characteristics of the leaves of essential oil-bearing plants from the family Lamiaceae. The present study shows the micromorphology, anatomy, and histochemistry of the leaves of the analysed species. The research aimed to determine the location of essential oil and other specialised metabolites in leaf tissues. The investigations of fresh and fixed material were carried out with the use of light, fluorescence, and scanning electron microscopy. Additionally, the content and composition of essential oil in the leaves were determined with the GC/MS method. The leaf epidermis had non-glandular unbranched trichomes and three types of glandular trichomes: peltate as well as long and short capitate trichomes. The results of the histochemical assays showed positive reactions to lipids and to some secondary compounds such as essential oil, terpenes, phenolic compounds, and flavonoids in all types of the glandular and non-glandular trichomes. The same compounds were found in the epidermis cells of the leaves. The results of the present study indicate that the intense smell of the leaves is associated with emission of essential oil not only by the glandular and non-glandular trichomes but also by the leaf epidermis cells. The main components in the essential oil (0.10%) include geranial, neral, geraniol, nerol, and trans-myrtanol acetate. Since D. moldavica has been used as an adulterant of Melissa officinalis L., the anatomical traits of leaves and the essential oil composition in both species were compared in the study.

Micromorphology and distribution of glandular and non-glandular trichomes on the above-ground organs of Inula helenium L. were investigated using light and scanning electron microscopy (SEM). Two types of biseriate glandular trichomes, i.e. sessile and stalk hairs, and non-glandular trichomes were recorded. Sessile glandular trichomes were found on all examined I. helenium organs (with their highest density on the abaxial surface of leaves and disk florets, and on stems), whereas stalk glandular trichomes were found on leaves and stems. Sessile trichomes were characterised by a slightly lower height (58–103 μm) and width (32–35 μm) than the stalk trichomes (62–111 μm x 31–36 μm). Glandular hairs were composed of 5–7 (sessile trichomes) or 6–9 (stalk trichomes) cell tiers. Apical trichome cell tiers exhibited features of secretory cells. Secretion was accumulated in subcuticular space, which expanded and ruptured at the top, and released its content. Histochemical assays showed the presence of lipids and polyphenols, whereas no starch was detected. Non-glandular trichomes were seen on involucral bracts, leaves and stems (more frequently on involucral bracts). Their structure comprised 2–9 cells; basal cells (1–6) were smaller and linearly arranged, while apical cells had a prozenchymatous shape. The apical cell was the longest and sharply pointed. Applied histochemical tests revealed orange-red (presence of lipids) and brow colour (presence of polyphenols) in the apical cells of the trichomes. This may suggest that beside their protective role, the trichomes may participate in secretion of secondary metabolites.