Morpho-anatomical features of the leaves and stems of Baccharis notosergila (Asteraceae) and their relationship with the environment and chemical control

Background and aims: Baccharis notosergila is an aggressive weed inhabiting the Salado river basin, Buenos Aires province, Argentina. The aims of this work were: to analyze the morpho-anatomy and histochemistry of aerial vegetative organs in order to understand the adaptation strategies that ensure its survival, as well as to expand knowledge on traits determining resistance to the control methods applied. M&M: The material collected was prepared and examined with conventional techniques of microscopy. Histochemical tests to identify starch, resins, polyphenols, and lipophilic substances were performed. Results: The major features found were small and deciduous leaves; uniseriate epidermis with massive and striate cuticle; stomata at level or slightly above the other epidermal cells and glandular trichomes secreting oily substances; stomata on both surfaces and isobilateral mesophyll. Tannins, starch and lipophilic substances were identified in leaves and stems; polyphenols, resins and lipids in ducts, and calcium oxalate crystals in leaves, stems and capitate trichomes. Conclusions: The aerial vegetative organs features of B. notosergila explain its tolerance to the unfavorable conditions of the Salado river basin area, as well as its high competitive ability over others species of the natural prairie. The reduced and deciduous leaves, the epidermal traits, and chemical substances found constitute a physical and chemical barrier reducing dehydration as well as the penetration of the herbicides applied for its control. Botanical knowledge of B. notosergila is the basis for the design and development of new and appropriate management methods for this species.

Micromorphological Traits of Balcanic Micromeria and Closely Related Clinopodium Species (Lamiaceae)

A study of the trichomes types and distribution and pollen morphology was carried out in nine Micromeria taxa (M. cristata ssp. cristata, M. cristata ssp. kosaninii, M. croatica, M. graeca ssp. graeca, M. graeca ssp. fruticulosa, M. juliana, M. kerneri, M. longipedunculata and M. microphylla) and five closely related Clinopodium species (C. dalmaticum, C. frivaldszkyanum, C. pulegium, C. serpyllifolium and C. thymifolium) from the Lamiaceae family of the Balkan Peninsula. By scanning electron microscope, non-glandular trichomes, peltate and capitate trichomes were observed on the calyx, leaves and stem of the studied species. Two subtypes of capitate trichomes were observed in Micromeria species: subtype 1 (consisting of a basal epidermal cell and an elliptically shaped head cell) and subtype 2 (consisting of a basal epidermal cell, two to three stalk cells and a round head cell). In Clinopodium species, three types of capitate trichomes were observed: subtype 1, subtype 3 (consisting of a basal epidermal cell, a short peduncle cell, and a single round head cell), and subtype 4 (consisting of a basal epidermal cell, a stalk cell, and an elongated head cell). These results support the recent transfer of Micromeria species from the section Pseudomelissa to the genus Clinopodium.

Volatile Organic Compounds of the Glandular Trichomes of Ocimum basilicum and Artifacts during the Distillation of the Leaves

Focusing on volatile organic compounds (VOC) of Ocimum basilicum, this study aims to determine the chemical composition of VOC in secretory trichomes and compare it with that of essential oil obtained by hydrodistillation of leaves. The technique of extracting the content of glandular trichomes refers to the microneedle shuttle analysis. Hydrodistillation of fresh leaves was done with a Clevenger distiller (EO). The chemical compositions were determined by GC/FID and GC/MS. The head of the capitate trichomes does not contain volatile compounds. Fifty volatile compounds were detected in the EO, and twenty-four volatile compounds were detected in the VOC; the main components were eugenol (from 15.47% ± 1.05% to 41.89% ± 2.83%) and linalool (from 32.05% ± 2.57% to 28.99% ± 2.32%), respectively. During the distillation of the basil leaves 26 artifacts are formed. The composition of the essential oil of O. basilicum therefore depends not only on the plant but also on the method used to obtain it.

Taxonomic relevance of petiole anatomical and micro-morphological characteristics of Clematis L. (Ranunculaceae) taxa from South Korea

We assessed the micro-morphological and anatomical structures of the petioles of 19 Clematis taxa from South Korea. The petiole surface features were observed with the help of stereomicroscopy and scanning electron microscopy, and the anatomical features are studied via microtomy and light microscopy. The results of this study showed that the presence/absence and abundance of trichomes, petiole cross-section outlines, upper surface wings and grooves, and the number of vascular bundles were useful for species discrimination in Clematis. Among the studied taxa, C. hexapetala was the only species with a glabrous petiole surface. Two types of trichomes were observed in the other 18 taxa: long, non-glandular and flagelliform trichomes and short, glandular capitate trichomes. We found four to six major vascular bundles and a maximum of eight interfascicular vascular bundles (C. heracleifolia and C. urticifolia) in the 19 taxa. A cluster analysis based on UPGMA identified six clusters with 18 nodes. Although the number of taxa investigated was limited, taxa from the sections Tubulosae, Viorna, and Astragene clustered with each other in the UPGMA phenogram due to the overall similarity of petiole features. Based on this observation, we can conclude that most of the petiole features are limited to the species level, and thus, the data obtained could be used as descriptive and/or diagnostic features for particular taxa, which may be useful for the investigation of problematic taxa in the genus.

THE ANATOMICAL-MORPHOLOGICAL FEATURES OF OREGANO ORDINARY ($ORIGANUM~VULGARE~\mathrm{L.}$) WIDLY GROWING IN ARMENIAN FLORA DURING THE PRE-BLOSSOMING PERIOD

The article reports the results of microscopic studies of the oregano leaf in the pre-blossom period. In particular, the following anatomical and morphological features of the oregano leaf during the pre-blossom period were revealed: sinuous cuticle, multicellular simple trichomes, capitate trichomes, stomata, essential oil glands. The latter were located only in the central part, and were absent at the margins. The essential oil glands were of high density mostly in the central part of the raw materials preparation, which were harvested from the regions of dry climatic conditions as opposed to the raw materials harvested from the region of wet climatic conditions. The results of the investigation were definitely conditioned by the climatic features of the regions.

Essential Oil Composition and Micromorphological Traits of Satureja montana L., S. subspicata Bartel ex Vis., and S. kitaibelii Wierzb. Ex Heuff. Plant Organs

The essential oil (EO) composition of Satureja plants is highly variable. Recent studies suggest that there is an even difference in the EO composition from different plant organs within the same plant. This study aims to examine the chemical profile of EOs and the micromorphological characteristics of different organs of three Satureja species. The relationship between the number of glandular trichomes and EOs profile and relative yield is also investigated. Individuals from five populations were visualized using a scanning electron microscope, while EOs of leaves, calyces, corollas, and whole aerial parts were isolated using simultaneous distillation and extraction and analyzed using gas chromatography/mass spectrometry. Three types of glandular trichomes were detected. Peltate trichomes were present on all plant organs of studied species, while two types of capitate trichomes show different organ and species preferences. The EOs profiles differed across the plant parts, but showed a species specific composition. Univariate and multivariate statistics were used to show a correlation between the peltate trichomes and EO yield, and chemophenetic significance of EO profiles.

Labellum and gynostemium micromorphology in Polystachya (Orchidaceae)

Polystachya is a large, pantropical orchid genus of 200 species, most of which occur as epiphytes in sub-saharan Africa. The three-lobed labellum of most Polystachya species possesses a fleshy callus and various types of trichomes and papillae. In this paper, we present the results of micromorphological studies on the labellum of 20 species, representing eight of the 13 sections in the genus, using scanning electron microscopy (SEM). Our results show the scale of infrageneric diversity of trichomes and papillae relative to the sampled sections. They also demonstrate the taxonomic value of labellar micromorphology at the sectional level. The study revealed seven types of papillae and five types of trichomes (uni- and multi-cellular) in Polystachya, some of which, are described here for the first time. Clavate trichomes are the most common and are present in 60% of the species studied. Moniliform trichomes mainly occur in sect. Polystachya and are strongly characteristic of the section. Pseudopollen is formed by fragmentation of moniliform trichomes or the detachment of other trichomes as bicellular units. We provide, for the first time, evidence for the detachment of the terminal cells of capitate trichomes.

Identification of the Volatile Compounds and Observation of the Glandular Trichomes in Opisthopappus taihangensis and Four Species of Chrysanthemum

Opisthopappus taihangensis (Ling) Shih, a wild relative germplasm of chrysanthemum, releases a completely different fragrance from chrysanthemum species. We aimed to identify the volatile compounds of the leaves of O. taihangensis and four other Chrysanthemum species using headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS). In total, 70 compounds were detected, and terpenoids accounted for the largest percentage in these five species. Many specific compounds were only emitted from O. taihangensis and not from the other four species. In particular, 1,8-cineole could be responsible for the special leaf fragrance of O. taihangensis as it accounted for the largest proportion of the compounds in O. taihangensis but a small or no proportion at all in other species. The glandular trichomes (GTs) in the leaves are the main organs responsible for the emission of volatiles. To explore the relationship between the emissions and the density of the GTs on the leaf epidermis, the shape and density of the GTs were observed and calculated, respectively. The results showed that the trichomes have two shapes in these leaves: T-shaped non-glandular trichomes and capitate trichomes. Histochemical staining analyses indicated that terpenoids are mainly emitted from capitate glandular trichomes. Correlation analysis showed that the volatile amount of terpenoids is highly related to the density of capitate trichomes. In O. taihangensis, the terpenoids content and density of capitate trichomes are the highest. We identified the diversity of leaf volatiles from O. taihangensis and four other Chrysanthemum species and found a possible relationship between the content of volatile compounds and the density of capitate trichomes, which explained the cause of the fragrance of O. taihangensis leaves.

Sites of secretion of bioactive compounds in leaves of Dracocephalum moldavica L.: anatomical, histochemical, and essential oil study

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.

SECRETORY STRUCTURES AND ESSENTIAL OIL COMPOSITION OF SELECTED INDUSTRIAL SPECIES OF LAMIACEAE

The objective of the study was to perform micromorphological analyses of the secretory structures of leaves and stems of oil-bearing industrial plants from the Lamiaceae family such as lemon balm (Melissa officinalis L.), peppermint (Mentha × piperita L.), sage (Salvia officinalis L.), marjoram (Origanum majorana L., syn. Origanum dubium Boiss.), rosemary (Rosmarinus officinalis L.) and common thyme (Thymus vulgaris L.) using light microscope and scanning electron microscope. In addition, an estimation of the content of volatile substances in the plant species under study was performed using GC-MS, as well as the qualitative and quantitative analysis of essential oil, that is an important component in terms of the estimation of raw material applicability for use in the industry. In the epidermal cells of studied plants, 2 types of Lamiaceae-type glandular trichomes were identified: short- and long-stalked capitate glandular trichomes with single- and bicellular secretory capitulum, and peltate glandular trichomes with eight- and over a dozen-cell secretory capitulum. Capitate trichomes were densely distributed on the surface of the epidermis, while peltate trichomes were sparse, though regular, and were situated in depressions. Glandular trichomes were found more frequently on leaves than on stems. The cuticle of the abaxial of leaf was characterized in most cases by the occurrence of larger average diameter peltate trichomes compared to the cuticle of the adaxial side of leaf. Peppermint produced the largest structures accumulating essential oil on the leaves (average diameter of peltate trichomes – 78.48 µm on the adaxial side of leaf, up to 96.43 µm), while on the stem, the highest average diameter of the peltate trichomes was observed in sage (an average of 75.53 µm, up to 85.99 µm). The lemon balm was characterized by the presence of capitate and peltate trichomes with the smallest diameter (an average of 44.26 µm). Lemon balm was characterized by the greatest density of glandular trichomes compared to other plant species. Among the plants studied, the highest content of oil was noted in the case of thyme and peppermint (2.22% and 2.20% v/w, respectively), and the lowest in green parts of lemon balm (0.17% v/w). The isolated essential oils contained predominantly components from the groups of monoterpenes and sesquiterpenes, and it is the presence of those substances that determines the possibility of utilizing the plants studied for a variety of purposes.