Investigations on the morpho-anatomy and histochemistry of Aconitum napellus L.

Aconitum napellus L. is a popular medicinal plant extensively used in homeopathy. This article provides detailed morphology and microscopy, including the anatomical and histochemical features of the herb, to aid authentication and quality control. In cross-section, the root in secondary growth shows the phloem surrounded by pericyclic fibers and a well-developed xylem. The stem is irregular in outline, displaying unicellular trichomes and many free collateral vascular bundles encircling the pith. The leaf is dorsiventral, hypostomatic with anomocytic and anisocytic stomata, and shows non-glandular trichomes. The floral parts are characterized by uniseriate epidermises, homogeneous mesophyll, anomocytic stomata on the abaxial surface, trichomes, and oval pollen grains. The tissue fragments in powdered herbs show these characteristics and have numerous starch grains with thimble-shaped, linear or star-shaped hilum. The detailed macroscopic and microscopic analysis provided in this study can help in the authentication and quality control of A. napellus raw materials. RESEARCH HIGHLIGHTS: Key anatomical, micromorphological, and microchemical features of Aconitum napellus are described. The results of the study can support the taxonomy of the genus Aconitum. Morphological standardization of the species reported here is helpful in the quality control of this herb.

Comparative microscopic investigations of leaf epidermis in four Ajuga species from Korea.

The genus Ajuga is widely distributed in temperate to subtropical regions, and four species are currently recognized in Korea (A. decumbens, A. multiflora, A. nipponensis, and A. spectabilis), but epidermal anatomical differences across these species have never been described. A comparative study of the leaf micromorphological characteristics of Korean Ajuga species was performed using light microscopy (LM) and scanning electron microscopy (SEM) to elucidate their taxonomic usefulness and to assess leaf micromorphological diversity. Considerable diversity in epidermal and stomatal anatomy was observed across Korean Ajuga species. Species had both hypostomatic or amphistomatic leaves, with anomocytic, anisocytic, diactyic, or actinocytic stomatal complexes. Guard cell length across species ranged from 17.66 ± 0.57 µm to 32.50 ± 2.38 µm and correlated with genome size. Abnormal stomata were frequently observed in three species (A. decumbens, A. multiflora, and A. nipponensis) but not in A. spectabilis. Three types of glandular trichomes were found: peltate in all species, short-stalked in all species, and long-stalked glandular trichomes in A. multiflora. Among the investigated leaf micromophological characters, trichome type, epidermal cell shape, and stomatal morphology were all taxonomically informative traits at a species level. RESEARCH HIGHLIGHTS: A comprehensive micromorphological description of the leaf surface is provided for Korean Ajuga species using scanning electron microscopic (SEM) and light microscopic (LM) analyses. The diverse range of stomatal development and the occurrence of polymorphic stomatal types are documented for the first time in Korean Ajuga species. The great diversity in stomatal and trichome morphology in Korean Ajuga species are taxonomically useful traits for species identification.

The putative cannabinoid-secreting trichome of Trema micrantha (L.) Blume (Cannabaceae).

Trema, a genus of the popularly known Cannabaceae, has recently been the subject of cannabinoid bioprospection. T. micrantha is a tree with pharmacological potential widely used in folk medicine. It has two types of glandular trichomes, bulbous and filiform, spread throughout the plant body. Considering the proximity of this species to Cannabis sativa and Trema orientalis, species containing cannabinoids, the glandular trichomes of T. micrantha are also expected to be related to the secretion of these compounds. Thus, this study aims to detail the morphology of secretory trichomes during the synthesis, storing and release of metabolites in T. micrantha. We tested the proposition that they could be a putative type of cannabinoid-secreting gland. Pistillate and staminate flowers and leaves were collected and processed for ontogenic, histochemical, and ultrastructural analyses. Both types of glandular trichomes originate from a protodermal cell. They are putative cannabinoid-secreting sites because: (1) terpene-phenols and, more specifically, cannabinoids were detected in situ; (2) their secretory subcellular apparatus is consistent with that found in C. sativa: modified plastids, polyribosomes, an extensive rough endoplasmic reticulum, and a moniliform smooth endoplasmic reticulum. Plastids and smooth endoplasmic reticulum are involved in the synthesis of terpenes, while the rough endoplasmic reticulum acts in the phenolic synthesis. These substances cross the plasma membrane by exocytosis and are released outside the trichome through cuticle pores. The study of the cell biology of the putative cannabinoid glands can promote the advancement of prospecting for natural products in plants.

From macro to micro: A close-up look at Hydrangea luteovenosa and Hydrangea serrata.

Understanding the anatomical traits of the foliar epidermis is essential for making precise species identification and categorization. In this study, scanning electron microscopy (SEM) was used to examine the taxonomically significant foliar epidermal traits of Hydrangea luteovenosa and H. serrata. The qualitative and quantitative traits observed included the epidermal cell form, cuticle presence, trichome morphology, stomatal type, and guard cell features. H. serrata had a thin and smooth cuticle, and epidermal cells organized compactly into cubic or hexagonal shapes. The stomata were of the anomocytic type and dispersed, while the trichomes were straightforward, unbranched, and distributed sparsely. The guard cells had distinct cell walls and a kidney-shaped morphology. These crucial traits for taxonomy were in line with an epidermis composed of three to five layers. Similar polygonal epidermal cells with a compact arrangement were observed in H. luteovenosa, together with a thin and smooth cuticle. The stomata were anomocytic and dispersed, while the trichomes were straightforward, unbranched, and sparsely distributed. The guard cells have distinct cell walls and a kidney-shaped morphology. The traits were indicative of an epidermal structure with three to five layers. These traits helped correctly identify and categorize these two species of Hydrangea. In addition to assisting in the taxonomic classification of these species and advancing knowledge of their ecological and evolutionary links, the SEM study provided insightful information into the structural variety of these species. RESEARCH HIGHLIGHTS: Microscopic characteristics of H. luteovenosa and H. serrata Understanding the anatomical traits of the foliar epidermis is essential for precise species identification and categorization.

Taxonomic studies based on leaf epidermal microanatomy using high-resolution microscopy in Lamiaceous species and their antimicrobial effects.

The knowledge of essential oil antimicrobial activity of Lamiaceous species is assessed to describe its effects. The comprehensive foliar trichomes and stomatal morphology of the leaves of essential oil-bearing plants from the family Lamiaceae revealed diverse antimicrobial properties. The aim of this study was to investigate the foliar anatomical traits of 19 Lamiaceous taxa belonging to different tribes using light and scanning electron microscopy to correctly diagnose the species. The microanatomy of the foliar epidermis, trichomes diversity, and the stomatal apertural complex was visualized. Quantitative measurements were noted to describe the variations and the qualitative aspects for example, polygonal shape epidermal cells were examined. The stomatal aperture of four types and trichomes appendages both non-glandular and glandular was identified. Significant variation was found in both quantitative and qualitative traits, including unique ornamentation on the trichomes. The taxonomic key was constructed for accurate identification using qualitative morpho-structural traits. The outcomes of this research explored taxonomically to accurately identify the Lamiaceous species using anatomical characters. This study will provide provides the ecological adaptation linked to evolutionary traits of leaf surfaces that evolve with time to adapt the harsh environmental conditions. RESEARCH HIGHLIGHTS: Investigated foliar anatomical traits of 19 Lamiaceous species The anatomy and antimicrobial activity of essential oil yielding Lamiaceae species. SEM revealed diverse aspects including peculiar sculptured trichomes Microscopic identification of different stomatal complex.

Micromorphological Sculptural Diversity in Foliar Epidermis and Trichomes Features among Invasive Species.

This study examines the role of light microscopic (LM) and scanning electron microscopic (SEM) micromorphological traits of the epidermis in identifying and classifying invasive plants. SEM was conducted to increase our understanding of microscopic qualities that are not visible in light microscopy and to elucidate unclear affinities among invasive species. The study examines invasive species' morphological and anatomical characteristics from the Pothohar Plateau of Pakistan for the first time. The results showed that various micromorphological features are very useful for species' accurate identification. Adaxial and abaxial surfaces of leaves showed variations in subsidiary cells, glands, anticlinal wall patterns, stomata, and epidermal cells. Epidermal cell shapes observed were irregular, elongated, rectangular, and polygonal. Epidermal cells having maximum length were calculated in Stellaria media (126.3 µm) on adaxial side. On the abaxial surface, the minimum length was noticed in Eucalyptus camaldulensis (28.5 µm). Both glandular and nonglandular trichomes were examined, ranging from unicellular to multicellular. Most of the investigated specimens of leaves were amphistomatic, while some were hypostomatic, like Alternanthera pungens, Calotropis procera, Cannabis sativa, Lantana camara, and Thevetia peruviana. Leaf epidermal morphology contains numerous useful systematic features for accurate identifications of plant species. The micromorphological attributes under observation provide a standard criterion to the researcher for identifications of invasive flora in future morpho-taxonomic studies.

Anatomical and histochemical characterization of some highly medicinal plants as a tool for quality control.

Medicinal plants are richest source of chemical compounds that can be used to evolve novel drugs. According to World Health Organization (WHO), in developing countries more than 3.5 billion people relay on herbal drugs for their primary health care. In the present study, an attempt was carried out to authenticate some selected medicinal plants (Fagonia cretica L., Peganum harmala L., Tribulus terrestris L., Chrozophora tinctoria L. Raf. and Ricinus communis L.) from family Zygophyllaceae and Euphorbiaceae using light and scanning electron macroscopic techniques. Macroscopic evaluation and comparative anatomy (Light Microscopy) of the root and fruits revealed great diversity in macro and microscopic features. Scanning electron microscopy (SEM) of root powder showed non-glandular trichomes, stellate trichomes, parenchyma cells and vessels. Fruits SEM exhibited non-glandular trichomes, glandular trichomes, stellate trichomes, peltate trichomes and mesocarp cells. Both macroscopic and microscopic evaluation plays a crucial role in the correct substantiation and validation of novel sources. These findings can serve as an essential source of information to accomplish the authenticity and to appraise the quality and purity of the herbal drugs in accordance to WHO guidelines. These parameters can be used to distinguish the selected plants from their commonly used adulterants. RESEARCH HIGHLIGHTS: In the current work, five plants (Fagonia cretica L., Peganum harmala L., Tribulus terrestris L., Chrozophora tinctoria L. Raf. and Ricinus communis L.) from Zygophyllaceae and Euphorbiaceae were investigated for macroscopy and microscopy (LM & SEM) for the first time. Macroscopic and microscopic evaluation disclosed great diversity in morphology and histology. Microscopy is the backbone of standardization process. Current study helped in correct identification and quality assurance of the plant materials. Their statistical investigation may possess great potency for plant taxonomists to further appraise the vegetative growth and tissue development which is requisite especially for fruit to enhance the yield of herbal drugs and their formulation. Further molecular studies, compounds isolation and characterization are required to deepen the knowledge of these herbal drugs.

Taxonomic significance of seed macro-micromorphology of Turkish Alcea L. (Malvaceae) through light microscopy and scanning electron microscopy.

Seed morphological properties of 19 taxa belonging to the genus Alcea L. (Malvaceae) distributed in Turkey were investigated using a light microscope and scanning electron microscope to identify their characters and to evaluate their diagnostic value. The seeds are reniform with a rounded apex and base, reniform in shape, and light to dark brown, grayish-brown, or blackish-brown in color. The seed length ranges from 2.22 to 6.5 mm and seed width from 1.72 to 6.5 mm. The indumentum at the ventral and dorsal regions of the seed differs in density. Three types of seed coat ornamentations were observed: reticulate, reticulate-rugulate, and reticulate-ruminate on the dorsal and lateral faces. Principal component analysis was used to evaluate the important seed morphological characteristics among the taxa studied, with four components accounting for 90.761% of the total variance. Numerical analysis revealed that seed size, color, seed surface patterns on dorsal and lateral sides, indumentum at dorsal and ventral regions, and periclinal surface sculpture of epidermal cells are particularly the most useful variables for discriminating the Alcea taxa. The findings also showed a partial relationship among the Alcea taxa clusters, based on seed morphology and the systematics of these taxa, based on general macromorphology. Taxonomic key using the seed features is provided to identify the species studied. The current work will contribute to the knowledge about the family Malvaceae, and microscopic macro-micromorphological analysis can be used for identification by the taxonomists for further studies on this family. RESEARCH HIGHLIGHTS: Seed color, indumentum and surface sculpturing have systematic value for separating the taxa. Seed morphology of the Alcea taxa was studied via light microscope and scanning electron microscope. Numerical analysis provided the contribution of seed characters to taxa relationships.

Overcoming the challenges of preserving lipid-rich Cannabis sativa L. glandular trichomes for transmission electron microscopy.

Cannabis glandular trichomes produce and store an abundance of lipidic specialised metabolites (e.g. cannabinoids and terpenes) that are consumed by humans for medicinal and recreational purposes. Due to a lack of genetic resources and inherent autofluorescence of cannabis glandular trichomes, our knowledge of cannabinoid trafficking and secretion is limited to transmission electron microscopy (TEM). Advances in cryofixation methods has resulted in ultrastructural observations closer to the 'natural state' of the living cell, and recent reports of cryofixed cannabis trichome ultrastructure challenge the long-standing model of cannabinoid trafficking proposed by ultrastructural reports using chemically fixed samples. Here, we compare the ultrastructural morphology of cannabis glandular trichomes preserved using conventional chemical fixation and ultrarapid cryofixation. We show that chemical fixation results in amorphous metabolite inclusions surrounding the organelles of glandular trichomes that were not present in cryofixed samples. Vacuolar morphology in cryofixed samples exhibited homogenous electron density, while chemically fixed samples contained a flocculent electron dense periphery and electron lucent lumen. In contrast to the apparent advantages of cryopreservation, fine details of cell wall fibre orientation could be observed in chemically fixed glandular trichomes that were not seen in cryofixed samples. Our data suggest that chemical fixation results in intracellular artefacts that impact the interpretation of lipid production and trafficking, while enabling greater detail of extracellular polysaccharide organisation.

Micromorphological studies of the leaf and stem of Camellia sinensis (L.) Kuntze with reference to their taxonomic significance.

The micro-morphological examinations of the leaf lamina, petiole and stem for Camellia sinensis (L.) Kuntze (Theaceae) was carried out using a variety of microscopic techniques widely implemented in the area of medicine. The objective of this study was the micromorphological characterization of stem, petiole, lamina, stomata, leaf trichomes and other internal characters. The anatomical studies included the cross section of stem and leaf of Camellia sinensis thereby exhibiting a typical pattern of arrangement of tissues similar to woody plants. Some idioblastic sclereids like astrosclereids, osteosclereids were found in the medullary parenchyma of tea stem and leaf. Large numbers of sclereids were found mainly in the parenchymatous tissue of leaf petiole. Other micro-morphological features like trichomes, stomata, and different tissue layer were also recorded. The leaf trichomes were unicellular, long and densely present in the lower surface of immature leaf but a decrease in amount of trichomes was seen in the mature leaf making it a prime taxonomic feature of the tea leaf. The microscopic morphological analysis of the stem, petiole, lamina, stomata, leaf trichomes of Camellia sinensis can be used for its identification. In addition, these techniques can be further implemented for the taxonomic characterization thereby establishing a genetic relationship and solving taxonomic disputes in the field of plant systematics.

Peltate trichomes in the dormant shoot apex of Metrodorea nigra, a Rutaceae species with rhythmic growth.

In Metrodorea nigra, a Rutaceae species with rhythmic growth, the shoot apex in the dormant stage is enclosed by modified stipules. The young organs are fully covered with peltate secretory trichomes, and these structures remain immersed in a hyaline exudate within a hood-shaped structure. Our study focused on the morpho-functional characterization of the peltate trichomes and cytological events associated with secretion. Shoot apices were collected during both dormant and active stages and processed for anatomical, cytochemical and ultrastructural studies. Trichomes initiate secretion early on, remain active throughout leaf development, but collapse as the leaves expand; at which time secretory cavities start differentiation in the mesophyll and secretion increases as the leaf reaches full expansion. The subcellular apparatus of the trichome head cells is consistent with hydrophilic and lipophilic secretion. Secretion involves two vesicle types: the smaller vesicles are PATAg-positive (periodic acid/thiocarbohydrazide/silver proteinate) for carbohydrates and the larger ones are PATAg-negative. In the first phase of secretory activity, the vesicles containing polysaccharides discharge their contents through exocytosis with the secretion accumulating beneath the cuticle, which detaches from the cell wall. Later, a massive discharge of lipophilic substances (lipids and terpenes/phenols) results in their accumulation between the wall and cuticle. Release of the secretions occurs throughout the cuticular microchannels. Continued protection of the leaves throughout shoot development is ensured by replacement of the collapsed secretory trichomes by oil-secreting cavities. Our findings provide new perspectives for understanding secretion regulation in shoot apices of woody species with rhythmic growth.

Foliar micromorphology of selected medicinal Lamiaceae taxa and their taxonomic implication using scanning electron microscopy.

In this research, 25 medicinally used Lamiaceae species belonging to 20 genera have been studied and identified for the nine disorders. We used scanning electron microscopy (SEM) for qualitative and quantitative morphological character identification. The micromorphological characters observed here were important for distinguishing the studied taxa. The highest medicinal values were reported for Vitex negundo and Scutellaria baicalensis for all considered categories except urinary and otorhinolaryngology disorders. The foliar epidermal anatomical characteristics revealed that the micromorphological features of the Lamiaceae species provide taxonomically significant and accurate identification information to delimitate the family species. Moreover, we focused on both qualitative (epidermal cell shape, stomata type, stomatal pore shape, subsidiary cell shape, glandular trichomes, and non-glandular trichome shape) as well as quantitative features (epidermal cell size, stomata size, stomatal pore size, subsidiary cell size, and trichomes size). The trichomes diversity was different in most species' on adaxial and abaxial surfaces. In most species, anomocytic stomata were observed, but other types such as diacytic, paracytic, and tetracytic type stomata were also examined. The diverse pattern of anatomical characters suggests that the studied taxa provide insight evidence for the taxonomic observation of the Traditional Chinese Medicinal plants from the Lamiaceae. This work sets an avenue for future research and taxonomic exploration of medicinal flora through microscopic investigations. RESEARCH HIGHLIGHTS: This research offers a thorough microscopic identification of the family Lamiaceae. Taxonomic information on the trichome characters and types for the accurate authentication. Qualitative and quantitative characterization of 25 medicinally used Lamiaceae taxa.

Light and scanning electron microscopic comparative studies of geminivirus infected and healthy Eclipta alba (L.).

Eclipta alba (L.) is a valuable medicinal plant. However, its medicinal efficacy can be affected by geminivirus infection. Therefore, identification of healthy specimen is essential before to use as medicine. The present study provided the taxonomic characterization of geminivirus infected and healthy E. alba plant by studying apparent morphology and microscopic features through light and scanning electron microscopy. Before taxonomic characterization infected and healthy specimens were separated through molecular detection of geminivirus. Results of morphological studies reported that geminivirus infected E. alba plant showed systematic symptoms of infection like stunted growth, distortion and chlorosis of leaves, decrease in size of root, shoot and fruit, and so forth in comparison to healthy specimen. Anatomical findings reported that in both plants anomocytic and anisocytic types of stomata with multicellular warty trichomes were present. However, variations were observed in quantitative measures such as size of trichomes, epidermal, subsidiary and guard cells. Palynological observations identifies that both plants possessed tricolporate type of pollen but variation was mainly observed in size and shape of pollen, thickness of exine and intine, P/E ratio, pore size, interspecific difference, size of colpi, and pollen ornamentation. Overall this study concluded that both healthy and infected E. alba do not reported much variations in qualitative taxonomic features, but can be differentiated in terms of quantitative taxonomic evidences. Future studies are recommended for pharmacological analysis of both healthy and virus infected plants. RESEARCH HIGHLIGHTS: Eclipta alba has incredible therapeutic worth, but due to geminivirus infection the plant is affecting badly. Hence, the present studies give a comprehensive taxonomic report on the geminivirus infected and healthy plant species.

Microscopic characterization of five Artemisia crude herbs using light microscopy, scanning electron microscopy, and microscopic quantitative analysis.

Artemisia annua, Artemisia argyi, Artemisia absinthium, Artemisia leucophylla and Artemisia lavandulaefolia are five herbal species of Artemisia usually misidentified, adulterated or substituted in commerce. Using light microscopy, scanning electron microscopy and microscopic quantitative analysis, the transverse sections, morphological, powder and quantitative microscopic features of glandular trichome density and area were observed for correct authentication. The results indicated that microscopic characteristics such as the distribution of fiber bundles in the vascular bundle of the main vein, the shape of xylem, the density and type of non-glandular trichomes, the morphology of T-shaped non-glandular trichomes, the type of calcium oxalate crystals, and the number and size of glandular trichomes can be used to authenticate the five Artemisia crude herbs. Differences in the morphology and density of glandular and non-glandular trichomes are key features for the identification of five Artemisia species. Therefore, our study provides a more comprehensive microscopic identification diagram and additional microscopic evidence for the five Artemisia species. HIGHLIGHTS: This study provides a more comprehensive microscopic identification diagram and statistical information on the glandular trichome density and area for accurate authentication of five Artemisia herbs using light microscopy, scanning electron microscopy and microscopic quantitative analysis.

Comparison of Bougainvillea spectabilis and Bougainvillea glabra species inhibited in Pakistan based on microscopic studies: Light microscope and scanning electron microscope.

The anatomical variations of two plants from the Nyctaginaceae family, Bougainvillea spectabilis and Bougainvillea glabra, were studied using light and scanning electron microscopy methods in this work. Bougainvillea is a dicotyledonous with defensive traits that can withstand extreme (hot and dry) settings; according to the findings, crystal inclusions in cells, woody spines, and an abnormal development pattern are all features that help them survive against predators and are unique to this species. The Bougainvillea plant's leaves are arranged in simple pattern, alternate to each other along stem having an undulate leaves edge and an oval form. The xylem and phloem, palisade, parenchyma midrib, spongy mesophyll, raphide crystal bundles, and trichomes were all visible when bracts and leaves were transversally sectioned and dyed with toluidine blue O (TBO). The presence of crystals was confirmed by a detailed examination of the transverse leaves by using bright-field and cross-polarizing microscopy. Dissecting microscopic examination showed that all the leaves revealed leaves venation pattern that had midvein, lateral veins areoles, and trichomes. Although trichomes have been identified on both sides, a closer look at a cleaned leaf dyed with TBO showed multicellular abundant trichomes on adaxial surface. Stomata complexes were typically found on the abaxial surface of the leaf according to epidermal peels. Present studies also showed that on adaxial side, stomata were lesser in number or were absent and also showed that the morphologies of the pavement cells on the adaxial and abaxial sides of the leaf differed.

A pair of DUF538 domain-containing proteins modulates plant growth and trichome development through the transcriptional regulation of GLABRA1 in Arabidopsis thaliana.

SMALLER TRICHOMES WITH VARIABLE BRANCHES (SVB) is an emerging plant growth regulator in trichome development, endoplasmic reticulum stress response, and phosphoinositide signaling, and belongs to the land plant-specific DUF538 domain-containing protein family. Despite its multifaceted roles, the functions of this protein family are poorly understood in plant growth and development. Here, we report that SVB-like (SVBL), the closest homolog of SVB, modulates plant growth and trichome development with SVB in Arabidopsis thaliana. Although none of the single mutants showed an obvious growth defect, the double mutants of svb svbl exhibited dwarfed plant growth. In trichome development, the defects in svb mutant were greatly enhanced by the additional mutation in SVBL, despite the single knockout of SVBL showing the mild defects. The double mutation reduced the transcript level of one of the central hub genes for trichome development, GLABRA1 (GL1), which in turn affects the other downstream genes, GLABRA2 (GL2), TRANSPARENT TESTA GLABRA2 (TTG2), TRIPTYCHON (TRY), CAPRICE (CPC), and ENHANCER OF TRY AND CPC1 (ETC1). In situ translational reporter assays showed that SVB and SVBL share highly similar localization patterns both at tissue and subcellular levels. The present study suggests that SVB and SVBL play a pivotal role in plant growth and trichome development by affecting a specific subset of known trichome developmental regulators, highlighting the importance of the DUF538 protein family in higher plants.

Microscopy and chemical analyses reveal flavone-based woolly fibres extrude from micron-sized holes in glandular trichomes of Dionysia tapetodes.

BACKGROUND: Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic "woolly" farina. This contrasts with some related Primula which instead form a fine powder. Farina is formed by specialized cellular factories, a type of glandular trichome, but the precise composition of the fibres and how it exits the cell is poorly understood. Here, using a combination of cell biology (electron and light microscopy) and analytical chemical techniques, we present the principal chemical components of the wool and its mechanism of exit from the glandular trichome. RESULTS: We show the woolly farina consists of micron-diameter fibres formed from a mixture of flavone and substituted flavone derivatives. This contrasts with the powdery farina, consisting almost entirely of flavone. The woolly farina in D. tapetodes is extruded through specific sites at the surface of the trichome's glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle and forming a tight seal between the fibre and hole. The data is consistent with formation and thread elongation occurring from within the cell. CONCLUSIONS: Our results suggest the composition of the D. tapetodes farina dictates its formation as wool rather than powder, consistent with a model of thread integrity relying on intermolecular H-bonding. Glandular trichomes produce multiple wool fibres by concentrating and maintaining their extrusion at specific sites at the cell cortex of the head cell. As the wool is extensive across the plant, there may be associated selection pressures attributed to living at high altitudes.

Multi-omics analysis of the bioactive constituents biosynthesis of glandular trichome in Perilla frutescens.

BACKGROUND: Perilla frutescens (L.) Britt is a medicinal and edible plant widely cultivated in Asia. Terpenoids, flavonoids and phenolic acids are the primary source of medicinal ingredients. Glandular trichomes with multicellular structures are known as biochemical cell factories which synthesized specialized metabolites. However, there is currently limited information regarding the site and mechanism of biosynthesis of these constituents in P. frutescens. Herein, we studied morphological features of glandular trichomes, metabolic profiling and transcriptomes through different tissues. RESULTS: Observation of light microscopy and scanning electron microscopy indicated the presence of three distinct glandular trichome types based on their morphological features: peltate, capitate, and digitiform glandular trichomes. The oil of peltate glandular trichomes, collected by custom-made micropipettes and analyzed by LC-MS and GC-MS, contained perillaketone, isoegomaketone, and egomaketone as the major constituents which are consistent with the components of leaves. Metabolomics and transcriptomics were applied to explore the bioactive constituent biosynthesis in the leaves, stem, and root of P. frutescens. Transcriptome sequencing profiles revealed differential regulation of genes related to terpenoids, flavonoids, and phenylpropanoid biosynthesis, respectively with most genes expressed highly in leaves. The genes affecting the development of trichomes were preliminarily predicted and discussed. CONCLUSIONS: The current study established the morphological and chemical characteristics of glandular trichome types of P. frutescens implying the bioactive constituents were mainly synthesized in peltate glandular trichomes. The genes related to bioactive constituents biosynthesis were explored via transcriptomes, which provided the basis for unraveling the biosynthesis of bioactive constituents in this popular medicinal plant.

Rice SPL10 positively regulates trichome development through expression of HL6 and auxin-related genes.

Trichomes function in plant defenses against biotic and abiotic stresses; examination of glabrous lines, which lack trichomes, has revealed key aspects of trichome development and function. Tests of allelism in 51 glabrous rice (Oryza sativa) accessions collected worldwide identified OsSPL10 and OsWOX3B as regulators of trichome development in rice. Here, we report that OsSPL10 acts as a transcriptional regulator controlling trichome development. Haplotype and transient expression analyses revealed that variation in the approximately 700-bp OsSPL10 promoter region is the primary cause of the glabrous phenotype in the indica cultivar WD-17993. Disruption of OsSPL10 by genome editing decreased leaf trichome density and length in the NIL-HL6 background. Plants with genotype OsSPL10WD-17993 /HL6 generated by crossing WD-17993 with NIL-HL6 also had fewer trichomes in the glumes. HAIRY LEAF6 (HL6) encodes another transcription factor that regulates trichome initiation and elongation, and OsSPL10 directly binds to the HL6 promoter to regulate its expression. Moreover, the transcript levels of auxin-related genes, such as OsYUCCA5 and OsPIN-FORMED1b, were altered in OsSPL10 overexpression and RNAi transgenic lines. Feeding tests using locusts (Locusta migratoria) demonstrated that non-glandular trichomes affect feeding by this herbivore. Our findings provide a molecular framework for trichome development and an ecological perspective on trichome functions.

Glandular trichomes of the flowers and leaves in Millingtonia hortensis (Bignoniaceae).

MAIN CONCLUSION: Three types of the glandular trichomes are developed on the flowers and leaves of Millingtonia hortensis. Morphology, cell ultrastructure and content of the volatile compounds are specific to each trichome type. The aim of this study was to characterize the structural and histochemical features of the glandular trichomes (GTs) of two types localized on the different flower parts and leaves in Millingtonia hortensis, as well as to identify the composition of the internal pool of metabolites. The peltate GTs are most common; they are founded on peduncle, calyx, ovary, and leaves. GTs consist of 12-24-cell disk-shaped head and a single-celled neck. The capitate GTs are located on corolla tube and have four to eight-cell head, single-celled neck and a wide multicellular stalk. A series of histochemical reactions and fluorescent microscopy revealed the various substances in the chemical composition of GTs. Acid polysaccharides are predominately identified in the capitate trichomes of the corolla tube and peltate trichomes of calyx, terpenes present in larger quantity in the trichomes of the corolla tube and ovary, whilst phenolic substances prevail in the trichomes of the calyx and ovary. GTs of each type are characterized by specific ultrastructural traits. Smooth endoplasmic reticulum (SER) and leucoplasts prevail in the peltate trichomes of peduncle, calyx and ovary; Golgi apparatus is the common organelle in the capitate trichomes of the corolla tube and peltate trichomes of calyx; the huge aggregates of the RER cisterns there are in cytoplasm of all leaf trichomes. Synthesized secretion accumulates in the subcuticular cavity of all GTs except the leaf peltate trichomes. In the trichomes of the leaves secretion is stored in the thick upper cell wall with the wide cutinized layer. For the first time content of the internal pool of metabolites from the flowers and leaves was identified by GC-MS. Seventeen compounds, including alcohols, fatty acid derivatives, monoterpenes, sesquiterpenes, and benzenoids were identified. 1-octen 3-ol, 3-carene, methyl salicylate, p-hydroxybenzeneethanol and 1-hydroxy-2,4-di-tertbutyl-benzene were the main compounds of the flower scent. We consider GTs of the reproductive organs in M. hortensis synthesizing acid polysaccharides and volatile compounds as secretory structures attracting of pollinators, whereas the leaf peltate trichomes accumulating predominately non-volatile phenols, protect young vegetative shoots against small herbivorous insects and pathogens.