Secretory Head Research Articles

A morphological and chemotaxonomic study of Teucrium arduini L. in Croatia, and Bosnia and Herzegovina

A study on the type and distribution of trichomes, morphological traits of the calyx and content of antioxidant compounds was conducted on Teucrium arduini L. populations in Croatia and in Bosnia and Herzegovina. Non-glandular trichomes, peltate trichomes and small capitate trichomes with four secretory head cells were observed on leaves, stems and calyx, whereas long capitate trichomes with a unicellular head cell were observed exclusively on the calyx. Average calyx length was 5.23–6.51 mm, calyx tube length 2.92–3.68 mm, lower lip length 1.25–2.42 mm and upper lip length 1.89–2.99 mm. The concentration of antioxidant compounds in all populations was the highest in leaves: total polyphenols (TP): 8.43–13.55%; tannins (T): 1.79–7.33%; flavonoids (TF): 0.28–0.40%; phenolic acids (TPA): 2.90–5.07%. Inflorescences generally contained the smallest amount of TP (5.89–11.42%), T (0.87–6.50%) and TPA (1.66–2.27%), while the smallest content of TF was obtained for the majority of stem samples (0.06–0.12%). The researched populations did not differ with regard to the type and overall distribution of the trichomes, though the Bosnian populations have a shorter calyx tube and longer upper lip. Some variability was observed in the TP and T content between sampling sites, while quite high variability was noted in the TF and TPA content.

Structure and histochemistry of the glandular trichomes on the leaves of Isodon rubescens (Lamiaceae)

The structure and histochemistry of the glandular trichomes on the surface of Isodon rubescens leaves were investigated. The main components in the secretion were identified. Morphological and histochemical study revealed one type of non-glandular and two types of glandular trichomes on the leaves of I. rubescens . These two types of glandular trichomes differed both anatomically and in the components of respective secondary metabolites. The glandular trichomes were classified into two subpopulations, namely the peltate and capitate glandular trichomes. The former was characterized by a short stalk and a large four-celled secretory head, while the latter was further subdivided into two groups; one has a short unicellular stalk and two-cellular head (type I), the other has a multicellular stalk and a globose unicellular head (type II). Peltate and capitate type I trichomes were constitutively present, whereas capitate type II was rarely found in all leaf samples. The secondary metabolites secreted by peltate trichomes were examined histochemically, which included terpenoids, flavonoids, carbohydrates, phenolics and alkaloids. The peltate trichomes are not only sites of oridonin accumulation, but also sites of oridonin biosynthesis in I. rubescens .

Trichomes in Echium amoenum Fisch & Mey petals: A micromorphological survey

Echium amoenum Fisch & Mey (Boraginaceae) grows widely in the northern highlands of Iran. Dried petals of E. amoenum have long been used for their anxiolytic, sedative, anti-inflammatory and analgesic effects in Iranian folk medicine (1). Phytochemical studies revealed a variety of substances of which rosmarinic acid and flavonoids showed antioxidant activity in humans (2). Inhibition of humoral antibody synthesis has also been reported (3). All the published studies on E. amoenum have concentrated on the therapeutic uses and/or the phytochemical analyses. No botanical data is available and the secretory structure has not been reported so far. This study was carried out to provide elements on the morphology and localization of the secretory structure, with regard to floral development. E. amoenum flowers were collected from Ghazvin, at four developmental stages. Petals were double fixed in glutaraldehyde and osmium tetroxide, dehydrated in acetone, air dried in hexamethyldisilazan, coated with gold and viewed under the scanning electron microscope. The youngest floral buds were densely covered with protective non glandular trichomes of different length. The same trichomes covered the outer epidermis of the young petals emerging from the sepals. Short stalked capitate trichomes, with one globular secretory head were observed between the protective hairs. During development, the number of non glandular trichomes decreased, but capitate trichomes increased in number, reaching their maximum in 3.5cm long petals at full bloom. Further histochemical studies will elucidate the variable nature of the secreted material, as well as the phases of the secretion process.

Cephalic modifications in dimorphic dwarf spiders of the genus oedothorax (Erigoninae, Linyphiidae, Araneae) and their evolutionary implications

Reproductive competition among males selects for a broad variety of strategies and traits from mate guarding to nuptial food gifts. Males of many dwarf spider species possess conspicuous secondary cephalic modifications, and the few studies available suggest that these cephalic structures are connected to extensive glandular tissue. Because females were observed to contact the male head structures during mating, these traits may have evolved in the context of sexual selection. We investigated the structure, glandular equipment, and sensory equipment of the cephalic regions of several species of the dwarf spider genus Oedothorax with varying degrees of sexual dimorphism using light and electron microscopy. In one Oedothorax species, there are two male morphs that exhibit a cephalic modification (O. gibbosus gibbosus) or not (O. gibbosus tuberosus). Our study demonstrates that all males investigated produce cephalic secretions, irrespective of the morphology of their cephalic region, however, they may differ in amount of secretion and in cellular organization. In males of O. apicatus, O. gibbosus gibbosus and O. retusus the gland cells are very abundant in the area of a cephalic hump, whereas in the less conspicuous O. agrestis, and O. gibbosus tuberosus the gland cells are restricted to a small area behind the ocular region or include the ocular region as in O. fuscus. The glandular tissue consists of two gland types in O. agrestis, O. fuscus, O. gibbosus tuberosus and O. retusus and of only one type in O. apicatus and O. gibbosus gibbosus. The setae present on the head structure of all species seem to function as mechano- and/or chemoreceptors. The implications of our findings for the evolution of secretory head structures are discussed along with their potential for driving speciation.

The taxonomic value of leaf anatomy and trichome morphology of the genus Cyclotrichium (Lamiaceae) in Turkey

The genus Cyclotrichium (Boiss.) Manden. & Scheng. is represented by six species in Turkey: C. glabrescens, C. leucotrichum, C. longiflorum, C. niveum, C. origanifolium and C. stamineum. They are aromatic perennial subshrubs used as spices or herbal teas in traditional Turkish medicine. The leaf anatomy and tomentum morphology of leaves and calyces of Cyclotrichium species in Turkey was investigated by scanning electron microscopy (SEM) and light microscopy (LM). The investigated species have equifacial (C. niveum, C. origanifolium) or bifacial leaves (C. glabressens, C. leucotrichum, C. longiflorum, C. stamineum). All species have peltate and capitate glandular, and simple (all species) or branched (C. niveum) eglandular trichomes and diacytic stomata. Peltate trichomes consist of a basal cell embedded in the epidermis, a stalk cell, and a broad 12 (–13)‐celled secretory head arranged in two concentric circles. The capitate trichomes observed in Cyclotrichium can be grouped into five types, differing in structure and size. They consist of either a pear‐shaped or globose unicellular head and uni‐or bicellular stalk, or a bicellular head and bicellular stalk. The density of peltate, capitate and eglandular trichomes differs between species. Peltate trichomes are densely spaced only on the calyx and on the leaf surface of C. niveum and C. origanifolium and on the abaxial leaf surface of C. longiflorum and C. stamineum. The significance of trichome architecture for taxonomy in Cyclotrichium and Lamiaceae in general is discussed.

Structural investigation of the glandular trichomes of endemic Salvia smyrnea L.

The morphology, anatomy and distribution of glandular trichomes on the aerial organs of Salvia smyrnea L. endemic to Turkey have been investigated with light microscopy (LM) and scanning electron microscopy (SEM). This species is evaluated in endangered (EN) category. Two morphologically distinct types of glandular trichomes were determined. Various types of capitate glandular trichomes consist of a 1–4 celled base, a 1–8 stalk celled or no stalk and a uni- or bicellular head. In capitate trichomes the neck cell that has an important role especially for xeromorfic plants, acting to prevent the backflow of secreted substance through the apoplast, has been distinctively observed in the investigated species. The capitate trichomes were present abundantly on all aerial organs of S. smyrnea. Peltate glandular trichomes had a large secretory head comprising 1–2 central and 4,6, 8–10 peripheral cells. This study pointed out that S. smyrnea was of rich glandular trichomes in point of diversity and quantity.

Structural investigation of the glandular trichomes of Salvia argentea

The morphology, anatomy and distribution of glandular trichomes on the aerial organs of Salvia argentea L. has been investigated. Two morphologically distinct types of glandular trichomes were determined. Capitate glandular trichomes forming a base 1-7 celled, a stalk 1-5 celled or no stalk and a head uni- or bicellular had various types. In capitate trichomes, the neck cell that has an important role especially for xeroformic plants, acting to prevent the backflow of secreted substance through the apoplast has been distinctively observed in the investigated species. The capitate trichomes were present abundantly on all aerial organs of S. argentea. Peltate glandular trichomes had a large secretory head forming 1-5, 8 central and 8-10, 12, 14 peripheral cells. Peltate trichomes are present on all aerial organs, except petiole, being the most abundant on calyx and corolla. Results were shown by tables and photographs.

The Histochemical Analysis of Thymus Malyi Ronninger Glandular Trichomes

ABSTRACTThe genus Thymus L. belongs to the family Lamiaceae, and comprises numerous aromatic species which are used for medical purposes and also as culinary herbs. Thymus malyi Ronninger is an endemic species from central Balkan which grows on serpentine hills. Histochemical analyses of the peltate and capitate glandular trichomes of Thymus malyi were carried out using light microscopy. Results of histochemical tests showed positive reaction to phenol compounds in the secretory heads of peltate trichomes. Positive reaction for terpenes was obtained in capitate trichomes and in the subcuticular spaces of peltate trichomes. Lipid reaction was positive in the stalk cell of the capitate trichomes, and in the peltate trichomes heads. Positive reaction for polysaccharides was observed in the secretory head of both types of glandular trichomes, with more intensive reaction in the capitate trichomes.

Micromorphology, anatomy and volatile constituents of leaf in some Lamiaceae species

The objective of this study is to determine the range of variation in certain micromorphological, anatomical and biochemical characters of leaf within three spontaneous Lamiaceae species: Hyssopus officinalis L. (from Montenegro Republic), Thymus comosus Heuff. and Ocimum basilicum L. (both from Romania) The research material was collected in anthesis stage of plant development. Anatomical characters of leaf epidermis were examined by light microscopy. Scanning electron microscopy was used to examine leaf surface and trichomes. The qualitative analysis of the volatile oils has been carried out using GC-MS. All examined species had bifacial heterofacial and amphistomatous leaf. The stomata are diacytic. The glandular hairs consist of one epidermic basal cell, a uni- or multicellular stalk and a uni- or multicellular secretory head. The non-glandular trichomes are simple, short or long, multicellular uniseriate. The variable micromorphological and anatomical characters of leaf are rather quantitative than qualitative, as follows: 1. the mesophyll thickness; 2. the density of stomata and trichomes; 3. the number and size of intercellular air spaces of spongy mesophyll. The volatile oils produced by the investigated species differ in their composition. The aromatic value and therapeutical efficiency of these products strictly depend on the moment of plant development, metabolic transformations and climatic conditions. Among the analyzed species, the main constituents of volatile oils are: thymol, carvacrol, β-cariophylene, germacrene D, δ-cadinol, linalool and methylchavicol.

Compositions of Essential Oils and Trichomes of Teucrium chamaedrys L. subsp. trapezunticumRech. fil. and subsp. syspirense (C. Koch) Rech. fil.

Teucrium chamaedrys L. is a member of the Lamiaceae family and is represented in the Flora of Turkey by six subspecies. The aerial organs of T. chamaedrys L. subsp. trapezunticum Rech. fil. and subsp. syspirense (C. Koch) Rech. fil. bears numerous eglandular and glandular trichomes. Eglandular trichomes are simple, long-multicellular with cuticular micropapillae, and glandular hairs are of peltate and capitate types. The peltate hairs consist of a basal cell, a short unicellular stalk, and multicellular secretory head, and the capitate ones possess 1-2 stalk cells and one glandular head cell. The aerial parts were subjected to microdistillation for the isolation of volatiles. The analysis was simultaneously performed by using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The major components were characterized as beta-caryophyllene (18%), nonacosane (12%), germacrene D (11%), caryophyllene oxide (7%), and alpha-pinene (7%) for subsp. trapezunticum, and caryophyllene oxide (23%), alpha-pinene (11%), and caryophyllenol II (5%) for subsp. syspirense.

Morphology and histochemistry of glandular trichomes of Cordia verbenacea DC. (Boraginaceae) leaves

The objective of this work was to study, using light and fluorescence microscopy and scanning electron microscopy, the morphology and secretory products of glandular trichomes of Cordia verbenacea DC. (Boraginaceae), known as 'baleeira', a species used in folk medicine as anti-inflammatory, analgesic, anti-ulcerogenic and healing agent. Two classes of glandular trichomes were recognized, globular and reniform. A morphological study of the secretory head and the characterization of the secretory product are also presented. Secretory products of globular trichomes consisted of essential oils, whereas reniform trichomes consisted basically of phenolic compounds such as flavonoids. No pre-established regions for releasing secretory products were found.

Glandular Hairs and Secretory Ducts ofMatricaria chamomilla(Asteraceae): Morphology and Histochemistry

The aim of the present work is to characterize the glandular hairs and the secretory ducts of Matricaria chamomilla (Asteraceae) morphologically, anatomically and histochemically. The glandular hairs are multicellular and biseriate with two basal cells, two peduncle cells and a secretory head composed of six cells. The histochemical tests show that the glands are positive for lipids, essential oils, sesquiterpene lactones, and pectic—like substances. The secretory ducts show a lumen surrounded by a layer of specialized cells, with the exception in the root where the ducts do not show any secretory epithelium. The histochemical tests show that the ducts are always positive for lipids, while the tests for the presence of essential oils and sesquiterpene lactones are heterogeneous in the plant organs considered.

Micromorphology of glandular trichomes of Nepeta congesta Fisch. & Mey. var . congesta (Lamiaceae) and chemical analysis of the essential oils

The micromorphology and distribution of foliar trichomes of Nepeta congesta var . congesta (Lamiaceae), a species endemic to Turkey, were investigated in order to evaluate the usefulness of this feature for systematic purpose. The aerial parts of N. congesta var . congesta bear an indumentum of glandular and non-glandular trichomes. Two types of glandular trichomes are identified. Peltate trichomes consist of a basal cell embedded in the epidermis, a stalk cell, and a four-celled secretory head. Capitate trichomes comprise either a unicellular head and uni- or bicellular stalk, or a bicellular head and unicellular stalk. Water-distilled essential oil of the aerial parts of N. congesta var . congesta was analysed by GC and GC/MS and the main components were found to be 1.8-cineole (29.9%), germacrene-D (20.3%) and sabinene (10.3%).

Hypericum elodes L. (Clusiaceae): The secretory structures of the flower

The type, structure, distribution, and ontogenesis of secretory structures of Hypericum elodes flowers were studied by light and scanning electron microscopy. This species, widespread in Western Europe but present in Italy in one site only (S. Rossore Estate, Pisa), is characterized by the presence of glandular emergences, stipitate glandular pockets, and secretory canals. Each glandular emergence consists of a multicellular peduncle and a multicellular secretory head. The head is a compact structure that looks like the well-known black nodules of H. perforatum. The stipitate glandular pockets consist of a short multicellular peduncle and a multicellular head with a cavity that collects an amber-colored secretion. Two types of secretory canals were identified: a type with a narrow lumen, and a type with a wide lumen. Histochemical analysis showed that secretion is similar in all secretory structures, and is rich in lipids, essential oils, alkaloids, and oleoresins.

The essential oil secretory structures of Prostanthera ovalifolia (Lamiaceae).

The structure of the essential oil secretory tissues of Prostanthera ovalifolia R.Br was investigated using bright- and dark-field optical microscopy, and scanning and transmission electron microscopy. The leaves of P. ovalifolia have glandular trichomes of the peltate type common to many Lamiaceae species. The trichomes consist of a basal cell embedded in the epidermis, a stalk cell with heavily cutinized walls and a 16-celled secretory head, but they differ from those of many previously reported Lamiaceae species in their morphological form defined by the elevated cuticle. The sub-cuticular space contains a mixture of lipid and aqueous phases. Secretory cells have dense cytoplasm with many leucoplasts present. Volatile terpenoids are eliminated from the cytoplasm into the sub-cuticular space, the site of essential oil accumulation, via granulocrine secretion.

Development and some histochemical aspects of foliar glandular trichomes of Stevia rebaudiana (Bert.) Bert. - Asteraceae

The ten-celled biseriate glandular trichome of Stevia rebaudiana (Bert.) Bert.-Asteraceae, found on both leaf surfaces, originates from a single protruding, protodermal cell undergoing an anticlinal division. A subsequent series of periclinal divisions, occurring in acropetal sequence, leads to the formation of the trichome, composed of five pairs of cells, one pair of basal cells, another of stalk cells and three pairs of secretory head cells. Developing, still two-celled glandular trichomes already occur on leaf primordia of the second pair (these primordia measuring, in some cases, ca. 0.30 mm in length), and most of the glandular trichomes are at the mature phase on very young, expanding leaves, for example on those of the sixth pair. The secretory material released by the head cells is stored in the trichome cavity (subcuticular space). Basic histochemical tests reveal that such material is lipophilic (mainly) and hydrophilic in nature.

Tricomas foliares em tomateiro com teores contrastantes do aleloquímico 2-tridecanona

Duas espécies de tomateiro, Lycopersicon esculentum Mill. (Linhagem TOM 556- padrão com baixo teor da metil cetona 2-tridecanona (2-TD) e Lycopersicon hirsutum Dunal var. glabratum Mill. (Linhagem PI 134417- padrão com elevado teor de 2-TD), foram analisadas em conjunto para identificação e quantificação de tricomas foliares. A parte experimental constou da identificação dos tricomas, baseado na presença ou ausência da cabeça secretora na extremidade apical dos tricomas, arranjo e número de células da cabeça, comprimento dos tricomas, e da quantificação do número de tricomas glandulares e não glandulares nos folíolos. O delineamento utilizado para o número de tricomas foi inteiramente casualizado e as médias comparadas pelo teste de Tukey, a 5%. A identificação e quantificação para as espécies foram: a) TOM 556: Tricomas não glandulares do tipo II + III + V (2590 cm-2 de área foliolar); glandular do tipo VI (16 cm-2); glandular do tipo VII (138 cm-2); b) PI 134417: não glandulares do tipo II + III + V (140 cm-2 de área foliolar); glandular do tipo I + IV (843 cm-2); glandular do tipo VI (83 cm-2); glandular do tipo VII (11 cm-2). As maiores concentrações da 2-TD nos folíolos, estão associadas às maiores densidades de tricomas glandulares presentes em ambas espécies.

Essential Oil Gland Number and Ultrastructure During Mentha arvensis Leaf Ontogeny

Alterations in essential oil gland number, distribution and fine structure, and the oil content in the leaf of Mentha arvensis L. were examined during its growth and senescence. Accumulation of essential oil occurred predominantly during the rapid leaf expansion phase followed by a similar decline. The oil gland (trichome) number increased upto leaf maturation and declined thereafter. Initially, cuticle remains tightly apposed to the secretory head of oil glands but progressively a sub-cuticular space appears to be created for the oil. Considerable enlargement of vacuole with ageing is witnessed, whereas cytoplasm gradually decreases to a thin peripheral layer. Some secretory cells from senescing leaf were found almost empty, having only a few remnant oil droplets.

Glandular Trichomes ofCalceolaria adscendensLidl. (Scrophulariaceae): Histochemistry, Development and Ultrastructure

This paper reports the results of a study of the morphology and development of glandular trichomes in leaves ofCalceolaria adscendensLidl. using light and electron microscopy. Secretory trichomes started as outgrowths of epidermal cells; subsequent divisions gave rise to trichomes made up of a basal epidermal cell, a stalk cell and a two-celled secretory head. Ultrastructural characteristics of trichome cells were typical of terpene-producing structures. Previous phytochemical studies had revealed thatC. adscendensproduces diterpenes. Comparison withC. volckmanni,which produces triterpenes, and has trichomes with eight-celled secretory heads, suggests that there could be a relationship between the type of glandular trichome and the class of terpene produced. Further work is needed to test the hypothesis and to develop trichome characters as taxonomic tools.

Ultrastructure of Mesophyll Glands Secreting the Aromatic Substances in Patchouli Leaves

The mesophyll gland in patchouli (Pogostemon patchouli) was composed of secretory materials covered with a cuticle, a secretory head cell, a stalk cell and a basal cell. A large number of polysomes, mitochondria and smooth-appearing endoplasmic reticula showing a contracted figure were observed in the secretory head cells. Some endoplasmic reticula were sometimes observed in ramiform profiles. The aromatic cyclic sesquiterpenes were assumed to secrete into a subcuticular space through the thick cell wall from the peripheral area of the secretory head cell. Some cytoplasmic inclusions were localized in the secretory head cells and were considered to have been caused by a viral infection. On the basis of the ultrastructural details of the mesophyll glands, we discuss the secretory machinery by which the cyclic sesquiterpenes are produced and the possibility of the disturbance by viruses of the production of aromatic substances.