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.     

Foliar secretory trichomes of Ocimum obovatum (Lamiaceae): micromorphological structure and histochemistry

This study characterises the micromorphology, ultrastructure and main chemical constituents of the foliar glandular trichomes of Ocimum obovatum using light and electron microscopy and a variety of histochemical tests. Two types of glandular trichomes occur on the leaves: large peltate and small capitate. The head of each peltate trichome is made up of four broad head cells in one layer. The head of each capitate trichome is composed of two broad head cells in one layer (type I) or a single oval head cell (type II, rare). In peltate heads, secretory materials are gradually transported to the subcuticular space via fracture in the four sutures at the connecting walls of the head cells. Release to the head periphery occurs through opposite fracture in the four sutures in the head cuticle. In type I capitate trichomes, release of the secretions to the subcuticular space occurs via a pore between the two head cells, and release to the head periphery occurs through the opposite pore in the head cuticle. In type II capitate trichomes, the secreted material is released from the head cell through a ruptured particular squared area at the central part of the head cuticle. These secretion modes are reported for the first time in the family Lamiaceae. Histochemical tests showed that the secretory materials in the glandular trichomes are mainly essential oils, lipophilic substances and polysaccharides. Large peltate trichomes contain a large quantity of these substances than the small capitate trichomes. Ultrastructural evidence suggests that the plastids produce numerous lipid droplets, and the numerous polysaccharide small vesicles are derived from Golgi bodies.     

Glandular trichomes of <Emphasis Type="Italic">Tussilago Farfara</Emphasis> (Senecioneae,Asteraceae)

Main conclusion

The glandular trichomes are developed on the aerial organs of Tussilago farfara ; they produce phenols and terpenoids. Smooth endoplasmic reticulum and leucoplasts are the main organelles of the trichome secretory cells. The aim of this study was to characterise the morphology, anatomy, histochemistry and ultrastructure of the trichomes in Tussilago farfara as well as to identify composition of the secretory products. Structure of trichomes located on the peduncles, bracts, phyllaries, and leaves were studied by light and electron microscopy. The capitate glandular trichomes consist of a multicellular head and a biseriate long stalk. Histochemical tests and fluorescence microscopy reveal phenols and terpenoids in the head cells. During secretory stage, the head cells contain smooth and rough endoplasmic reticulum, Golgi apparatus, diversiform leucoplasts with opaque contents in lamellae, chloroplasts, mitochondria, and microbodies. In the capitate glandular trichomes of T. farfara subcuticular cavity is absent, unlike glandular trichomes in other Asteraceae species. For the first time, content of metabolites in the different vegetative and reproductive organs as well as in the isolated capitate glandular trichomes was identified by GC–MS. Forty-five compounds, including organic acids, sugars, polyols, phenolics, and terpenoids were identified. It appeared that metabolite content in the methanol extracts from peduncles, bracts and phyllaries is biochemically analogous, and similar to the metabolites from leaves, in which photosynthesis happens. At the same time, the metabolites from trichome extracts essentially differ and refer to the above-mentioned secondary substances. The study has shown that the practical value of the aerial organs of coltsfoot is provided with flavonoids produced in the capitate glandular trichomes.

     

Novel reports of glands in Neotropical species of Indigofera L. (Leguminosae,Papilionoideae)

By considering controversial discussions in the literature with regard to gland denomination in Indigofera species, as well as the taxonomic value of secretory structures in Leguminosae, we aim to morphologically detail glands that had been previously observed in I. microcarpa and I. sabulicola, and to investigate the occurrence of glands in vegetative and reproductive organs of other six Neotropical species that belong to the genus. Glands analyzed through scanning electronic microscopy (SEM) in combination with anatomic analyses correspond to secretory trichomes that are classified into seven types. Main variations in relation to types occurred with regard to head shape and peduncle size. Trichome heads were multicellular, with a thin cuticle. Hollow heads with conspicuous inner space characterized only one type (type 1); the other trichome types had massive heads. Peduncles, which varied from biseriate to multiseriate, had thick, pecto-cellulosic cell walls. Trichomes were found on stems, stipules, petioles, rachis, petiolules, leaflets, bracteoles, sepals, standards and fruits, more commonly along the margins. Each of the eight Indigofera species analyzed had at least two different trichome types out of the seven types that occurred in reproductive and vegetative organs of these taxa. Various types of secretory trichomes were found in I. campestris, I. lespedezioides, I. microcarpa, I. spicata, I. suffruticosa and I. truxillensis. Stems and rachis were the vegetative organs in which a greater variety of trichomes occurred, and sepals were parts of reproductive organs with the same status. Five out of the seven secretory trichome types occurred on both vegetative and reproductive organs. Distribution and gland types differed between species and these gland distribution patterns can be used as diagnostic characters. Reports of glands in Indigofera campestris, I. hirsuta, I. lepedezioides, I. suffruticosa, I. spicata and I. truxillensis, their recognition as secretory trichomes, and the morphological variety of types found for such trichomes are novel data for Indigofera.     

龙葵腺毛发育的细胞学研究

利用光学显微镜、扫描电镜和透射电镜技术,观察了龙葵“四叶一心”期时叶片及茎表皮的腺毛的种类、分布,探究了不同类型腺毛的起源、生长、成熟、分泌、衰老等发育过程的细胞学特征;通过组织化学染色和荧光显微技术,观察了龙葵腺毛成分、分布,为龙葵的进一步开发利用提供参考。结果表明：（1）龙葵腺毛分为单细胞头腺毛和多细胞头腺毛两类,前者主要分布于茎表面和叶上下表皮,后者主要分布于茎表面的单细胞头腺毛之间、叶脉及叶边缘;（2）龙葵腺毛发育起始于表皮细胞突起,单细胞头腺毛行顶端生长,具1-4个柄细胞,四种类型;多细胞头腺毛可再分为一层、两层与三层多细胞头腺毛,另具三种特殊类型;（3）龙葵成熟腺毛具分泌能力,通过皮下空间的物质积累导致腺毛头细胞表面形成突起、包块、破口,最终释放分泌物;而头细胞与柄细胞随即皱缩、衰老。（4）超微结构显示,腺毛头细胞中内质网与高尔基体极为丰富,合成代谢及分泌活动活跃,产生大量包裹嗜锇物质的囊泡,囊泡与细胞壁融合,进而将嗜锇物质转移至细胞壁并积累,随后储存在角质层下的皮下空间直至分泌释放;（5）组织化学染色结果表明,腺毛含有萜类、生物碱、脂类、蛋白质、酚类和多糖。头细胞中主要含有萜类、生物碱、脂类、蛋白质、酚类和中性多糖;柄细胞中主要含有萜类、生物碱、脂类。     

Light, conventional and environmental scanning electron microscopy of the trichomes of Cucurbita pepo subsp. pepo var. styriaca and histochemistry of glandular secretory products

BACKGROUND AND AIMS: In the present study, the differences between glandular and non-glandular trichomes, the secretory process and the method of secretion were studied. Previous studies on leaves of Styrian oil pumpkin (Cucurbia pepo var. styriaca) plants have shown that four morphologically and ontogenetically independent glandular and non-glandular trichome types and one bristle hair type can be distinguished. The four types of trichomes can be categorized into three glandular trichome types: type I, a short-stalked trichome with four head cells including a 'middle-cell', two stalk cells and one basal cell; type II, a long-stalked trichome with two head cells, a 'neck-cell' region and a long stalk area; type IV, a 'stipitate-capitate' trichome with a mesophyll cell basement, a short stalk and a multicellular head; type III, a non-glandular 'columnar-digit' trichome, which consists of two head cells continuous with three-celled stalk, and the basal cell. METHODS: The histochemical studies (the main classes of metabolite in secreted material of glandular trichomes) were conducted in fresh and fixed hand sections, using the following tests: Sudan black B, Nile blue A, osmium tetroxide, neutral red, Naturstoffreagent A, FSA (fuchsin-safranin-astra blue), NADI (naphthol + dimethylparaphenylenediamine) and ruthenium red. Each suggested differences in the intercalations during the ontogenetical development of each trichome during the development stage. KEY RESULTS: The histochemical reactions revealed the main components of the materials secreted by all types of trichomes, which include lipids, flavones and terpenes and the different cell wall compositions. Glandular secretions were observed during environmental scanning electron microscopy (ESEM) and the trichomes compared with those seen by conventional scanning electron microscopy (CSEM). CONCLUSIONS: Scanning electron microscopy and histochemical analysis demonstrated that each of the trichomes studied produced and released secretory products in a characteristic way.     

木香薷腺毛形态结构发生发育规律的研究

采用常规石蜡切片法及扫描电镜技术对木香薷(Elsholtzia stauntoni Benth)腺毛发生发育及其规律进行了研究。结果表明：木香薷表皮上主要有两种表皮毛：无分泌细胞的表皮毛与有分泌细胞的腺毛。前者包括单细胞乳头状毛、2~3细胞管状毛、分枝状毛及多细胞管状毛;后者包括头状腺毛与盾状腺毛。成熟头状腺毛头部由1、2或4个分泌细胞构成,头部呈圆球形或半圆球形;成熟盾状腺毛头部由8~12个分泌细胞构成,分泌细胞横向扩展形成盾状头部。木香薷腺毛主要在茎端幼叶处大量发生,从茎端第一对幼叶处开始产生;从幼叶期到成熟期均有腺毛发生,大部分腺毛在幼叶期发生发育,只有极少部分在叶的成熟期进行发生发育。     

Foliar appendages in certain species ofSalvia (studies inLamiaceae VI)

Foliar appendages of eight species ofSalvia L. have been studied. Eleven types of non glandular and five types of glandular appendages have been observed. They have been classified under three major categories: (1) glandular capitate; (2) non glandular filiform and (3) non glandular capitate. Five new types of trichomes have been reported fromLamiaceae for the first time. On the basis of trichome types different species ofSalvia can be identified. A tentative key has been presented.     

线纹香茶菜叶上腺毛发育的细胞学研究

为进行中药溪黄草基原植物的品种鉴定,采用光镜和电镜对线纹香茶菜(原变种)[Isodon lophanthoides var.lophanthoides]叶上腺毛的发育进行细胞学研究。结果表明,线纹香茶菜具有头状腺毛和盾状腺毛2种类型。头状腺毛无色透明,由1个基细胞、1个柄细胞和1或2个头部分泌细胞构成;盾状腺毛为红色,由1或2个基细胞、1个柄细胞和4~8个分泌细胞构成头部。2种腺毛均由原表皮细胞经两次平周分裂形成,后因柄细胞和头部细胞所处的分化状态不同而形成两类腺毛。2种腺毛超微结构表明,质体、高尔基体和粗面内质网为主要分泌物产生和运输的细胞器。当盾状腺毛成熟时,角质层下间隙充满了分泌物,其分泌物的性质很可能决定了线纹香茶菜腺毛的颜色。     

Glandular trichomes of Ceratotheca triloba (Pedaliaceae): morphology, histochemistry and ultrastructure

This study was initiated to characterize the distribution, morphology, secretion mode, histochemistry and ultrastructure of the glandular trichomes of Ceratotheca triloba using light and electron microscopy. Its leaves bear two morphologically distinct glandular trichomes. The first type has long trichome with 8-12 basal cells of pedestal, 3-14 stalk cells, a neck cell and a head of four cells in one layer. The second type has short trichome comprising one or two basal epidermal cells, a unicellular or bicellular stalk and a multicellular head of two to eight cells. There is a marked circular area in the upper part of each head cell of the long trichome. This area is provided with micropores to exudate directly the secretory product onto the leaf surface by an eccrine pathway. The secretory product has copious amount of dark microbodies arising from plastids which are positive to Sudan tests and osmium tetroxide for unsaturated lipids. The secretion mode of short trichomes is granulocrine and involves two morphologically and histochemically distinct vesicle types: small Golgi-derived vesicles which are positive to Ruthenium Red test for mucilaginous polysaccharides; the second type is dark large microbodies similar to that of long trichomes with low quantity. These two types are stored in numerous peripheral vacuoles and discharge their contents accompanied by the formation of irregular invaginations of the plasmalemma inside the vacuoles via reverse pinocytosis. These two secretion modes of long and short trichomes are reported for the first time in the family Pedaliaceae. The long trichomes have more unsaturated lipids, while the short trichomes contain more mucilaginous polysaccharides.     

DEVELOPMENT,STRUCTURE AND FUNCTION OF SECRETORY TRICHOMES IN PSYCHOTRIA BACTERIOPHILA (RUBIACEAE)

Mucilage-secreting dendroid trichomes develop from the adaxial epidermis of young stipules surrounding the shoot apex. Each trichome consists of a multicellular stalk from which radiate many branch cells. The trichome has no cuticle and the branch cell walls distally are loose cellulosic frameworks. Dictyosomes produce vesicles whose products are secreted through the plasma-lemma and cell wall. Enlarged portions of the ER are frequently associated with dictyosomes and may be part of the system for synthesis and transport of secretion products. Bacteria, which later occur in leaf nodules, are present in the mucilage surrounding trichomes and young leaves. The latter develop stomata through which the bacteria enter. As stipules and leaves grow out of the apical region, the secretory trichomes degenerate and are replaced by non-secretory ones.     

The anatomical and micromorphological characteristics of <Emphasis Type="Italic">Salvia vermifolia</Emphasis> (Section <Emphasis Type="Italic">Aethiopis</Emphasis> Bentham,Lamiaceae) from Central Anatolia,Turkey

The gross anatomical features, namely stem, blade and petiole and the micromorphological features, trichome, pollen and nutlet of Salvia vermifolia Hedge & Hub.-Mor. (Sect. Aethiopis Bentham, Lamiaceae) were examined using light microscopy (LM) and scanning electron microscopy (SEM). S. vermifolia is a perennial endemic herb growing on igneous and serpentine slopes in Sivas province, Central Anatolia, Turkey. The results obtained from anatomical studies show that the stem is made up of 4–8-layers of collenchyma cells and 1-3-layers chlorenchyma cells. The blade is amphistomatic, bifacial, with 2-3-layered palisade cells on the adaxial. The petiole has three large central bundles and six small subsidiary bundles. Peltate glandular, capitate glandular and non-glandular trichomes are present in S. vermifolia. The peltate glandular trichomes are present in abundance on the calyx and corolla, and capitate glandular trichomes are predominant on the calyx, inflorescence axis, pedicel and stem. The acicular non-glandular trichomes are mainly situated on the calyx, corolla, inflorescence axis and pedicels whereas the floccose non-glandular trichomes are common on both sides of the leaf, inflorescence axis and petiole. The pollen grains are hexacolpate to octacolpate, medium to large (P, polar axis=45.29–62.49 μm; E, equatorial axis=45.32-62.38 μm), oblate-spheroidal to prolate-spheroidal (P/E=0.91–1.02) and their exine ornamentation is bireticulate. The nutlets are 2.70–2.90 mm long and 1.90–2.13 mm wide, brown, ovoid-oblong in their outline, rounded-trigonous in transverse section, and their surface is glabrous and colliculate.     

ULTRASTRUCTURE OF GLANDULAR TRICHOMES OF LEAVES OF NICOTIANA TABACUM L., cv XANTHI

Electron microscopy confirms previous light microscope observations that tobacco leaf trichomes are glandular and that there are two different types. Both the tall trichome (multicellular stalk, unicellular or multicellular head) and the short trichome (unicellular stalk; multicellular head) exhibit characteristics common to gland cells—a dense cytoplasm, numerous mitochondria, and little vacuolation. The tall trichome contains structurally well developed chloroplasts and an elaborate network of endoplasmic reticulum. The short trichome contains undifferentiated plastids and endoplasmic reticulum which parallels the nucleus and plasmalemma. Few dictyosomes are seen either in the short trichome or in the tall trichome. The short trichome appears to undergo structural changes concurrently with the appearance of secretory product within the cells. The most noticeable change is the formation of the extraplasmic space between the cell wall and the plasmalemma. Electron dense secretory product is observed between the plasmalemma and the cell wall and within the intercellular spaces.     

Development and morphology of secretory trichomes of Calceolaria volckmanni (Scrophulariaceae)

The development and morphology of secretory trichomes of Calceolaria volckmanni was examined with light and electron microscopy. The formation and development of the glandular trichomes began with the outgrowth of a single epidermal cell which progressively increased in height and evolved into a pear-shaped cell. Subsequent divisions generated a mature trichome formed by a basal cell, a stalk "endodermal" cell and an 8-celled glandular head. Histochemical tests revealed the lipophilic nature of the secretion, the presence of terpenes and flavonoids, and displayed a particular cutinization of the walls of the stalk cell. The observed ultrastructural features of the lipophilic glandular hairs suggested the function of plastids in the secretory process.     

Isolation of secretory cells from plant glandular trichomes and their use in biosynthetic studies of monoterpenes and other gland products.

The natural products that accumulate in or exude from plant glandular trichomes are biosynthesized by secretory cells located at the apex of the trichome. To investigate the formation of glandular trichome constituents in several species of mints (Lamiaceae), a new procedure was developed for isolating large numbers of highly purified secretory cells. In this method, the leaf surface is gently abraded with glass beads in a way that fragments the glandular trichomes and yields clusters of intact secretory cells. The isolated, intact secretory cells and cell-free preparations derived from them are very active in monoterpene biosynthesis and provide useful starting materials for the purification of several key enzymes of monoterpene metabolism. The procedure described is adaptable to a broad range of plant species and should find wide application in the preparation of whole cell and cell-free systems for biosynthetic studies of plant natural products found in glandular trichomes.     

Presence of the anther gland is a key feature in pollination of the early‐branching papilionoids Dipteryx alata and Pterodon pubescens (Leguminosae)

• The presence of glandular appendages in the anthers is a rare condition in angiosperms. In Leguminosae it occurs in species of the Mimosoid clade and in early‐branching clades of papilionoids such as Dipterygeae. In Dipterygeae such appendages surprisingly exhibit a secretory cavity instead of secretory emergences as is the case for the Mimosoid clade. Thus, the objective of this study was to elucidate the function of anther glands in Dipteryx alata and Pterodon pubescens, species in the Dipterygeae clade that exhibit a pollen release mechanism that is intermediate between the explosive and valvular types.
• Flower buds and flowers were processed for surface, anatomical, histochemical and ultrastructural analyses.
• Anther glands consist of a cavity secreting sticky substances (oleoresins and polysaccharides) that play a key role during the flower's lifespan by aggregating pollen grains and attaching them to the floral visitor's body. Other floral features that are important for understanding the pollen release mechanism that is intermediate between the valvular and the explosive types are: (i) keel petals intertwined with tector trichomes; (ii) glandular appendages in the abaxial and lateral sepals and in petals composed of secretory ducts; and (iii) a continuous secretion process of the anther glands followed by an asynchronous dehiscence of anthers.
• The well‐adapted papilionoid flag blossom with anther glands and keel petals intertwined with trichomes provided the foundation for a successful canalisation toward a pollen release mechanism intermediate between the explosive and valvular types inside early‐branching papilionoids.

     

Anatomy,trichome morphology and palynology of Salvia chrysophylla Stapf (Lamiaceae)

The anatomy, palynology, morphology and distribution of the trichomes on the aerial parts of Salvia chrysophylla Stapf, an endemic species in Turkey, were studied in order to understand the usefulness of these characteristics for systematic purposes. Some anatomical characters such as (1–)2–24-rowed pith rays in roots, dorsiventral leaves, obviously larger upper epidermal cells, and two to three large vascular bundles in the center and two to four small subsidiary bundles in the wings of petiole provide information of taxonomical significance. Three main types of trichomes were observed on the stem, inflorescence axis, leaf and calyx surfaces of S. chrysophylla. They are peltate, capitate glandular and non-glandular. Capitate glandular and non-glandular trichomes were further subdivided into several kinds. Glandular trichomes are present in abundance on the inflorescence axis and calyx, but non-glandular ones were mainly situated on the leaf and stem. Scanning Electron Microscopy (SEM) studies on the pollen grains have revealed that they are oblate-spheroidal and their exine ornamentation is bireticulate-perforate.