Localization of salvinorin A and related compounds in glandular trichomes of the psychoactive sage, Salvia divinorum

BACKGROUND AND AIMS: Salvia divinorum produces several closely related neoclerodane diterpenes. The most abundant of these, salvinorin A, is responsible for the psychoactive properties of the plant. To determine where these compounds occur in the plant, various organs, tissues and glandular secretions were chemically analysed. A microscopic survey of the S. divinorum plant was performed to examine the various types of trichomes present and to determine their distribution. METHODS: Chemical analyses were performed using thin layer chromatographic and histochemical techniques. Trichomes were examined using conventional light microscopy and scanning electron microscopy. KEY RESULTS: It was found that neoclerodane diterpenes are secreted as components of a resin that accumulates in peltate glandular trichomes, specifically in the subcuticular space that exists between the trichome head cells and the cuticle that encloses them. Four main types of trichomes were observed: peltate glandular trichomes, short-stalked capitate glandular trichomes, long-stalked capitate glandular trichomes and non-glandular trichomes. Their morphology and distribution is described. Peltate glandular trichomes were only found on the abaxial surfaces of the leaves, stems, rachises, bracts, pedicles and calyces. This was consistent with chemical analyses, which showed the presence of neoclerodane diterpenes in these organs, but not in parts of the plant where peltate glandular trichomes are absent. CONCLUSIONS: Salvinorin A and related compounds are secreted as components of a complex resin that accumulates in the subcuticular space of peltate glandular trichomes.     

Glandular trichomes of Humulus lupulus var. Brewer's Gold: Ontogeny and histochemical characterization of the secretion

Leaves of Humulus lupulus possess two types of glandular trichomes: - peltate (lupulin) and bulbous.
Peltate trichomes are formed from a protodermal cell by two anticlinal divisions in perpendicular planes, followed by two periclinal ones that give rise to the initials of the head cells, the basal and the stalk cells. Head cells divide successively in radial and irregular planes. Fully developed peltate trichomes are built of a glandular head consisting of 30 to 72 cells, four stalk cells and four basal cells.
Bulbous trichomes are also formed from a protodermal cell by an anticlinal division followed by two periclinal ones that produce the initials of the glandular head cells, and the basal and stalk cells. Fully developed bulbous trichomes consist of four (occasionally eight) head glandular cells, two stalk cells and two basal cells.
The density of peltate trichomes decreases with the expansion of the leaves.
Both peltate and bulbous trichomes secrete essential oils. Peltate trichomes are the preferential site for the synthesis of bitter resins. Tannic acids could not be detected histochemically either in peltate or in bulbous trichomes. Both types of trichomes produce secretion that accumulates in the subcuticular space, being released, in the case of bulbous trichomes, by rupture of the cuticle.     

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。     

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 on Vegetative and Reproductive Organs of Leonotis leonurus (Lamiaceae)

The types of glandular trichomes, their ontogeny and patternof distribution on the vegetative and reproductive organs ofLeonotis leonurus at different stages of development, are studiedby light and scanning electron microscopy. Two morphologicallydistinct types of glandular trichomes (peltate and capitate)are described. Peltate trichomes, at the time of secretion,are characterized by a short stalk, which is connected witha large spherical head composed of eight cells in a single layer.Capitate trichomes can be divided into various types. Generally,they consist of a four-celled head supported by one or threestalk cells. The two kinds of trichomes differ in the secretionprocess. In the peltate trichomes, the secretory product seemsto remain accumulated in a subcuticular space, unless an externalfactor damages it. In the capitate trichomes, this product probablybecomes released through micropores. On the leaves peltate andcapitate trichomes are abundant, while on the flowers only thepeltate trichomes are numerous and the capitate are rare orabsent.Copyright 1995, 1999 Academic Press Leonotis leonurus R. Br., lion's ear, lion's tail, Lamiaceæ, glandular trichomes, morphology, ontogeny     

Bidirectional Secretions from Glandular Trichomes of Pyrethrum Enable Immunization of Seedlings

Glandular trichomes are currently known only to store mono- and sesquiterpene compounds in the subcuticular cavity just above the apical cells of trichomes or emit them into the headspace. We demonstrate that basipetal secretions can also occur, by addressing the organization of the biosynthesis and storage of pyrethrins in pyrethrum (Tanacetum cinerariifolium) flowers. Pyrethrum produces a diverse array of pyrethrins and sesquiterpene lactones for plant defense. The highest concentrations accumulate in the flower achenes, which are densely covered by glandular trichomes. The trichomes of mature achenes contain sesquiterpene lactones and other secondary metabolites, but no pyrethrins. However, during achene maturation, the key pyrethrin biosynthetic pathway enzyme chrysanthemyl diphosphate synthase is expressed only in glandular trichomes. We show evidence that chrysanthemic acid is translocated from trichomes to pericarp, where it is esterified into pyrethrins that accumulate in intercellular spaces. During seed maturation, pyrethrins are then absorbed by the embryo, and during seed germination, the embryo-stored pyrethrins are recruited by seedling tissues, which, for lack of trichomes, cannot produce pyrethrins themselves. The findings demonstrate that plant glandular trichomes can selectively secrete in a basipetal direction monoterpenoids, which can reach distant tissues, participate in chemical conversions, and immunize seedlings against insects and fungi.     

UV-B is required for normal development of oil glands in Ocimum basilicum L. (sweet basil)

Plants of Ocimum basilicum L. grown under glass were exposed to short treatments with supplementary UV-B. The effect of UV-B on volatile essential oil content was analysed and compared with morphological effects on the peltate and capitate glandular trichomes. In the absence of UV-B, both peltate and capitate glands were incompletely developed in both mature and developing leaves, the oil sacs being wrinkled and only partially filled. UV-B was found to have two main effects on the glandular trichomes. During the first 4 d of treatment, both peltate and capitate glands filled and their morphology reflected their 'normal' mature development as reported in the literature. During the following days there was a large increase in the number of broken oil sacs among the peltate glands as the mature glands broke open, releasing volatiles. Neither the number of glands nor the qualitative or quantitative composition of the volatiles was affected by UV-B. There seems to be a requirement for UV-B for the filling of the glandular trichomes of basil.     

Comparative analysis of ultrastructure of glandular trichomes in two Nepeta cataria chemotypes (N. cataria and N. catena var. citriodora)

Glandular trichomes from the leaf surface of Nepeta cataria and N. cataria vai.citriodora have been examined using transmission and scanning electron microscopy. Peltate glands and capitate hairs type I were found on leaves of N. cataria. Both types had single stalk cells. Leaves of N. cataria var. citriodora bore peltate glands with unicellular or bicellular stalk, capitate hairs type I (with unicellular stalk) and capitate hairs type II (with unicellular or bicellular stalk). Peltate glands of N. cataria and of N. cataria var. citriodora were characterized by numerous leucoplasts sheathed by smooth reticular tubules and smooth endoplasmic reticulum; they are proposed to synthesize terpenes. The secretory cells of capitate hairs type I of N. cataria and those of N. cataria var. citriodora had well developed rough endoplasmic reticulum and dictyosomes. They had plastids with protein inclusions. These glands are supposed to produce slime. Capitate hairs type II of N. cataria var. citriodora had no analogs in N. cataria. Their secretory cells exhibited abundance of tubular endoplasmic reticulum and had unsheathed plastids with starch grains. Probably, these glands synthesize terpenes. The results of the study indicate that there is an obvious difference both in morphology and in ultrastructure of glandular trichomes in different chemotypes of N. cataria.     

An investigation of the storage and biosynthesis of phenylpropenes in sweet basil

Plants that contain high concentrations of the defense compounds of the phenylpropene class (eugenol, chavicol, and their derivatives) have been recognized since antiquity as important spices for human consumption (e.g. cloves) and have high economic value. Our understanding of the biosynthetic pathway that produces these compounds in the plant, however, has remained incomplete. Several lines of basil (Ocimum basilicum) produce volatile oils that contain essentially only one or two specific phenylpropene compounds. Like other members of the Lamiaceae, basil leaves possess on their surface two types of glandular trichomes, termed peltate and capitate glands. We demonstrate here that the volatile oil constituents eugenol and methylchavicol accumulate, respectively, in the peltate glands of basil lines SW (which produces essentially only eugenol) and EMX-1 (which produces essentially only methylchavicol). Assays for putative enzymes in the biosynthetic pathway leading to these phenylpropenes localized many of the corresponding enzyme activities almost exclusively to the peltate glands in leaves actively producing volatile oil. An analysis of an expressed sequence tag database from leaf peltate glands revealed that known genes for the phenylpropanoid pathway are expressed at very high levels in these structures, accounting for 13% of the total expressed sequence tags. An additional 14% of cDNAs encoded enzymes for the biosynthesis of S-adenosyl-methionine, an important substrate in the synthesis of many phenylpropenes. Thus, the peltate glands of basil appear to be highly specialized structures for the synthesis and storage of phenylpropenes, and serve as an excellent model system to study phenylpropene biosynthesis.     

Glandular Trichomes on the Leaves and Flowers of Plectranthus ornatus: Morphology, Distribution and Histochemistry

The types of glandular trichomes and their distribution on leavesand flowers of Plectranthus ornatus were investigated at differentstages of their development. Five morphological types of glandulartrichomes are described. Peltate trichomes, confined to theleaf abaxial surface, have, in vivo, an uncommon but characteristicorange to brownish colour. Capitate trichomes, uniformly distributedon both leaf surfaces, are divided into two types accordingto their structure and secretory processes. In long-stalkedcapitate trichomes, a heterogeneous secretion (a gumresin) isstored temporarily in a large subcuticular space, being releasedby cuticle rupture, whereas, in the short-stalked capitate trichomes,the secretion, mainly polysaccharidic, is probably exuded viamicropores. On the leaves, digitiform trichomes, which do notshow a clear distinction between the apical glandular cell andthe subsidiary cells, occur with a similar distribution to thecapitate trichomes. They do not develop a subcuticular space,and secrete small amounts of essential oils in association withpolysaccharides. The reproductive organs, particularly the calyxand corolla, exhibit, in addition to the reported trichomes,unusual conoidal trichomes with long unicellular conical heads.A large apical pore, formed by tip disruption, releases thesecretion (a gumresin) stored in a rostrum-like projection.On the stamens and carpels, digitiform, capitate and conoidaltrichomes are absent, but peltate trichomes are numerous. Theyoccur between the two anther lobes, on the basal portion ofthe style, and between the four lobes of the ovary. The resultspresented are compared with those of other studies on Lamiaceaeglandular trichomes. Copyright 1999 Annals of Botany Company Plectranthus ornatus Codd, Lamiaceae, glandular trichomes, morphology, histochemistry, essential oils and mucilage secretion.     

Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): developmental ultrastructure and secretion in relation to function

BACKGROUND AND AIMS: Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc. METHODS: Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber. KEY RESULTS: Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative. CONCLUSIONS: The continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality.     

甘草腺毛的形态发生和组织化学研究

利用扫描电镜及薄切片技术对甘草的腺毛形态发生和发育过程进行了观察,并对腺毛发育过程中黄酮类成分积累进行了组织化学定位研究。结果表明：甘草腺毛为多细胞构成的盾状腺毛,有长柄和短柄2种类型;前者主要分布在花萼片上,而后者主要分布于叶片上。组化鉴定结果显示：腺毛中存在着黄酮类成分、其他亲脂类和非纤维素多糖类成分;在腺毛的发育过程中,黄酮类物质是随腺毛的发育成熟,在头部盘状结构的分泌细胞及角质层下腔中积累。研究结果对进一步探讨甘草叶中黄酮类成分的合成及其作用提供科学依据。     

Cytological development and sesquiterpene lactone secretion in capitate glandular trichomes of sunflower

The secretion of sesquiterpene lactones (STL) in capitate glandular trichomes from the anther appendages of Helianthus annuus L. (Asteraceae) was observed by light and fluorescence microscopy and HPLC analysis. Disk flowers within the sunflower capitulum showed the known ontogenetic progression from the centre to the margin. During development of the florets, the trichomes in the anther appendages secreted their metabolites into the subcuticular secretion storage space in front of the two apical cells. All stages of forming the cuticular globe, from the pre-secretory to the post-secretory phase, could be observed microscopically and secretory activity was simultaneously monitored. Six germacrolides and heliangolides of known structure were selected for quantitative analysis. The increase in STL content during extension of the subcuticular space was monitored by HPLC analysis. Thereby, the start and termination of STL biosynthesis was defined in relation to other developmental stages of floret ontogenesis, particularly, the pollen formation. Part of the secreted material showed autofluorescence which could be attributed to a hydroxy-trimethoxy-flavone, as determined by NMR and mass spectroscopy. The anther trichomes were cytologically and chemically similar to foliar glandular trichomes of sunflower and represent the multicellular capitate glandular trichome type common to many Asteraceae. The ease with which anther trichomes of H. annuus can be harvested and analyzed suggests that they can provide a valuable model system for investigation of STL and flavonoid metabolism in Asteraceae.     

羽叶薰衣草表皮毛的发育解剖学研究

对羽叶薰衣草(LavandulapinnataL.)茎和叶上两种表皮毛(腺毛和非腺毛)发育的解剖学观察表明,两者的发生都源于茎或叶的原表皮细胞,但外部形态、发育过程及功能明显不同。腺毛有头状腺毛和盾状腺毛两种类型,均由1个基细胞、1个柄细胞和头部细胞构成。头状腺毛的头部只有1个或2个分泌细胞,盾状腺毛由8个分泌细胞构成头部。非腺毛由3-20个细胞组成,可分为三种类型:单列不分枝、二叉分枝和三叉及三叉以上多分枝的树状分枝。非腺毛的顶部细胞由基部到顶部逐渐变细,先端成尖形。腺毛发育由原表皮细胞经两次平周分裂形成,由于柄细胞和头部细胞所处的分化状态不同而发育成两类腺毛。非腺毛由非腺毛原始细胞经二次或多次平周分裂和不均等分裂,再发育成数个至二十多个子细胞。     

Morphology and histochemistry of the glandular trichomes of Lippia scaberrima (Verbenaceae)

BACKGROUND AND AIMS: Lippia scaberrima, an aromatic indigenous South African plant, with medicinal application, potentially has economic value. The production of essential oil from this plant has not been optimized, and this study of the chemico-morphological characteristics was aimed at determining the location of oil production within the plant. Furthermore, the locality of other secondary metabolites important in medicinal applications needed to be ascertained. This information would be useful in deciding the protocol required for isolation of such compounds. METHODS: The morphology of the glandular trichomes was investigated using a combination of scanning electron and light microscopy. Concurrently, the chemical content was studied by applying various chemical reagents and fluorescence microscopy. KEY RESULTS: Three types of trichomes were distinguished on the material investigated. Large, bulbous peltate glands containing compounds of terpenoid nature are probably the main site of essential oil accumulation. Small glands were found to be both peltate and capitate and fluorescent stain indicated the possible presence of phenolic compounds. The third type was a slender tapered seta with an ornamented surface and uniseriate base, and evidently secretory in nature. CONCLUSIONS: This study linking the chemical content and morphology of the glandular trichomes of L. scaberrima has contributed to the knowledge and understanding of secretory structures of Lippia spp. in general.     

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。     

冬凌草腺毛的形态学及组织化学研究

利用光学显微镜对药用植物冬凌草地上部分腺毛的形态、分布和组织化学进行了研究。结果表明:(1)冬凌草的叶表皮有3种形态显著不同的毛,即非腺毛、盾状腺毛和头状腺毛;盾状腺毛和头状腺毛均具1个基细胞、1个柄细胞和头部;成熟的盾状腺毛的头部一般由4个分泌细胞组成,而头状腺毛头部由2个分泌细胞组成。(2)组织化学鉴定结果显示:2种腺毛中均含有黄酮类成分,盾状腺毛中还含有单萜、倍半萜等萜类成分;冬凌草甲素可能只存在于盾状腺毛中,但需要更直接的证据证明。研究认为,高密度的盾状腺毛可以作为筛选冬凌草高甲素含量品种的一项重要依据。     

Peltate glandular trichomes of Colquhounia seguinii harbor new defensive clerodane diterpenoids

Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defen-sive chemicals against herbivore attack. The morphology and secondary metabolites of the peltate g...     

Micromorphological traits and essential oil of Micromeria longipedunculata Bräuchler (Lamiaceae)

Micromeria longipedunculata Bräuchler (syn. M. parviflora (Vis.) Rchb.) is an endemic Illyric-Balkan plant species from Bosnia and Herzegovina, Montenegro, and Albania. We investigated types and distribution of trichomes, pollen morphology, and chemical composition of essential oil (analysed by GC and GC-MS) in M. longipedunculata. Non-glandular trichomes, peltate trichomes, and two types of capitate trichomes (type 1 composed of one basal epidermal cell, and one head cell with subcuticular space; type 2 composed of one basal epidermal cell, two or three stalk cells, and one head cell with subcuticular space) were observed on leaves, bracteoles, the calyx, corolla, and the stem. The pollen grains had six apertures which were set in the equatorial pollen belt and showed medium reticulate ornamentation. A phytochemical analysis of essential oils from four different localities is characterized by similar chemical composition with spathulenol (23.7–39.5%), piperitone oxide (7.7–12.1%) and piperitone (7.3–8.9%) as the major compounds.     

The trichomes of pericarp in Juglans (Juglandaceae): scanning microscopy, fluorescent microscopy amd histochemistry

Four types of glandular and non-glandular trichomes of pericarp in four Juglans species (J. ailanthifolia, J. cordiformis, J. mandshurica and J. regia) from Juglandaceae were studied by scanning electron microscopy, fluorescent light microscopy and histochemistry. The capitate trichomes on short stalk, the capitate trichomes on long stalk and the peltate trichomes belong to glandular trichomes; the simple hairs concern to non-glandular trichomes. The investigated species differ one from another in dimensions and distribution oftrichomes as well as the chemical content and the mechanism of secretion. The fluorescent markers and histochemical tests show the presence of flavonoids, tannins and polyphenols in trichomes on short and long stalk. In peltate trichomes the flavonoids and tannins were found in lesser quantity and the polyphenols are absent. In simple hairs the phenolic substances have not been recognized. It has been come out with the suggestion about a functional role of each type of trichomes.