Subcuticular Cavity Research Articles

Morphology, histochemistry and ultrastructure of the floral glandular trichomes in three Doronicum species (Asteraceae).

Previously, it was found that four types of glandular trichomes (GTs) are developed on the surface of all aerial organs in Doronicum species. A detailed study of leaves had shown that only two types of GTs form in them. Nothing was known about any differences of GTs on vegetative and reproductive organs. Current work studies morphological, histochemical and ultrastructural features of two types of GTs arising on floral elements in three Doronicum species. The straight GTs there are on all elements of the inflorescence (peduncle, phyllaries, ray and disk florets); they have a short stalk and do not have a clearly visible head. The capitate GTs are located only on the inflorescence peduncle and phyllaries; the trichomes form a long stalk and a distinct head. The chemical composition of the secretion is confirmed by histochemical reactions. Both types of GTs have the specific ultrastructural features and secretory mechanisms. In capitate GTs, a smooth endoplasmic reticulum is the main organelle of cytoplasm and takes part in a synthesis of the phenolic substances. Phenols accumulate in the numerous small vacuoles and thick cell wall. In straight trichomes, leucoplasts of various shapes with plastoglobuli and peripheral reticulum predominate. Terpenes synthesized in leucoplasts are stored in the subcuticular cavity and are released when the cavity ruptures. The acidic polysaccharides are the additional components of a straight trichome secretion. The studied species of Doronicum differ from each other in localization, size and structure of the GTs.

Ultrastructure of the ejaculatory duct of Terrobittacus implicatus (Mecoptera: Bittacidae).

The unique mating behavior of Bittacidae has been extensively studied, yet the mechanisms underlying internal sperm transport and temporary storage before mating remain enigmatic. Herein, we aim to elucidate these mechanisms by investigating the fine structure of the ejaculatory duct, which serves for sperm transport and temporary storage. The ultrastructure of the ejaculatory duct of Terrobittacus implicatus (Mecoptera: Bittacidae) was examined by light and transmission electron microscopy for the first time in this study. The ejaculatory duct is composed of a median duct and a pair of symmetrical accessory sacs. In the proximal fifth portion, the two accessory sacs encompass the median duct in two loose layers. In the remaining distal portion, the median duct remains centrally positioned, and two accessory sacs symmetrically enclose its lateral and ventral surfaces. The distal median duct consists of a basal lamina, an unevenly arranged epithelium, a large subcuticular cavity, and a narrow inner cuticle. The distal accessory sac can be divided into three areas with distinct ultrastructural features. The ejaculatory duct exhibits conspicuous secretory activity, and given the absence of an ectodermal accessory gland in males, it is possible that the ejaculatory duct may fulfill additional glandular function. The narrow lumen and the reduced muscular sheath of the ejaculatory duct may be associated with the unique mechanism of ejaculation and mating.

Ultrastructure of Ejaculatory Ducts of Cerapanorpa nanwutaina and Furcatopanorpa longihypovalva (Mecoptera: Panorpidae).

The ultrastructure of the ejaculatory duct was investigated in the scorpionflies Cerapanorpa nanwutaina (Chou 1981) and Furcatopanorpa longihypovalva (Hua & Cai, 2009) (Mecoptera: Panorpidae) using light and transmission electron microscopy. The ejaculatory ducts of both species comprise a median duct and an accessory sac. The median duct consists of a basal lamina, a mono-layered epithelium, a subcuticular cavity, and an inner cuticle. The accessory sac contains a single layer of epithelium and a basal lamina. A muscular layer is present in the accessory sac of C. nanwutaina and in the median duct of F. longihypovalva. The epithelia in the median duct and the accessory sac are well developed, their cells containing numerous cisterns of rough endoplasmic reticulum, mitochondria, and microvilli. The secretions of the median duct are first extruded into the subcuticular cavity and then into the lumen through an inner cuticle, while the secretions of the accessory sac are discharged directly into the lumen. The ejaculatory duct of F. longihypovalva is longer and has thicker epithelium with more cell organelles and secretions than that of C. nanwutaina.

Structure and functions of the glandular trichomes in three Arnica species (Asteraceae), depending on their location on leaves and flowers

The aim of this study was to characterize the structural and histochemical features of the glandular trichomes (GTs) of two types localized on the leaves and flowers in three Arnica species. GTs of the first type are found on leaves, peduncle, calyx, ovary, and petal base. They are biseriate, have a cylindrical form and 5 to 9 cell layers. GTs of the second type are located on the peduncle and calyx; they have a biseriate head of two to four cell layers and a long stalk. In each Arnica species differences between GTs of two types include dimensions, intensity of coloration by histochemical dyes, as well as ultrastructural features of the cells. According to the results of fluorescence microscopy and histochemical tests, phenols, terpenes, sesquiterpene lactones and polysaccharides are revealed in all GTs of the studied species; at the same time, the amount and composition of primary and secondary compounds are specific for trichomes of each organ. In the leaf GTs, phenols and terpenes prevail; in the GTs of the first type situated on the peduncle and calyx, acid polysaccharides are met in larger amount then in trichomes of other organs; in the GTs of the second type, sesquiterpene lactones are the main metabolites. At the secretory stage, the apical cells of GTs contain smooth and rough endoplasmic reticulum, diversiform leucoplasts with black inclusions in lamellae, chloroplasts, mitochondria, and Golgi apparatus. A single subcuticular cavity is formed in GTs of the first type, unlike GTs of the second type, where many small subcuticular cavities appear. In these GTs, the head surface looks porous. Although there are structural modifications between trichomes of the same type in different species of Arnica, the functional variations between trichomes of the different types are more significant.

Ultrastructural Alterations in Cells of Sunflower Linear Glandular Trichomes during Maturation.

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not been studied in detail so far. Light, fluorescence and transmission electron microscopy were employed to investigate the functional structure of different trichome cells and their subcellular compartmentation in the pre-secretory, secretory and post-secretory phase. It was shown that the trichome was composed of four cell types, forming the trichome basis with a basal and a stalk cell, a variable number (mostly from five to eight) of barrel-shaped glandular cells and the tip consisting of a dome-shaped apical cell. Metabolic activity started at the trichome tip sometimes accompanied by the formation of small subcuticular cavities at the apical cell. Subsequently, metabolic activity progressed downwards in the upper glandular cells. Cells involved in the secretory process showed disintegration of the subcellular compartments and lost vitality in parallel to deposition of fluorescent and brownish metabolites. The subcuticular cavities usually collapsed in the early secretory stage, whereas the colored depositions remained in cells of senescent hairs.

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

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.

Glandular trichomes of the leaves in three Doronicum species (Senecioneae, Asteraceae): morphology, histochemistry, and ultrastructure.

Two types of glandular tichomes (GTs) develop on the leaves in three Doronicum species. The purpose of the work was to establish common and distinctive morphological, anatomical, histochemical, and ultrustructural features of the trichomes. It turned out that differences between types of trichomes are more significant than interspecific ones. For each Doronicum species, differences between GTs of two types include the dimensions, intensity of coloration by histochemical dyes, as well as ultrastructural features of the cells. The GTs of the first type are higher than GTs of the second type. Two to three upper cell layers of the first trichomes develop histochemical staining, whereas in the second ones, only apical cells give a positive histochemical reaction. In all trichomes, polysaccharides, polyphenols, and terpenoids are detected. In the GTs of the first type, polysaccharides are synthesized in larger quantity; in the GTs of the second type, synthesis of the secondary metabolites predominates. Main ultrastructural features of the GTs of the first type include proliferation of RER and an activity of Golgi apparatus denoting the synthesis of enzymes and pectin; however, development of SER, diversiform leucoplasts with reticular sheaths, and chloroplasts with peripheral plastid reticulum also demonstrate the synthesis of lipid substances. The ultrastructural characteristics of the second type GTs indicate the primary synthesis of lipid components. Secretion is localized in a periplasmic space of the upper cell layers. The secretory products pass through the cell wall, accumulate in the subcuticular cavity, and rupture it.

Glandular trichomes of Tussilago Farfara (Senecioneae, Asteraceae).

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.

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.

Structure of trichomatous nectaries in flowers of Lonicera kamtschatica (Sevast.) Pojark.

The structure of the floral nectaries of <i>Lonicera kamtschatica</i> was examined using light microscopy, scanning electron microscopy and transmission electron microscopy. Nectariferous tissues are located in the lower portion of the corolla tube. It was found that the secretory tissue of the nectary was composed of two layers of epidermal formations: short papillae and about 3x longer unicellular trichomes. They cover the adaxial surface of a small spur. Nectar secretion takes place through the apical portion of the trichomes and papillae. The cell wall of the upper part of the trichome has protuberances participating in nectar transfer to the subcuticular space which reaches large dimensions. The lateral walls of the trichomes are saturated with cutin. The papillae have much thicker walls than the trichomes. In the papillae, there are no wall protuberances. Less secretion accumulates in the subcuticular cavities of the papillae than in the trichomes.

Ultrastructure of male reproductive accessory glands and ejaculatory duct in the Queensland fruit fly, Bactrocera tryoni (Diptera: Tephritidae)

Ultrastructure of male reproductive accessory glands and ejaculatory duct in the Queensland fruit fly (Q-fly), Bactrocera tryoni, were investigated and compared with those of other tephritid flies. Male accessory glands were found to comprise one pair of mesodermic glands and three pairs of ectodermic glands. The mesodermic accessory glands consist of muscle-lined, binucleate epithelial cells, which are highly microvillated and extrude electron-dense secretions by means of macroapocrine transport into a central lumen. The ectodermic accessory glands consist of muscle-lined epithelial cells which have wide subcuticular cavities, lined with microvilli. The electron-transparent secretions from these glands are first extruded into the cavities and then forced out through small pores of the cuticle into the gland lumen. Secretions from the two types of accessory glands then flow into the ejaculatory duct, which is highly muscular, with epithelial cells rich in rough endoplasmic reticulum and lined with a thick, deeply invaginated cuticle. While there are some notable differences, reproductive accessory glands of male Q-flies generally resemble those of the olive fruitfly, Bactrocera oleae, and to a lesser extent the Mediterranean fruit fly, Ceratitis capitata.

Genetic control of pungency in C. chinense via the Pun1 locus

Capsaicin, the pungent principle in hot peppers, acts to deter mammals from consuming pungent pepper pods. Capsaicinoid biosynthesis is restricted to the genus Capsicum and results from the acylation of the aromatic compound, vanillylamine, with a branched-chain fatty acid. The presence of capsaicinoids is controlled by the Pun1 locus, which encodes a putative acyltransferase. In its homozygous recessive state, pun1/pun1, capsaicinoids are not produced by the pepper plant. HPLC analysis confirmed that capsaicinoids are only found in the interlocular septa of pungent pepper fruits. Immunolocalization studies showed that capsaicinoid biosynthesis is uniformly distributed across the epidermal cells of the interlocular septum. Capsaicinoids are secreted from glandular epidermal cells into subcuticular cavities that swell to form blisters along the epidermis. Blister development is positively associated with capsaicinoid accumulation and blisters are not present in non-pungent fruit. A genetic study was used to determine if the absence of blisters in non-pungent fruit acts independently of Pun1 to control pungency. Screening of non-pungent germplasm and genetic complementation tests identified a previously unknown recessive allele of Pun1, named pun1(2). Sequence analysis of pun1(2) revealed that a four base pair deletion results in a frameshift mutation and the predicted production of a truncated protein. Genetic analysis revealed that pun1(2) co-segregated exactly with the absence of blisters, non-pungency, and a reduced transcript accumulation of several genes involved in capsaicinoid biosynthesis. Collectively, these results establish that blister formation requires the Pun1 allele and that pun1(2) is a recessive allele from C. chinense that results in non-pungency.

Comparative fine structural analysis of the male reproductive accessory glands in Bactrocera oleae and Ceratitis capitata (Diptera, Tephritidae)

The morphology and ultrastructure of the male reproductive accessory glands from Bactrocera oleae and Ceratitis capitata were comparatively investigated. In both insects, there are two types of glands, mesoderm‐ and ectoderm‐derived, which open in the ejaculatory duct. The mesoderm‐derived glands are sac‐like in B. oleae and very long tubules in C. capitata, whereas the ectodermic glands, generally branched finger‐like structures, are longer in B. oleae than in C. capitata. Despite their different morphology, the ultrastructure of the two types of glands is quite similar in both Tephritids. The epithelium of the mesoderm‐derived glands consists of binucleate and microvillate secretory cells. In C. capitata, but not in B. oleae, the secretory cells contain smooth endoplasmic reticulum and, in the sexually mature males, enlarged polymorphic mitochondria. The gland lumen is filled with a dense or sometimes granulated secretion. The ectoderm‐derived glands undergo a cycle of maturation, by which their epithelial cells form a large subcuticular cavity filled with an electron‐transparent secretion. Electrophoretic analysis of accessory gland secretion reveals in both species the presence of low molecular weight protein bands. A major band of about 29 kDa or 30 kDa in B. oleae and C. capitata, respectively, is revealed.

Ultrastructure of the male reproductive accessory glands in the medfly Ceratitis capitata (Diptera: Tephritidae) and preliminary characterization of their secretions

The morphology and the ultrastructure of the male accessory glands and ejaculatory duct of Ceratitis capitata were investigated. There are two types of glands in the reproductive apparatus. The first is a pair of long, mesoderm-derived tubules with binucleate, microvillate secretory cells, which contain smooth endoplasmic reticulum and, in the sexually mature males, enlarged polymorphic mitochondria. The narrow lumen of the gland is filled with dense or sometimes granulated secretion, containing lipids. The second type consists of short ectoderm-derived glands, finger-like or claviform shaped. Despite the different shape of these glands, after a cycle of maturation, their epithelial cells share a large subcuticular cavity filled with electron-transparent secretion. The ejaculatory duct, lined by cuticle, has epithelial cells with a limited involvement in secretory activity. Electrophoretic analysis of accessory gland secretion reveals different protein profiles for long tubular and short glands with bands of 16 and 10 kDa in both types of glands. We demonstrate that a large amount of accessory gland secretion is depleted from the glands after 30 min of copulation.

Analysis of monoterpenoids in glandular trichomes of the catmint Nepeta racemosa

Plants within the Lamiaceae are characterized by their production of essential oils, largely composed of monoterpenoids. They also possess on their aerial surfaces different types of trichomes, including relatively large peltate glandular trichomes. Observation of leaves of the catmint Nepeta racemosa, using cryogenic scanning electron microscopy, showed that around 3000 peltate trichomes are present on a single expanded leaf. An approach has been developed for sampling directly from the subcuticular cavity of such trichomes, in order to characterize qualitatively and quantitatively their contents. Gland samples from Nepeta spp. were analysed by combined gas chromatography‐mass spectrometry. These analyses have confirmed that the monoterpenoids characteristic of these species (nepetalactones) accumulate within the subcuticular cavity of peltate glandular trichomes. Qualitative analysis showed that three different nepetalactone stereoisomers were accumulated in different proportions in peltate glands from individual N. racemosa plants. Quantitative analysis showed that individual peltate glands accumulate around 30 ng of nepetalactone by maturity, and that accumulation of nepetalactone probably occurs exclusively within this gland type.

Leaf anatomy and ultrastructure of the North American marine angiospermPhyllospadix(Zosteraceae)

The leaf anatomy and ultrastructure of the North American Phyllospadix species P. serrulatus Rupt. ex Aschers., P. scouleri Hook, and P. torreyi Watson are described. The unique anatomical and ultrastructural features of these species are compared with those of other seagrasses and their possible functional significance is discussed. All three species have ultrastructures similar to those in other members of the family Zosteracae. Subcuticular cavities, wall ingrowths, and numerous mitochondria and chloroplasts with well-developed grana are present in the blade epidermal cells and the adaxial sheath epidermal cells, indicating that these cells may play a major role in photosynthesis, osmoregulation, and absorption. Plasmodesmata are present occasionally between adjacent epidermal cells, and also between epidermal and mesophyll cells, suggesting that solutes can be transferred symplastically between these tissues. The vascular bundle sheath cells are not easy to recognize, as cell walls are thin and not suberized. The phloem contains both normal and nacreous-walled sieve tubes that may be functional. The walls of the phloem parenchyma cells facing nacreous-walled sieve tubes possess weak wall ingrowths, leading to speculation that these parenchyma cells may play an important role in solute translocation. The absence of suberin lamella in bundle sheath cells and the presence of a small xylem element in each vascular bundle suggest that the water flow in xylem elements in these seagrasses may be limited and that water is taken directly from the water column by leaf epidermal cells and is transported apoplastically along cell walls. The three North American Phyllospadix species can be separated by anatomical characters such as number of vascular bundles, the shape of epidermal cells in both transverse sectional and surface views, and the distribution of fibre bundles. It is proposed that P. serrulatus is taxonomically more closely related to the Japanese P. iwatensis Makino than to P. scouleri and P. torreyi and that there is no detectable hybrid species occurring between P. scouleri and P. torreyi. Key words: anatomy, ultrastructure, seagrasses, Phyllospadix, North America.

Gland Development on Leaf Surfaces of Nepeta racemosa

Trichomes present on the leaf surface of catmint (Nepeta racemosa L.) were examined using both scanning and transmission electron microscopy. Three types of trichomes were observed: (a) multicellular, uniseriate, nonglandular hairs, (b) small capitate glands with two cells in the head, and (c) large, peltate glands with four secretory/head cells. Secretory cells of capitate glands exhibited typical transfer cell morphology, with an abundance of RER and Golgi bodies, indicative of secretion of mainly hydrophilic substances. Mature peltate glands exhibited a distended cuticle and large subcuticular cavity, presumably containing the essential oils. Morphologically well-developed peltate glands were observed on young leaf primordia, with development occurring earlier at the leaf apex and along the midvein than at the leaf margins or base. Four major stages in the development of the peltate gland secretory cells were identified. The first stage was marked by highly vacuolated cytoplasm and normal distribution ...

Anatomical, histochemical and ultrastructural features of the seagrass Phyllospadix scouleri hook

Aspects of the anatomy, histochemistry and ultrastructure of vegetative organs of the North American seagrass Phyllospadix scouleri Hook. (Family Zosteraceae) were investigated. It can be distinguished from Japanese species of the same genus on the basis of leaf anatomy and ultrastructure. In common with other members of the family, leaf blades of P. scouleri possess epidermal cells with transfer cell features, subcuticular cavities in the outer wall of these cells, sieve tube elements with nacreous walls, and vascular parenchyma cells with transfer cell characteristics. Some anatomical and ultrastructural features of P. scouleri could be considered to represent adaptations to its habitat (rocky substrate and surf exposure). These include the development of mechanical tissues composed of cellulose cell walls in all vegetative organs to allow for flexibility, secretion of material by the roots for adhesion to the rocks, modification of the nodal regions of rhizomes to cope with strong water movements, and development of a thick cuticular covering over the rhizome surface for protection.

The Sensory Tubercle On the Eyestalk of the Shrimp Crangon Crangon (Linnaeus, 1758) (Decapoda, Caridea)

Abstract Many podophthalmous Crustacea present a more or less salient external structure near and in proximal position to the compound eyes. It is called sensory pore, eye papilla or eye tubercle, according to shape and author. Some SEM and TEM ultrastructural studies on several Caridea and Penaeidae have revealed a complex structure with at least two chemoreceptor-like organs: the main sensory pore (MSP) and the lateral sensory pore (LSP). MSP is a thin discoidal cuticular zone perforated by micropores. Beneath it there is a layer of sensory-like cells, each with two ciliary outer segments branching into a sub-cuticular cavity. The dcndrite parts of the sensory cells are surrounded by supporting cells. The tissue organisation reminds of that of a Vertebrate olfactive mucosa. The LSP consists of a cluster of bipolar sensory cells often ending in a pit similar to an invaginated chemoreceptive seta, found in Arthropoda. The present study deals with the common shrimp Crangon crangon (Linnaeus, 1758), which displays a highly salient conical papilla. This differs in shape from the sensory pores anatomically studied so far. Ultrastructural observations show an important LSP which ends at the tip of the cone rather than in a pit. The equivalent of the MSP is sunken into the base of the cone. This pattern is original and closer to that found in the Penaeidae than to that of the Caridea observed. Therefore, the MSP-LSP complex of Decapoda, in spite of a similar basic structure, presents very different external aspects in different species. It is also confirmed that this complex is very close to, but separate from, the internal organ of Bellonci.

Evidence that abaxial leaf glands are the sites of salt secretion in leaves of the mangrove Avicennia marina (Forsk.) Vierh

summaryPieces of leaf from the halophyte Avicennia marina (Forsk,) Vierh. were freeze‐substituted and sectioned with special precautions to keep specimens always dry. Spot energy dispersive X‐ray microanalysis and X‐ray mapping showed that vacuoles of water parenchyma and palisade mesophyll cells had much more sodium and chlorine than the cytoplasm of the same cells. Potassium and phosphorus were also found in the vacuoles of the palisade mesophyll cells but in the water parenchyma cell vacuoles, sodium and chlorine generated most of the X‐ray counts. This is consistent with a function for the water parenchyma cells of vacuolar salt storage. No sodium and chlorine were detected in the peltate cells of the abaxial epidermal hairs, and there was very little sodium in the vacuoles of their basal cells, potassium apparently being the major cation. Salt crystals were not detected in substomatal cavities. Abaxial epidermal glands contained sodium and chlorine in the collecting cell, stalk cell, secretory cells and the subcuticular cavity. Material just outside the glands gave extremely high X‐ray counts for sodium and chlorine. We conclude that the material was salt that had been secreted, and that the glands are the secretory apparatus on the abaxial surface of the leaves.