The Ultrastructure of the Digestive Glands in Pinguicula vulgaris L. (Lentibulariaceae) Relative to their Function. II. The Changes on Stimulation

The secretory cells of the digestive glands remain highly activeduring the entire period of prey digestion and absorption ofnutrients. They appear to play a major role in gland activity.A model of the digestive gland's activity on stimulation isproposed. It is very similar to that suggested earlier for Dionaeamuscipula. After the digestion and absorption cycle, destructiveprocesses are initiated in the glands. These appear similarto those observed in the glands of the ageing, unstimulatedleaf and are not associated with feeding. Pinguicula vulgaris L. carnivorous plant, digestive glands, ultrastructure, protein secretion absorption, senescence     

Ultrastructure of the Resin Ducts of Mangifera indica L. (Anacardiaceae). 2. Resin Secretion in the Primary Stem Ducts

The resin of the mango stem consists mainly of terpenes. Theterpenes seem to be produced primarily by plastids, termed heresecretoplasts. At the beginning of the process of secretion,osmiophilic droplets are seen at the envelope of the secretoplastsand at elemints of periplastidal ER. In addition, such dropletsoccur also at Golgi bodies and occasionally in association withmitochondria. Later osmiophilic material fills the well-developbdER, which at this stage is mainly tubular. It appears that theER is involved in the transport of the sareted material towardsthe plasmalemma. Mangifera indica L., mango, Anacardiaceae, resin, resin ducts, secretion, secretoplasts, ultrastructure     

THE FINE STRUCTURE AND FUNCTION OF THE SALIVARY GLANDS OF NUCELLA LAPILLUS (GASTROPODA: MURICIDAE)

The fine structure of the tubular and acinous salivary glandsof Nucella lapillus (L.) has been studied and some histochemicaland enzyme tests have been carried out. The clusters of subepithelialcells of the tubular glands secrete a glycoprotein composedof chains of tubular macromolecules resembling secretions knownto have adhesive properties which may assist in boring. Thesecretion is rich in disulphide groups, as are many toxins,and is believed to be responsible for the recently demonstratedpharmacological activity of the glands. It is proposed thatflaccid paralysis is induced in prey by envenomation with thissecretion during rasping, after soft parts have been exposedby an ‘anti-predator’ reaction to secretion fromthe hypobranchial gland of Nucella. The secretory vesicles ofboth types of gland cells in the acinous glands have heterogeneouscontents indicating that their secretions are complex. The majorcomponent in those of the mucous cells is an acid mucopolysaccharidetypical of a lubricant or releasing agent. The ciliated basalcells resemble typical enzyme-secreting cells and the majorconstituent of their secretion is a finely granular glycoprotein. (Received 8 January 1990; accepted 5 June 1990)     

Salt Glands in the Zoysieae

Salt glands were found in two species of the genus Zoysia ofthe tribe Zoysieae, sub-family Chloridoideae (Poaceae). Glandsprotrude from and are recumbent to the leaf epidermis, and consistof two cells, a basal cell and upper cap cell. Glands were betterdeveloped on the adaxial surfaces. Those on the abaxial surfaceappear to be non-functional. Zoysia matrella, the more salt-tolerantspecies, had a higher density of larger glands, and secretedmore sodium per unit leaf mass, resulting in much lower leafsap osmolalities than those of the more salt-sensitive Z. japonica.The finding of salt glands in the tribe Zoysieae confirms itsrelation to the four other tribes within the sub-family Chloridoideaein which salt glands have previously been reported. Salt glands, Zoysieae, Poaceae, Japanese lawngrass, Zoysia japonica, Manilagrass, Zoysia matrella, sodium chloride, salt tolerance, secretion     

Epidermal Peels of Avicennia germinans (L.) Stearn: A Useful System to Study the Function of Salt Glands

Adaxial peels were made from fully expanded leaves of Avicenniagerminans (L). Stearn. The peels consisted of the epidermis,epidermal salt glands, and underlying hypodermal cells. Electronmicroscopic examinations showed that the structural integrity(except for the innermost hypodermal cells) of all cell typeswas not altered in making the peels. When the peels were floatedon salt solutions, the glands were shown to be functionallycompetent in secretion. Secretion also occurred when the peelswere floated on distilled water, presumably from salts storedin the hypodermis. Secretion occurred in the dark and sinceall cell types in the peels lacked chloroplasts, glandular functioncould not be directly coupled energetically to photosynthesis.However, secretion was shown to be temperature dependent andinhibited by azide and dinitrophenol, which indicates that theenergy cost underlying secretion is mitochondrial and most likelycoming from the mitochondria-enriched gland cells. Inhibitorsknown to affect membrane H⁺ ATPase activity and membrane transportalso inhibited secretion, indicating that membrane transportis probably the primary mechanism underlying secretion. Lanthanum,a membrane calcium antagonist, also inhibited secretion. Avicennia germinans (Avicenniaccac), salt glands, metabolic inhibitors, ultrastructure, secretion     

Aquaporins in complex tissues. I.Developmental patterns in respiratory and glandular tissues of rat

Developmentalexpression of aquaporin water transport proteins is not well understoodin respiratory tract or secretory glands; here we define aquaporinprotein ontogeny in rat. Expression of aquaporin-3 (AQP3), AQP4, andAQP5 proteins occurs within 2 wk after birth, whereas AQP1 firstappears before birth. In most tissues, aquaporin protein expressionincreases progressively, although transient high-level expression isnoted in distal lung (AQP4 at postnatal day+2) and trachea (AQP5 at postnatalday +21 and AQP3 at postnatal day+42). In mature animals, AQP5 is abundant in distallung and salivary glands, AQP3 and AQP4 are present in trachea, andAQP1 is present in all of these tissues except salivary glands.Surprisingly, all four aquaporin proteins are highly abundant innasopharynx. Unlike AQP1, corticosteroids did not induce expression ofAQP3, AQP4, or AQP5 in lung. Our results seemingly implicate aquaporinsin proximal airway humidification, glandular secretion, and perinatalclearance of fluid from distal airways. However, the studies underscorea need for detailed immunohistochemical characterizations anddefinitive functional studies.

     

Pathways for Nutrient Transport in the Pitchers of the Carnivorous Plant Nepenthes alata

Glands of the carnivorous pitcher plant Nepenthesalata are activein transport of materials into and out of the pitcher lumen,indicating dual functions in both secretion and absorption.This study examined the potential for open transport throughthese glands using the ultrastructural tracer lanthanum, whichis restricted to the apoplast, and the fluorescent symplastictracer, 6(5)carboxyfluorescein. Glandular uptake of lanthanumfrom the pitcher fluid occurred through the outer cell wallbetween irregularly spaced cutinized deposits, but was blockedfrom entering the underlying mesophyll cell walls by thick endodermal-likeregions. Similarly, lanthanum localization showed an open apoplasticpathway from the petiole to the endodermal regions in the glandbase. Thus, transport of materials into or out of the glandmust occur through the symplast. 6(5)Carboxyfluorescein showedthat these glands transport fluids directly from the pitcherfluid into vascular endings immediately beneath them via a symplasticroute. When applied to the petiolar vascular system, the fluorescenttracer freely entered immature pitchers, but was blocked fromentering the lumen of the mature pitcher by an endodermal zone.An ultrastructural survey showed infrequent pits with plasmodesmatalconnections to adjoining subepidermal cells. These results indicatethat the function of the gland is developmentally regulated.Prior to maturity, the primary function of the gland appearsto be secretion. However, at maturity, secretion is blockedby an endodermal layer, which limits the function of the glandto absorption. These studies support the theory that the glandsof Nepenthesalata are specialized for the bi-directional transportof materials.Copyright 1999 Annals of Botany Company Apoplastic transport, 6(5)carboxyfluorescein, carnivorous plants, digestive glands, endodermal layer,Nepenthesalata Blanco, lanthanum, pitcher plants.     

Development, Structure and Cytochemistry of Resin-secreting Colleters of Gardenia gummifera (Rubiaceae)

The structure, ontogeny and cytochemistry of stipular colletersof Gardenia gummifera are described. The repeated division ofa few adaxial protodermal and subprotodermal cells of the youngstipule and the subsequent elongation by the latter resultsin the formation of a standard-type colleter. A developed colleterhas outer palisade-like glandular cells covered by a continuouscuticle and inner layers of elongated columnar cells. Enzymelevels in the palisade-like epidermal cells in the colletersindicate their active role in secretion. The secretion is resinous,occurs in the young colleters, and accumulates between the cellsand the cuticle. The cuticle later ruptures and releases thesecretory product, which drenches the young shoot apex. Gardenia gummifera L, stipule, colleters, resin, ontogeny, cytochemistry     

The Ultrastructure of the Digestive Glands in Pinguicula vulgaris L. (Lentibulariaceae) Relative to their Function. I. The Changes During Maturation

The digestive glands of Pinguicula vulgaris become fully maturewhilst still enclosed in the bud. All the gland cells remainintact on the fully expanded unstimulated leaves. As the secretoryhead cells mature, a special layer forms between the plasmalemmaand the cell wall. This layer is shown to be different fromthe typical labyrinthine wall of transfer cells and serves forthe storage of digestive enzymes. Ultrastructural analysis,including morphometry, indicates that the digestive enzymesare synthesized on the RER of the head cells and transferredinto the cell wall, particularly into the slime layer, and vacuoles.This transfer is achieved firstly through continuity of theendoplasmic reticulum with vacuoles (static) and the periplasmicspace (dynamic) and, secondly, into the latter through exocytosisof coated Golgi vesicles and of some vacuoles filled with enzymes. Pinguicula vulgaris L., carnivorous plant, digestive glands, ultrastructure, protein synthesis secretion     

Intracellular Transport and Elimination of Resin from Epithelial Duct-cells of Pinus halepensis

The ultrastructure of the resin secreting cells of root ductsof young Pinus halepensis seedlings was studied. It is suggestedthat the endoplasmic reticulum (ER) in addition to taking partin resin synthesis also plays a role in transporting the resinfrom the plastids, mitochondria and nuclear envelope to theplasmalemma. By fusing with the plasmalemma the ER releasesthe resin to the outside of the protoplast. The resin producedin the ground cytoplasm and by the Golgi apparatus seems tobe eliminated by plasmalemma invaginations. Pinus halepensis, resin secretion, root ducts, endoplasmic reticulum     

An X-ray Microanalysis Study of the Salt Glands and Intracellular Calcium Crystals of Tamarix

X-ray microprobe analyses of the secreted salts from glandsof 20 Tamarix aphylla (L.) Karst trees growing in alluvial soilsin the north western district of Victoria, Australia, show thatthe glands secrete a variety of elements including calcium,magnesium and sulphur. However, sodium, potassium and chloride,common ions reported to be secreted predominantly in other studies,are present in relatively low amounts in the secreted salts.Calcium, the major cationic element in the secretory productof the gland, was not detected in the symplasm of the secretoryand collecting cells or in the vacuoles of the collecting cells.Some evidence indicates that silicon may be secreted by theglands but further corroboratory data are required. Our resultssupport previous suggestions that the glands of Tamarix havea low level of selectivity. Large, spherical aggregates of calcium crystals were observedin the vacuoles of the mesophyll cells and quantitative X-raymicroanalysis suggested that the chemical composition of thecrystalline aggregates was CaSO₄, 2H₂O. The predominant elementsin the vacuolar sap were magnesium and sulphur, probably presentas MgSO₄, whereas the major elements in the cytoplasm were potassium,sulphur and phosphorus. In Tamarix aphylla the calcium contentof the leaf appears to be regulated by both the secretion ofcalcium salts from the leaf and by intracellular calcificationin mesophyll cells.Copyright 1994, 1999 Academic Press X-ray microanalysis, Tamarix, salt gland, secretion, salts, ions, calcium crystals, compartmentation     

The Relationship Between Oil Gland and Fruit Development in Washington Navel Orange (Citrus sinensis L. Osbeck)

Changes in structure, size and number of oil glands locatedin the fruit rind were assessed in developing fruit of the WashingtonNavel orange (Citrus sinensis L. Osbeck) from pre-anthesis tofruit maturity. Initiation of oil glands was found to be restrictedto early fruit development. Glands continued to develop throughoutfruit growth, until all reached maturity by a fruit size of30 to 50 mm diameter. Mature glands continued to enlarge withfruit growth. Mature fruit had between 8 000 and 12 000 oilglands. Anatomical studies of the fruit rind were carried outusing light microscopy on samples prepared by different tissueprocessing methods. Glands were found to develop from a clusterof cells adjacent to the fruit epidermis, into a structure consistingof a central cavity surrounded by several layers of epithelialcells. All glands were joined to the fruit epidermis, irrespectiveof their stage of development. Neither lignin nor suberin waspresent in the gland. Gland cavity formation appeared to involveschizogeny. Copyright 2001 Annals of Botany Company Washington Navel orange, Citrus sinensis L. Osbeck, fruit development, secretory cavity, oil gland, image analysis, light microscopy     

MORPHOLOGICAL AND CHEMICAL CAMOUFLAGE OF THE MEDITERRANEAN NUDIBRANCH DISCODORIS INDECORA ON THE SPONGES IRCINIA VARIABILIS AND IRCINIA FASCICULATA

The nudibranch Discodoris indecora shows a perfect camouflageon its prey, the dictyoceratid sponge Ircinia variabilis. Shapeand colour of the nudibranch are remarkably similar to thatof the sponge which is widespread in the shallow waters of theMediterranean Sea. The metabolite pattern of I. variabilis isdominated by unusual molecules, the sesterter-penoids palinurinand variabilin, containing 25 carbons and displaying at theends a ß-substituted furan ring and a tetronic acid.However, a chemical polymorphism has been recently describedfor I. variabilis. Some specimens contain either palinurin orvariabilin whereas others possess a mixture of both sestertepenoids.During the study of Mediterranean sponges, a linear sesterterpenoidrelated to palinurin and variabilin was found in Ircinia fasciculata,that from a taxonomic point of view is closely relatedto Irciniavariabilis. Discodoris indecora shows a typical defence behaviourwhen it is disturbed, secreting a copious white slime that containslarge amounts of palinurin and variabilin. Most likely the animalis able to transfer the sponge metabolites from the digestiveglands to mantle glands. Electron micrographs of the nudibranchmantle showed the presence of unicellular glands characterizedby a cylindrical vacuole with a big nucleus on the basis. Theglands were concentrated in the most conspicuous tubercles ofthe dorsal mantle. Probably, the sponge metabolites are storedin these glands. Comparative chemical analysis of mucous secretions, dorsal tubercles,mantle, foot, digestive glands and hepatopancreas of D. indecoraconfirmed this hypothesis. Palinurin and fasciculation were,of course, present in the digestive glands but they were alsofound in the mucus and in the mantle sections enriched by theabove described unicellular glands. The defensive role of palinurinand variabilin, strongly suggested by their anatomical location,was supported by recording the induction of feeding-deterrencein the fresh-water fish Carassius auratus and in the marinefish Chromis chromis and Sparus auratus. (Received 15 March 1996; accepted 27 January 1997)     

The Ultrastructure of Ion-Secreting and Non-Secreting Salt Glands of Limonium platyphyllum

The ultrastructure of salt glands in developing leaves of Limoniumplatyphyllum is described prior to exposure to 3% NaCl solution(with non-secreting glands) and after 4.5 and 18 h exposureto the salt solution. It is shown that in most glands, the transitionto active chloride transport was accompanied by the displacementof vacuoles toward the cell periphery and by the establishmentof plasmalemma contact sites with the tonoplast which appearedsimilar to gap junctions in animal epithelial cells. No evidencefor the exocytosis of vacuoles was found. It is suggested thatgland vacuoles may have a primary role in chloride secretionand that the tonoplast may be functionally asymmetrical, sothat the free part facing the hyaloplasm bears ion pumps, whereashighly permeable ion channels are active along the zone of contactwith the plasmalemma. It follows that the active step in chloridetransport in Limonium glands is the influx of ions into thevacuoles. Within the inner cup cells of the gland, vacuolescome into contact with the plasmalemma only at sites where thecell wall is adjacent to secretory and accessory cells. Suchan asymmetry appears to ensure the directed flux of ions intothis cell wall. Wall protuberances in the gland cells are rudimentaryand presumably not involved directly in NaCl secretion. Thenucleolus is activated during secretion and the frequency offree ribosomes is significantly increased, which is suggestiveof their involvement in the synthesis of membrane transportproteins. The ultrastructure of about one-third of the glandsremained unchanged in salt-treated leaves. Key words: Salt glands, ultrastructure, ion fluxes     

Second Messengers and the Action of Prothoracicotropic Hormone in Manduca sexta

SYNOPSIS. The large (26 kDa) prothoracicotropic hormone of Manducasexta stimulates ecdysteroid secretion by the prothoracic glandsthrough the action of cyclic AMP (cAMP). Adenylate cyclase inthe prothoracic glands is sensitive to calcium/calmodulin, andenhancement of intracellular calcium levels may be the meansby which PTTH stimulates cAMP synthesis. The cyclic nucleotidein turn activates cAMP-dependent protein kinase and proteinphosphorylation, most notably of a 34 kDa membraneassociatedprotein. It does not appear that protein kinase C plays a rolein the acute action of PTTH, nor has the hormone been foundto stimulate formation of inositol trisphosphate undercurrentassay conditions. PTTH rapidly increases protein synthesis bythe prothoracic glands, and translation inhibitors block PTTH-stimulatedecdysteroid secretion. Connections between protein phosphorylation,protein synthesis, and ecdysone secretion remain to be clarified.     

The Fine Structure and Function of the Anterior Foregut Glands of Cymatium Intermedius (Cassoidea: Ranellidae)

The fine structure of the salivary glands of Cymatium intermediusis described. It is concluded that both the posterior acid secretingand anterior acinous lobes are homologous with the salivaryglands of other prosobranchs. At least six different types ofsecretion have been identified and their possible roles discussed.The anterior lobes secrete mucin and proteins believed to beenzymes, and the posterior lobes are specialized for acid productionas well as secreting protein (probably a peptide toxin). Themechanisms of acid secretion and protection from damage to thesnail before its release are also considered. (Received 12 January 1998; accepted 1 March 1998)     

Ultrastructure of Resin Ducts in Pinus halepensis Development, Possible Sites of Resin Synthesis, and Mode of its Elimination from the Protoplast

Development of the resin duct cavity, sites of resin synthesisin the epithelial cells and elimination of resin from the protoplastwere studied in roots of young Pinus halepensis seedlings. Itis suggested that the Golgi bodies are involved in dissolutionof the middle lamella in the region of the future duct cavityby secretion of lytic enzymes into the cell walls. In earlystages of duct development osmiophilic droplets were observedin plastids, periplastidal and cytoplasmic ER, Golgi vesicles,mitochondria, nuclear envelope and in the cytoplasm. In thelatter they were often observed to be surrounded by a membrane.Electron micrographs suggested that elimination of resin dropletsfrom the protoplast occurs by their becoming surrounded by plasmalemmainvaginations.     

Feeding of the Cymatiid Gastropod, Argobuccinum argus, in Relation to the Structure of the Proboscis and Secretions of the Proboscis Gland

Several gastropod families belonging to the superfamily Tonnaceaare known to bore into the calcareous shells of echinoids andbivalves, but little work has been done on the family Cymatiidae.New observations show that the cymatiid, Argobuccinum argus,which feeds on the tubicolous polychaete, Gunnarea capensis,possesses large proboscis glands which secrete 0.4 to 0.5N H₂SO₄;further, the secretion dissolves greater amounts of pure CaCO₃than does O.47N H₂SO₄, alone. A toxin is also present, whichabolishes responses to light and touch in several invertebrates. The proboscis is atypically pleurembolic, having a permanentproboscis sheath. Retraction is due to the muscles ot the probosciswall, and the contracted proboscis is not inverted. Unlike othermesogastropods, the Tonnacea have three pairs ofglands associatedwith the foregut: proboscis glands, true salivary glands, anda small, partly paired gland of unknown function immediatelyposterior to the buccal mass. It is concluded that because of an abundance of readily availablefood in the form of Gunnarea, A. argus does not drillinto animalsprotected by a calcareous shell. The presence of a CaCO₃ dissolvingmechanism indicates that the Cymatiidae ingeneral may be ableto employ this method of feeding.     

Inhibition of Sugar and Salt Elimination by Glands with the Amino Acid Analog p-Fluorophenylalanine

The amino acid analog p-fluorophenylalanine (FPA) inhibitedsugar and K⁺ secretion by nectary glands. FPA specifically reducedthe net excretion of Na⁺ and Cl^– by the salt glands ofthe halophyte Limonium vulgare and ³⁶Cl^–excretion by theglands of the pitcher walls of the carnivorous plant Nepenthes.Net uptake and net accumulation of Na⁺ and Cl^– by Limoniumleaf tissue and ³⁶Cl^– accumulation in Nepenthes pitchertissue were much less inhibited than excretion. The resultsare discussed in relation to literature reporting similar specificeffects of FPA on transport of ions from the symplast of barleyroots into the dead xylem elements. Limonium vulgare, Nepenthes hookeriana, salt-glands, excretion, p-fluorophenylalanine