Salt Glands in Pappophorum (Poaceae)

Salt glands were observed in two species of Pappophorum, belongingto the tribe Pappophoreae (Chloridoideae, Poaceae). Glands resemblethose described in other genera of the Gramineae; they comprisetwo cells, a large basal one and smaller upper one. Gland densityper unit surface was much higher in P. philippianum, a facultativehalophyte, than in P. pappiferum, a glycophyte. The relevanceof the recretion process for the elimination of accumulatedNa in these two species is considered. The evolutionary significanceof the presence of glands in Pappophoreae and other membersof the Chloridoideae is discussed. Salt glands, Pappophorum philippianum, P. pappiferum, Poaceae     

The Ultrastructure of Frankenia Salt Glands

The ultrastructure of the salt gland of Frankenia has been investigated.Glands were examined after treatment with distilled water andafter 4 h, 15 h, and 36 h of salt treatment. Characteristiccytoplasmic features can be correlated with each of these treatments.The results suggest that the acquisition and maintenance ofthe secreting state involves the vesiculation of endoplasmicreticulum.     

Functional Aspects of the Salt Glands of the Plumbaginaceae

X-ray microanalysis and diffuse reflectance infrared Fouriertransform spectrometry were used to determine the presence andratios of elements in salt secretions from salt glands of greenhouseand experimentally-manipulated leaves of five species of thePlumbaginaceae Sodium, magnesium, silica, sulphur, phosphorus,chloride, potassium, calcium and carbonate were detected insecretions of greenhouse-grown plants. The salt glands of excisedleaves challenged by solutions of KI, KCl, NaCl, Na₂SO₄, MgCl₂and MgSO₄ secreted principally the ions of the challenging solutions. Key words: Ion transport, secretion     

Structural Aspects of the Salt Glands of the Plumbaginaceae

Faraday, C. D. and Thomson, W. W. 1986. Structural aspects ofthe salt glands of the Plumbaginaceae.—J. exp. Bot. 37:461–470. The epidermal salt-secreting glands of 11 species from six differentgenera within the Plumbaginaceae were examined Gland ultrastructurewas considered with respect to species, secretory activity,and secretory product. All mature glands had a similar ultrastructure.Cytoplasmically dense secretory cells contained a full complementof organelles and structures which included numerous mitochondriaand few plastids. Reconstruction of serial paradermal sectionsthrough entire glands revealed that each gland cell generallycontained one or two vacuoles with a convoluted tonoplast inboth secreting and non-secreting states. The absence of numerousvacuoles and vesicles during secretory activity suggested thation secretion was by a transmembrane pathway rather than bya vesicle-mediated pathway. Key words: Salt glands, ultrastructure, Plumbaginaceae     

The Apoplastic Pathway of Transport to Salt Glands

The availability of the apoplastic route for ion transport tosalt glands was assessed by electron microscope examinationsand by the use of lanthanum as an electron-dense tracer to demarcatethe apoplast. The results show that this solute can reach thesalt glands via the apoplast and this observation is discussedin relation to current ideas concerning salt gland function.     

Isolation of Salt Glands from the Larval Brine Shrimp Artemia salina

Use of isolated cell preparations have been a powerful approachto understanding cellular and biochemical processes of a widevariety of tissues, including transporting epithelia. A methodfor isolating the extra-renal organ or salt gland from a larvalbrachiopod crustacean, the brine shrimp, has been developed.This preparation is unique as it is the first isolated epithelialcell preparation from a crustacean and is derived from an earlystage of development. As both the removal and purification protocolsdiffer markedly from previous cell isolation methods, detailsof their development have been described. This preparation hasallowed measurement of the Na$K AT Pase specific activity inthesalt gland and intestine for the first time. Use of the isolatedsalt glands will facilitate cellular and subcellular studiesof both the structure and function of this ion transportingepithelium.     

Morphometric Analysis of Limonium Salt Glands in Relation to Ion Efflux

Faraday, C. D. and Thomson, W. W. 1986. Morphometric analysisof Limonium salt glands in relation to ion efflux.—J exp.Bot. 37: 471–481. Surface areas and volumes of compartments within rapidly secretingand slowly secreting Limonium perezii salt glands were determinedto be similar. Molecular and volume efiluxes of secreted saltsolutions were calculated by the application of secretion ratesto plasmalemma surface areas. If ion efflux from the glandswas a transmembrane phenomenon, fluxes of 1?04?l0^–5 equivalentsm^–2 s^–1 would have been necessary to match secretionrates. These fluxes were a thousand times higher than fluxesestimated for most plant cells. Correlated with these high membranefluxes was the fact that mitochondria occupied 10% of the protoplastvolume. Thirty-two percent of the plasmalemma available forefflux was associated with wall protuberances. Wall protuberancesamplified the plasmalemma surface area by a factor of 1?6. Key words: Salt glands, ultrastructure, ion fluxes     

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     

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     

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     

Salt Glands on Leaves of Rhodes Grass (Chloris gayana Kth.)

Existence of salt glands on leaves of Chloris gayana is established.Such glands are comprised of two cells: a basal large cell andan upper small one. The secreted salts crystallize in a formof whiskers on top of the upper gland cell. The significanceof the process is discussed.     

不同阴离子对二色补血草盐腺Na~+分泌速率的影响

本文以二色补血草(Limonium bicolor)为实验材料,用Hoagland营养液和200mmol·L-1NaCl、NaBr、NaNO3溶液分别处理12h,测定二色补血草盐腺的Na+分泌速率、叶片Na+含量和MDA(丙二醛)含量以及质膜透性,并利用非损伤微测技术探索可能与盐腺相关的转运蛋白,以探讨不同阴离子对二色补血草盐腺分泌Na+的作用及其可能原因。结果表明:在NaCl处理12h时二色补血草叶片Na+分泌速率达到最大,然后逐渐下降;不同钠盐处理下叶片Na+分泌速率为NaCl>NaBr=NaNO3>Hoagland,而叶片Na+含量为NaBr>NaCl>NaNO3>Hoagland;不同盐处理下叶片质膜透性和MDA含量无显著性差异;利用Na-K-Cl共转运体专一性抑制剂bumetanide处理发现Na+分泌速率显著降低。这些结果表明Na-K-Cl共转运体可能参与盐腺分泌Na+。     

Parathyroid Glands in Reptiles

The parathyroid glands in reptiles generally develop from thethird and fourth pharyngeal pouches. In lizards and crocodiles,usually only one pair of glands (from the third pouch) persists,while turtles and snakes generally retain both pairs of glandsin adults. The glands consist of cell cords and are similarin structure to those of birds and mammals. A common featureof reptilian parathyroids is the organization of cells arounda lumen in a follicular arrangement. The few physiological studieswhich have been made indicate that parathyroid function in reptilesis in many respects similar to that of mammals. For example,in lizards, parathyroidectomy results in tetanic convulsionsand lowered values of plasma calcium, while administration ofparathyroid extract increases mine phosphate and serum calciumin turtles, and increases the number of osteoclasts in boneof lizards and turtles. However, there are some obvious differencesbetween parathyroid function in reptiles and mammals, on whichmuch more work is needed.     

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