Absorption and long distance transport by isolated stele of maize roots in relation to the dual mechanisms of ion absorption

Summary Ion absorption and transport by intact roots, isolated cortex and isolated stele were compared shortly after tissue isolation and after aging. Absorption isotherms in the low and in the high concentration range show that in stripped-stele, which absorbs at a very low rate immediately after isolation, the capacity of system 1 but not system 2 is built up with aging. In agreement with this result analysis of individual fluxes across plasmamembrane and tonoplast reveals that only the influx from the medium into the cytoplasm increases considerably with aging of stele. Changes observed in aging excised roots and in isolated cortex are much less significant. In spite of the increase of absorption with aging by isolated stele, long distance transport, which is essentially passive through freshly stripped stele, decreases with aging. The reported results reflect the marked permeability of the plasmamembrane of fresh isolated stele, and demonstrate the importance of the cortex as a tissue collecting ions for long distance transport. New evidence for the theory of symplasmatic transport of ions into the xylem vessels is thus provided.

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Zusammenfassung Die Ionenaufnahme durch intakte Wurzeln, isolierte Rinde und isolierte Zentralzylinder und der Ferntransport durch intakte und entrind ete Wurzeln wurden verglichen, und zwar kurz nach der Isolierung und nach Altern der Gewebe. Frisch isolierte Zentralzylinder akkumulieren Io nen nur in ganz geringem Maße oder überhaupt nicht. Von den beiden Systemen der metabolischen Ionenaufnahme, die in einem niedrigen (System 1: bis 0,5 meq/l) und in einem hohen Konzentrationsbereich (System 2: 1-50 meq/l) die Geschwindigkeit der Ionenaufnahme durch intakte Wurzeln und isolierte Wurzelrinde bestimmen, entwickelt sich während des Alterungsprozesses in isolierten Zentralzylindern System 1, nicht aber System 2.In Übereinstimmung mit diesem Befund zeigt die Analyse der Einzelfluxe am Plasmalemma und am Tonoplasten, daß nur der Influx aus der Außenlösung in das Cytoplasma beim Altern der Zentralzylinder beträchtlich ansteigt. Veränderungen beim Altern von abgeschnittenen, intakten Wurzeln und isolierter Rinde sind viel weniger ausgeprägt.Obwohl die Ionenaufnahme beim Altern isolierter Zentralzylinder steigt, verringert sich der Ferntransport, der bei frisch isolierten Zentralzylindern rein passiv ist. Die mitgeteilten Ergebnisse zeigen die ausgeprägte Permeabilität frisch isolierter Zentralzylinder und demonstrieren die Bedeutung der Wurzelrinde als ein Gewebe, das Ionen für den Ferntransport sammelt. Auf diese Weise werden neue Anhaltspunkte für die Theorie des symplasmatischen Transportes der Ionen in die Gefäße gewonnen.

     

Ammoniten mit Kieferapparat und Radula aus Lias-Geschieben

Jaws and radula have been found in two adult microconch specimens of the Liassic ammonite speciesEleganticeras elegantulum (Young & Bird, 1828) from glacial drift boulders near Hamburg. They are more similar to those of recent dibranchiates than ofNautilus, the radula having seven longitudinal rows of teeth instead of thirteen in recentNautilus. Since bothOwens classification of the cephalopods into Dibranchiata and Tetrabranchiata according to the number of gills (which cannot be observed in fossil cephalopods) andSchwarz’ division into Ecto- and Endocochlia according to the (assumed) relative position of body and shell are rather unfortunate, the radula is suggested as a sound basis of classification. It is acceptable to paleo- as well as to neozoologists. As yet, the known evidence is sufficient for a twofold division only: Class Cephalopoda Subclass Lateradulata: Nautiloidea Subclass Angusteradulata: Ammonoidea Coleoidea     

Bellevalia ciliata (Cyr.) Nees (Hyacinthaceae) neu für Bulgarien

(Bellevalia ciliata was recorded in north-east Bulgaria south of the Dobrudsha, within field and steppe vegetation. Vegetation records and a distribution map are presented. Based on taxonomic studies it is proposed to combineB. ciliata, B. sarmatica (Pall.) Wor. andB. speciosa Wor. under the oldest nameB. ciliata (Cyr.) Nees.     

Influence of Phospholipids on Growth, Sporulation and Virulence of the Endoparasitic Fungi Drechmeria coniospora, Verticillium balanoides and Harposporium anguillulae in Liquid Culture

Verticillium balanoides mycelial growth was stimulated on solid corn meal agar (1.7 %) and in liquid corn meal broth (0.2 %) upon the addition of phospholipids at various concentrations. Sporulation differed with phospholipid products and was highest in pure corn meal. Drechmeria coniospora mycelial growth increased upon addition of phospholipids at all concentrations in solid or liquid culture. Sporulation increased at high concentration (1000 ppm) and decreased at low concentration (100 ppm) of phospholipids in the medium. For both fungi, infectivity of conidia produced in liquid culture decreased when compared to conidia from parasitized nematodes. Addition of phospholipids partly restored this effect. Harposporium anguillulae mycelial growth and sporulation was not affected by addition of phospholipids to solid or liquid corn meal medium.     

Cu(I)-thionein release from copper-loaded yeast cells

Summary The release of intact CU(I)₈-thionein from copper-resistant copper-loaded yeast cells, strain X 2180-1Aa, has been shown. This copper(I)-thiolate-rich protein was characterized and compared with the chemical and physicochemical properties of intracellular yeast Cu-thionein. The same molecular mass and stoichiometry of 8 mol copper atoms/mol protein was found. No detectable difference between the Cu-thioneins was seen in luminescence emission, electronic absorption in the ultraviolet region, chiroptical data or amino acid composition. The importance of stable Cu(I)-thiolates in Cu-thionein as a safe vehicle for transporting copper in a non-reactive manner is confirmed.     

Fusion of cultured dog kidney (MDCK) cells: I. Technique,fate of plasma membranes and of cell nuclei

Summary The evaluation of the intracellular signal train and its regulatory function in controlling transepithelial transport with electrophysiological methods often requires intracellular measurements with microelectrodes. However, multiple impalements in epithelial cells are hampered by the small size of the cells. In an attempt to avoid these problems we fused cells of an established cell line, Madin Darby canine kidney cells, originally derived from dog kidney, to giant cells by applying a modified polyethylene glycol method. During trypsin-induced detachment from the ground of the petri dish, individual cells grown in a monolayer incorporate volume and mainly lose basolateral plasma membrane by extrusion. By isovolumetric cell-to-cell fusion, spherical giant cells are formed within 2 hr. During this process a major part of the individual cell plasma membranes is internalized. Over three weeks following cell plasma membrane fusion degradation of single cell nuclei and cell nuclear fusion occurs. We conclude that this experimental approach opens the possibility to investigate ion transport of epithelia in culture by somatic cell genetic techniques.     

Duplication of an Xp segment that includes the ZFX locus causes sex inversion in man

Summary Two 46,XY females with tandem duplications of an X short arm segment were studied by cytogenetic and Southern blot analysis. The results show that the duplicated segment in each case included the Xp21.2–Xp22.2 interval, resulting in a double dose of ZFX on the single active X chromosome. The results from our two cases, in conjunction with those reported by other workers, lead us to conclude that the duplication is the reason for the sex inversion. If ZFY and ZFX are indeed sex-determining gene loci, these findings favour a model of sex determination characterized by antagonistic interaction between these genes.     

Leaf thionins, a novel class of putative defence factors

Leaf thionins of barley have been identified as a novel class of highly abundant polypeptides with antifungal activity, which are present in walls and vacuoles of barley leaf cells. Similar thionins occur not only in monocotyledonous but also in various dicotyledonous plants. The leaf thionins of barley are encoded by a complex multigene family, which consists of at least 50–100 members per haploid genome. The toxicity of these thionins for plant pathogenic fungi and the fact that their synthesis can also be triggered by pathogens strongly suggest that leaf thionins are involved in the mechanism of plant defence against microbiol infection.     

Comparative measurements of the xylem pressure ofNicotiana plants by means of the pressure bomb and pressure probe

Determination of the pressure in the water-conducting vessels of intactNicotiana rustica L. plants showed that the pressure probe technique gave less-negative values than the Scholander-bomb method. Even though absolute values of the order of −0.1 MPa could be directly recorded in the xylem by means of the pressure probe, pressures between zero and atmospheric were also frequently found. The data obtained by the pressure probe for excised leaves showed that the Scholander bomb apparently did not read the actual tension in the xylem vessles ofNicotiana plants. The possibility that the pressure probe gave false readings was excluded by several experimental controls. In addition, cavitation and leaks either during the insertion of the microcapillary of the pressure probe, or else during the measurements were easily recognized when they occurred because of the sudden increase of the absolute xylem tension to that of water vapour or to atmospheric, respectively. Tension values of the same order could also be measured by means of the pressure probe in the xylem vessels of pieces of stem cut from leaves and roots under water and clamped at both ends. The magnitude of the absolute tension depended on the osmolarity of the bathing solution which was adjusted by addition of appropriate concentrations of polyethylene glycol. Partial and uniform pressurisation of plant tissues or organs, or of entire plants (by means of the Scholander bomb or of a hyperbaric chamber, respectively) and simultaneous recording of the xylem tension using the pressure probe showed that a 1∶1 response in xylem pressure only occurred under a few circumstances. A 1∶1 response required that the xylem vessels were in direct contact with an external water reservoir and/or that the tissue was (pre-)infiltrated with water. Corresponding pressure-probe measurements in isolated vascular bundles ofPlantago major L. orP. lanceolata L. plants attached to a Hepp-type osmometer indicated that the magnitude of the tension in the xylem vessels was determined by the external osmotic pressure of the reservoir. These and other experiments, as well as analysis of the data using classical thermodynamics, indicated that the turgor and the internal osmotic pressure of the accessory cells along the xylem vessels play an important role in the maintenance of a constant xylem tension. This conclusion is consistent with the cohesion theory. In agreement with the literature (P.E. Weatherley, 1976, Philos. Trans. R. Soc. London Ser. B23, 435–444; 1982, Encyclopedia of plant physiology, vol. 12B, 79-109), it was found that the tension in the xylem of intact plants under normal and elevated ambient pressure (as measured with the pressure probe) under quasi-stationary conditions was independent of the transpiration rate over a large range, indicating that the conductance of the flow path must be flow-dependent.