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  • Turbellaria
  • Zea
  • Springer  (86)
  • Springer Science + Business Media
  • 1980-1984  (86)
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Keywords
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  • Springer  (86)
  • Springer Science + Business Media
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Enzymes of nitrogen assimilation in maize roots (1980)
    Springer
    Planta 148 (1980), S. 477-484 
    Details
    ISSN: 1432-2048
    Keywords: Enzymes ; Nitrogen assimilation ; Root ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The enzymes nitrate reductase (NR), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthetase (GS) and asparagine synthetase (AS) have been assayed in various regions along the seedling root ofZea mays L. In the intact attached root and calculated on a protein basis NR, GOGAT, and GS are found to have slightly higher specific activities in the apical 5 mm than in more mature regions of the root. GDH and AS, on the other hand, are much more active in extracts prepared from mature regions of the root than in the apical region. In excised root tips incubated in the presence of NH4 + and NO3 − there was a marked increase in GDH and AS, and a slight decrease in GOGAT and GS. Additions of NO3 − are required for NR activity but neither NO3 − nor NH4 + additions altered the activity levels of the other four enzymes. Additions of glucose to the medium inhibited the development of AS and GDH activities and resulted in higher activity levels of NR, GS and GOGAT. Glucose additions also enhanced the incorporation of acetate-14C and leucine-14C into protein. Additions of cycloheximide inhibit the development of NR, AS and GDH activities and also the incorporation of acetate-14C and leucine into protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395318
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  • 2
    Electronic Resource
    Electronic Resource
    Auxin action on proton influx in corn roots and its correlation with growth (1980)
    Springer
    Planta 148 (1980), S. 510-512 
    Details
    ISSN: 1432-2048
    Keywords: Auxin ; Cell wall pH ; Growth (roots) ; Proton flux and growth ; Root growth ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At concentrations inhibitory to the elongation of corn (Zea mays L.) roots, the auxins, indole-3-acetic acid (IAA) and α-naphthaleneacetic acid (α-NAA), cause an increase in the pH of the bathing medium; this increase occurs with an average latent period shorter than the latent period for the inhibitory effect of these auxins on elongation. Indole-2-carboxylic acid, an inactive structural analogue of IAA, and β-naphthaleneacetic acid, an inactive analogue of α-NAA, affect neither growth nor the pH of the medium. Since acid pH is known to promote and basic pH to inhibit root elongation, the data are consistent with the hypothesis that hormone-induced modification of cell-wall pH plays a role in the control of elongation of roots, as has been proposed for elongation of stems and coleoptiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395322
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  • 3
    Electronic Resource
    Electronic Resource
    The phytochrome system in light-grown Zea mays L. (1980)
    Springer
    Planta 149 (1980), S. 91-96 
    Details
    ISSN: 1432-2048
    Keywords: Light-grown plants ; Phytochrome ; SAN 9789 ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytochrome system is analyzed in light-grown maize (Zea mays L.) plants, which were prevented from greening by application of the herbicide SAN 9789. The dark kinetics of phytochrome are not different in the first, second or third leaf. It is concluded that in light-grown maize plants phytochrome levels are regulated by Pr formation and Pfr and Pr destruction, rather than by Pfr→Pr dark reversion. Pr undergoes destruction after it has been cycled through Pfr. The consequences of this Pr destruction on the phytochrome system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386232
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  • 4
    Electronic Resource
    Electronic Resource
    Auxin uptake and action of N-1-naphthylphthalamic acid in corn coleoptiles (1981)
    Springer
    Planta 151 (1981), S. 15-25 
    Details
    ISSN: 1432-2048
    Keywords: Auxin (uptake, transport) ; Benzoic acid ; N-1-Naphthylphthalamic acid ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The validity of a chemiosmotic hypothesis for uptake of weak acids as an explanation for the accumulation of auxin by cells has been explored further by comparing the uptake of indole-3-acetic acid (IAA) by 1-mm segments of corn (Zea mays L.) coleoptiles with that of benzoic acid and two neutral indoles, indoleethanol and indoleacetonitrile, which do not ionize. These substances, while structurally related to IAA lack both auxin activity and polar transport. Uptake of IAA and benzoic acid increase with decreasing external pH, whereas the uptake of the two neutral indoles is independent of external pH. Although metabolism of IAA, during 90 min or less, is minimal and without significant effect on its uptake, metabolism of benzoic acid appears responsible for the apparent saturation of benzoic acid uptake at high concentrations. An inhibitor of auxin transport, N-1-naphthylphathalamic acid (NPA), stimulates uptake of IAA but has no effect on uptake of either benzoic acid or the two neutral indoles. Thus, NPA does not affect the driving forces for accumulation of weak acids but probably specifically decreases the flux of the auxin anions relative to undissociated auxin. Since the electrochemical potential of auxin anions is usually higher in than outside cells, blocking the anion flux with NPA would enhance auxin uptake. Azide, which abolishes accumulation of both IAA and benzoic acid, may simply collapse the pH gradient across the plasma membrane. In the absence of NPA, increasing concentrations of auxins or the analogoue β-naphthaleneacetic acid (β-NAA) exert two opposing effects on the uptake of IAA-depression and stimulation. Stimulation results from saturating the anion flux. With uptake fully stimulated by NPA, however, increasing concentrations of auxins or analogues only depress uptake of [3H]IAA. These results are consistent with more than one path for auxin transport each with a different dependence on concentration. In depressing NPA-stimulated IAA uptake, the effectiveness of β-NAA≧IAA≫α-NAA≫ benzoic acid, a specificity similar to that of an auxin binding site in vitro that has been implicated by others in auxin transport. The results support the general hypothesis that cellular auxin uptake and polar transport through tissues are chemiosmotically coupled to the electrochemical potential of auxin and protons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384232
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  • 5
    Electronic Resource
    Electronic Resource
    Isolation and characterization of aminopterin-resistant cell lines in maize (1981)
    Springer
    Planta 153 (1981), S. 436-442 
    Details
    ISSN: 1432-2048
    Keywords: Aminopterin-resistant variants ; Cell culture ; Folate analog ; Variant selection ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aminopterin-resistant cell lines of maize were isolated by two different procedures of callus selection and by plating suspension cultures on drugcontaining medium after mutagen treatment. Efficiencies of different methods of variant selection were compared. Four aminopterin-resistant cell lines were shown to be 10–40 times more resistant than the parental cell line, and they were also resistant to another folate analog, methotrexate. The results suggest that alterations in at least three different cell properties could be responsible for resistance; 1) increased dihydrofolate reductase activity, 2) altered aminopterin sensitivity of dihydrofolate reductase, and 3) reduced drug uptake. One of the resistant cell lines showed more than one alteration, but its resistance proved to be unstable. The results suggest that stable changes which may or may not be of genetic origin and also unstable physiological changes or a combination of both could lead to aminopterin resistance in maize cell cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394982
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of zearalenone (F-2) on pea stem, maize root, and rat liver mitochondria (1981)
    Springer
    Planta 153 (1981), S. 443-446 
    Details
    ISSN: 1432-2048
    Keywords: ATPase ; Mitochondria ; Mycotoxin ; Pisum ; Zea ; Zearalenone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At 5 and 10 μg ml-1 concentration, zearalenone (F-2), a mycotoxin produced by a number of species of the genus Fusarium, causes an inhibition of the oxidative phosphorylation of isolated plant mitochondria, while at 20 and 40 μg ml-1 it causes uncoupling. However, when the mitochondria are pre-incubated for 20 min with F-2, the uncoupling appears to be the prevailing effect. F-2 is also able to inhibit the mitochondrial ATPase activity (Mg2+-dependent). Conversely, F-2 (40 μg ml-1) does not alter the ATP level of maize roots and only slightly affects the ATPase activity of pea stem and maize root microsomal fractions. In addition, F-2 (10–40 μg ml-1) inhibits ATP synthesis catalyzed by rat liver mitochondria. It is suggested that the phytotoxicity of F-2, also known for its ability to collapse the transmembrane electric potential of maize roots, may be mainly linked to its ability to increase the proton permeability of the cell, similar to the common uncouplers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394983
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  • 7
    Electronic Resource
    Electronic Resource
    Light-induced inhibitors from intact and cultured caps of Zea roots (1981)
    Springer
    Planta 153 (1981), S. 471-475 
    Details
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Geotropism (root) ; Growth inhibitor ; Light and root-cap inhibitor ; Root cap (inhibitor) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth inhibitors were assayed from extracts of intact (attached) and of excised (cultured) root caps of Zea mays L., cv. Merit, the roots of which show a positive geotropic response only after exposure to light. If caps are intact at the time of illumination, at least two inhibitory substances are produced, an acid inhibitor and a neutral inhibitor, whereas if caps are detached from roots, placed in culture and then illuminated only the neutral inhibitor is formed. Cycloheximide retards inhibitor production in both intact and cultured caps. When [14C]mevalonic acid is included in the culture medium and the caps are illuminated, 15–25% of the recoverable 14C cochromatographs with the neutral inhibitor, whereas in caps cultured in the dark, this radiolabelling pattern is not observed. Cyloheximide in the light reduces the incorporation of 14C into compounds cochromatographing at the Rf of the neutral inhibitor. It is suggested that the neutral inhibitor may be important in the light-induced bending of roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394989
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  • 8
    Electronic Resource
    Electronic Resource
    Levels of indole-3-acetic acid in intact and decapitated coleoptiles as determined by a specific and highly sensitive solid-phase enzyme immunoassay (1981)
    Springer
    Planta 153 (1981), S. 561-571 
    Details
    ISSN: 1432-2048
    Keywords: Auxin (immunoassay) ; Avena ; Coleoptiles (physiological tip) ; Enzyme immunoassay ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A specific solid-phase enzyme immunoassay for the detection of as little as 3–4 pg of indole-3-acetic acid (IAA) is described. The assay involves minimal procedural efforts and requires only standard laboratory equipment. Up to 50 samples in triplicate, processed simultaneously, can be assayed and evaluated in 2.5 h. As little as 1 mg oat coleoptile tissue is sufficient for a quantitative IAA analysis and little or no extract purification is necessary. Using this assay, levels of IAA have been determined in coleoptiles of maize and oat. The distribution of IAA within single coleoptiles was quantitated and the production of IAA during the regeneration of the physiological tip in Avena coleoptiles was investigated. The changes in levels of IAA and other major phytohormones were quantitated during the growth of oat coleoptiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385542
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  • 9
    Electronic Resource
    Electronic Resource
    The rhizosphere in Zea: new insight into its structure and development (1982)
    Springer
    Planta 156 (1982), S. 45-61 
    Details
    ISSN: 1432-2048
    Keywords: Cells, detached ; Mucilage ; Rhizosphere ; Root, structure and development ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Some of the nodal roots of field-grown Zea mays L. bear a persistent soil sheath along their entire length underground except for a glistening white soil-free zone which extends approximately 25 mm behind the root cap. These roots are generally unbranched. The histology of the surface and the rhizosphere of the sheathed roots has been examined by correlated light and electron microscopy. All mature peripheral tissues including root hairs, are largely intact and apparently alive where enclosed by the soil sheath. The sheath is permeated by extracellular mucilage which is histochemically distinct from the mucilage at the epidermal surface, but similar to that produced by the root cap. Isolated cells resembling those sloughed from the sides of the root cap persist in the soil sheath along the length of these roots. Fresh whole mounts of the sheath show that these detached cells may be alive and streaming vigorously even at some distance from the root cap. Rhizosphere mucilage is associated with the isolated cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393442
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  • 10
    Electronic Resource
    Electronic Resource
    Importance of the cap cells in maize root gravireaction (1982)
    Springer
    Planta 156 (1982), S. 95-96 
    Details
    ISSN: 1432-2048
    Keywords: Gravireaction (root) ; Growth inhibitor ; Root (gravireaction) ; Root cap ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The length of the maize root cap differs significantly from one root to another. The gravireaction of roots appears to depend upon the cap length; when it is smallest, the downward curvature is lowest. Using a freezing technique, it was possible to destroy a part of the root cap and to observe that the smaller the number of root cap cells which remained, the less pronounced was the gravitropic response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393449
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  • 11
    Electronic Resource
    Electronic Resource
    Zeta potential of protoplasts from gravireacting maize roots (1984)
    Springer
    Planta 162 (1984), S. 17-22 
    Details
    ISSN: 1432-2048
    Keywords: Gravireaction ; Plasmalemma ; Protoplast (zeta potential) ; Root (protoplasts) ; Zea ; Zeta potential (protoplasts, root)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts were isolated from cortical cells of the elongating zone of maize (Zea mays L. cv. LG 11) roots and submitted to microelectrophoresis. Significant and transient differences in zeta potential between protoplasts from upper and lower root sides were compared with the gravireaction and the differential elongation of these roots. The maximum difference in the zeta potential was obtained between protoplasts from the upper and lower cortical cells after 90 min, exactly the time of gravipresentation for which the maximum rate of gravireaction was observed. In addition, this almost corresponded to the time for which the difference between the elongation rates of upper and lower sides of the extending zone began to increase. Consequently, the changes in the charges of the plasmalemma of the cortical cells from the growing part of roots could be more or less directly related to the root graviresponse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397415
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  • 12
    Electronic Resource
    Electronic Resource
    Reactivation of phloem export in mature maize leaves after a dark period (1982)
    Springer
    Planta 155 (1982), S. 444-448 
    Details
    ISSN: 1432-2048
    Keywords: Glucose ; Leaf (phloem activity) ; Phloem transport ; Starch ; Sucrose ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mature leaves of corn plants (Zea mays L. cv. Prior) which were darkened for 48 h contain neither bundle-sheath starch nor glucose, and their sucrose content is below 5 μM. In such leaves phloem export has ceased. When re-illuminated, photosynthetic sucrose production starts without delay, but the sucrose: glucose ratio is 1.25:1. Obviously, most of the new-formed sugar is utilized locally. Labeling with 14CO2 has shown that phloen export starts 30 to 40 min after the onset of photosynthesis, when the sucrose: glucose ratio has increased to 13:1. The first newly formed starch can be detected when phloem export is reactivated. Glucose content remains constantly low af about 2 μM for at least 2 h, and it never exceeds 10 μM. Radioactivity in the exporting veins is about five times higher after 2 to 7 h of re-illumination than in the 14-h-day plant. Therefore, phloem export is either intensified during the period of reactivation or exported assimilates are partly unloaded along their way. Comparison of photosynthetic activity of equal-sized leaf strips has shown that both accumulation of photosynthates and radioactivity of exporting veins are about three times higher in the detached strip than in the strip which remained attached to the mother plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394474
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  • 13
    Electronic Resource
    Electronic Resource
    Exoglucanases fromZea mays L. seedlings: their role inβ-D-glucan hydrolysis and their potential role in extension growth (1982)
    Springer
    Planta 155 (1982), S. 467-472 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall (autolysis) ; Glucan (β-D) ; Glucanase (exo-β-D) ; β-Glucosidase ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exoglucanases of corn seedlings were examined and evaluated in terms of their participation in the hydrolysis of cell-wall β-D-glucan and their possible role in extension growth. An exo-β-1,3-glucanase (EC 3.2.1.58), a component of the protein dissociated from isolated wall by use of high salt solutions, was purified using gel-filtration and ion-exchange chromatography. The purified enzyme hydrolyzed a number of polymeric and oligosaccharide substrates, including those of mixedlinkage, and their direct conversion to monosaccharide was evidence that the enzyme was capable of hydrolyzing both β1–4 and β1–3 linkages. The enzyme was considerably more active toward glucan that had been previously hydrolyzed by a cell-wall endo-β-D-glucanase. Similarly, the capacity of the purified exo-β-D-glucanase to degrade isolated wall was enhanced by more than 60% when the wall had been previously treated with the endoenzyme. The exo-β-D-glucanase did not exhibit growth-promoting properties nor was its activity, measured in vivo, enhanced by auxin. Another glucanase was obtained from the soluble fraction of seedling homogenates. It functioned strictly as a β-glucosidase and did not appear to participate in the hydrolysis of wall β-D-glucan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01607569
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  • 14
    Electronic Resource
    Electronic Resource
    The control of cellulose microfibril deposition in the cell wall of higher plants (1982)
    Springer
    Planta 154 (1982), S. 489-500 
    Details
    ISSN: 1432-2048
    Keywords: Cellulose microfibril deposition ; Membrane flow ; Pinus ; Pit field ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In maize (Zea mays L.) and pine (Pinus taeda L.) seedlings, cellulose microfibril impressions are present on freeze-fractured plasma membranes. It has been proposed that impressions of newly synthesized microfibrils are a record of the movement of terminal synthesizing complexes through the plasma membrane (Mueller and Brown, 1980, J. Cell Biol. 84, 315–326). The association of terminal complexes with the ends of microfibril impressions or with the ends of microfibrils torn through the membrane indicates the orientation of microfibril tips. Unidirectionally-oriented microfibril tips (all pointing in the same direction) are associated with the organized deposition of parallel arrays of microfibrils. Multidirectionally-oriented microfibril tips were observed in a cell in which microfibril deposition was unusually disorganized. Microfibril patterns around pit fields are asymmetric and resemble flow patterns. Unidirectionally-oriented tears are associated with these microfibrils. Although microfibril orientations are deflected around pit fields, the main axis of microfibril orientation is maintained across the surface of the cell. The hypothesis is proposed that the interaction of a flowing plasma membrane with microfibril synthesizing complexes in the plane of the membrane may result in unidirectional deposition and asymmetric microfibril impressions around pit fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402993
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  • 15
    Electronic Resource
    Electronic Resource
    The control of cellulose microfibril deposition in the cell wall of higher plants (1982)
    Springer
    Planta 154 (1982), S. 501-515 
    Details
    ISSN: 1432-2048
    Keywords: Cellulose microfibril deposition ; Colchicine ; Cytoskeleton ; Ethylene ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells of maize (Zea mays L.) seedling that are not fixed or cryoprotected contain the impressions of cellulose microfibrils on freeze-fractured plasma membranes. Impressions of the most recently deposited microfibrils have terminal complexes associated with them (see preceding paper). The orientations of microtubules in cytoplasmic fractures are parallel to the newest microfibrils observed on adjacent plasma membrane fractures. Small groups of microfibrils, distinguished from the next older layer by their new orientation, are sometimes observed directly adjacent and parallel to individual microtubules. Whereas microtubules are parallel to microfibril orientations which vary from transverse to occasionally longitudinal, microfilaments are parallel to the longitudinal cell axis. After colchicine treatment, cytoplasmic microtubules are absent, as are the bands of microfibrils that are observed on the membrane of control cells. Parallel orientations of microfibrils and normal pitfield outlines are often still observed after colchicine treatment. However, on some membranes, multidirectionally-oriented microfibril tips occur, associated with perturbations of microfibril orientation and rounded pit-field outlines. In ethylene-treated cells, some membranes have microfibril tips oriented in only one direction in new layers of longitudinal microfibrils. On other membranes, longitudinal bands of microfibril tips are oriented in opposing directions. We propose that after colchicine treatment, the patterns of microfibrils reflect an orientation mechanism which has been uncoupled from the influence of microtubules but which is still under some other form of cellular control. We propose that membrane flow could orient the lateral movement of synthesizing complexes in the membrane and that microtubules modulate this movement, apparently organizing the microfibrils into parallel bands in newly-forming wall layers.
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    URL: http://dx.doi.org/10.1007/BF00402994
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  • 16
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    Partial purification of endo- and exo-β-D-glucanase enzymes from Zea mays L. seedlings and their involvement in cell-wall autohydrolysis (1981)
    Springer
    Planta 151 (1981), S. 206-214 
    Details
    ISSN: 1432-2048
    Keywords: Cell-wall autohydrolysis ; β-D-Glucan ; Glucanase ; Hemicellulose ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The proteins dissociated from isolated Zea seedling cell wall using high-ionic-strength salt solutions have been found to include a number of enzymes which appear to participate in autolytic reactions of the cell wall. These enzymes caused extensive degradation of enzymatically inactive cell wall, liberating as much as 100 μg/mg dry weight over a 48-h period. Lithium chloride (3M) was shown to be most effective in yielding protein and wall-degrading activities. Molecular-sieve chromatography of the cell-wall protein resolved endo-β-D-glucanase and exo-β-1,3-glucanase (EC 3.2.1.58) activities when Avena glucan and laminarin, respectively, were employed as substrates. The exoenzyme (molecular weight around 60,000) was strongly inhibited by inorganic mercury at a concentration which suppressed the release of monosaccharide from autolytically active cell wall. The endo-β-D-glucanase (MW around 26,000), which showed a marked preference for substrates of mixed-linkage, exhibited features indicating that it initiates the autolytic solubilization of wall glucan. Cell-wall β-D-glucan, recovered as a component of an alkali-soluble cell-wall fraction, served as a substrate for the purified glucanases. Their hydrolysis pattern, assessed using gel exclusion chromatography and product analysis, confirmed that they hydrolyze β-D-glucan. The products generated by the endoglucanase were similar in molecular-size distribution to those liberated from autolytically active-wall. Exoglucanase activity was required for extensive hydrolysis of β-D-glucan in vitro. During coleoptile development the autolytic activity of the cell wall increased dramatically. This increased activity, however, did not parallel the growth potential of the tissue, but more closely reflected an increase in cell-wall β-D-glucan, the primary substrate for autolytic reactions.
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    URL: http://dx.doi.org/10.1007/BF00395171
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  • 17
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    pH-Dependent accumulation of indoleacetic acid by corn coleoptile sections (1980)
    Springer
    Planta 147 (1980), S. 457-466 
    Details
    ISSN: 1432-2048
    Keywords: Auxin (transport, accumulation) ; Chemiosmotic hypothesis ; Coleoptile ; Transport (auxin) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The uptake of auxin by 1-mm slices of corn (Zea mays L.) coleoptiles, a tissue known to transport auxin polarly, depends on the pH of the medium. Short-term uptake of indole-3-acetic acid (IAA) in coleoptiles increases with decreasing pH of the buffer as would be expected if the undissociated weak acid, IAA·H, were more permeable than the auxin anion, IAA-, and IAA- accumulates in the tissues because of the higher pH of the cytoplasm. Although uptake of [3H]IAA is reduced in neutral buffers, it is greater than expected if it were limited to just the extracellular space of the tissue. The radioactivity accumulated by the tissue can be quantitatively extracted by organic solvents and identified as IAA by thin-layer chromatography. The tissue radioactivity is freely mobile and can efflux from the tissue. Thus these cells in pH 5 buffer are able to retain an average internal concentration of mobile IAA that is at least several times greater than the external concentration. A prominent feature of auxin uptake from acidic buffers is enhanced accumulation at high auxin concentration. This indicates that, in addition to fluxes of IAA·H, a saturable site is involved in auxin uptake. Whenever the auxin-anion gradient is directed outward, saturating the efflux of auxin anions increases accumulation. Furthermore, the observed slowing of short-term uptake of radioactive IAA by increasing concentrations of IAA or K+ indicates either an activation of the presumptive auxin leak or saturation of another carrier-mediated uptake system such as a symport of auxin anions with protons. By contrast in neutral buffers, effects of concentration on uptake rates disappear. This implies that at neutral pH the anion leak is decreased and influx depends on the symport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380188
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  • 18
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    Acid growth effects in maize roots: Evidence for a link between auxin-economy and proton extrusion in the control of root growth (1981)
    Springer
    Planta 152 (1981), S. 285-291 
    Details
    ISSN: 1432-2048
    Keywords: Acid growth ; Auxin ; Growth ; Root ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of proton excretion in the growth of apical segments of maize roots has been examined. Growth is stimulated by acidic buffers and inhibited by neutral buffers. Organic buffers such as 2[N-morpholino] ethane sulphonic acid (MES) — 2-amino-2-(hydroxymethyl)propane-1,3 diol (Tris) are more effective than phosphate buffers in inhibiting growth. Fusicoccin(FC)-induced growth is also inhibited by neutral buffers. The antiauxins 4-chlorophenoxyisobutyric acid (PCIB) and 2-(naphthylmethylthio) propionic acid (NMSP) promote growth and H+-excretion over short time periods; this growth is also inhibited by neutral buffers. We conclude that growth of maize roots requires proton extrusion and that regulation of root growth by indol-3yl-acetic acid (IAA) may be mediated by control of this proton extrusion.
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    Small RNA species in maize tissue (1980)
    Springer
    Planta 150 (1980), S. 406-411 
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    ISSN: 1432-2048
    Keywords: Maize tissue ; RNA metabolism ; Small RNA species ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The low molecular weight RNA components of maize have been analyzed after labeling callus and leaf tissue with [3H]uridine in vitro. Electrophoresis of the isolated RNA on acrylamide slab gels reveals, apart from 5S and transfer RNA, three major and about five minor RNA species with chain lengths between 140 and 280 nucleotides. These RNA molecules are labeled as rapidly as 5S, transfer RNA, and do not represent degradation products of large ribosomal RNA molecules. Furthermore, like 5S and transfer RNA, these small RNA species are stable and show no detectable turnover within forty-eight hours. Fractionation of the tissue into crude subcellular fractions indicates a preferential association of some of the small stable RNA species with the nucleus, while others appear to be located in the cytoplasm. The low molecular weight RNA spectrum from the leaf is similar to that observed in callus, with the major small RNA species equally present in both tissues.
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    URL: http://dx.doi.org/10.1007/BF00390177
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    Effects of high temperature on the germination of maize (Zea mays L.) (1981)
    Springer
    Planta 151 (1981), S. 68-74 
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    ISSN: 1432-2048
    Keywords: Energy metabolism ; Germination (seeds) ; Protein synthesis ; Temperature and seed germination ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Poor emergence of maize seedlings, due to high soil temperatures, is a major limitation of crop potential in the lowland tropics. Ability to germinate at high temperature (〉c. 37° C) is related to the temperature sensitivity of the embryo, and there is considerable genotypic variation for this character. Respiration and mitochondrial phosphorylation proceed normally in seeds imbibing at 41° C, and ATP levels are adequate for germination. However, the specific activities of several important enzymes are lower, and the rate of protein synthesis is severely reduced compared with seeds imbibing at 28° C. The depression of the rate of protein synthesis in the embryos of several tropical hybrids imbibing at high temperature correlated with their known temperature sensitivity. It is concluded that protein synthesis is an especially temperature sensitive process in germinating maize embryos, and that this is the principal reason for the sensitivity of germinating maize seeds to high temperature.
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    Effects of high temperature on protein synthesis during germination of maize (Zea mays L.) (1981)
    Springer
    Planta 151 (1981), S. 75-80 
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    ISSN: 1432-2048
    Keywords: Embryos (protein synthesis) ; Germination (seeds) ; Protein synthesis and temperature ; Temperature and protein synthesis ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The poor germination of maize seeds at high temperatures (〉37°C) is related to the low rate of protein synthesis by the embryo. The apparatus of translation was not heat-labile when embryos were incubated for 2 h at 41°C, and cell free extracts from seeds imbibed for 16 h at this temperature were able to translate exogenous mRNA, indicating that ribosomes and other subcellular components were present and functional. Analysis of polysome profiles from embryos imbibing at high temperature indicated that the low rate of protein synthesis was due to the non-availability of active mRNA.
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    Uptake of isolated plant chromosomes by plant protoplasts (1981)
    Springer
    Planta 151 (1981), S. 141-145 
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    ISSN: 1432-2048
    Keywords: Chromosome isolation ; Petroselinum ; Polyethylene-glycol ; Protoplast (uptake of chromosomes) ; Triticum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For mass isolation of plant metaphase chromosomes, cultured cells of wheat (Triticum monococcum) and parsley (Petroselinum hortense) were synchronized by hydroxyurea and colchicine treatment. This synchronization procedure resulted in high mitotic synchrony, especially in suspension cultures of parsley in which 80% of the cells were found to be at the metaphase stage. Mitotic protoplasts isolated from these synchronized cell cultures served as a source for isolation of chromosomes. The described isolation and purification method yielded relatively pure chromosome suspension. The uptake of the isolated plant chromosomes into recipient wheat, parsley, and maize protoplasts was induced by polyethylene-glycol treatment. Cytological studies provided evidences for uptake of plant chromosomes into plant protoplasts.
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    Differential growth of georeacting maize roots (1981)
    Springer
    Planta 151 (1981), S. 146-150 
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    ISSN: 1432-2048
    Keywords: Georeaction (root) ; Growth inhibitors ; Growth (root) ; Root (georeaction, growth) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth rate of the two sides of 10-mm apical segments prepared from primary roots and of intact primary roots of maize has been analyzed in both vertical and horizontal positions, using a filming method allowing continuous growth recording. The data showed that the georeaction began by a decrease in the overall elongation rate of the roots. This inhibition is effective on the lower side of the bending zone, where the growth is practically stopped during the period of maximum rate of geocurvature. In contrast, the growth is slightly enhanced on the upper part of the elongating zone.
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    In vitro binding of riboflavin to subcellular particles from maize coleoptiles and Cucurbita hypocotyls (1980)
    Springer
    Planta 147 (1980), S. 312-319 
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    ISSN: 1432-2048
    Keywords: Cucurbita ; Endoplasmic reticulum ; Light (blue) receptor ; Plasmalemma ; Riboflavin binding ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Saturable and reversible in vitro binding of [14C]riboflavin was found to occur on subcellular, sedimentable particles from maize coleoptiles and Cucurbita hypocotyls. The KD was ca. 6 μM, the pH optimum was near 6.0, and the number of binding sites amounted to 0.1–0.5 μM on a fresh-weight basis. When the reducing agent dithionite was present, riboflavin binding increased-the KD was 2.5 μM, and the pH optimum above 8.0. The binding was specific: flavin mononucleotide (FMN) and flavin adenosine-dinucleotide (FAD) bound less tightly to these sites than riboflavin and another major soluble flavin, the previously described riboflavin-analog “FX”, occurring in grass coleoptiles. These flavin-binding sites were localized on vesicles derived from plasmalemma and endoplasmic reticulum by analyzing sucrose and metrizamide density gradients and marker enzymes.
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    Daily changes in nitrate influx, efflux and metabolism in maize and pearl millet (1981)
    Springer
    Planta 152 (1981), S. 319-324 
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    ISSN: 1432-2048
    Keywords: Nitrate influx (efflux, metabolism) ; Pennisetum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L.) and pearl millet (Pennisetum americanum (L.) Leeke) seedlings were exposed to [15N]nitrate for 1-h periods at eight times during a 24-h period (16–8 h light-dark for maize; 14–10 h for millet). Influx of [15N]nitrate as well as its reduction and translocation were determined during each period. The efflux of previously absorbed [14N]nitrate to the uptake solution was also estimated. No marked diurnal changes in [14N]nitrate efflux or [15N]nitrate influx were evident in maize. In contrast, [14N]nitrate efflux from millet increased and eventually exceeded [15N]nitrate influx during the late dark and early light periods, resulting in net nitrate efflux from the roots. The dissimilarity of their diurnal patterns indicates that influx and efflux are independently regulated. In both species, [15N]nitrate reduction and 15N translocation to shoots were curtailed more by darkness than was [15N]nitrate influx. In the light, maize reduced 15% and millet 24% of the incoming [15N]nitrate. In darkness, reduction dropped to 11 and 17%, respectively. Since the accumulation of reduced-15N in shoots declined abruptly in darkness, whereas that in roots was little affected, it is suggested that in darkness [15N]nitrate reduction occurred primarily in roots. The decrease in nitrate uptake and reduction in darkness was not related to efflux, which remained constant in maize and did not respond immediately to darkness in pearl millet.
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    Enzymes of nitrogen assimilation in maize roots (1980)
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    Planta 148 (1980), S. 477-484 
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    ISSN: 1432-2048
    Keywords: Enzymes ; Nitrogen assimilation ; Root ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The enzymes nitrate reductase (NR), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthetase (GS) and asparagine synthetase (AS) have been assayed in various regions along the seedling root ofZea mays L. In the intact attached root and calculated on a protein basis NR, GOGAT, and GS are found to have slightly higher specific activities in the apical 5 mm than in more mature regions of the root. GDH and AS, on the other hand, are much more active in extracts prepared from mature regions of the root than in the apical region. In excised root tips incubated in the presence of NH4 + and NO3 − there was a marked increase in GDH and AS, and a slight decrease in GOGAT and GS. Additions of NO3 − are required for NR activity but neither NO3 − nor NH4 + additions altered the activity levels of the other four enzymes. Additions of glucose to the medium inhibited the development of AS and GDH activities and resulted in higher activity levels of NR, GS and GOGAT. Glucose additions also enhanced the incorporation of acetate-14C and leucine-14C into protein. Additions of cycloheximide inhibit the development of NR, AS and GDH activities and also the incorporation of acetate-14C and leucine into protein.
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    Auxin action on proton influx in corn roots and its correlation with growth (1980)
    Springer
    Planta 148 (1980), S. 510-512 
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    ISSN: 1432-2048
    Keywords: Auxin ; Cell wall pH ; Growth (roots) ; Proton flux and growth ; Root growth ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At concentrations inhibitory to the elongation of corn (Zea mays L.) roots, the auxins, indole-3-acetic acid (IAA) and α-naphthaleneacetic acid (α-NAA), cause an increase in the pH of the bathing medium; this increase occurs with an average latent period shorter than the latent period for the inhibitory effect of these auxins on elongation. Indole-2-carboxylic acid, an inactive structural analogue of IAA, and β-naphthaleneacetic acid, an inactive analogue of α-NAA, affect neither growth nor the pH of the medium. Since acid pH is known to promote and basic pH to inhibit root elongation, the data are consistent with the hypothesis that hormone-induced modification of cell-wall pH plays a role in the control of elongation of roots, as has been proposed for elongation of stems and coleoptiles.
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    Ca2+ transport in mitochondrial and microsomal fractions from higher plants (1980)
    Springer
    Planta 150 (1980), S. 1-8 
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    ISSN: 1432-2048
    Keywords: Calcium uptake ; Microsomes ; Mitochondria ; Transport (Ca2+) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria from etiolated corn possess a much greater Ca2+ uptake capacity per mg protein than microsomes from the same source. Differences in energy requirements, sensitivity to specific inhibitors, and sedimentation properties enabled us to study both Ca2+ uptake mechanisms without mutual contamination. The microsomal Ca2+ uptake does not vary much among different plants as compared to the mitochondrial Ca2+ uptake; this is also true for different organs of the same plant. Mitochondrial Ca2+ uptake is more dependent on the age of the seedlings than microsomal uptake, because of changes in active Ca2+ uptake activity rather than of changes in efflux. Intactness and the oxidative and phosphorylative properties of the mitochondria remained unchanged during this time period. Na+ and Mg2+ do not induce Ca2+ release from mitochondria.
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    Effect of indoleacetic acid, abscisic acid, root tips and coleoptile tips on growth and curvature of maize roots (1980)
    Springer
    Planta 150 (1980), S. 32-36 
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    ISSN: 1432-2048
    Keywords: Abscisic Acid ; Auxin ; Geotropism ; Root tip ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of externally applied indoleacetic acid (IAA) and abscisic acid (ABA) on the growth of roots of Zea mays L. was measured. Donor blocks of agar with IAA or ABA were placed laterally on the roots and root curvature was measured. When IAA was applied to vertical roots, a curvature directed toward the donor block was observed. This curvature corresponded to a growth inhibition at the side of the root where the donor was applied. When IAA was applied to horizontal roots from the upper side, normal geotropic downward bending was delayed or totally inhibited. The extent of retardation and the inhibition of curvature were found to depend on the concentration of IAA in the donor block. ABA neither induced curvature in vertical roots nor inhibited geotropic curvature in horizontal roots; thus the growth of roots was not inhibited by ABA. However, when, instead of donor blocks, root tips or coleoptile tips were placed onto vertical roots, a curvature of the roots was observed.
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    Energetics of the response of maize coleoptile tissue to indoleacetic acid (1981)
    Springer
    Planta 151 (1981), S. 499-505 
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    ISSN: 1432-2048
    Keywords: Auxin ; Calorimetry ; Coleoptile ; Energetics ; Growth regulator ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) promotes an increase in steady-state heat production by corn (Zea mays L.) coleoptile tissue; this increase is associated with an elevation in aerobic respiration rates. A detailed time dependence of the exothermic response to IAA was obtained using flow calorimetry. The latent period and magnitude of response were evaluated as a function of IAA concentration and pH. The data indicate that more than one response may occur. The optimal change in heat production was produced by an IAA concentration of 3·10-5 M. It was initiated within 5 min after the start of the IAA treatment, and reached a magnitude in excess of 25% of the tissue's basal heat production. Concentrations of IAA greater than 1·10-4 M resulted in diminished response(s), but the effect was strongly pH dependent. Several possibilities for the increased heat production triggered by IAA are discussed.
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    A possible plasma membrane particle containing malic enzyme activity (1981)
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    Planta 151 (1981), S. 506-511 
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    ISSN: 1432-2048
    Keywords: Cell fractionation ; Cucurbita ; Malic enzyme ; Plasma membrane ; Subcellular localization ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A definite membrane fraction from Cucurbita hypocotyls, maize coleoptiles, and other plant tissues contains a NADP-dependent malic enzyme activity, up to 10% of overall tissue activity, and probably other soluble proteins. This “malic enzyme particle” is identified as plasmalemma on the basis of sedimentation behavior, density distribution in sucrose gradients, in comparison with enzyme markers, and sluggish penetration by the sugar Metrizamide. Enzyme binding to the plasma membrane is stable and scarcely sensitive to salts and EDTA, although all activity is released to the supernatant in the presence of Triton-X-100 or under hypotonic conditions. The properties of bound enzyme are similar to those of free enzyme in cell extracts. It is proposed that osmotically sensitive plasma membrane vesicles, containing cytoplasm fragments, are formed during homogenization. Low malic enzyme activities are also associated with Cucurbita proplastids.
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    Comparative analyses of the effect of triacontanol on photosynthesis, photorespiration and growth of tomato (C3-plant) and maize (C4-plant) (1981)
    Springer
    Planta 152 (1981), S. 44-49 
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    ISSN: 1432-2048
    Keywords: Lycopersicon ; Phetorespiration ; Photosynthesis ; Triacontanol ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tomato (C3-plants) and maize (C4-plants) were grown in a nutrient solution to which triacontanol was added twice a week. After about 4 weeks the triacontanol treatment caused a significant increase in the dry weight of the tomato plants. Leaf area and dry weight measurements of tomato leaves at different stages of development showed that the largest increase in growth was obtained when triacontanol treatment was initiated before bud formation. In maize, no effect of the triacontanol treatment on dry wieght was observed. Photosynthesis was inhibited by 27% in young leaves from triacontanol-treated tomato plants and 39% in the controls, when the oxygen concentration was raised from 2% to 21%. In maize no change in photosynthesis could be observed, neither after altered oxygen concentration nor after triacontanol treatment. The difference in the response of C3- and C4-plants to triacontanol indicates that it regulates processes related to photosynthesis.
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    Extent of intracellular pH changes during H+ extrusion by maize root-tip cells (1981)
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    Planta 152 (1981), S. 74-78 
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    ISSN: 1432-2048
    Keywords: Cytoplasmic pH ; Fusicoccin ; Hydrogen-ion extrusion ; pH-stat ; Root ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 31P-Nuclear-magnetic-resonance spectra of maize (Zea mays L.) root tips, that had been induced to extrude large amounts of H+ in response to fusicoccin (FC) in the presence of potassium salts, indicate that the cytoplasmic pH does not become higher than that of controls. In fact, the cytoplasmic pH may become slightly (approx. 0.1 pH unit) lower in cells extruding H+. Estimations of the buffer capacity of the cells show that without active intracellular pH regulation, H+ extrusion caused by FC would cause the intracellular pH to rise by at least 0.6 pH unit h-1. Our results indicate that intracellular pH is tightly regulated even during extreme rates of acid extrusion, and that a rise in cytoplasmic pH is not the signal linking H+ extrusion with enhanced organic-acid synthesis or other intracellular responses to H+ pumping.
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    Correlations between proton-efflux patterns and growth patterns during geotropism and phototropism in maize and sunflower (1981)
    Springer
    Planta 152 (1981), S. 239-241 
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    ISSN: 1432-2048
    Keywords: Acid growth ; Geotropism ; Helianthus ; Phototropism ; Proton secretion ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By placing seedlings of sunflower (Helianthus annuus L.) or maize (Zea mays L.) on agar plates containing a pH indicator dye it is possible to observe surface pH patterns along the growing seedling by observing color changes of the indicator dye. Using this method we find that in geotropically stimulated sunflower hypocotyls or maize coleoptiles there is enhanced proton efflux on the lower surface of the organ prior to the initiation of curvature. As curvature develops the pattern of differential acid efflux becomes more intense. A similar phenomenon is observed when these organs are exposed to unilateral illumination, i.e. enhanced acid efflux occurs on the dark side of the organ prior to the initiation of phototropic curvature and the pattern of differential acid efflux intensifies as phototropic curvature develops. These observations indicate that differential acid efflux occurs in response to tropistic stimuli and that the acid efflux pattern may mediate the development of tropistic curvatures.
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    Selection and characterization of a feedback-insensitive tissue culture of maize (1980)
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    Planta 148 (1980), S. 183-187 
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    ISSN: 1432-2048
    Keywords: Amino acids ; Feedback inhibition ; Mutant selection ; Tissue culture ; Variants, resistant ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tissue culture selection techniques were used to isolate a maize (Zea mays L.) variant D33, in which the aspartate family pathway was less sensitive to feedback inhibition by lysine. D33 was recovered by successively subculturing cultures originally derived from immature embryos on MS medium containing growth-inhibitory levels of lysine+threonine. The ability of D33 to grow vigorously on lysine+ threonine medium was retained after growth for 12 months on nonselection medium. New cultures initiated from shoot tissues of plants regenerated from D33 also were resistant to lysine+threonine inhibition. The Ki of aspartokinase for its feedback inhibitor, lysine, was about 9-fold higher in D33 than for the enzyme from unselected cultures. The free pools of lysine, threonine, isoleucine and methionine were increased 2–9-fold in D33 cultures. This was consistent with the observed change in feedback regulation of aspartokinase, the first enzyme common to the biosynthesis of these amino acids in the aspartate pathway. The accumulated evidence including the stability of resistance in the cultures, the resistance of cultures initiated from regenerated plants, the altered feedback regulation, and the increased free amino acids, indicates a mutational origin for these traits in line D33.
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    Fusicoccin receptors. Evidence for endogenous ligand (1980)
    Springer
    Planta 148 (1980), S. 208-210 
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    ISSN: 1432-2048
    Keywords: Endogenous ligands ; Fusicoccin ; Proton extrusion ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The binding of fusicoccin to the microsomal preparations of maize roots in vitro is increased several-fold when segments of the tissue are washed for 2 h in distilled water before homogenization. Addition of freeze-dried wash solution to microsomal preparations of spinach leaves or fresh roots, washed roots, or coleoptiles of maize inhibited the binding of fusicoccin to particulate fractions. The freeze-dried material also blocked fusicoccin-promoted H+ extrusion from maize root segments. Roots may contain one or more water-soluble compounds competing with fusicoccin at the receptor level; such ligands might play a physiological role as modulators of the H+/K+ exchange system in higher plants.
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    The action of specific inhibitors of auxin transport on uptake of auxin and binding of N-1-naphthylphthalamic acid to a membrane site in maize coleoptiles (1981)
    Springer
    Planta 152 (1981), S. 13-18 
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    ISSN: 1432-2048
    Keywords: Auxin uptake ; Coleoptile ; Fluorescein ; Morphactin ; Naphthylphthalamic acid ; Triiodobenzoic acid ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using both 1-mm segments of corn (Zea mays L.) coleoptiles and a preparation of membranes isolated from the same source, we have compared the effectiveness of several inhibitors of geotropism and polar transport in stimulating uptake of auxin (indole-3-acetic acid, IAA) into the tissue and in competing with N-1-naphthylphthalamic acid (NPA) for a membrane-bound site. Low concentrations of 2,3,5-triiodobenzoic acid (TIBA), NPA, 2-chloro-9-hydroxyfluorene-9-carboxylic acid (morphactin), and fluorescein, eosin, and mercurochrome all stimulated net uptake of [3H]IAA by corn coleoptile tissues while higher concentrations reduced the uptake of both [3H]IAA and another lipophilic weak acid, [14C]benzoic acid. Since low concentrations of fluorescein and its derivatives competed for the same membrane-bound site in vitro as did morphactin and NPA, the basis for both the specific stimulation of auxin accumulation and the inhibition of polar auxin transport by all these compounds may be their ability to interfere with the carrier-mediated efflux of auxin anions from cells. At higher concentrations, the decrease in accumulation of weak acids was nonspecific and thus may be the result of acidification of the cytoplasm and a general decrease in the driving force for uptake of the weak acids. Triiodobenzoic acid was an exception. Low concentration of TIBA (0.1–1 μM) were much less effective than NPA in competing for the NPA receptor in vitro, but little different from NPA in ability to stimulate auxin uptake. One possibility is that TIBA, a substance which is polarly transported, may compete with auxin for the polar transport site while NPA, morphactin, and the fluorescein derivatives may render this site inactive.
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    Evidence for proteins specific for vascular elements in intact and cultured tissues and cells of maize (1980)
    Springer
    Planta 148 (1980), S. 116-123 
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    ISSN: 1432-2048
    Keywords: Antigen ; Callus ; Cell suspension cultures ; Proteins (in differentiation) ; Seedling ; Vascular cylinder (stele) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A group of antigenically distinct proteins characteristic for the tissue complex of the vascular cylinders was found in maize (Zea mays L.) seedlings using an immunofiltration technique. Specific stelar antigens present in the fully developed stele (vascular cylinder) of the primary root were also found in steles extracted from adventitious roots and from the mesocotyl but were absent, within the limits of sensitivity of the immunodiffusion tests employed, in root cortex and epidermis. Some of the stelar antigens were also evident in the meristem of the primary root and were present in traces in the scutellum, the mesocotyl node, and the primary leaves plus coleoptile. The specific stelar antigens could be traced in 13- and 15-day-old developing embryos and were definitely expressed by the 21 st day after pollination. Several stelar-specific antigens were found in embryo-derived callus tissues and in stem-derived cells maintained in serial suspension culture. Higher resolution of the stelar antigens by a modified technique of crossed immunoelectrophoresis was used to demonstrate several minor stelar antigens that were presumably characteristic exclusively of the completely differentiated stele. This technique along with sequential immunoprecipitation of labelled proteins provided a semiquantitative estimate of the specific stelar antigens in the meristem and the stele of the primary root, and in suspension-cultured cells which were devoid of noticeable signs of vascular differentiation.
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    Rearrangement of enzyme patterns in maize callus and suspension cultures (1980)
    Springer
    Planta 148 (1980), S. 108-115 
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    ISSN: 1432-2048
    Keywords: Callus ; Cell proliferation ; Cell suspension ; Coleoptile ; Cytodifferentiation ; Dedifferentiation ; Enzyme profile ; Internode ; Root tip ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of enzyme patterns was followed in the course of: (a) the irreversible cell differentiation via division and expansion to maturity in the root tip and coleoptile of the intact seedlings, (b) the irreversible cell dedifferentation associated with induction and establishment of callus from the growing internodes, and (c) the growth cycle (proliferation⇋stationary phase) in callus and cell-suspension cultures of maize (Zea mays L.). By measuring the activities of glycolytic, mitochondrial, microbody and hydrolytic enzymes cells proliferating in vivo and in vitro could be compared and changes related to cessation or resumption of cell division could be studied. Proliferating cells of callus and suspension cultures maintained by serial culture did not differ from those of the root meristem and coleoptile in the specific activities of hexokinase, phosphoglycerate kinase and phosphopyruvate hydratase. Proliferation in vitro resulted in an enormous increase in the ratio g glutamate-dehydrogenase/cytochrome-oxidase activity and in the level of acid-phosphatase activity, with concomitant drop in galactosidase and xylosidase activity. A 3-5-fold increase of alcohol-dehydrogenase, lactate-dehydrogenase and catalase activities was characteristic of dividing callus cells, while a ca. 100-fold increase in the fructofuranosidase-to-glucosidase activity ratio marked cell proliferation in suspension-cultured cells. Changing enzyme activities after cessation of proliferation were quite similar in root tips and coleoptiles, except those of alcohol dehydrogenase and catalase. The enzyme rearrangement during callus establishment and in the growth cycle of callus cultures was in most cases comparable to that in the intact tissues, while the changes from the dividing to the non-dividing cells in suspension cultures, in contrast, differed widely from those in the intact tissues and callus. Galactosidase and xylosidase were the only activities that showed a similar trend of changes in all the investigated, intact and in-vitro-grown cells. Thus, judged by the pattern of enzyme development, the cell suspension appears to be a unique system, virtually unrelated to the growing cells of the intact tissues. It is also very difficult to draw a definite distinction between the metabolic consequences of cell growth and enzyme modulations in cell suspensions as the cells adapt their metabolism to the environmental changes in liquid medium.
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    Low and high voltage electron microscopy of mitosis and cytokinesis in maize roots (1981)
    Springer
    Planta 152 (1981), S. 397-407 
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    ISSN: 1432-2048
    Keywords: Cytokinesis ; High voltage electron microscopy ; Mitosis ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structure and distribution of cytoplasmic membranes during mitosis and cytokinesis in maize root tip meristematic cells was investigated by low and high voltage electron microscopy. The electron opacity of the nuclear envelope and endoplasmic reticulum (ER) was enhanced by staining the tissue in a mixture of zinc iodide and osmium tetroxide. Thin sections show the nuclear envelope to disassemble at prophase and become indistinguishable from the surrounding ER and polar aggregations of ER. In thick sections under the high voltage electron microscope the spindle is seen to be surrounded by a mass of tubular (TER) and cisternal (CER) endoplasmic reticulum derived from both the nuclear envelope and ER, which persists through metaphase and anaphase. At anaphase strands of TER traverse the spindle between the arms of the chromosomes. The octagonal nuclear pore complexes disappear by metaphase, but irregular-shaped pores persist in the membranes during mitosis. It is suggested that these form a template for pore-complex reformation during telophase. Phragmoplast formation is preceded by an aggregation of TER across the spindle at anaphase. Evidence is presented to suggest that the formation of the desmotubule of a plasmodesma is by the squeezing of a strand of endoplasmic reticulum between the vesicles of the cell plate.
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    Auxin binding in roots: A comparison between maize roots and coleoptiles (1981)
    Springer
    Planta 153 (1981), S. 447-452 
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    ISSN: 1432-2048
    Keywords: Auxin binding ; Root (auxin) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin binding onto membrane fractions of primary roots of maize seedlings has been demonstrated using naphth-1yl-acetic acid (NAA) and indol-3yl-acetic acid (IAA) as ligands. This binding is compared with the already well characterized interaction between auxins and coleoptile membranes. The results indicate that while kinetic parameters are of the same order for root and coleoptile binding, a number of differences occur with respect to location in cells and relative affinity. The possible significance of the existence of such binding sites in root cells is discussed in relation to auxin action.
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    Abscisic acid distribution in horizontal maize root segments (1981)
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    Planta 153 (1981), S. 453-458 
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    ISSN: 1432-2048
    Keywords: Abscisic acid ; Gravireaction ; Growth inhibitors ; Root ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using gas chromatography-mass spectrometry (GC/MS) techniques of analyses, it has been found that endogenous abscisic acid (ABA) becomes asymmetrically distributed in the elongation zone of horizontal Zea mays (cv. LG 11) roots which are showing a positive gravitropic response. There is a relative increase in the ABA content of the lower half and a concomitant decrease for the upper half in such roots. Asymmetric distribution of ABA is also detected in the elongation zone of half-decapped roots.
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    Patterns of polypeptide synthesis in various maize organs under anaerobiosis (1980)
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    Planta 150 (1980), S. 89-94 
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    ISSN: 1432-2048
    Keywords: Anaerobiosis ; Protein synthesis, organspecific ; Stress ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pattern of protein synthesis was compared in several organs of maize (Zea mays L.) under aerobic and anaerobic conditions. Protein synthesis was measured by [35S]methionine incorporation and analysis by two-dimensional native-SDS (sodium lauryl sulfate) polyacrylamide gel electrophoresis and fluorography. The aerobic protein-synthesis profiles were very different for root, endosperm, scutellum and anther wall. However, except for some characteristic qualitative and quantitative differences, the patterns of protein synthesis during anaerobiosis were remarkably similar for these diverse organs and also for mesocotyl and coleoptile. The proteins synthesized were the anaerobic polypeptides (ANPs) which have been previously described in anaerobic roots of seedlings. Leaves exhibited no detectable protein synthesis under anaerobic conditions, and died after a short anaerobic treatment. Evidence is presented that the ANPs are not a generalized response to stress. This indicates that the ANPs are synthesized as a specific response to anaerobic conditions such as flooding.
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    Inhibition by silver ions of gas space (aerenchyma) formation in adventitious roots of Zea mays L. subjected to exogenous ethylene or to oxygen deficiency (1981)
    Springer
    Planta 153 (1981), S. 217-224 
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    ISSN: 1432-2048
    Keywords: Aerenchyma ; Ethylene ; Gas space ; Oxygen and gas-space formation ; Roots, adventitious ; Silver ions ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied the role of ethylene in accelerating the lytic formation of gas spaces (aerenchyma) in the cortex of adventitious roots of maize (Zea mays L.) growing in poorly aerated conditions. Such roots had previously been shown to contain increased concentrations of ethylene. Ten day-old maize plants bearing seminal roots and one whorl of emerging adventitious roots were grown in nutrient solution bubbled with air, ethylene in air (0.1 to 5.0 μl l−1), or allowed to become oxygen-deficient in nonaerated (but not completely anaerobic) solution. Additions of 0.1 μl l−1 ethylene or more promoted the formation of aerenchyma, with lysis of up to 47% of the cortical cells. The effects of non-aeration were similar to those of exogenous ethylene. When silver ions, an ethylene antagonist, were present at low, non-toxic concentrations (circa 0.6 μM), aerenchyma formation was prevented in ethylene treated roots and in those exposed to oxygen deficiency. Silver ions also blocked the inhibiting effect of exogenous ethylene on root extension. By contrast, the suppression of aerenchyma formation by silver ions under oxygendeficient conditions was associated with a retardation of root extension, indicating the importance of aerenchyma for root growth in poorly aerated media. Rates of production of ethylene by excised roots were stimulated by a previous non-aeration treatment. The effectiveness of Ag+ in inhibiting equally the action on cortical cells of exogenous ethylene and of non-aeration, supports the view that gas space (aerenchyma) formation in adventitious roots ‘adpted’ to oxygendeficient environments is mediated by increased concentrations of endogenous ethylene. The possibility that extra ethylene could arise from increased biosynthesis of a precursor in root tissues with a restricted oxygen supply is discussed.
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    Carriers for abscisic acid and indole-3-acetic acid in primary roots: their regional localisation and thermodynamic driving forces (1983)
    Springer
    Planta 157 (1983), S. 53-63 
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    ISSN: 1432-2048
    Keywords: Abscisic acid transport ; Auxin transport ; Carriers (auxin, abscisic acid) ; Driving forces (growth substances, carriers) ; Helianthus ; Phaseolus ; Pisum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A carrier for the uptake of abscisic acid (ABA) is present in the tips and elongating zones of primary roots of both leguminous (runner bean, French bean, pea) and non-leguminous (sunflower, maize) seedlings. No ABA carrier was present in more mature root regions. For indole-3-acetic acid both carrier-mediated uptake and a 2,3,5-triiodobenzoate-sensitive efflux component are present in growing and in non-elongating runner-bean root tissues. Both ABA and indole-3-acetic acid carriers were inactivated by protein-modifying reagents. The driving forces for the carrier systems were studied using reagents, (KCl, fusicoccin, vanadate, dicyclohexylcarbodiimide, proton ionophores and azide) known to modify transmembrane pH (ΔpH) and electricla gradients (ΔE) and whose effects were independently monitored using radiolabelled, lipophilic, weak acids as probes. For abscisic acid the carrier-mediated uptake depend on ΔpH and the nonsaturable component of uptake, due to diffusion of undissociated ABA. The maximum velocity of the carrier is greater at pH 4 than at pH 5, although the Michaelis constants are similar. Modification of ΔE did not alter ABA net uptake but effects on the indole-3-acetic acid system consistent with perturbation of an electrogenic 2,3,5-triiodobenzoate-sensitive component were observed. It is suggested that the ABA carrier is an ABA anion/hydrogen ion symport or, less likely, represents facilitated diffusion of undissociated ABA.
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    Effects of chilling temperatures on root cell membranes as viewed by freeze-fracture electron microscopy (1984)
    Springer
    Protoplasma 122 (1984), S. 75-85 
    Details
    ISSN: 1615-6102
    Keywords: Cucurbita ; Zea ; Hordeum ; Roots ; Membranes ; Chilling ; Freeze-fracture ; Plasmodesmata ; Intramembrane particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cortical cell membranes of maize and marrow roots grown at normal, or chilling, temperatures have been studied by freeze-fracture electron microscopy. Using computer-assisted methods to analyse intramembraneous particle (IMP) frequencies, diameters and distribution, no significant trends in differences between normal and chilled roots were found. While this result does not correspond with the findings from similar experiments on microorganisms, it is compatible with contemporary ideas concerning temperature-induced phase transitions in the lipids of higher plant cell membranes. The cortical cell membranes of barley roots that had been subjected to cold osmotic shock also showed no differences from untreated roots as demonstrable in freeze-fracture replicas. IMPs were found to cluster around plasmodesmata after chilling but the physiological significance of this, if any, remains to be investigated further. While these negative results only indirectly help towards understanding how cell membranes react to chilling, the techniques described open the way for more detailed analyses of IMP characteristics in plant cell membranes.
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    Effect of growth conditions on carboxylating enzymes of Zea mays plants (1982)
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    Photosynthesis research 3 (1982), S. 53-58 
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    ISSN: 1573-5079
    Keywords: carboxylating enzymes ; leaf age ; light intensity ; C3−C4 photosynthesis ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) and ribulose-1,5-bisphospate (RuBP) carboxylase (EC 4.1.1.39) activities in leaves of different maize hybrids grown under field conditions (high light intensity) and in a growth chamber (low light intensity) were determined. Light intensity and leaf age affected PEP carboxylase activity, whereas RuBP carboxylase was affected by leaf age only at low light intensity. PEP carboxylase/RuBP carboxylase activity ratio decreased according to light intensity and leaf age. Results demonstrate that Zea mays grown under field conditions is a typical C4 species in all leaves independently from their position on the stem, whereas it may be a C3 plant when it is grown in a growth chamber at low light intensity
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    Experimental sediment disturbances on a tidal flat: Responses of free-living Platyhelminthes and small Polychaeta (1984)
    Springer
    Hydrobiologia 118 (1984), S. 73-81 
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    ISSN: 1573-5117
    Keywords: meiofauna ; Wadden Sea ; sand flat ; disturbance ; recolonization ; Turbellaria ; Polychaeta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small-scale sediment disturbances on a sandy tidal flat in the North Sea changed the pattern of abundances in free-living platyhelminths (Turbellaria) and small Polychaeta, but not the species composition. Patches of 0.25 m2 were made anoxic, were regularly raked at the surface, or the upper layer of sediment was inverted. Recolonization after temporary anoxia proceeded very slowly. Raking caused diatom-feeding platyhelminths and the polychaetes to emigrate. Turning the upper 5 cm of the sediment upside down was harmful to both taxa, but platyhelminths recolonized quickly. Background densities were temporarily surpassed, first by predators, then by diatom feeders. Coherent responses of trophic guilds in platyhelminths do not suggest that release from competition is involved but indicate that such disturbances alter the availability of food resources and the organisms immigrate accordingly.
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    Ultrastructure of the epidermis of adult and embryonic Paravortex species (Turbellaria, Eulecithophora) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 241-252 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Eulecithophora ; Paravortex ; Cerastoderma ; parasites ; ultrastructure ; epidermis ; embryo capsule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The epidermis and associated structures of adult and embryonic Paravortex cardii and Paravortex karlingi, internal parasites of Cerastoderma edule, have been examined using scanning and transmission electron microscopy. The cellular epidermis of adult Paravortex bears cilia and microvilli which differ in number and distribution between P. karlingi and P. cardii. Cellular organelles include mitochondria, lipid bodies, Golgi bodies, and ultrarhabdites. Epidermal nuclei are located in the proximal portion of the cells. The development of the tegument of embryo Paravortex has been described and a possible origin for the embryo capsule is suggested. These findings are discussed in relation to the phylogenetic status of the Turbellaria in relation to other Platyhelminthes and in the functional adaptation of the epidermis for a parasitic mode of life.
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    The ultrastructure of the eyes in larval and adult polyclads (Turbellaria) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 267-275 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Polycladida ; epidermal eye ; cerebral eye ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Examination of the larvae of Thysanozoon brocchii and Stylochus mediterraneus shows that they have both epidermal and cerebral eyes, while the young worms of Notoplana alcinoi have only cerebral eyes. A description is given of the ultrastructure of both kinds of eyes. The epidermal eye consists of one cup-shaped pigmented cell, whose cavity is filled with lamellae of ciliary origin. A small covering cell is located over the cup-opening. The cerebral eye is made up of three cells: one pigmented cell with ciliary projections and two rhabdomeric-type photoreceptor cells. The cerebral eye in the adult is formed of a pigmented cup without cilia and at least three rhabdomeric-type photoreceptors. A number of remarks of a morpho-onthological nature are presented.
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    Observations on the ultrastructure of the copulatory organ of Archilopsis unipunctata (Fabricius, 1826) (Proseriata, Monocelididae) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 277-285 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Proseriata ; Archilopsis unipunctata ; ultrastructure ; copulatory organ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The copulatory organ in adult specimens of Archilopsis unipunctata has been studied by transmission electron microscopy. This copulatory organ is of the conjuncta-duplex type with eversible cirrus. The seminal vesicle, lined with a nucleate epithelium, is surrounded by spirally arranged muscles. The fibres are enclosed in a sheath that is continuous with the septum of the bulbus and the basement lamina of the male canal epithelium. Distally to the seminal vesicle the bulbus is filled with the secretory cell-necks of the prostate glands. The male canal shows three different parts: seminal duct, ejaculatory duct and eversible cirrus. At the transition of seminal duct and ejaculatory duct two prostate ducts open into the lumen. The structure of the epithelium lining the different parts of the canal is described. The transition into the cirrus may be recognized by an abrupt change in the thickness, the electron density and the stratification in the basement lamina and by the disappearance of the epithelium absent indeed in the cirrus. The material found inside the cirrus-lumen is different according to the zone considered. The origin of this material and of the cirrus teeth is discussed.
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    The karyotypes of Dugesia species from Spain (Turbellaria, Tricladida) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 45-52 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; Dugesia ; karyology ; Spain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Some species of Planarians, new to Spain, are recorded. Dugesia polychroa, D. sicula, D. iberica and D. gonocephala s. 1. have been investigated karyologically. The former possesses a diploid complement characteristic of the biotype A (2n = 8); the second is diploid with 2n = 18; diploidy and triploidy were found in sexual populations of D. iberica with n = 8. Triploidy occurred in all the asexual strains of the D. gonocephala group with a basic number of either 8 or 9. In this latter case B-chromosomes were occasionally found.
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    The ecology of the Turbellaria with special reference to the freshwater triclads (1981)
    Springer
    Hydrobiologia 84 (1981), S. 87-90 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; ecology ; freshwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To attempt a complete review of turbellarian ecology in the time and space available would result in superficiality. Therefore, I have restricted this account to the four basic ecological processes which have and continue to determine flatworm distribution and abundance. These are: (1) historical or zoogeographical events which permit or prevent a species from reaching a habitat; (2) physiological limitations of the species vis à vis the habitat; (3) access to suitable energy sources and (4) the effects of competition, predation and parasitism, referred to collectively as bionomic processes.
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    Notes on the biology of some psammophile Turbellaria of the Black Sea (1981)
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    Hydrobiologia 84 (1981), S. 129-130 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Cercyra ; Pseudomonocelis ; ecology ; reproduction ; feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The biology of two marine turbellarians, Cercyra hastata (Tricladida) and Pseudomonocelis ophiocephala (Proseriata) has been studied over a period of five years. They are the main components of the biocoenosis of the saccocirrus sand of Sevastopol Bay. These species have a significant role in the processes of secondary production and transformation of the organic matter in the coastal zone.
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    Development of cilia in embryos of the turbellarian Macrostomum (1981)
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    Hydrobiologia 84 (1981), S. 231-239 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Macrostomum ; ultrastructure ; ciliogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Electron microscopy of Macrostomum hystricinum raised in culture shows that ciliogenesis in the worm's epidermal blastomeres begins in embryos 39–41 h old with kinetosomal and de novo genesis of presumptive basal bodies, which are morphologically distinguishable from centrioles of the mitotic apparatus, and proceeds by the migration of basal bodies to the apical plasma membrane of the cells and their production there of ciliary axonemes by an age of 51–53 h when the bastomeres emerge between yolk cells on the embryo's surface. Ciliogenesis continues throughout development with the addition of cilia virtually one by one to the expanding epidermal cells' surfaces. At no time in ciliogenesis are stages seen that might show derivation of these multiciliated cells from the primitive monociliated cell type presumably present in the ancestors of the Turbellaria.
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    Ultrastructural observations on paracnids. I: Coelogynopora axi Sopott (Turbellaria, Proseriata) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 253-257 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Proseriata ; Coelogynoporidae ; ultrastructure ; paracnids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ‘Schlauchdrüsen’ or paracnids of Coelogynopora axi Sopott, 1972 consist of two components: a muscle cell and a secretory cell. The secretory cell is provided with a tube, which bears a border of microvilli. In the normal position the tube is situated in the interior of the secretory cell, and the microvilli stand at the inner side of the tube. After expulsion of the tube the microvilli are situated at its free surface. The evagination takes place in response to chemical stimuli and is effected by the contraction of the myofibrils of the muscle cell. The paracnids are supposed to be mechanisms of defense. However, conformities with nematocysts and spirocysts of the cnidarians do not exist. The paracnids in other species of the Coelogynoporidae, for example in Invenusta paracnida (Karling, 1966) and Carenscoilia bidentata Sopott, 1972 differ from those of C. axi in many details.
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    50 years of turbellarian research (1981)
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    Hydrobiologia 84 (1981), S. 1-5 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; T. G. Karling ; biography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    Karyological observations on Polyclads (1981)
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    Hydrobiologia 84 (1981), S. 31-44 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Polycladida ; karyology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A karyological analysis of eight species of Polyclads has been carried out. A chromosome number of n = 10 for Stylochus alexandrinus and for Stylochus mediterraneus was ascertained on germinal lines. A chromosome number of 2n = 20 was ascertained from metaphasic plates from regenerative blastemas of Notoplana alcinoi and Leptoplana tremellaris. A karyometric analysis of this last species permitted the reconstruction of an idiogram. An idiogram was also prepared from metaphasic plates of Stylostomum ellipse obtained from early embryonic mitoses. The chromosome number of this species also was 2n = 20. Chromosome numbers of n = 8 and 2n = 16 were ascertained on germinal lines and metaphasic plates of blastemas in Echinoplana celerrima and on germinal lines and early embryonic mitoses of Stylochoplana maculata. Finally the diploid number 2n = 18 was ascertained on metaphasic plates from regenerative blastema of Yungia aurantiaca.
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    Karyological and taxonomic studies of Dugesia japonica Ichikawa et Kawakatsu in the Far East (1981)
    Springer
    Hydrobiologia 84 (1981), S. 53-68 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; Dugesia ; karyology ; taxonomy ; Japan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A review of previous studies on the taxonomy, karyology and chorology of a polymorphic species Dugesia japonica from the Far East is presented. Two subspecies are now known: D. j. japonica (n = 8, 2x = 16, 3x = 24) and D. j. ryukyuensis (n = 7, 2x = 14, 3x = 21). An attempt has also been made to determine the definition of the B-chromosome as LB and SB and the variation of the karyotypes of both subspecies is described. Every known karyotype of D. japonica is classified into six groups (see Table 2). D. japonica from many localities has a diploid karyotype (2x), a triploid karyotype (3x) and an orthoploidic mixoploid karyotype of 2x & 3x. The origin and the karyological significance of these karyotypes are discussed.
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    Physiological adaptations to entosymbiosis in three species of graffillid rhabdocoels (1981)
    Springer
    Hydrobiologia 84 (1981), S. 147-153 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Graffillidae ; entosymbionts ; physiology ; nutrition ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three entosymbiotic graffillid rhabdocoels (Paravortex scrobiculariae, P. cardii and Graffilla buccinicola) from marine bivalve and gastropod molluscs show several physiological adaptations to their life-style which are intimately related to the nutritional physiology and ecology of their respective hosts. All three species feed on their hosts' partially digested food plus the cellular debris released at the end of the hosts' own digestive cycle. G. buccinicola supplements this diet by actively removing intact cells from the host's digestive epithelium. Host enzymes, ingested with the food, are utilized for digestion within the flatworms' gut; there is concomitant reduction in the types and amounts of endogenous enzymes and the gastrodermal gland cells characteristically found in free-living species are absent. Food reserves in the three species consist mainly of glycogen, following the pattern seen in other entosymbiotic flatworms (Turbellaria, Digenea, Cestoda); in P. scrobiculariae this primary adaptation, believed to be linked in all entosymbiotes to the ready availability of food and to high fecundity, probably has a secondary function, in relation to anaerobic respiration, of the type found in cestodes. Other adaptive features, closely correlated with host ecology, are the occurrence of a physiologically active haemoglobin in the brain and pharynx of P. scrobiculariae and, in this species and P. cardii, the differential occurrence and distribution of dehydrogenase systems concerned with aerobic respiration (Krebs cycle), the pentose phosphate shunt and anaerobic respiration (glycolysis). P. scrobiculariae and P. cardii are viviparous and the normal provision of yolk for embryonic nutrition is supplemented by direct passage of materials to the later larvae from the parental gut, thus facilitating extended development of the larva until its birth as an immature miniature adult.
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    The phyletic status of the Paludicola (1981)
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    Hydrobiologia 84 (1981), S. 7-12 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; Paludicola
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Is the assumption of the monophyly of the Paludicola (freshwater triclads) justified? There seems little doubt on morphological grounds of the close relationship between the Planariidae and the Dendrocoelidae but it is difficult to connect, phylogenetically, the Dugesiidae with these groups. A connection between the former and some of the latter has been unknowingly implied by the author in previous papers, thus raising an anomaly since this would mean that the Dugesiidae are not monophyletic. Is it possible that the Dugesiidae and the Planariidae + Dendrocoelidae have arisen independently from marine ancestors? The implications of such a speculation are examined.
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    Intraspecific pairing of planaria,Dugesia tigrina andDugesia dorotocephala (Platyhelminthes: Turbellaria), and observations on lipophilic excretory-secretory worm products (1982)
    Springer
    Journal of chemical ecology 8 (1982), S. 901-909 
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    ISSN: 1573-1561
    Keywords: Dugesia tigrina ; Dugesia dorotocephala ; Platyhelminthes ; Turbellaria ; planaria ; intraspecific pairing ; chemical attractants ; lipids ; excretory-secretory products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Intraspecific pairing of the planaria,Dugesia tigrina andD. dorotocephala, was studied for 24 hr at 22 ± 1 °C in Petri dish cultures containing an agar substrate and a water overlay. Pairing of fed planaria in the light and dark and starved planaria in the light was studied, and worms in contact or within 5 mm of each other were considered paired. Fed planaria of both species paired significantly in the light and dark, whereas starved planaria did not pair. Our results suggest that worm-emitted chemical factors are involved in intraspecific pairing of planaria. Thin-layer chromatographic analysis was used to study the release of lipophilic worm products. Phospholipids, free sterols, and free fatty acids were detected in all trials, and triglycerides in most. Thin-layer densitometric analysis was used to quantitate the weight of free sterols released by planaria.
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    A comparative study of the food niches of lake-dwelling triclads and leeches (1981)
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    Hydrobiologia 84 (1981), S. 91-102 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Polycelis ; Dugesia ; Dendrocoelum ; Erpobdella ; Glossiphonia ; Helobdella ; serological technique ; diet ; British lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The food niches of four species of triclads and three species of non-parasitic leeches living in the littoral zone of British lakes of different trophic status were investigated, over one year, using a serological technique. Antisera against ten potential prey groups were employed. The basic data were adjusted to compensate for differences in predator size and seasonal changes in field temperatures. Data on two of the leech species have been presented elsewhere, but comparisons of the diet of all seven predator species are made in this paper. Much overlap in diet between the various predator species occurs, but, with one exception, each of the genera has a major food resource. The Polycelis spp. feed extensively on oligochaetes, Dugesia polychroa on molluscs, Dendrocoelum lacteum on Asellus, Erpobdella octoculata on chironomids and Glossiphonia complanata on molluscs. Helobdella stagnalis is a generalist feeder. Problems of coexistence of the leech species, and of the leech and triclad species are discussed.
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    Oxygen availability, redox and the distribution of some Turbellaria Schizorhynchidae and other forms (1981)
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    Hydrobiologia 84 (1981), S. 103-112 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; distribution ; oxygen availability ; redox ; phylogeny
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    Topics: Biology
    Notes: Abstract Records from a considerable number of meiofaunal samples are reexamined in relation to the depth within sediment distribution of various taxa especially Schizorhynchidae and the main turbellarian orders. Frequency and density records in samples with particular oxygen flow rates and redox potentials confirm that the ranges of Schizochilus, Proschizorhynchus and Neoschizorhynchus spp. within these factors may help account for congeneric occurrence within cores. However, statistical analysis of the records is seldom able to confirm apparent differences. There is, for example, a statistically significant difference in distribution in relation to redox potential between the red schizorhynchians Pseudoschizorhynchides ruber, Diascorhynchus rubrus and the red acoelan Paratomella rubra but not in relation to oxygen availability and depth within sediment. On one beach Gnathostomula aff. paradoxa was found at Eh and O2 availability values under which it must be assumed to be living anaerobically. Contingency and other analyses are extended to differences between higher taxa and the results discussed in relation to habitat evolution of the Turbellaria. The suggestion that structural complexity of turbellarians has increased with increased oxygenation of the environment is tentatively supported.
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    The diet of three species of umagillid neorhabdocoel turbellarians inhabiting the intestine of echinoids (1981)
    Springer
    Hydrobiologia 84 (1981), S. 155-162 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Umagillidae ; symbiosis ; nutrition ; Syndisyrinx ; Syndesmis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three species of umagillid turbellarians were found to have different nutritional relationships with their echinoid hosts: Syndisyrinx franciscanus ingests host intestinal tissue and ciliates that are symbiotic in the intestine of the host; Syndesmis dendrastrorum consumes intestinal tissue and materials that have been ingested by the host; an umagillid that closely resembles Syndesmis echinorum subsists entirely on host intestinal tissue.
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    The problem of cell totipotency, dedifferentiation and transdifferentiation in Turbellaria (1981)
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    Hydrobiologia 84 (1981), S. 171-179 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; cell differentiation ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    Quantitative analysis of cell types during growth, degrowth and regeneration in the planarians Dugesia mediterranea and Dugesia tigrina (1981)
    Springer
    Hydrobiologia 84 (1981), S. 181-194 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia ; cell types ; growth ; degrowth ; regneration ; maceration-technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method of tissue maceration (dissociation) of planarian tissues into single cells was used to characterize the basic cell types in the planarians Dugesia mediterranea and Dugesia tigrina, and to determine the total cell number and distribution of cell types during growth, degrowth and regeneration. Using this method, 13 basic cell types have been determined for both species. The total number of cells increases with body length and volume whereas the distribution of cell types is only slightly affected. Growth and degrowth occur mainly through changes in total cell number leaving cell distribution only moderately affected. During regeneration, an increase in neoblast density in the blastema followed later on by increases in nerve cells are the more significant changes detected. These results are discussed in relation to mechanisms of cell renewal, blastema formation and maintenance of tissue polarity.
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    On some commensal Turbellaria of the Canadian East Coast (1981)
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    Hydrobiologia 84 (1981), S. 131-137 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Crustacea ; Mollusca ; commensalism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The brachyurans Chionoecetes opilio and Hyas araneus collected from the east coast of Canada harbour two species of commensal turbellarians. Ectocotyla hirudo (Levinsen) and E. multitesticulata Fleming & Burt are found on the gills and branchial chambers of male and female crabs. The molluscs Crassostrea virginica and Mytilus edulis collected from several locations where they are cultured along the Northumberland strait carry two commensal eulecithophoran turbellarians, both on the gills, viz., Urasloma cyprinae (Graff) and Paravortex gemellipara (Linton), the latter being a new host record. Aspects of the biology and life-history of these turbellarians are discussed, especially in relationship to the biology of their hosts.
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    Reproductive biology of Dugesia sanchezi, a fresh-water planarian from Chile (1981)
    Springer
    Hydrobiologia 84 (1981), S. 163-165 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia ; karyology ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dugesia sanchezi reproduces in nature both sexually and by fission. Laboratory cultures have shown that fissioning is controlled by genetic factors. From sexual specimens randomly mated, 105 sexual and five fissiparous offspring were obtained. The former produced almost exclusively sexual descendents while the latter gave rise to fissiparous individuals, although successively many of them became sexual. These ex-fissiparous specimens show a high fertility and their offspring were almost all fissiparous, with the same characteristics displayed by the preceeding fissiparous generation. Some hypotheses are advanced in order to attempt a genetical interpretation of these results.
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    Relationship between variations of cAMP, neuromediators and the stimulation of nucleic acid synthesis during planarian (Polycelis tenuis) regeneration (1981)
    Springer
    Hydrobiologia 84 (1981), S. 195-201 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; regeneration ; cAMP ; neuromediators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regenerating planarians of the species Polycelis tenuis have been studied with respect to the two distinct phases which occur during regeneration, viz., the first 24 h involving cellular activation, and the following days when differentiation of the blastema occurs after a period of cellular proliferation. We have studied particularly the biochemical events that control regeneration with respect to the nature of the signals which induce cellular activation, the membrane receptors of these signals, and the consequences of these signals for the cellular metabolism of DNA, RNA and proteins. The roles of neurohormones such as serotonin, dopamine, and noradrenaline are assessed, and a provisional model of the process of cellular activation is proposed which takes account of all the information that is now available concerning planarian regeneration.
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    Morphology of the Turbellaria at the ultrastructural level (1981)
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    Hydrobiologia 84 (1981), S. 213-229 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; morphology ; ultrastructure ; body wall ; nervous system ; protonephridia ; parenchyma ; digestive system ; reproductive system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper reviews the following systems: body wall, nervous system, protonephridia, parenchyma, digestive system, reproductive system, and includes a summary of the literature. New information is presented for the catenulid and neoophoran body wall-construction, the kalyptorhynch proboscis, the catenulid and haplopharyngid protonephridial construction, and the prolecithophoran spermatozoon and female germ cell. Examples of new features, as well as examples of how electron microscopy has clarified the relative position of structures and their substructures are given from the subcellular level to the organization of whole organs. Fine structural features linking different turbellarian orders are summarized. They apparently support Karling's (1974) latest assessment of the affinities between the turbellarian orders which is based primarily on light histological data, they add the recognition of a special link between the Macrostomida and Haplopharyngida and they suggest the existence of three main evolutionary lines within the Turbellaria.
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    A new species of freshwater turbellarian from Africa, predatory on mosquitoes: Mesostoma zariae n. sp. (Typhloplanoida) (1981)
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    Hydrobiologia 84 (1981), S. 19-22 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Typhloplandoe ; Mesostoma zariae
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    Topics: Biology
    Notes: Abstract A new species of the genus Mesostoma Ehrenberg 1935, M. zariae n.sp. is described and its relationship discussed. The new species belongs to the M. lingua species-group and is characterised by the presence of two kinds of prostate secretions and a pear-shaped penis papilla. It occurs in small standing or slowly running waters at Zaria, Nigeria. It has previously been proven (Mead 1978) that this species is predatory on the aquatic stages of mosquitoes.
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    Contrasting power of the factors for fission and sexuality in a polyploid planarian (1981)
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    Hydrobiologia 84 (1981), S. 167-169 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia ; reproduction ; karyology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One of the biotypes of the planarian Dugesia benazzii is triploid in the somatic line, hexaploid in the female line owing to a chromosome set doubling, and diploid in the male line due to a haploid set elimination. In a population of this biotype only 50% of the oocytes are hexaploid, the others being triploid as a results of the lack of set doubling; the male line is always diploid. After a long period of laboratory culture most of the individuals became asexual and fissiparous. Almost all the oocytes of the few specimens which have remained sexual showed triploid complement; B-chromosomes also appeared. These events represent the manifestation of a new genetic background which act upon the two germ lines in different ways and moments. These topics are discussed.
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    Studies on the speciation of Japanese freshwater planarian Polycelis auriculata based on the analysis of its karyotypes and constitutive proteins (1981)
    Springer
    Hydrobiologia 84 (1981), S. 69-77 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; karyology ; mixoploidy ; electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Various kinds of chromosomal polymorphisms or karyotypic variations are found in the Japanese freshwater planarian Polycelis auriculata. Within this species, there are found worms whose chromosome numbers are 2n = 6, 10, 11, 12 and others, and 3x = 6 and 9. There are some which have cells with triploidy and tetraploidy complements (3x = 6 & 4x = 8), and others which have cells with triploidy and hexaploidy complements (3x = 6 & 6x = 12). These worms with such varied karyotypes are usually found in separate habitats, though occasionally they occur together. Electrophoretic analysis of the proteins extracted from the karyotipically different worms which belong to three different local populations shows some dissimilarity in the constitutive proteins according to their karyotypic differences. The results obtained suggest that this species is still in the process of speciation or chromosomal evolution.
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    Cell activation during regeneration of planarians (1981)
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    Hydrobiologia 84 (1981), S. 203-207 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; regeneration ; neurohormones ; adenylate cyclase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Planarians are a good subject for studies of cell differentiation. Each multicellular organism is maintained by continuous production, differentiation and ageing of cellular elements. Each cell has a specific position defined by specific regional boundaries. After amputating a part of the body this positional information changes, involving, probably, the first range of cellular activation, the activation of membrane receptors. At the same time in an injured organism the level of neurohormones, which can be now coupled with activated receptors, increases. In the opinion of many authors neurohormones act on the regenerative cells through the medium of adenylate cyclase. This enzyme converts ATP to cAMP and by means of this cyclic nucleotide the second range of cellular activation is initiated i.e. changes of activation of cAMP dependent protein kinases. The sequence of these processes plays the principal role in the ensuing cell differentiation.
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    Studies on the speciation of the European freshwater planarians Polycelis nigra and Polycelis tenuis based on the analysis of enzyme variation by means of iso-electric focusing (1981)
    Springer
    Hydrobiologia 84 (1981), S. 79-86 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; Polycelis ; speciation ; Europe ; enzyme variation ; iso-electric focusing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polycelis nigra Ehrenberg and Polycelis tenuis Ijima differ morphologically and karyologically. No difference, however, was found in the isozyme pattern of malate dehydrogenase and tetrazolium oxidase, indicating a close relationship. Most sibling species differ at half of the loci. It could be deduced that the reproductive behaviour of a single population of Polycelis nigra in a Dutch pond was not panmictic. Two genetically different strains retained their identities during two years of observation. If pseudogamy occurs in this diploid planarian, the presence of heterozygous specimens indicates the absence of a true meiosis. The iso-electrofocusing technique by which these population-genetical studies were carried out, also lends itself to a comparison of overall protein banding patterns. The membrane proteins especially are conservative. The sodium dodecyl sulphate extracted proteins of Polycelis nigra-tenuis, Planaria torva and Phagocata vitta were very similar, while their water soluble proteins were not. This technique may be of great help in taxonomic studies of the higher taxa.
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    Sand dwelling Turbellaria from the Netherlands Delta area (1981)
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    Hydrobiologia 84 (1981), S. 113-127 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; meiobenthos ; fauna composition ; taxonomy ; Netherlands Delta area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sand dwelling Turbellaria from the Delta of the Rivers Rhine, Meuse and Scheldt have been investigated. Thirty-eight samples taken from littoral and sublittoral stations in the Grevelingen, Eastern and Western Scheldt have been analysed. Thirty-three species were recorded (Acoela were not considered); twenty-four of them are new for the area and seven new species are described. Density and diversity of Turbellaria were higher in the Eastern Scheldt than in the Western Scheldt or in the Lake Grevelingen. A maximum density of 82 ind./100 cm3 was noted. A tentative calculation on relative abundance of the representatives of the different Turbellaria orders is established. Proseriata seem to be dominant in the localities studied.
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    New England Coelogynoporidae (1981)
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    Hydrobiologia 84 (1981), S. 139-145 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Proseriata ; Coelogynoporidae ; taxonomy ; New England
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eleven species of the proseriate turbellarian family Coelogynoporidae have been encountered between Cape Cod, Mass. and the southern shore-line of New Brunswick, Canada. The distributions of Coelogynopora schultzii, C. biarmata and Cirrifera cirrifera are reported. Four new species belonging to the genus Coelogynopora, one new species of Cirrifera and a species belonging to a new genus are described. Two species remain undescribed. Biological observations on a laboratory-reared colony of C. biarmata maintained since 1978 are reported.
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    Paravortex karlingi sp. nov. from Cerastoderma edule L., in Britain (1981)
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    Hydrobiologia 84 (1981), S. 23-30 
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    ISSN: 1573-5117
    Keywords: Turbellaria ; Neorhabdocoela ; Paravortex ; parasites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paravortex karlingi sp. nov. collected from the intestine of the bivalve mollusc Cerastorderma edule from the Ythan Estuary, N. E. Scotland, and elsewhere, is distinguished from a closely related species, P. cardii, also occurring in this host, on the basis of differences in habitat occupied by the two species as well as behavioural and morphological differences. P. karlingi is smaller, has fewer embryos in the gravid adult and shows a different behaviour pattern when released from the host intestine. It is also negatively phototactic whereas P. cardii is initially positively phototactic, only later becoming negatively phototactic. The occurrence of both species in Britain is briefly described.
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    The geographical and bathymetrical distribution of the Fecampiidae (Turbellaria, Rhabdocoela) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 13-16 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Rhabdocoela ; Fecampiidae ; parasites ; crustaceans ; distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All members of the Fecampiidae are endoparasites. Since 1964 when only four species were known, four new species and 11 cocoon types, made by as many unknown species, have been described. The Fecampiidae are distributed in all major oceans from shallow waters to more than 5000 m depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026157
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  • 81
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    Adenylate cyclase in regenerating tissues of the planarian Dugesia lugubris (O. Schmidt) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 209-212 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia lugubris ; regeneration ; ultracytochemistry ; adenylate cyclase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adenylate cyclase (AC) was localized ultracytochemically in certain tissues of the regenerating planarian Dugesia lugubris. Studies were carried out from one hour after injury up to the 5th day of regeneration. It was found that the greatest amount of active AC appears during the initial hours of regeneration in the membranes of the muscle cells near the wound, in the epithelial cells surrounding the wound, and in rhabdite-forming cells and neoblasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026182
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  • 82
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    The system of epidermal ciliary rootlets in Turbellaria (1981)
    Springer
    Hydrobiologia 84 (1981), S. 240-240 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Acoela ; ultrastructure ; ciliary rootlets ; glycogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The rootlets of the kinetic cilia form patterns of different types in the different turbellarian subgroups (cf. Rieger 1981). In the Acoela a rather complex system of ciliary rootlets is found in the epidermis (Dorey 1965; Hendelberg & Hedlund 1973; Bedini & Papi 1974). In the acoel Childia groenlandica (Levinsen) the four rootlets of each cilium make contact with those of adjacent cilia at two levels (Hendelberg & Hedlund 1974). Distinct granules are found in the interior of the main rootlets (Hendelberg & Hedlund 1974; Bedini & Papi 1974, Fig. 16) and basal bodies (Silveira 1972; Hendelberg & Hedlund 1974) of the epidermal kinetic cilia of acoels. Similar granules, probably of identical structure, can be seen in nemertodermatids, in the same positions (Tyler & Rieger 1977, Figs. 3 & 6). Such granules were studied in C. groenlandica with histochemical methods adapted for electron microscopy. Like Silveira (1972) I found the granules of the basal bodies to be Thiéry-positive, and thus evidently to be made up of or at least to contain polysaccharide material. The granules of the main rootlets were also found to be Thiéry-positive (Hendelberg 1976). Digestion experiments (Hendelberg & Hellmén 1978 and unpublished results) strongly support the concept that the granules are glycogen beta-particles. We know that cilia can function as kinetic organelles without any rootlets. But we are still uncertain about the function of the rootlets when occurring. Most probably they form an anchorage, a function which may be favoured by branching rootlets making contact with each other. Another function which has been discussed is the transmittance of impulses regulating the ciliary beat. Glycogen granules represent an energy deposit. The functional implication of these granules in the interior of the ciliary rootlets and basal bodies is not clear. However, the observations raise the question of how energy is transmitted to the cilia. Are the ciliary rootlets, when occurring, involved? This question will be further discussed, with references, in a future full report on the digestion experiments (to be published elsewhere).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026185
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  • 83
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    Ultrastructure of the eye of Urastoma cyprinae (Turbellaria, Alloeocoela) (1981)
    Springer
    Hydrobiologia 84 (1981), S. 276-276 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; ultrastructure ; eye ; Urastoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Urastoma cyprinae (Graff) is a microturbellarian which has been recorded both as a free-living organism by Westblad (1955) and Marcus (1951) and as a commensal in various lamellibranch molluscs (see Burt & Drinnan 1968). The material used in this study came from oysters, Crassostroea virginica, collected off the coast of Prince Edward Island, in which hosts it occurs in large numbers especially during the summer months when the oysters are spawning (Fleming et al. 1981). When U. cyprinae is exposed to light as happens, for example, when an oyster is opened, it shows a marked negative phototactic response. Preliminary work on the fine structure of the photoreceptors in U. cyprinae shows that the two eyes each consists of: (1) a single cup cell full of relatively large, electron-dense pigment granules; (2) a tripartite conical lens system; and (3) what appear to be two photosensitive rhabdomes. The pigment cup cell has a single, well defined nucleus situated basally and close to the membrane of the pigment cell furthest away from the rhabdomeres. The lens system consists of a cone made up of three, separate but equal, parts. Each part has two, flat inner surfaces which join at an angle of 120°, an outer rounded surface, and a rounded upper surface. When these three parts fit together, the cone-shaped lens is formed with the apex of the lens within the ‘cup’ of the pigment cell and the rounded, convex, broad end of the cone lying more or less at the same level as the top of the pigment cup and below the epidermis layer. The rhabdomeres lie between the electron dense lenses and the inside of the pigment cup. They show connections to the visual cells which are bipolar: one extension joining the rhabdomeres; the other constituting the axon which extends into the centrally situated brain or into the longitudinal, lateral nerves. The axons that enter the brain, form connections with other axons from the other eye. The axons that extend posteriorly in a lateral position, presumably play a role in facilitating the avoidance reaction. The chemical nature of the unusual lens has not yet been determined. This is presently under investigation and will be reported later at which time our work will be discussed in relation to other types of rhabdomeric eyes in the Turbellaria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026190
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  • 84
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    Ultrastructure of epidermal eyespots of Microstomum lineare (Turbellaria, macrostomida) (1980)
    Springer
    Cell & tissue research 210 (1980), S. 21-32 
    Details
    ISSN: 1432-0878
    Keywords: Eyespots ; Photoreceptor ; Chemoreceptor ; Turbellaria ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The eyespots of Microstomum lineare were studied by electron microscopy, light microscopy, and fluorescence microscopy. Each eyespot consists of two ciliary photoreceptor cells shielded by pigment cells and additional sensory cells. The photoreceptor cells are characterized by a distal intracellular cavity lined with 50–100 interwoven cilia. The other sensory cells are of two ultrastructurally different types, one with long cilia predominating and the other with balloonlike cilia. The pigment cells, which envelop processes of the sensory cells, contain pigment vacuoles varying in size and content and give a bright red fluorescence by the Falck-Hillarp method. The eyespots are suggested to perform a dual function as photoreceptors and chemoreceptors. The evolutionary significance of ciliary photoreceptors in Turbellaria is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232138
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  • 85
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    The nervous system of Microstomum lineare (Turbellaria, Macrostomida) (1980)
    Springer
    Cell & tissue research 211 (1980), S. 31-40 
    Details
    ISSN: 1432-0878
    Keywords: Nervous system ; Turbellaria ; Fluorescence histochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The nervous system (NS) of Microstomum lineare (Turbellaria, Macrostomida) was studied by electron and light microscopy, combined with fluorescence histochemistry (Falck-Hillarp method for biogenic monoamines). The NS is primitively organized, with a bilobed brain, two lateral nerve cords lacking commissures, and peripheral nerve cells scattered along the nerve cords. The stomatogastric NS, with a pharyngeal nerve ring, is joined to the central NS by a pair of connective ganglia. A green fluorescence in all parts of the NS indicates catecholaminergic neurons as the dominant neuron type. Ultrastructurally, two types of neurons were identified on the basis of their vesicle content: 1. Aminergic (catecholaminergic) neurons containing densecore vesicles of varying electron-density and size, i.e., small dense-core vesicles (diameter 50–100 nm), vesicles with a highly electron-dense core (60–140 nm), and vesicles with an eccentric dense-core. 2. Presumed peptidergic neuro-secretory neurons containing large granular vesicles (diameter about 200 nm) in the stomatogastric NS and peripheral parts of the central NS. In light microscopy, paraldehyde-thionin stained neurons were observed in the same areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233720
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  • 86
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    The nervous system of Microstomum lineare (Turbellaria, Macrostomida) (1981)
    Springer
    Cell & tissue research 218 (1981), S. 375-387 
    Details
    ISSN: 1432-0878
    Keywords: Nervous system ; Turbellaria ; Synaptic contacts ; Release of neurosecretory material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of release sites of neurochemical messenger substances in the microturbellarian Microstomum lineare was examined. Aminergic neurites form conventional synapses and synapse-like structures (SLS). Variants of true synapses include: “single” synapses with symmetric pre- and postsynaptic densities, “shared” synapses, i.e., contacts between 1 pre- and 2 postsynaptic fibres, en passant synapses between parallel axonal membranes, and synapses without thickenings having only clustered vesicles in the presynaptic terminal. SLS on a nerve cell soma or facing an intercellular stromal channel near muscles are described. Peptidergic neurites containing large granular vesicles (LGV) form synaptoids and signs of putative neurosecretory release. Synaptoids between neurites and between neurite and muscle have lucent vacuoles (about 100nm) and dense material at the contact site. In en passage synaptoids dense-core vesicles are embedded in electron-dense material at the contact site. Putative signs of release of neurosecretory material other than “typical” exocytosis have been observed.
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    URL: http://dx.doi.org/10.1007/BF00210351
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