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  • 1
    Electronic Resource
    Electronic Resource
    Electrical impedance analysis in plant tissues: on the biological meaning of Cole-Cole α in Scots pine needles (1995)
    Springer
    European biophysics journal 24 (1995), S. 99-106 
    Details
    ISSN: 1432-1017
    Keywords: Pinus sylvestris L. (Scots pine) ; Electrical impedance ; Membrane capacitance ; Transmission line ; Cole-Cole α ; Air space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Electrical impedance spectra (80 Hz–1 MHz) in Scots pine needles were found to be characterized by spectrum skewness in the Cole-Cole plot. These spectra were subjected to analysis with two distributed models: (i) the Cole-Cole function and (ii) an equivalent circuit which takes account of the presence of air spaces within the needles (Model-A). In analysis with untreated needles (without artificial infiltration with water), Model-A fitted better than the Cole-Cole function to the experimental data. After infiltration of water into the needles, the extent of spectrum skewness was substantially decreased compared with the pre-infiltration condition and the Cole-Cole function fitted better than Model-A to the measured impedance data. The Cole-Cole α decreased from 0.47 in non-infiltrated needles to 0.42 in the infiltrated needles. The exceptionally large value of α in non-infiltrated needles can be explained by the presence of air spaces, which produce transmission line properties in the mesophyll. In support of the validity of Model-A, this new model provided specific membrane resistances of 1190 ± 83 Ω cm2 in cold hardened and non-hardened needles respectively. These specific membrane resistance are comparable with previous reports of membrane resistances in other biological systems. It is concluded that in this exceptionally spongy tissue, Cole-Cole α is likely to be due to the effects of the transmission line properties of cells which are surrounded by air spaces and only thin cell walls outside the insulating cell membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211405
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  • 2
    Electronic Resource
    Electronic Resource
    A mechanism for the pinocytosis of latex spheres by tomato fruit protoplasts (1971)
    Springer
    Journal of bioenergetics and biomembranes 2 (1971), S. 371-382 
    Details
    ISSN: 1573-6881
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Plant protoplasts isolated from tomato fruit locule tissue take up 0·12 μ polystyrene latex spheres by an endocytotic process. Freeze-etching enables the process to be clearly visualized in the electron microscope and provides important data from face view membrane fractures. When protoplasts are glutaraldehyde fixed prior to mixing with latex, the spheres adhere to the plasmalemma and cause some localized membrane distortion. This shows that adhesive forces are sufficient to initiate the invagination process. Freeze-etch membrane fracture faces carry numerous granules, the density of which is lower in the invaginating region. This reduction is in accordance with the expected value if only that part of the membrane which comes in intimate contact with the sphere expands to surround it. There is no change in the granule densities in the surrounding membrane. In fractured membrane surface views distinct phases can be delimited, and their relative occurrence indicates that the second half of the invagination process (i.e. after the diameter of the sphere has reached the membrane plane) is some thirty times quicker than the first half. It is proposed this indicates operation of surface tension forces during the fast phase, and it may be that cellular energy is required only for the initial slow phase of membrane expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01963831
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  • 3
    Electronic Resource
    Electronic Resource
    Cell-wall regeneration by isolated tomato-fruit protoplasts (1967)
    Springer
    Protoplasma 64 (1967), S. 460-480 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using both light microscopy and electron microscopy of thin sections, and surface replicas, it has been shown that isolated tomato fruit locule tissue protoplasts regenerate a new cell wall when maintained in suitable culture media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666544
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  • 4
    Electronic Resource
    Electronic Resource
    An examination of the developing cotton fiber: Wall and plasmalemma (1977)
    Springer
    Protoplasma 92 (1977), S. 21-41 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of developing cotton fibers has been examined using novel modifications of the techniques of surface replication, freeze-etching and thin-sectioning. The fiber surface was found to be coated with a lamellar cuticle, which is stretched and thinned as the fiber elongates. It is marked by bars which run parallel with the fiber long axis. Beneath the cuticle, the outermost microfibrils of the primary wall lie parallel with the fiber axis, while those adjacent to the plasma membrane are transverse. Primary wall microfibrils are present in bundles, disposed in left-handed and right-handed helices, which correspond with the fibrils observed optically. Microfibrils within bundles form in-phase waves, with wavelengths and amplitudes in the ranges 0.3–7 μm and 0.01–0.1 μm in primary and secondary walls respectively. As elongation proceeds bundles become displaced towards the cell axis. Microfibrils of the secondary wall, disposed around the cell as fast helices, are similarly bundled and wavy (though with a reduced amplitude). In surface-replicas, large (20–30 nm) granules are present on the cytoplasmic face of the wall which probably correspond with 20–40 nm low prominences visible on freeze-etch EF plasma membrane fracture faces. It is proposed that these may be microfibril-synthesizing centers. Plasma membranes fracture such that the membrane-associated-particles segregate 60∶40 between P and E fracture moieties, but the prominence and total number of these particles is reduced at the stage of secondary wall formation as compared with primary wall formation. Beneath the plasmalemma the axes of microtubules parallel secondary wall microfibril orientation. Cross-bridges, which stain heavily after glutaraldehyde/tannic acid fixation, link microtubules to plasma membrane. The use of butyl benzene to cement fragments of cotton fibers, employed in this work, may prove useful in other freeze-etch studies of long fibers which are readily ruptured during preparation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280198
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  • 5
    Electronic Resource
    Electronic Resource
    Bodies of wall-like material (“wall-bodies”) produced intracellularly by cultured isolated protoplasts and plasmolysed cells of higher plants (1974)
    Springer
    Protoplasma 82 (1974), S. 223-236 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Unusual bodies are of general occurrence in cultured protoplasts isolated from tomato “Ailsa Craig” fruit locule tissue. They are also common in the equivalent cultured plasmolysed tissue, but do not occur when the culture medium is non-plasmolysing. Similar bodies are of universal occurrence in cultured protoplast spontaneous fusion bodies from tobacco “Xanthi” leaves, but are not found when the cultured protoplasts are not initially fused. Bodies also occur in cultured protoplasts isolated from leaves of rye “Dominant”. They do not occur in cultured protoplasts from rose “Paul's Scarlet” cells. These bodies have been studied by light and electron microscopy. Schiff and periodic acid—Schiff—phosphotungstic acid stains indicate the presence in them of cellulose, and this is also suggested by their fluorescence with calcofluor and their appearance in the electron microscope. Some of them fluoresce with aniline-blue. Some material within the bodies stains with phosphotungstic acid-chromic acid, suggesting that some of the contents of the bodies is plasmalemma-like. The bounding membrane is only partly stained with phosphotungstic acid-chromic acid. There is a general parallel between the composition of the wall regenerated by the protoplasts and the composition of these bodies, and between the timing and extent of their development and that of the regenerated wall. On the basis of these observations, these bodies are named “wall-bodies” and regarded as composed of similar materials to those making up the regenerated wall. The observations, especially of wall-body production by tobacco fusion bodies, strongly suggest a plasmalemma origin for the membranes of the vesicles in which these bodies arise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276309
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  • 6
    Electronic Resource
    Electronic Resource
    A model for the pattern of deposition of microfibrils in the cell wall of Glaucocystis (1978)
    Springer
    Planta 141 (1978), S. 51-58 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall ; Cellulose ; Freeze-etching ; Glaucocystis ; Microfibrils (cellulose) ; Morphogenesis ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freeze-fracturing of Glaucocystis nostochinearum Itzigsohn cells during cell-wall microfibril deposition indicates that unidirectionally polarized microfibril ends are localized in a “zone of synthesis” covering about 30% of the sarface area of the plasma membrane. Within this zone there are about 6 microfibril ends/μm2 cell surface. It is proposed that microfibrils are generated by the passage of their tips over the cell surface and that the pattern of microfibril organization at the poles of the cells, in which microfibrils of alternate layers are interconnected at 3 “rotation centres”, results directly from the pattern of this translation of microfibril tips. In a model of the deposition pattern it is proposed that the zone of synthesis may split into 3 sub-zones as the poles are approached, each sub-zone being responsible for the generation of one rotation centre. It is demonstrated that the microfibrillar component of the entire wall could be generated by the steady translation of the microfibril tips (at which synthesis is presumed to occur) over the cell surface at a rate of 0.25–0.5 μm min-1. Microcinematography indicates that the protoplast rotates during cell-wall deposition, and it is proposed that this rotation may play a role in the generation of the microfibril deposition pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387744
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cell wall of bromegrass (Bromus inermis Leyss) cell suspension culture (1986)
    Springer
    Plant cell reports 5 (1986), S. 448-451 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thin sections of a bromegrass (Bromus inermis Leyss) cell suspension culture, examined electron microscopically, revealed unusual, often lens-shaped, spaces in cell walls. Freeze-fracture replicas of similar material demonstrated the presence of lamellae within the cell walls, both within comparable lens-shaped spaces and more extensively at cell wall surfaces. The cell wall also displayed strong yellow-green autofluorescence. It is proposed that lipidic material is present in these cell walls, the chemical identity of which is presently under investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269639
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  • 8
    Electronic Resource
    Electronic Resource
    Plant cell-wall microfibril disposition revealed by freeze-fractured plasmalemma not treated with glycerol (1975)
    Springer
    Planta 126 (1975), S. 93-96 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The plasmalemmata of root tip cells of Phaseolus vulgaris L. appear to be well preserved in freeze-fractured material in which no glycerol pre-treatment has been used. The plasmalemmata retain the impressions made by the microfibrils and pit-fields of the cell walls against which these membranes are pressed in turgid cells. Material freeze-fractured in this way is therefore more suitable than glycerol-treated material (in which these impressions are not retained) for the study of membrane features which may be related to microfibril synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389363
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  • 9
    Electronic Resource
    Electronic Resource
    Further observations on cell-wall formation around isolated protoplasts of tobacco and tomato (1978)
    Springer
    Planta 140 (1978), S. 53-58 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall ; Cellulose ; Lycopersicum ; Nicotiana ; Plasmalemmasomes ; Plasma membrane ; Protoplasts ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freeze-etch observations of protoplasts isolated from tobacco (Nicotiana tabacum L.) mesophyll tissue and tomato (Lycopersicum esculentum Mill.) fruit locule tissue are described which clarify earlier observations (Burgess, J., Fleming, E.N., Planta 131, 173–178, 1976; Planta 133, 267–273, 1977), obtained using scanning electron microscopy. of “fibres” associated with “projections” from these cell surfaces. It is demonstrated (1) that the “fibres” consist of bundles of small numbers of microfibrils which have become artifactually thickened by the deposition of coating materials, and (2) that the apparent association between “fibres” and “projections” results from microfibrils being lifted preferentially from protoplast surfaces in regions rich in “projections” (plasmalemmasomes). With the higher resolution available using freeze-etching it can be demonstrated that microfibril deposition does not occur in discontinuous zones on these protoplast surfaces. Globules associated with microfibril termini in radish (Raphanus sativus L.) roots are illustrated and it is proposed that turgor pressure differences between isolated protoplasts and intact tissue may account for the absence of similar globules from isolated protoplast surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389379
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  • 10
    Electronic Resource
    Electronic Resource
    Wheat tissues freeze-etched during exposure to extracellular freezing: distribution of ice (1985)
    Springer
    Planta 163 (1985), S. 295-303 
    Details
    ISSN: 1432-2048
    Keywords: Frost damage ; Ice in tissue ; Temperature (freezing) ; Triticum (freezing, stress)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pieces excised from leaf bases and laminae of seedlings of Triticum aestivum L. cv. Lennox were slowly frozen, using a specially designed apparatus, to temperatures between 2° and 14° C. These treatments ranged from non-damaging to damaging, based on ion-leakage tests to be found in the accompanying report (Pearce and Willison 1985, Planta 163, 304–316). The frozen tissue pieces were then freeze-fixed by rapidly cooling them, via melting Freon, to liquid-nitrogen temperature. The tissue was subsequently prepared for electron microscopy by freeze-etching. Ice crystals formed during slow freezing would tend to be much larger than those formed during subsequent freeze-fixation. Ice crystals surrounding the excised tissues were much larger in the frozen than in the control tissues (the latter rapidly freeze-fixed from room temperature). Large ice crystals were present between cells of frozen laminae and absent from controls. Intercellular spaces were infrequent in control leaf bases and no ice-filled intercellular spaces were found in frozen leaf bases. Intracellular ice crystals were smaller in frozen tissues than in controls. It is concluded that all ice formation before freeze-fixation was extracellular. This extracellular ice was either only extra-tissue (leaf bases), or extra-tissue and intercellular (laminae). Periplasmic ice was sometimes present, in control as well as slowly frozen tissues, and the crystals were always small; thus they were probably formed during freeze-fixation rather than during slow freezing. The plasma membrane sometimes showed imprints of cell-wall microfibrils. These were less abundant in leaf bases at 8° C than in controls, and were present on only a minority of plasma membranes from laminae. Therefore, extracellular ice probably did not compress the cells substantially, and changes in cell size and shape were possibly primarily a result of freezing-induced dehydration. Fine-scale distortions (wrinkles) in the plasma membrane, while absent from controls, were present, although only rarely, in both damaged and non-damaged tissues; they were therefore ice-induced but not directly related to the process of damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395139
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