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  • 1
    Electronic Resource
    Electronic Resource
    Water droplets in intercellular spaces of barley leaves examined by low-temperature scanning electron microscopy (1985)
    Springer
    Planta 166 (1985), S. 335-340 
    Details
    ISSN: 1432-2048
    Keywords: Apoplast ; Evaporation sites (leaf) ; Intercellular space ; Hordeum (apoplasmic water) ; Leaf (apoplasmic water) ; Water (apoplasmic, leaf)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Low-temperature scanning electron microscopy was used to examine fracture faces in leaf blades taken from well-watered or drought-stressed barley (Hordeum vulgare L. cv. Mazurka) seedlings. The leaf blades were freeze-fixed while hydrated and were examined with or without gold-coating. There were ‘droplets’ (with a smooth surface at the resolution achieved) on the surface of cell walls in leaf blades (0.91 g-1 water content) from well-watered seedlings grown in an environment of 67% relative humidity. These were mainly on the vascular bundle sheath, the guard and subsidiary cells, and on some mesophyll cells around the substomatal cavity and between the stoma and vascular bundle. The droplets occurred, more abundantly, in the same places in seedlings from 100% relative humidity. They occurred on a few guard cells from wilting leaf blades (0.81 g·g-1 water content) and were absent from severely drought-stressed leaf blades (0.15 g·g-1 water content). The droplets sublimed at the same moment as both water which was in leaf cells and water which was allowed to condense (after freeze-fixation) on the wall surface. It is suggested that the droplets are aqueous. Their possible origin and importance is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401170
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural damage due to freezing followed by thawing in shoot meristem and leaf mesophyll cells of tall fescue (Festuca arundinacea Schreb.) (1977)
    Springer
    Planta 134 (1977), S. 159-168 
    Details
    ISSN: 1432-2048
    Keywords: Festuca ; Frost damage ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tillers of Festuca arundinacea Schreb. were subjected to-8°C in a bath of methylated spirits for three-quarters of an hour. They were thawed at room temperature and some material taken from the shoot apical meristem and leaf blade for electron microscopy. Similar material was taken from control plants for electron microscopy. Nine tillers subjected to-8°C and thawed subsequently failed to regrow. Nine control tillers regrew. All the treated meristem cells and about half the treated leaf mesophyll cells were extensively altered. Their nuclei were contracted, organelles were swollen or partly disrupted, plasmalemma and nuclear membranes were broken or absent and vacuoles were sometimes disrupted. Strongly osmiophilic material accumulated in the vicinity of membranes. About half the leaf mesophyll cells differed from the control mesophyll cells only in having more spherosomes and narrower thylakoids. Parallels with other ultrastructural studies of stress damage and the indications the results give of possible primary damaging events are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384966
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    A freeze-etch study of the effects of extracellular freezing on cellular membranes of wheat (1985)
    Springer
    Planta 163 (1985), S. 304-316 
    Details
    ISSN: 1432-2048
    Keywords: Frost damage ; Membrane reorganization ; Plasma membrane ; Temperature (freezing) ; Triticum (freezing, stress)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seedlings of Triticum aestivum L. cv. Lennox were grown in different environments to obtain different hardiness. Pieces of laminae and leaf bases were slowly cooled to sub-zero temperatures and the damage caused was assessed by an ion-leakage method. Comparable pieces of tissue were slowly cooled to temperatures between 2° and-14°C and were then freeze-fixed and freeze-etched. Membranes generally retained their lamellar structures indicated by the abundance of typical membrane fracture faces in all treatments, and some membrane fracture faces had patches which lacked the usual scattering of intramembranous particles (IMP). These IMP-free areas were present in the plasma membrane of tissues given a damaging freezing treatment, but were absent from the plasma membrane of room-temperature controls, of supercooled tissues, and of tissues given a non-damaging freezing treatment. The frequency of IMP-free areas and the proportion of the plasma membrane affected increased with increasing damage. In the most damaged tissue (79% damage; leaf bases exposed to-8°C), 20% of the plasma membrane was IMP-free. The frequencies of IMP at a distance from the IMP-free areas were unaffected by freezing treatments. There was a patchy distribution of IMP in other membranes (nuclear envelope, tonoplast, thylakoids, chloroplast envelope), but only in the nuclear envelope did it appear possible that their occurrence coincided with damage. The IMP-free areas of several membranes were sometimes associated together in stacks. Such membranes lay both to the outside and inside of the plasma membrane, indicating that at least some of the adjacent membrane fragments arose as a result of membrane reorganization induced by the damaging treatment. Occasional views of folded IMP-free plasma membrane tended to confirm this conclusion. The following hypothesis is advanced to explain the damage induced by extracellular freezing. Areas of plasma membrane become free of IMP, probably as a result of the freezing-induced cellular dehydration. The lipids in these IMP-free patches may be in the fluid rather than the gel phase. The formation of these IMP-free patches, especially in the plasma membrane, initiates or involves proliferation and possibly fusion of membranes, and during or following this process, the cells become leaky.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395140
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  • 5
    Electronic Resource
    Electronic Resource
    Low-temperature-responsive barley genes have different control mechanisms (1994)
    Springer
    Plant molecular biology 24 (1994), S. 879-888 
    Details
    ISSN: 1573-5028
    Keywords: barley ; cold acclimation ; gene expression ; low temperature genes ; nuclear run-on transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several low-temperature-responsive (LTR) genes from barley have been shown to have high steady-state transcript levels. Run-on transcription was used to determine the control of expression of these LTR genes. Six of these are shown to be transcriptionally regulated (blt 4/9, blt 101, blt 1015, blt 63, blt 49, blt 410) whilst three are post-transcriptionally regulated (blt 14, blt 411, blt 801). Two transcriptionally regulated genes (blt 4/9 and blt 101) and one post-transcriptionally regulated gene (blt 14) have been used in expression studies. The time course for the appearance and decay of these transcripts is given. Initial appearance and steady-state levels of individual transcripts have different temperature characteristics but no single gene correlates with the cold acclimation response. We suggest that these different response profiles may represent a means of fine-tuning the low-temperature response. One gene, blt 4/9, also accumulated high steady-state levels of transcript in response to drought and a nutrient stress. However, only drought has an acclimating effect on barley plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014442
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  • 6
    Electronic Resource
    Electronic Resource
    Extracellular ice and cell shape in frost-stressed cereal leaves: A low-temperature scanning-electron-microscopy study (1988)
    Springer
    Planta 175 (1988), S. 313-324 
    Details
    ISSN: 1432-2048
    Keywords: Dehydration ; Freezing (extracellular, intercellular) ; Frost stress (leaf) ; Hordeum (frost stress) ; Leaf (frost stress) ; Secate (frost stress)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Low-temperature scanning electron microscopy was used to examine transverse fracture faces through cereal leaf pieces subjected to frost. Specimens were studied before and after sublimation of the ice. The position of extracellular ice in the leaf was inferred from the difference between the specimen before and after sublimation and from ridges and points which occurred in the extracellular ice during sublimation. Steps in the fracture surface indicated that the fracture plane passed through the extracellular ice crystals as well as through cells and also helped identify extracellular ice. The cells in controls were turgid and extracellular ice was absent. Leaf pieces from hardened rye were excised and frost-stressed to-3.3°,-21° and-72°C, cooling at 2–12°·h-1. Cell collapse and extracellular ice were evident at-3.3°C and increased considerably by-21° C. At-21° and-72°C the leaf pieces were mainly filled with extracellular ice and there were few remaining gas spaces. The epidermal and mesophyll cells were laterally flattened, perpendicular to their attachment to adjacent cells, and phloem and vascular sheath cells were more irregularly deformed. Leaf pieces from tender barley were cooled at 2°C·min-1 to-20° C; they were then mainly filled with extracellular ice, and the cells were highly collapsed as in the rye. In rye leaves frozen to-3.6° C before excision, ice crystals occurred in peri-vascular, sub-epidermal and intervening mesophyll spaces. In rye leaf pieces frozen to-3.3° C after excision or to-3.6° C before excision, mesophyll cells were partly collapsed even when not covered by ice, indicating that collapse of the cell wall, as well as the enclosed protoplast, was driven by dehydration. No gas or ice-filled spaces were found between wall and the enclosed protoplast. It is suggested that this can be explained without invoking chemical bonding between cell wall and plasma membrane: when the wall pores are filled by water, the pore size would reduce vapour pressure so making penetration of the wall by ice or gas less likely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396336
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  • 7
    Electronic Resource
    Electronic Resource
    Cell shape and localisation of ice in leaves of overwintering wheat during frost stress in the field (1992)
    Springer
    Planta 188 (1992), S. 324-331 
    Details
    ISSN: 1432-2048
    Keywords: Frost stress ; Ice formation (leaf) ; Leaf (ice formation) ; Stress (freezing) ; Triticum (frost stress)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wheat leaf pieces were excised and freeze-fixed in the field, preparatory to low-temperature scanning electron microscopy to study distribution of ice within leaf blades, and associated cell shapes, during natural frosts. Pieces of leaf blades from wheat plants (Triticum aestivum L. 7942H1-20-8) overwintering in Indiana, USA (January, 1991), were excised and immediately freeze-fixed by manually plunging in melting freon. Cells in controls were turgid and extracellular ice was absent. The leaves of the frost-stressed plants froze at about — 2.4° C, and at that temperature extracellular ice was mainly located sub-epidermally, including in the substomatal cavity, and occupied about 14% of the fracture faces. The frequency of ice particles per unit leaf area in two specimens was 14 and 210 · mm−2 (about 140 and 2100 · g−1 leaf fresh-weight basis). At -9.0° C, ice filled the extracellular spaces, occupying 61% of the fracture faces. Cells were somewhat collapsed at -2.4° C and were much more collapsed at -9.0° C. The epidermal cells were more collapsed than the mesophyll cells. Tissue structure (connections with adjacent cells), wall flexibility, and ice growth may all have influenced the shapes of the collapsing cells. The experiments demonstrate the feasibility of freeze-fixation in the field. The sub-epidermal location of most ice indicates that in the field either (i) ice is nucleated sub-epidermally (implying both the presence of nucleators and the presence of liquid water in the sub-epidermal spaces) or (ii) ice is nucleated on the leaf surface, then propagates into the leaf probably through stomata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192798
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  • 8
    Electronic Resource
    Electronic Resource
    The membranes of slowly drought-stressed wheat seedlings: a freeze-fracture study (1985)
    Springer
    Planta 166 (1985), S. 1-14 
    Details
    ISSN: 1432-2048
    Keywords: Drought stress ; Membrane damage ; Plasma membrane ; Triticum (drought, membrane damage) ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seedlings of Triticum aestivum L. cv. Neepawa were slowly drought-stressed by witholding water after sowing in pots. Leaf extension stopped during development of the third leaf. Damage was assessed by rewatering the pots and measuring regrowth; 1–5 d after growth stopped, rewatering induced significant regrowth within several hours; 6–13 d after growth stopped, regrowth was delayed; from 14 d after growth stopped, no regrowth occurred after rewatering. Leaf bases were excised from the drought-stressed seedlings during this period of increasing damage, and were freeze-etched. Intramembranous particles (IMP) were evenly scattered in the plasma membrane in those plants which regrew immediately after rewatering. In the plants which regrew after a delay or which did not regrow on rewatering, there were patches without IMP in plasma membrane, nuclear envelope, and other membranes. Plasma membrane, nuclear envelope and possibly other membranes were sometimes partly replaced by vesicles, possibly formed from the original membrane. Such vesiculation occurred in a few cells in plants which survived the stress with a delayed regrowth, and was commoner in the plants which did not recover. The results support the idea that slow drought induces IMP-free patches in membranes including the plasma membrane, this induces membrane reorganisation including vesiculation of membranes and coagulation of protoplasm, and that these are expressed as delayed or failed regrowth. Some IMP-free patches in the plasma membrane had a faint ordered sub-structure, possibly a hexagonal lipid phase. Such patches were infrequent and IMP sometimes occurred in areas of plasma membrane having an apparently similar sub-structure. Thus the IMP-free patches could not be explained by a lamellar-hexagonal phase transition. As the stress became damaging, vesicles and endoplasmic reticulum accumulated immediately next to the plasma membrane. Mainly during the early period of damaging stress (6–10 d after growth stopped), depressions, invaginations, and rarer “lesions” occurred in the plasma membrane, sometimes associated with some of the IMP-free patches. In the same period, many nuclear envelopes had exceptionally large nuclear pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397380
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  • 9
    Electronic Resource
    Electronic Resource
    Behaviour in culture of isolated protoplasts from “Paul's scarlet” rose suspension culture cells (1973)
    Springer
    Protoplasma 77 (1973), S. 165-180 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protoplasts were enzymatically isolated from “Paul's scarlet” rose suspension culture cells. They were cultured in medium similar to that used to culture the cells from which they were isolated with the addition of sucrose as an osmotic stabiliser. They were studied by light and electron microscopy and their changes in size and number per culture were recorded. Expansion was greater when the protoplasts were cultured in medium plus 12% sucrose than with 24% sucrose. Budding was observed. In medium plus 12% sucrose about 45% of the protoplasts divided but in medium plus 24% sucrose far fewer divided. Cytokinesis was abnormal: the phragmoplast disappeared soon after cytokinesis began and the cell plate became a groove and then a fibril-lined or filled tongue which progressed across the vacuole, unconnected by strands to other parts of the protoplast. The wall regenerated after several days culture in medium plus 12% sucrose fluoresced with calcofluor. The wall regenerated in medium with 24% sucrose fluoresced usually only after several weeks culture. Cytokinesis hastened formation of a wall fluorescing with calcofluor. In the electron microscope the wall was seen to contain fibrils and non-fibrillar material. The latter was the minor component in medium plus 12% sucrose but was usually the major component in medium plus 24% sucrose. The growth in plasmolysing and nonplasmolysing medium of the cells from which protoplasts are isolated was also studied. It appears that loss of the wall alters the potential of protoplasts to expand and possibly also to regenerate a wall and to divide. Wall regeneration is initially linked with expansion and cytokinesis. Osmotic pressure of the external medium is also an important factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276755
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  • 10
    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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