%0 Journal Article %1 citeulike:1584913 %A Pearce, R. S. %D 1988 %J Planta %K anatomy, cellular, citeulikeExport cryo, damage, freezing, grass, ice, leaf, snowgumpapermaybe %N 3 %P 313--324 %R 10.1007/bf00396336 %T Extracellular ice and cell shape in frost-stressed cereal leaves: A low-temperature scanning-electron-microscopy study %U http://dx.doi.org/10.1007/bf00396336 %V 175 %X 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.

@article{citeulike:1584913, 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.}}, added-at = {2019-03-31T01:14:40.000+0100}, author = {Pearce, R. S.}, biburl = {https://www.bibsonomy.org/bibtex/26f196f757287ea93793c039df188b97e/dianella}, citeulike-article-id = {1584913}, citeulike-linkout-0 = {http://dx.doi.org/10.1007/bf00396336}, comment = {(private-note)Cytorrhysis, even distal to ice formation. mesophyll cytorrhysis. vascular bundle cytorrhysis too except for the xylem vessels Sensible cooling rates: 2oC per hour down to lowish temperatures, then faster to lower ones some attached, some not attached during freeze ICF not clear because not planed. freezing to -21 and -72oC gave similar levels of cytorrhysis Rye Light microscopy has been used to study extracellular freezing and cell collapse in separate cells and small groups and chains of cells (Olien and Smith 1977; Asahina 1978; Steponkus et al. 1982; Morris et al. 1986). Light microscopy can also reveal ice masses in organs (Terumoto 1960; Sakai 1979, 1982; Ishikawa and Sakai 1981, 1985; Beck et al. 1984). Idle (1966) used a fluorescence light optical method to infer ice propagation at the cut surface of a rachis. Nuclear magnetic resonance shows that during slow cooling after initiation of freezing, most tissue water freezes before the temperature reaches -10 \~{} to -15\~{} (Gusta et al. 1975). irregularities in the etching extracellular ice surface were initially small and numerous giving a stippled appearance to the ice (Fig. 5), and as sublimation progressed they became fewer and more prominent (Fig. 11). This indicates that they were not eutectic bars, which would not become less frequent as sublimation progressed. Pure ice has these appearances during sublimation, as shown by transmission-electron- microscopy replicas of etching ice-crystal surfaces (Davy and Branton 1970; Staehelin and Bertaud 1971). Initial sublimation creates etch pits of about 1 gm diameter; with further etching at -60\~{} or -75\~{} these enlarge, giving a rough surface (Davy and Branton 1970) to which the image in Fig. 5 may correspond. Freezing speads very rapidly in woody plants from any site of nucleation, probably through the xylem (reviewed by Sakai and Larcher 1987, Chpt. 2). Cell collapse. The shape taken by cells in the froststressed leaves varied with cell type, possibly reflecting the different structure of different tissues. The lateral collapse of the epidermal and mesophyll cells, becoming flattened, could be accounted for by their attachment to other cells at only some points (mesophyll) or edges (epidermis); the phloem cells were attached to other cells on all sides. A similar explanation was offered for the variation in shape between cell types during drought stress (Pearce and Beckett 1987), and in both cases individual wall properties could also be a factor. Drought and frost gave roughly similar shapes for a number of cell types Folds in the mesophyll cell walls radiated from points of attachment to adjacent cells reflecting volume collapse combined with tension in the direction in which the folds ran. Walls not attached to adjacent cells tended to bow inwards. Suggest that cytorrhysis occurs instead of plasmolysis because the ice can't penetrate the cell wall... because the pores are too narrow.}, day = 1, doi = {10.1007/bf00396336}, interhash = {94bb1ea1bdc756a9979313abd386e91c}, intrahash = {6f196f757287ea93793c039df188b97e}, journal = {Planta}, keywords = {anatomy, cellular, citeulikeExport cryo, damage, freezing, grass, ice, leaf, snowgumpapermaybe}, number = 3, pages = {313--324}, posted-at = {2007-08-23 08:34:47}, priority = {0}, timestamp = {2019-03-31T01:16:26.000+0100}, title = {{Extracellular ice and cell shape in frost-stressed cereal leaves: A low-temperature scanning-electron-microscopy study}}, url = {http://dx.doi.org/10.1007/bf00396336}, volume = 175, year = 1988 }