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  • 1
    Electronic Resource
    Electronic Resource
    Protein bodies in ray cells of Populus x canadensis Moench ‘robusta’ (1988)
    Springer
    Planta 173 (1988), S. 31-34 
    Details
    ISSN: 1432-2048
    Keywords: Populus ; Protein body ; Protein storage ; Ray cell ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light- and electron-microscopical investigations revealed distinct intravacuolar protein aggregates of 0.3–0.8 μm in diameter in ray cells of poplar during the dormant season. In semi-thin sections, these bodies showed positive protein staining and enzymatic digestibility with pepsin, indicating their proteinaceous nature. Morphometric measurements showed such protein bodies in 7–13% of the area of the ray-cell lumen. This amount corresponded with the protein content of the wood determined biochemically, e.g. 2.0–5.0 μg·mg-1 dry weight. Polyacrylamide gel electrophoresis of the total protein fraction extracted from wood showed prominent polypeptide species with an apparent molecular weight of 30–32 kilodaltons. The results indicate considerable protein storage in ray cells, especially in the form of protein-storage vacuoles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394483
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  • 2
    Electronic Resource
    Electronic Resource
    Pith cells of poplar contain photosynthetically active chloroplasts (1993)
    Springer
    Planta 189 (1993), S. 70-73 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast ; Light-harvesting chlorophyll a/b protein ; Photosynthesis (low light) ; Pith ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pith cells of young poplar (Populus x canadensis Moench) twigs were found to contain chlorophylls a and b. In addition, it was shown that pith cells also have a considerable amount of light-harvesting chlorophyll a/b protein (LHCP), which was identified by Western blotting and localized by immunogold labelling of ultrathin sections. The data strongly indicate that these cells, though they are completely covered by wood and bark and thus are accessible only to very low amounts of light, possess a functionally active photosynthetic apparatus. Evidence for this was found by feeding isolated longitudinal sections of pith with radioactively labelled carbon dioxide and exposing them to light. After incubation, reduced carbohydrates could be detected by thinlayer chromatography, indicating that photosynthesis occurs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201345
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  • 3
    Electronic Resource
    Electronic Resource
    Plasmodesmatal frequency and radial translocation rates in ray cells of poplar (Populus x canadensis Moench ‘robusta’) (1986)
    Springer
    Planta 168 (1986), S. 377-380 
    Details
    ISSN: 1432-2048
    Keywords: Plasmodesma (frequency) ; Populus ; Ray parenchyma ; Sugar translocation ; Translocation rate (sugar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The minimum radial translocation rate of sugars has been determined from the starchaccumulation rate for the wood rays of Populus x canadensis Moench ‘robusta’, and related to ultrastructural peculiarities of the cell walls to be passed. The minimum radial flux or flow of sugars through the tangential walls, the pit fields, and per plasmodesma was 80.7 pmol · cm-2 · s-1, 400 to 800 pmol · cm-2 · s-1, and 1.0 to 1.7 · 10-7 pmol · plasmodesma-1 · s-1, respectively. These values exclude a transmembrane flux mechanism and indicate that the radial translocation in this tissue must proceed via plasmodesmata. In the isolation cells of the ray center we found 39 plasmodesmata per μm2 of pit field, 8.0 per μm2 of tangential wall, and 1.98% of the wall occupied by plasmodesmata. Cells of the ray margins show plasmodesmata on only 1.16% of their tangential wall area and thus appear to be slightly inferior for radial translocation. As judged from both the observed plasmodesmatal frequencies and the translocation rates, the ray parenchyma cells are comparable to cells specialized in short-distance translocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392363
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  • 4
    Electronic Resource
    Electronic Resource
    Seasonal variation of amino acids in the xylem sap of “Populus x canadensis” and its relation to protein body mobilization (1992)
    Springer
    Trees 7 (1992), S. 26-32 
    Details
    ISSN: 1432-2285
    Keywords: Amino acids ; Populus ; Protein bodies ; Vessels ; Xylem transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal changes in the pattern of 21 amino acids occurring in the xylem vessels of Populus twigs have been studied in connection to the mobilization of protein bodies in ray parenchyma cells at the electron microscopic level. Hydrolysis of protein bodies in spring and movement of amino acids into vessels are found to be closely linked. Comprising more than 75% of total amino acid content, glutamine (Gln) is by far the dominant N-constituent of the sap. Gln reaches up to 11 μmol ml-1 in the spring sap while other amino acids only show 1/20 to 1/100 of this amount. From the measured Gln accumulation rates in the vessels in nature and in the vessels of isolated shoots, a minimum flux rate for Gln of 5.6 pmol cm-2 min-1 is calculated for the ray contact cell/vessel interface. Furthermore, because Gln constitutes 75% of the amino acid content of the sap but only 1.3% of the amino acids in the 32 kDa storage protein of the ray cells in the wood (Clausen and Apel 1991), it becomes evident that most amino acids originating from protein body mobilization do not enter the vessels but are used for Gln synthesis preceding Gln release into the vessels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225228
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  • 5
    Electronic Resource
    Electronic Resource
    Seasonal changes in the efflux of sugars from parenchyma cells into the apoplast in poplar stems (Populus × canademis “robusta”) (1988)
    Springer
    Trees 2 (1988), S. 242-249 
    Details
    ISSN: 1432-2285
    Keywords: Sugars ; Xylem sap ; Wood ; Parenchyma ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The efflux of sugars from parenchyma cells into the apoplast has been studied in the wood of Populus × canadensis “robusta” in relation to the sugar level of the tissue and the sugar content of the tracheal sap during all physiological stages of the year. In poplar, the spring maximum in sugar content of the tracheal sap is clearly not the result of continuous exosmosis during winter but is reached within a short period in spring. The seasonal patterns of starch and sugar content of the wood and of the sugar content of the tracheal sap are described. The efflux of sugars from tissue sections changes drastically over the year, i.e., from 0.3 to 8.3 μg mg−1DWT day−1. In general, it is high in fall and winter, and low during late spring and summer. However, high tissue sugar levels proved not always to be correlated with high efflux rates or with high sugar levels in the tracheal sap, indicating that the intracellular compartmentalization of sugars, their passive and catalysed release into, and their re-uptake from the apoplast are all essentially involved in determining the actual sugar content of the sap. Sucrose, which is the dominant sugar in the tracheal sap during winter (pH 7.0–7.5) and in the efflux experiments at pH 7.5, in contrast to the hexoses which prevail in the spring sap (pH around 5.5) and also in the efflux experiments at pH 5.6, is considered to be preferentially released in poplar and to become extraplasmatically hydrolysed. The reasons for tree-specific differences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202379
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in hydraulic conductivity upon freezing of the xylem of Populus x canadensis Moench “robusta” (1991)
    Springer
    Trees 5 (1991), S. 117-121 
    Details
    ISSN: 1432-2285
    Keywords: Freezing stress ; Hydraulic conductivity ; Populus ; Vessels ; Water conduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The impact of freezing stress on the hydraulic conductivity was studied in 4- to 6-year-old branches of Populus x canadensis Moench “robusta” under gravity flow conditions. In fresh branch segments, the hydraulic conductivity was approximately 3–6×10-2 1 h-1kPa-1m and the specific conductivity approximately 22 1 h-1kPa-1m-1. Depending on the gas content of the solutions fed to the xylem of the segments, their hydraulic conductivity was lowered by a freezing-thawing cycle by 20–50%. However, full recovery of hydraulic conductivity was found after about 2 days. Degassed solutions in contrast showed no impediment to flow after the same treatment. The results give evidence, firstly, that the harmful effect of freezing on functioning of water conducting elements is due to the formation of bubbles in xylem sap containing gas in solution, and secondly, that recovery from this impediment is possible in microporous vessels within a period of about 2 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227494
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  • 7
    Electronic Resource
    Electronic Resource
    Storage, mobilization and interrelations of starch, sugars, protein and fat in the ray storage tissue of poplar trees (1994)
    Springer
    Trees 8 (1994), S. 297-304 
    Details
    ISSN: 1432-2285
    Keywords: Cold acclimation ; Fat ; Populus ; Protein ; Sugars ; Storage parenchyma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The seasonal pattern in starch, various sugars, protein, and fat, and their interrelationship, has been followed in 3-year-old branch wood of poplar trees (Populus x canadensis Moench ‘robusta’) under natural site conditions. The deposition of starch, protein and fat proceeds at different times. Starch accumulates from May until October, fat mainly during the summer months, and protein when the leaves are yellowing in September and October. The maximum concentrations in the branch wood were 15–18 μg starch, 6–9 μg protein, 4–8 μg fat, 10–15 μg sucrose, and up to 30 μg total sugars per milligram dry weight (DW). During starch deposition periods no increased sucrose level is found in the tissue. The maximum daily starch deposition rate was 0.2–0.4 μg starch/day/mg DW of wood. During starch hydrolysis in late autumn and winter, a dramatic increase in sucrose and its galactosides is measured (up to 15–27 μg/mg DW in total). In early spring, before budbreak, the concentrations of these sugars diminishes sharply. In contrast to this clear-cut starch-to-sugar conversion in autumn no significant starch-to-fat conversion is detected. An elevated content of free glycerol, however, is found in winter. In spring, starch and storage protein are mobilized completely, or almost completely, in poplar twig wood. A noteworthy pool of maltose is found transiently during autumn (up to 8 μg/mg DW) and again in spring. The results demonstrate that the individual storage materials, e.g. starch, protein, and fat, are accumulated fairly independently in the wood storage parenchyma. Tissue sugar levels, in contrast, appear to be closely related to the seasonal variations in starch content, on the one hand, and to the acclimation and deacclimation of the cells, on the other. The interrelations of the storage materials and sugars are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202674
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  • 8
    Electronic Resource
    Electronic Resource
    Changes in carbohydrates and ultrastructure in xylem ray cells ofPopulus in response to chilling (1987)
    Springer
    Protoplasma 137 (1987), S. 45-55 
    Details
    ISSN: 1615-6102
    Keywords: Carbohydrates ; Chilling effects ; Populus ; Sugars ; Ultrastructure ; Xylem ray cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of xylem ray cells inPopulus was studied in conjunction with their content of individual sugars and of starch. They differ considerably in structure and in carbohydrate content at the three chosen stages,i.e., of starch deposition (August), of starch maximum (November), and of starch dissolution (January). The transition from the summer to winter stage was also induced experimentally by storage of tissue at 0°C. Both in nature and after cold-storage, sucrose and its galactosides raffinose and stachyose were accumulated to a great extent, contributing up to 69.7 and 57.3% of total sugar content, respectively. They originated parallel to the breakdown of starch and to the appearance of abundant vesicular and dilated ER cisternae. Results indicating that they are the specific sites of sucrose accumulation, and/or its galactosides, are discussed. The occurrence of phytoferritin-like crystalloids in amyloplasts and of vacuolar flocculent material, which condenses into electron-dense bodies of suspectedly proteinaceous nature, is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281175
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  • 9
    Electronic Resource
    Electronic Resource
    Immunochemical localization of a willow storage protein with a poplar storage protein antibody (1989)
    Springer
    Protoplasma 149 (1989), S. 175-177 
    Details
    ISSN: 1615-6102
    Keywords: Immunogold labelling ; Populus ; Protein bodies ; Protein storage ; Ray cells ; Salix ; Xylem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Antibodies raised from a 32 kDa storage protein of poplar wood are found to bind specifically to protein bodies in willow wood ray cells when the immunogold method is used. A polypeptide of ca. 32 kDa is also obtained from the willow wood which reacts with the poplar storage protein antibodies when the immunoblotting technique is used. The results indicate that willow possesses a storage protein which appears closely related to that of poplar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322989
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