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  • 1
    Electronic Resource
    Electronic Resource
    Microautoradiographic studies of phloem loading and transport in the leaf of Zea mays L. (1983)
    Springer
    Planta 159 (1983), S. 193-206 
    Details
    ISSN: 1432-2048
    Keywords: Assimilate transport ; Leaf (14C transport) ; Phloem loading ; Sieve tube ; Vascular bundle ; Zea (14C transport)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microautoradiographs showed that [14C]sucrose taken up in the xylem of small and intermediate (longitudinal) vascular bundles of Zea mays leaf strips was quickly accumulated by vascular parenchyma cells abutting the vessels. The first sieve tubes to exhibit 14C-labeling during the [14C]sucrose experiments were thick-walled sieve tubes contiguous to the more heavily labeled vascular parenchyma cells. (These two cell types typically have numerous plasmodesmatal connections.) With increasing [14C]sucrose feeding periods, greater proportions of thick- and thin-walled sieve tubes became labeled, but few of the labeled thin-walled sieve tubes were associated with labeled companion cells. (Only the thin-walled sieve tubes are associated with companion cells.) When portions of leaf strips were exposed to 14CO2 for 5 min, the vascular parenchyma cells-regardless of their location in relation to the vessels or sieve tubes-were the most consistently labeled cells of small and intermediate bundles, and label (14C-photosynthate) appeared in a greater proportion of thin-walled sieve tubes than thick-walled sieve tubes. After a 5-min chase with 12CO2, the thin-walled sieve tubes were more heavily labeled than any other cell type of the leaf. After a 10-min chase with 12CO2, the thin-walled sieve tubes were even more heavily labeled. The companion cells generally were less heavily labeled than their associated thin-walled sieve tubes. Although all of the thick-walled sieve tubes were labeled in portions of leaf strips fed 14CO2 for 5 min and given a 10-min 12CO2 chase, only five of 72 vascular bundles below the 14CO2-exposed portions contained labeled thick-walled sieve tubes. Moreover, the few labeled thick-walledsieve tubes of the “transport region” always abutted 14C-labeled vascular parenchyma cells. The results of this study indicate that (1) the vascular parenchyma cells are able to retrieve at least sucrose from the vessels and transfer it to the thick-walled sieve tubes, (2) the thick-walled sieve tubes are not involved in long-distance transport, and (3) the thin-walled sieve tubes are capable themselves of accumulating sucrose and photosynthates from the apoplast, without the companion cells serving as intermediary cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397525
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf vasculature in sugarcane (Saccharum officinarum L.) (1982)
    Springer
    Planta 156 (1982), S. 136-151 
    Details
    ISSN: 1432-2048
    Keywords: Leaf vasculature ; Saccharum ; Sievetube area ; Tracheary-element area ; Vascular bundle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The vascular system of the leaves of Saccharum officinarum L. is composed in part of a system of longitudinal strands that in any given transverse section may be divided into three types of bundle according to size and structure: small, intermediate, and large. Virtually all of the longitudinal strands intergrade, however, from one type bundle to another. For example, virutually all of the strands having large bundle anatomy appear distally in the blade as small bundles, which intergrade into intermediates and then large bundles as they descend the leaf. These large bundles, together with the intermediates that arise midway between them, extend basipetally into the sheath and stem. Most of the remaining longitudinal strands of the blade do not enter the sheath but fuse with other strands above and in the region of the blade joint. Despite the marked decrease in number of bundles at the base of the blade, both the total and mean cross-sectional areas (measured with a digitizer from electron micrographs) of sieve tubes and tracheary elements increase as the bundles continuing into the sheath increase in size. Linear relationships exist between leaf width and total bundle number, and between cross-sectional area of vascular bundles and both total and mean cross-sectional areas of sieve tubes and tracheary elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395428
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on the leaf of Amaranthus retroflexus (Amaranthaceae): ultrastructure, plasmodesmatal frequency, and solute concentration in relation to phloem loading (1982)
    Springer
    Planta 155 (1982), S. 377-387 
    Details
    ISSN: 1432-2048
    Keywords: Amaranthus ; Leaf ultrastructure ; Phloem loading ; Plasmodesmata ; Veins (minor)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both the mesophyll and bundle-sheath cells associated with the minor veins in the leaf of Amaranthus retroflexus L. contain abundant tubular endoplasmic reticulum, which is continuous between the two cell types via numerous plasmodesmata in their common walls. In bundle-sheath cells, the tubular endoplasmic reticulum forms an extensive network that permeates the cytoplasm, and is closely associated, if not continuous, with the delimiting membranes of the chloroplasts, mitochondria, and microbodies. Both the number and frequency of plasmodesmata between various cell types decrease markedly from the bundle-sheath — vascular-parenchyma cell interface to the sicve-tube member — companion-cell interface. For plants taken directly from lighted growth chambers, a stronger mannitol solution (1.4 M) was required to plasmolyze the companion cells and sieve-tube members than that (0.6 M) necessary to plasmolyze the mesophyll, bundle-sheath, and vascular-parenchyma cells. Placing plants in the dark for 48 h reduced the solute concentration in all cell types. Judging from the frequency of plasmodesmata between the various cell types of the vascular bundles, and from the solute concentrations of the various cell types, it appears that assimilates are actively accumulated by the sieve-tube — companion-cell complex from the apoplast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394465
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  • 4
    Electronic Resource
    Electronic Resource
    Studies onArtemisia afra Jacq.: The phloem in stem and leaf (1981)
    Springer
    Protoplasma 109 (1981), S. 217-231 
    Details
    ISSN: 1615-6102
    Keywords: Anatomy ; Artemisia ; Cell wall composition ; Compositae ; Phloem ; Sieve element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The structure of the phloem was studied in stem and leaf ofArtemisia afra Jacq., with particular attention being given to the sieve element walls. Both primary and secondary sieve elements of stem and midvein have nacreous walls, which persist in mature cells. Histochemical tests indicated that the sieve element wall layers contained some pectin. Sieve element wall layers lack lignin. Sieve elements of the minor veins (secondary and tertiary veins) lack nacreous thickening, although their walls may be relatively thick. These walls and those of contiguous transfer cells are rich in pectic substances. Transfer cell wall ingrowths are more highly developed in tertiary than in secondary veins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01287443
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of UV-B and UV-C radiation on sugar beet leaves (1983)
    Springer
    Protoplasma 117 (1983), S. 7-16 
    Details
    ISSN: 1615-6102
    Keywords: Beta vulgaris ; Chloroplast ; Ultrastructure ; Ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of UV-C (254 nm) and UV-B (290–320 nm) radiation on leaves ofBeta vulgaris L. at the ultrastructural level was investigated. Although the damage caused by UV-C radiation was more striking than that resulting from UV-B radiation, several structural changes were seen in the UV-B treated material. Generally the effects of UV-B and UV-C radiation were different, suggesting different mechanisms of action, discernible even at the ultrastructural level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281779
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  • 6
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    Microautoradiographic studies of phloem loading and transport in the leaf of Zea mays L. (1983)
    Springer
    Details
    Publication Date: 1983-11-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 7
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    Studies on the leaf of Amaranthus retroflexus (Amaranthaceae): ultrastructure, plasmodesmatal frequency, and solute concentration in relation to phloem loading (1982)
    Springer
    Details
    Publication Date: 1982-09-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 8
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    Leaf vasculature in sugarcane (Saccharum officinarum L.) (1982)
    Springer
    Details
    Publication Date: 1982-11-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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