Access

You are not currently logged in.

Access JSTOR through your library or other institution:

login

Log in through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Sieve Tubes in Action

Michael Knoblauch and Aart J. E. van Bel
The Plant Cell
Vol. 10, No. 1 (Jan., 1998), pp. 35-50
DOI: 10.2307/3870627
Stable URL: http://www.jstor.org/stable/3870627
Page Count: 16
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Sieve Tubes in Action
Preview not available

Abstract

A method was designed for in vivo observation of sieve element/companion complexes by using confocal laser scanning microscopy. A leaf attached to an intact fava bean plant was mounted upside down on the stage of a confocal microscope. Two shallow paradermal cortical cuts were made in the major vein. The basal cortical window allowed us to observe the phloem intact. The apical window at 3 cm from the site of observation was used to apply phloem-mobile fluorochromes, which identified living sieve elements at the observation site. In intact sieve tubes, the sieve plates did not present a barrier to mass flow, because the translocation of fluorochromes appeared to be unhindered. Two major occlusion mechanisms were distinguished. In response to intense laser light, the parietal proteins detached from the plasma membrane and formed a network of minute strands and clustered material that aggregated and pressed against the sieve plate. In response to mechanical damage, the evenly distributed P plastids exploded, giving rise to the formation of a massive plug against the sieve plate. In case of mechanical damage, the parietal proteins transformed into elastic threads (strands) that extended throughout the sieve element lumen. Our observations cover the phenomena encountered in previous microscopic and electron microscopic studies and provide a temporal disentanglement of the events giving rise to the confusing mass of structures observed thus far.

Page Thumbnails

  • Thumbnail: Page 
[35]
    [35]
  • Thumbnail: Page 
36
    36
  • Thumbnail: Page 
37
    37
  • Thumbnail: Page 
38
    38
  • Thumbnail: Page 
39
    39
  • Thumbnail: Page 
40
    40
  • Thumbnail: Page 
41
    41
  • Thumbnail: Page 
42
    42
  • Thumbnail: Page 
43
    43
  • Thumbnail: Page 
44
    44
  • Thumbnail: Page 
45
    45
  • Thumbnail: Page 
46
    46
  • Thumbnail: Page 
47
    47
  • Thumbnail: Page 
48
    48
  • Thumbnail: Page 
49
    49
  • Thumbnail: Page 
50
    50