Expression of a yeast-derived invertase in companion cells results in long-distance transport of a trisaccharide in an apoplastic loader and influences sucrose transport

Planta ◽  
2004 ◽  
Vol 218 (5) ◽  
pp. 759-766 ◽  
Author(s):  
Ellen Zuther ◽  
Marion Kwart ◽  
Lothar Willmitzer ◽  
Arnd G. Heyer
Keyword(s):  
Sucrose Transport ◽  
Long Distance ◽  
Long Distance Transport ◽  
Companion Cells ◽  
Distance Transport

The Fine Structure of Phloem Cells

1985 ◽  
Vol 43 ◽  
pp. 632-635
Author(s):  
James Cronshaw
Keyword(s):  
Structural Studies ◽  
High Concentration ◽  
Long Distance ◽  
Phloem Tissue ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Companion Cells ◽  
Electron Microscopical ◽  
Distance Transport

Long distance transport in plants takes place in phloem tissue which has characteristic cells, the sieve elements. At maturity these cells have sieve areas in their end walls with specialized perforations. They are associated with companion cells, parenchyma cells, and in some species, with transfer cells. The protoplast of the functioning sieve element contains a high concentration of sugar, and consequently a high hydrostatic pressure, which makes it extremely difficult to fix mature sieve elements for electron microscopical observation without the formation of surge artifacts. Despite many structural studies which have attempted to prevent surge artifacts, several features of mature sieve elements, such as the distribution of P-protein and the nature of the contents of the sieve area pores, remain controversial.

The fine structure of corn phloem

1972 ◽  
Vol 50 (4) ◽  
pp. 839-846 ◽  
Author(s):  
A. P. Singh ◽  
L. M. Srivastava
Keyword(s):  
Fine Structure ◽  
Long Distance ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Vascular Parenchyma ◽  
Predominant Orientation ◽  
Distance Transport

The differentiation of sieve elements, companion cells, and vascular parenchyma in leaf bundles of corn is described. The sieve elements have plastids with distinctive crystalline inclusions, lack P-protein, and have nacreous walls in which the predominant orientation of microfibrils seems to be at right angles to the length of the cell. The companion and vascular parenchyma cells have numerous, well-developed mitochondria. These and other results are discussed in relation to long distance transport in the sieve elements.

The anatomy of the pathway of sucrose unloading within the sugarcane stalk

2005 ◽  
Vol 32 (4) ◽  
pp. 367 ◽  
Author(s):  
Kerry B. Walsh ◽  
Russell C. Sky ◽  
Sharon M. Brown
Keyword(s):  
Cell Layer ◽  
Sink Strength ◽  
Vascular Bundles ◽  
Sucrose Transport ◽  
Long Distance ◽  
Long Distance Transport ◽  
Sugarcane Stalk ◽  
Storage Parenchyma ◽  
Phloem Fibre ◽  
Distance Transport

The physical path of sucrose unloading in the sugarcane stalk is described. About 50% of the vascular bundles in the internodes were located within 3 mm of the outside of the stalk. These bundles were inactive in long distance sucrose transport, as assessed by dye tracers of phloem flow. A sheath of fibres isolates the phloem apoplast from that of the storage parenchyma. In bundles associated with long distance transport (i.e. in the central region), the fibre sheath is narrowest to either side of the phloem fibre cap, and consists of living cells with plasmodesmata within pits in the secondary wall. Plasmodesmata were also arranged into pit fields between cells of the storage parenchyma. Since the vascular apoplast is isolated from the apoplast of the storage parenchyma, sucrose must move through the symplast of the fibre sheath. The calculated flux of sucrose through plasmodesmata of this cell layer was at the low end of reported values in the literature. Sucrose unloading within the storage parenchyma may also follow a symplastic route, with unloading into the apoplast of the storage parenchyma occurring as part of a turgor mechanism to increase sink strength.

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