The Phloem

5. Sieve element plastids 

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The Phloem

Sieve tube structure

Sieve plate

P-Proteins

Forisomes

Sieve element plastids

Mitochondria and ER

Sieve tube function

Literature 

Current activities in phloem research

Sieve element plastids (SE plastids) are a plastid type ocurring in sieve elements only. As other plastids, they derive from proplastids. They may contain starch and/or proteins. They are classified based on their components. It has been recognized that their content is highly family specific and they have been used for taxonomic classification (see literature by Dr. Dietmar Behnke, University Heidelberg, Germany). Besides their structure, little is known about their function. However, given the importance of other plastid types for plants, one can expect that they play a major role in phloem function.

Figure legend: Confocal micrograpf of sieve elements (SE) in broabean (left). Numerous SE-plastids are visible (arrowheads). Transmission electron micrograph of a broadbean SE-plastids containing proteins (right). Left image from Knoblauch and Van Bel  (1998) Sieve tubes in action. Plant Cell 10 35-50. Copyright: American Society of Plant Biologists. Right image from Ehlers et al. (2000) Ultrastructural features of well preserved and injured sieve elements: minute clamps keep the phloem transport conduits free for mass flow. Protoplasma 214, 80-92. Copyright: Springer Verlag, Berlin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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