Potassium in the Apoplast of the Root Sink Region

Potassium in the Apoplast of the Root Sink Region Using carboxyfluorescein, a fluorochrome transported along the phloem, we demonstrated that symplasmic phloem unloading in the watermelon root occurred in the basal zone of the meristem adjusting to the elongation zone. In the similar zones of maize and pumpkin roots, a high level of potassium was detected by X-ray microanalysis in the cell walls and intercellular spaces. Potassium concentration in these compartments comprised two-thirds of that in the cytoplasm. Such proportion between potassium concentrations in the cytoplasm and apoplast was characteristic of both the cortex and stele. Since potassium is a dominant osmotically active component in root tissues, such a proportion between its intracellular and apoplastic concentrations provides for a low turgor pressure in the cells of the sink region, in the phloem in particular. This might increase a turgor pressure gradient along the translocation route between source and sink tissues, which is a driving force for phloem assimilate transport. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Potassium in the Apoplast of the Root Sink Region

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Publisher
Springer Journals
Copyright
Copyright © 2005 by MAIK “Nauka/Interperiodica”
Subject
Life Sciences; Plant Sciences; Plant Physiology
ISSN
1021-4437
eISSN
1608-3407
D.O.I.
10.1007/s11183-005-0078-6
Publisher site
See Article on Publisher Site

Abstract

Using carboxyfluorescein, a fluorochrome transported along the phloem, we demonstrated that symplasmic phloem unloading in the watermelon root occurred in the basal zone of the meristem adjusting to the elongation zone. In the similar zones of maize and pumpkin roots, a high level of potassium was detected by X-ray microanalysis in the cell walls and intercellular spaces. Potassium concentration in these compartments comprised two-thirds of that in the cytoplasm. Such proportion between potassium concentrations in the cytoplasm and apoplast was characteristic of both the cortex and stele. Since potassium is a dominant osmotically active component in root tissues, such a proportion between its intracellular and apoplastic concentrations provides for a low turgor pressure in the cells of the sink region, in the phloem in particular. This might increase a turgor pressure gradient along the translocation route between source and sink tissues, which is a driving force for phloem assimilate transport.

Journal

Russian Journal of Plant PhysiologySpringer Journals

Published: Aug 9, 2005

References

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