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- Title
A Working Model of a Sieve Tube.
- Authors
LANG, ALEXANDER
- Abstract
A working model of a sieve tube is described, based upon the Pressure-Flow Hypothesis. The flow of solution in the sieve tube is envisaged as being due to the joint influence of an axial turgor pressure gradient and a lateral water potential difference which causes an intake of water along the tube. In this second respect the model differs from that originally suggested by Münch. The model comprises a length of dialysis tubing rendered semi-permeable, incorporating capillary resistances at regular intervals. A sucrose solution is pumped into one end and collected at the other, the whole being submerged in water. Turgor pressures and concentrations along the model were recorded at intervals; thus the approach to the steady state was followed. In the steady state C-sucrose was introduced to the solution being pumped and its approach to a steady distribution in the model was followed. Important conclusions reached are that the Munch Pressure-Flow Hypothesis implies a pressure profile , a velocity down the phloem, and an exponential fall in tracer concentration without its lateral leakage.
- Publication
Journal of Experimental Botany, 1973, Vol 24, Issue 5, p896
- ISSN
0022-0957
- Publication type
Article