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Cell wall pH and auxin transport velocity
1Department of Botany, San Diego State University, California 92182, USA.
Plant Physiology
|September 1, 1984
Summary
This study challenges the chemiosmotic hypothesis for auxin transport. Acidic conditions aid auxin uptake but do not increase its transport speed or secretion, contrary to predictions.
Area of Science:
- Plant Biology
- Molecular Biology
- Biochemistry
Background:
- The chemiosmotic polar diffusion hypothesis predicts that decreasing cell wall pH enhances auxin transport.
- Auxin (indole-3-acetic acid, IAA) is a critical plant hormone regulating growth and development.
Purpose of the Study:
- To experimentally test the chemiosmotic hypothesis regarding the effect of cell wall pH on auxin transport.
- To investigate the relationship between cell wall pH, auxin uptake, pulse velocity, and basal secretion.
Main Methods:
- Avena coleoptile sections were treated with fusicoccin, cycloheximide, or pH 4.0/8.0 buffers.
- Polar transport capacities, auxin uptake, and IAA pulse velocity were measured.
- The effect of receiver pH on auxin delivery was assessed.
Main Results:
- Fusicoccin enhanced IAA uptake, while cycloheximide and pH 8.0 buffer reduced it.
- Fusicoccin decreased IAA pulse velocity, whereas cycloheximide increased it.
- Acidic cell wall pH facilitated IAA uptake but did not enhance pulse velocity or basal secretion.
Conclusions:
- The findings contradict the chemiosmotic hypothesis for auxin transport.
- Cellular IAA uptake is influenced by acidic wall pH, but this does not correlate with increased transport velocity or secretion.