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Effect of pH on IAA Uptake by Maize Root Segments
1Institute of Plant Biology and Physiology, Biology Building, University of Lausanne, 1015 Lausanne, Switzerland.
Plant Physiology
|February 1, 1987
Summary
Zea mays root uptake of indoleacetic acid (IAA) involves saturable and nonsaturable processes. Saturable uptake is pH-dependent and requires a proton gradient, suggesting active transport mechanisms in root growth.
Area of Science:
- Plant Physiology
- Molecular Biology
- Biochemistry
Background:
- Indoleacetic acid (IAA) is a crucial plant hormone regulating root growth and development.
- Understanding the mechanisms of IAA uptake is vital for comprehending plant hormone signaling pathways.
Purpose of the Study:
- To investigate the kinetic and mechanistic aspects of IAA uptake in Zea mays (corn) root segments.
- To determine the role of proton gradients and pH in the saturable component of IAA uptake.
Main Methods:
- Utilized radiolabeled [5-(3H)]indoleacetic acid (IAA) to quantify uptake in Zea mays root segments.
- Assessed the effect of pH and the proton ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone on IAA uptake kinetics.
Main Results:
- Identified both nonsaturable and saturable processes governing IAA uptake.
- The saturable component exhibited a pH optimum of 5.0 and was inhibited by a proton ionophore, indicating proton gradient dependency.
- Non-saturable uptake was unaffected by the proton ionophore.
Conclusions:
- The saturable uptake of IAA in Zea mays roots is an active, proton-gradient-dependent process.
- High proton extrusion in root elongation zones likely enhances both saturable and nonsaturable IAA uptake, supporting root growth.
