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THE EFFECT OF AUXINS UPON PROTOPLASMIC STREAMING
1Biological Laboratories, Harvard University, Cambridge.
The Journal of General Physiology
|October 30, 2009
Summary
Auxins, plant hormones, accelerate protoplasm streaming in Avena coleoptiles at low concentrations, influencing growth. Higher concentrations inhibit streaming, mirroring effects on elongation.
Area of Science:
- Plant Physiology
- Molecular Biology
- Biochemistry
Background:
- Plant growth is regulated by auxins, a class of plant hormones.
- Previous research suggested auxin's growth-promoting effects are mediated by cellular components rather than the cell wall.
Purpose of the Study:
- To investigate the effect of auxins on protoplasm streaming in Avena coleoptiles.
- To determine if auxin's influence on streaming is linked to its growth-promoting activity.
Main Methods:
- Quantitative measurement of protoplasm streaming rate in Avena coleoptile epidermal cells.
- Treatment with varying concentrations of indole-3-acetic acid and other auxins.
- Comparison with control groups and non-auxin substances.
Main Results:
- Indole-3-acetic acid accelerated protoplasm streaming at concentrations of 0.002–0.5 mg/L, with optimal effect at 0.01 mg/L.
- Higher concentrations (>0.5 mg/L) of indole-3-acetic acid inhibited streaming.
- Other auxins (coumaryl-3-acetic acid, allocinnamic acid) showed similar effects on streaming, correlating with their known activities.
- Substances like ethylene chlorhydrin, histidine, and urea did not affect streaming.
Conclusions:
- Auxin's effect on protoplasm streaming is immediate and occurs within a concentration range similar to that which promotes growth.
- The observed effects on streaming are likely an early, integral step in auxin-mediated plant growth processes.
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