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PROTOPLASMIC POTENTIALS IN HALICYSTIS
1Laboratories of The Rockefeller Institute for Medical Research.
The Journal of General Physiology
|October 30, 2009
Summary
Halicystis cells establish a steady electrical potential difference (P.D.) across their protoplasm. This P.D. is sensitive to external salt solutions, indicating ion transport mechanisms.
Area of Science:
- Plant physiology
- Cellular electrophysiology
Background:
- The electrical properties of plant cell membranes are crucial for understanding transport processes.
- Halicystis, a marine alga, provides a model system for studying cellular electrophysiology.
Purpose of the Study:
- To investigate the electrical potential difference (P.D.) across the protoplasm of Halicystis cells.
- To determine the effect of various ionic solutions on the cellular P.D.
Main Methods:
- Impaling Halicystis cells on capillaries to measure electrical potential difference.
- Exposing cells to different solutions including sap, balanced salt mixtures, and individual salt solutions (NaCl, CaCl(2), KCl, MgSO(4), MgCl(2)).
Main Results:
- A steady P.D. of 60-80 millivolts was recorded, with the outer protoplasm surface being positive.
- Contact with sap and balanced NaCl-CaCl(2) mixtures reduced the P.D.
- Complete abolition of P.D. occurred in solutions of NaCl, CaCl(2), KCl, MgSO(4), and MgCl(2).
- Prompt recovery of P.D. was observed upon return to seawater.
Conclusions:
- Halicystis cell membranes exhibit significant electrical potential differences.
- The P.D. is dependent on the ionic composition of the external environment.
- Specific ions play a critical role in maintaining the cellular electrophysiological state.
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