PROTOPLASMIC ASYMMETRY IN NITELLA AS SHOWN BY BIOELECTRIC MEASUREMENTS

Area of Science:

• Plant physiology
• Cell biology
• Electrophysiology

Background:

• Understanding the electrical properties of plant cell membranes is essential for elucidating cellular functions.
• Previous studies have indicated potential differences across protoplasmic surfaces, but detailed characterization is ongoing.

Purpose of the Study:

• To investigate and quantify the electromotive force across the protoplasmic surfaces of Nitella cells.
• To determine if a radial polarity exists and to compare it with findings in other plant species.

Main Methods:

• Utilizing multinucleate Nitella cells, one end was selectively killed with chloroform to serve as a zero potential reference.
• Measuring the potential difference across the protoplasm by leading off from an active point to the killed region.

Main Results:

• A significant electromotive force of approximately 15.9 millivolts was detected between the inner and outer protoplasmic surfaces when both were in contact with cell sap.
• The inner protoplasmic surface was found to be positive relative to the outer surface, indicating a consistent radial polarity.
• This observed radial polarity in Nitella is comparable to findings in Valonia, suggesting a conserved cellular mechanism.

Conclusions:

• The protoplasmic surfaces of Nitella cells exhibit distinct electrical potentials, establishing a phenomenon termed radial polarity.
• This finding contributes to the understanding of bioelectrical phenomena in plant cells and provides a basis for further electrophysiological research.