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STUDIES ON PENETRATION OF DYES WITH GLASS ELECTRODE : IV. PENETRATION OF BRILLIANT CRESYL BLUE INTO NITELLA FLEXILIS
1Laboratories of The Rockefeller Institute for Medical Research.
The Journal of General Physiology
|October 30, 2009
Summary
Cresyl blue free base penetrates Nitella vacuoles, increasing sap pH. The dye salt does not affect pH, confirming cresyl blue
Area of Science:
- Plant physiology
- Cell biology
- Biochemistry
Background:
- Understanding intracellular pH regulation is crucial for plant cell function.
- Dyes are often used as pH indicators, but their ability to cross cell membranes varies.
- Nitella, a large alga, is a model organism for studying plant cell physiology.
Purpose of the Study:
- To investigate the effect of cresyl blue on the pH of Nitella sap.
- To determine if cresyl blue penetrates the vacuole and alters its pH.
- To confirm that the observed pH changes are due to cresyl blue itself.
Main Methods:
- Glass electrode pH measurements of Nitella sap.
- In vitro experiments adding cresyl blue (free base and salt) to sap.
- Spectrophotometric analysis to identify the dye within the vacuole.
Main Results:
- Cresyl blue free base significantly increased Nitella sap pH, similar to in vitro addition.
- Cresyl blue salt did not alter sap pH.
- Spectrophotometry confirmed cresyl blue as the primary penetrating dye.
- Protoplasm extrusion into sap also resulted in a higher pH, mimicking dye effects.
Conclusions:
- Cresyl blue free base effectively penetrates Nitella vacuoles, alkalinizing the sap.
- The pH-raising effect is specific to the free base form of the dye.
- This study validates cresyl blue as a useful tool for probing vacuolar pH in plant cells.
