Quick Answer:The Ganong’s Potometer is a borosilicate glass potometer on a base, about 250 mm × 150 mm, with a graduated horizontal capillary, a reservoir with ground-glass stopcock and a wide-mouth specimen arm.
Last updated: 19 October 2026
Key Features
Borosilicate glass 3.3.
Permanent high-contrast scale on the horizontal capillary arm.
Vertical glass reservoir with ground-glass stopcock for quick resets.
Wide-mouth vertical arm with a rubber bung for airtight shoot insertion.
Mounted on a stable base.
Technical Specifications
Specification
Value
Material
Borosilicate glass 3.3
Size
About 250 mm × 150 mm
Capillary
Horizontal, permanent graduated scale
Reservoir
Vertical glass cylinder, ground-glass stopcock
Specimen arm
Wide mouth, rubber bung
How It Is Used
With every part filled with water, a shoot cut under water is sealed into the specimen arm, and a single air bubble is let in by lifting the capillary end briefly out of the water beaker. Transpiration pulls water from the tube and moves the bubble across the scale; opening the reservoir stopcock sends it back to the start. It is used to demonstrate the transpiration pull and the cohesion–tension theory.
Frequently Asked Questions
How is an air bubble introduced in the Ganong’s Potometer?
The far end of the capillary is lifted briefly out of the beaker of water, letting in a single bubble that then moves along the scale.
