Using a Bubble Potometer for Measuring Transpiration

Overview

A bubble potometer is a device used to measure the rate of water uptake by a plant, which is often related to the rate of transpiration. This process involves setting up the potometer and conducting several readings to determine the rate at which an air bubble travels along a capillary tube.

Setup Instructions

1. Immerse the Potometer

   • Fully immerse the bubble potometer in water.
   • Ensure no air bubbles are trapped inside.

2. Prepare the Plant Shoot

   • Cut a leafy shoot from a plant.
   • Fit the shoot tightly into the potometer while under water.

3. Secure the Potometer

   • Remove the potometer from the water.
   • Immediately close the tap of the reservoir.
   • Place a beaker of water at the end of the capillary tube.

4. Seal and Equilibrate

   • Smear all junctions with Vaseline to prevent water leakage.
   • Dry the leafy shoot with tissue paper.
   • Wait for about 5 minutes for equilibration.

Measurement Process

1. Introduce an Air Bubble

   • Lift the end of the capillary tube out of water briefly to introduce an air bubble.
   • Ensure the bubble moves into the graduated part of the capillary tube.

2. Record Positions

   • Record the initial position of the air bubble.
   • After a set period (e.g., 15 minutes), record the final position.

3. Repeat the Measurement

   • Open the reservoir tap to reset the bubble to the starting position.
   • Repeat the measurement process for at least two more readings.

Calculations

• Calculate the distance traveled by the air bubble.
• Determine the rate of movement of the air bubble as an indication of transpiration rate.