Transpiration
The transpiration rate will be determined using a small piece of a plant. The plant will be attached to a PASPORT Barometer Sensor, and the change in pressure at the end of the plant stem will be recorded as the transpiration rate. In addition, the system will be challenged by increasing the humidity (using a plastic bag over the plant) to determine the effect of humidity on the rate of transpiration.
Students will observe that rate of transpiration is greater when the fan is operating and evaporation increases.
Lab Summary
In this exploration, students use a barometer as a potometer to measure the rate of water uptake in plants due to transpiration. This activity demonstrates the concept of "transpiration pull." In addition, the investigation will explore the effects of environmental factors (air movement) on the rate of transpiration.
Downloads
- Computer-based lab (PDF, 620 KB) (619 KB, .pdf)
(student version)
- Xplorer GLX-based lab (PDF, 604 KB) (537 KB, .pdf)
(student version)
Method
Use the Barometer as a potometer to measure the rate of water uptake in plants due to transpiration.
Here's What You Need
U.S. Educator prices shown.
Probeware
PASPORT Barometer/Low Pressure Sensor (PS-2113A) - $89
Measures atmospheric pressure changes and doubles as a low pressure sensor. For use with PASPORT Interfaces.
Xplorer GLX (PS-2002) - $349
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
Other Products
Small Tripod Base and Rod (SE-9451) - $24
The steel rod is 9.5 mm (3/8 in.) in diameter and 50 cm long.
Buret Clamp (SE-9446) - $12
The V-shaped, plastic-coated jaws will gently hold a buret and lock at any angle.
Other Materials
- Electric Fan
- Razor Blade or Scissors
- Eye Dropper
- Protective Gear
- Modeling Clay 5.0 g
- Plant Seedling
- Water, 1.0 L
- Glycerin (C3H5(OH)3), 1.0 mL
