Featured in PASCO’s College Biology Instructor Guide

College Biology Instructor Guide


College Instructor edition with 26 experiments covering introductory and general biology topics.


Lab Summary

Use a barometer to explore the effects of environmental factors, such as air movement, on the rate of transpiration in a plant.


Students observe the rate of transpiration in a plant and then test the effects of various environmental factors on that rate. Students also observe the differences between monocot and dicot stems and relate their structure to their functions.

  • Students measure the effects of wind, light, and humidity on transpiration rate.
  • Students relate the properties of water to water transport in plants.
  • Students study the organization of the xylem in a plant stem as it relates to its function.


Students gain experience conducting the following procedures:

  • Setting up a potometer and a barometer sensor to measure the rate of transpiration in a plant.
  • Measuring the rate of transpiration under different environmental factors (wind, light, and humidity).
  • Calculating the surface area of the leaves used in the transpiration experiment.
  • Observing prepared slides of monocot and dicot stems.

Sensors / Equipment Used:

PASPORT Barometer/Low Pressure Sensor


Measures atmospheric pressure changes and doubles as a low pressure sensor. For use with PASPORT Interfaces.

PASPORT Sensor Extension Cable


Allows an additional two meter length extension on all PASPORT sensors.

Materials Used:

100-watt light source 
Compound light microscope 
Dicot stem prepared slide 
Disposable pipet 
Electronic Balance - 1 per class
Glycerin - A few drops
Heat sink (large beaker or aquarium filled with water)
Knife or single-edge razor blade 
Large Base and Support Rod 
Monocot stem prepared slide 
Petroleum jelly - 2 to 3 g
Plant seedlings, 12-25 cm tall 
Spray bottle with water 
Three-Finger Clamp 
Transparent plastic bag 
Utility Clamp 
Wide, shallow bowl or tub filled with water 

The Associated Bundle:

College Biology Bundle


A complete probeware bundle designed for PASCO's College Biology curriculum

Interface Required

This experiment may require software and an interface for data collection.