Featured in PASCO’s Advanced Biology through Inquiry Teacher Guide

Advanced Biology through Inquiry Teacher Guide

(PS-2852)

This manual features 22 challenging, standards-based, inquiry lab activities for AP, IB, and honors programs.

Transpiration

Lab Summary

Students use a low pressure sensor (barometer) and a weather sensor to investigate the rate of transpiration in plants under normal and humid conditions.

Theory

Students investigate the rate of transpiration in plants under normal and humid conditions and have an opportunity to conduct inquiry experiments of their own design to test additional factors. In the Initial Investigation, students create a potometer using a pressure sensor and they monitor microclimate conditions using a weather sensor. The potometer measures transpiration by detecting the change in pressure due to the evaporation of water from the leaves of a plant sample.

The Initial Investigation provides students with sample data from a “whole-plant” transpiration experiment to introduce students to this alternate method of measuring transpiration. For experiments of their own design, students can use either the potometer method or whole-plant method to measure how certain factors affect the rate of transpiration.

Method

  • In order for transpiration to occur, it is critical that there is an unbroken water column that extends from the water in the tubing to the water in the xylem of the plant. Any air bubbles in the tubing or at the cut surface of the stem will affect the data. This is why the tubing and plant stem must remain submerged in the tub of water during the setup.
  • The assembly is difficult for one person to coordinate. Students should work in pairs to complete the procedures.
  • The stem of the plant sample must fit tightly in the opening of the tubing. If students collect plant samples from the schoolyard or home, they should take the tubing outside with them to test for a good fit of the stem in the tubing. When using plants obtained this way, students do not need to immerse the plant samples in water in the field. They can cut the sample from a plant in the schoolyard and then cut the stem again (as specified) during the procedure of the Initial Investigation.
  • To ensure an airtight seal, a small piece of paraffin film can be wrapped around the tubing edge where the plant stem is inserted. Alternatively, a dab of petroleum jelly can be applied at the edge of the tubing. However, the paraffin film or jelly is not sufficient to provide a seal if there is a gap between the stem and tubing. Avoid getting jelly in the tubing as it is difficult to remove.

Sensors / Equipment Used:

PASPORT 6-in-1 Weather Sensor

(PS-2154A)

Measures barometric pressure, relative altitude, absolute and relative humidity, dew point, and temperature. For use with PASPORT Interfaces.

PASPORT Colorimeter Sensor

(PS-2121)

Our PASPORT Colorimeter records all 4 wavelengths simultaneously--no need to guess at wavelength to get a quality measurement.

Materials Used:

ME-6667 EcoChamber

The Associated Bundle:

Advanced Biology Standard Sensor Bundle

(PS-2851)

Contains an EcoChamber, a Metabolism Chamber and all the probeware needed to perform the activities in the Advanced Biology through Inquiry lab manual.

Interface Required

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