Leaf Photosynthetic Rates

Photosynthesis is the process used by plants to use light energy to convert carbon dioxide (CO₂) and water into carbohydrates. The photosynthetic rates of leaves can be quanitifed by measuring the rates of CO₂ consumed by the leaf using an infrared gas analyzer. The difference between the input levels of CO₂ versus the output levels of CO₂ can be converted into a photosynthetic rate per unit of leaf area. Negative values indicate respiration by the leaf which can occur at low light intensities. In this lab you will measure the photosynthetic rates of goldenrod leaves at different illuminations.

Click on the "New leaf" button to start a new experiment. Use the up and down triangles on the light control box to increase or decrease the light intensity. Click the Measure button to take a measurment. (It will take a little time for the measurements to settle down to a steady-state value.) Click the add data button to add your data to the table. Measure the photosynthetic rates at light intensities of 0, 50, 100, 150, 200, 250, 300, 350 μmol photons/m²/s. These data will be used for your lab assignment.

This material is provided under the terms of the Creative Commons public license. You may copy, adapt, distribute, and transmit the work or its derivatives. You must attribute the work and its derivatives to Robert A. Desharnais, Ph.D. at California State University, Los Angeles. This work may not be used for commercial purposes.