The first part of this module was first designed to replace a first year practical within a Biochemistry and Cell Biology course where students study the effects of light of different wavelengths on photosynthesis in the aquatic plant Egeria. The experiment is a very elegant demonstration of a key concept in photosynthesis but the practicality of running it in large introductory classes was a nightmare. The results were extremely unreliable, often the opposite to that expected and were a poor introduction to the complex process of photosynthesis. With practical classes of 80 students (400 total enrollment) the solution has been the production of a simulation to replace this practical.

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Light Response Curves

The second simulation in this module considers the effect of light quantity on the rate of O2 evolution. Students can use plants collected from the surface of the pond (sun plants) or from deeper water (shade plants). By altering the amount of light incident on the plants, the students can investigate the light levels at which the photosynthetic rate is saturated and are introduced to the concept of light response curves.

Since variation is built into the results students working in groups can produce a set of “replicated” data from which they can calculate means and standard deviations. Module 2 contains complementary material for this second simulation, allowing students to understand the theoretical aspects of plant adaptation to various light levels.

The image below shows the window in which students can enter their results from the simulation. Shown is one of the three sets of sample data to give students some ideas of what kind of light levels to set and (approximately) what kind of curves they may expect to obtain.

CONCEPTS COVERED

Introduction to Photosynthesis
Effect of Light on Pigments
Experimental Procedure
Simulation

Light Response Curve Introduction
Experimental Method
Simulation
Calculations