Integrated Natural Science Wgu Task 3

Photosynthesis

A. Project Plan/Problem Statement

How do you determine photosynthetic rates? What is observed as photosynthetic rates are compared at different wavelengths, light intensities and temperatures? What differences will be observed in unboiled, boiled and dark chloroplasts.

The objective of this experiment is to study how various factors quantitatively affect the rate of photosynthesis in spinach leaves (Spinach oleracea). Factors that will be tested include wavelength of light, boiled, unboiled and dark chloroplasts. These factors will be measured in two different ways.

This experiment is relevant because photosynthesis is important for all life on Earth. Photosynthesis is the only method by which chemical energy is added to the ecosystem (Cummings, Helms & Kosinski, 1997). Only green plants can convert light into chemical energy and store it. All animals depend on this energy. Therefore, it is very important to have an understanding of what variables may or may not affect the all important process of photosynthesis.

A1. Literature Review

This laboratory has been field tested in numerous courses including introductory courses, gifted and talented programs as well as university honors programs. The experimental design is simple and the success rate is high (Ortez, R., 1994). The following sites have conducted similar experiments and were referenced for this lab.

Williamson, Brad. Measuring the rate of Photosynthesis with the Floating Leaf Disk Assay. http://www.elbiology.com/labtools/Leafdisk.html

Richard, David S. Measure of Photosynthetic rate in Leaf Disks. http://www.susqu.edu/FacStaff/r/richard/photosynthlab.html

A2a. Experimental Design Steps

1A. Floating Disk Assay

1. Prepare a 0.2% (1/8 teaspoon per 300 mL water) sodium bicarbonate solution for each trial. This serves as an alternate source of carbon dioxide for photosynthesis and infuses CO2 into the leaves.

2. Add 1 drop of liquid soap to the solution to allow the...