What are the Effects of Light Intensity on the Rate of Photosynthesis and Oxygen Production in Plants? (page 2)

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Author: Michael Calhoun

Research Questions

  • What isPhotosynthesis?
  • During process of sugar production in this project carbon dioxide combines with water to form glucose sugar and what gas is released?
  • Would this investigation have worked if a light source was not present?
  • Does distance (intensity) of light from the planet increase the rate oxygen production? 

Terms, Concepts and Questions to Start Background Research

Photosynthesis, chlorophyll, oxygen

Experimental Procedure

  • Get a sprig of elodea. Remove several leaves from around the cut end of the stem. Slice off a portion of the stem at an angle and lightly crush the cut end of the stem.
  • Place the plant under the funnel as shown and filled with water. Add a pinch of baking soda powder to the test tube. Then fill the test tube with water and place on top of the funnel as shown in figure 1 make sure there is no air in the test tube.

Figure 1

  • Place this set-up in a darken room or closet for several hours, after the set time period has pasted check to see if gas has collected in the test tube.
  • Next, place a light source 5 cm from the plant. After one minute, count and record the number of oxygen bubbles rising from the cut end of the stem. Count bubbles seen for five minutes.

  • Move the lamp so it is 10 cm from the plant. After one minute count and record bubbles for five-minutes. Repeat the same procedure, but this time move the light source 15 cm away and count the bubbles seen. Record the results.
  • Light a thin piece of wood with a match, and blow out the flame. Remove the test tube, invert it, and insert the glowing wooden splint into the test tube as shown to the left. Note any evidence of it re-lighting.  

Distance of light source 

5 cm

10 cm

15 cm

Number of bubbles

  • Using graph paper or a computer equipped with Excel® visually display the data in the table by plotting a bar or line graph showing the rate of oxygen production along the vertical (Y) axis verses the distance of the light source along the horizontal (X) axis. 


Title: Photosynthesis, Authors: David O. Hall and Krishna Rao, Publisher: Cambridge University Press, ISBN-10: 0521644976 ISBN-13: 978-0521644976

This book is a clear, concise and vivid account of the process of photosynthesis. The attractive presentation of this book, including the frequent use of line illustrations and color plates, leads the reader into a fascinating introduction to this sometimes complex topic. The details of photosynthetic processes at the macro and molecular level are discussed based on the results of biochemical, biophysical, and genetic studies. To aid students in their practical work, a set of simple experiments are described and explained along with a comprehensive further reading list is included. Although aimed primarily at college students however; the young investigator and his or her parents (teachers) can use this book as a general reference resource.

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