CARBON DIOXIDE INTAKE RATES UNDER DIFFERENT LIGHT WAVELENGTHS

1. CARBON DIOXIDE INTAKE RATES UNDER DIFFERENT LIGHT WAVELENGTHS Andrea Liu ArieleAndalon Emilie Biondi Lauren Heller Stephanie Lee

2. Research Question Which wavelength of light (green, red, yellow) promotes the greatest rate of carbon dioxide intake (ppm/s)?

3. So What? • Breeding plants in greenhouses: how to improve rates of plant growth (since carbon dioxide intake is directly related to photosynthesis) • Environmental effects—most effective ways to remove excess carbon dioxide from the atmosphere via plants

4. Variables Independent variable: • Wavelength of light (green, red, yellow) Dependent variable: • Carbon dioxide concentration levels (parts per million or “ppm”) • Controlled variables on next slide

5. Controls

6. Materials • Pasco Xplorer GLX • PS-2110 Carbon Dioxide Gas Sensor • 2 250mL sampling bottles • 5 Ecobulb party lightbulbs (blue, indigo, yellow, red, green) • Dechlorinated tap water • Tub of Lemna minor fronds • 1 metric ruler • 2 lemna stirring sticks • 2 200 mL beakers • Ring stand • Utility clamp

7. Method for each of the 2 Trials • Measure out and pour 100 mL of dechlorinated tap water into each of two 250 mL sampling bottles (two trials) • Set up a ring stand and attach a 60W light bulb of a certain wavelength (red, green, yellow) • Calibrate the Xplorer GLX • Place enough lemna minor into the sampling bottle to cover the surface of the water • Insert the GLX probe securely into the sampling bottle • Turn on the GLX to collect carbon dioxide concentration (ppm) data every 30 seconds • Collect data for 30 minutes

8. Picture 1: Adding the Lemna minor to 100 mL of dechlorinated tap water

9. Picture 2: Distance from 60W light bulb to Lemna minor fronds Light bulb 25 cm from the lemna fronds (diagonally)

10. Picture 3: Lab set-up 60W light bulb PS-2110 Carbon Dioxide Gas Sensor Lemna minor fronds in 100 mL of dechlorinated tap water Sampling bottle Pasco Xplorer GLX

11. Results

12. Results: Data Table #1 Rate of Carbon Dioxide Intake (ppm/s) of Lemna minor under Green, Red, and Yellow Wavelengths of Light *Note: Rates are positive even though carbon dioxide levels decrease because the plant itself is gaining carbon dioxide

13. Results: Graph #1 Rate of Carbon Dioxide Intake (ppm/s) of Lemna minor under Green, Red, and Yellow Wavelengths of Light

14. Results: Biological Explanation of Carbon Dioxide Intake Rates (ppm/s) Under Red Wavelength of Light • The Lemna minor exposed to the red light wavelength exhibited the fastest rate of carbon dioxide intake (0.10375 ppm/s). • Fastest rate of carbon dioxide intake means that the Calvin Cycle (which requires carbon fixation) is occurring most frequently, so photosynthesis is triggered at the highest rate2(Campbell 172). • Red light is the most effective type of visible light for plant growth because it is absorbed best by chlorophyll pigments in chloroplasts to trigger photosynthesis1(Bareja).

15. Results: Biological Explanation of Carbon Dioxide Intake Rates (ppm/s) Under Yellow Wavelength of Light • The Lemna minor exposed to the yellow light wavelength exhibited the next fastest rate of carbon dioxide intake (0.08765 ppm/s). • The yellow light is absorbed at a lesser rate and reflected at a higher rate than the red light1(Bareja).

16. Results: Biological Explanation of Carbon Dioxide Intake Rates (ppm/s) Under Green Wavelength of Light • The Lemna minor exposed to the green wavelength showed the slowest rate of carbon dioxide intake (0.0239 ppm/s). • Chlorophyll reflects the green wavelength of light at the highest rate, making it less useful for photosynthesis. • This also explains why chloroplasts and, in turn, the Lemna themselves are green, as the wavelength of visible light that is most reflected is the one that is mainly perceived by the human eye.

17. Sources of Error • Lemna are continuously photosynthesizing in a closed system—there is no replenishment of carbon dioxide or nutrients in the water (by the time it gets to the last IDV, it has less resources available for photosynthesis). • The lemna used in the experiment may only be a strain representative of lemna in the local environment and may not necessarily be representative of lemna in other areas.

18. Suggested Improvements • Could get lemna grown from multiple environments for results that are representative of a more widespread area. • Between trials, take the stopper off for a longer period of time to allow for carbon dioxide replenishment. • Conduct more trials for more accurate data. • Include additional IDVs if possible to account for more of the color spectrum.

19. Ideas for Further Research • Perform the experiment on different kinds of plants (ex: non-aquatic plants or aquatic plants that thrive beneath the surface). • Observe the effects of different IDVs on rates of carbon dioxide intake: • Temperature • Light bulb wattage • Nutrients in the water • Distance from the light bulb to plant • pH of liquid • Amount of water

20. Citations 1Bareja, Ben G. “What is Light Quality, Effects on Plant Growth.” CropsReview.Com. N.p., Apr. 2011. Web. 21 Jan. 2013. <http://www.cropsreview.com/light-quality.html>. 2Campbell, Neil A., and Jane B. Reece. Biology. 7th ed. San Francisco: Pearson, Benjamin Cummings, 2005.