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Science Exit Project

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James Nightengale

on 25 May 2013

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Transcript of Science Exit Project

Bending Plants and Colorful Lights THE IDEA Phototropism is when plants lean toward their light source, which in most cases, is the sun. Auxins, which are a hormone found in plants, hate sunlight. So they move to the side of the plant that is shady and tell it to grow, and when the shady side becomes heavier than the side with light shining on it, a lean is created. But what if the light source wasn't the sun? How would that affect the amount of phototropism a plant would display? I decided to find out. My Question: How do different colors of light affect phototropism in plants? Hypothesis My Hypothesis: If seeds of the same type are planted and put under different colors of light, then the resulting plants will lean the most towards lights that show the widest spectrum of color like fluorescent and blue, and less towards lights that have a smaller spectrum because those colors will limit the phototropic effect, and the fuller spectrum light will not. Variables Independent: Different colors of light
Dependent: The amount the plant bends from its original position
Controlled: The type of seed, type of soil, amount of watering, amount of time in each lighting environment, amount of space in each environment Experiment Setup The bulk of the experiment was constructed out of cardboard, and a fluorescent light was fit in to the side. The different colors would be gels taped onto the fluorescent bar. The plants were genetically designed to grow very fast, to offer rapid results. The experiment would last as long as it needed to, or until the plants died. Experiment Begins Trial 1 The five colors used in the first trial were green, purple, orange, blue, and unfiltered fluorescent light. Green Purple Orange Blue Unfiltered In this experiment, which lasted from February 6th to the 14th, five plants of the same type were put under different light spectrums to see which ones would bend the most. In the graph above, the higher the number, the more the plant bent toward the light source (ex: 0 would be no bending, 1 would be some bending, and 2 would be extreme bending). The data gathered from Trial 1 shows that unfiltered fluorescent light was extremely effective at getting a large phototropic response from the plants. Other lights, such as green and purple, did not do as well. On Day 4, all of the plants felt a decrease in growth. This is probably because the watering of the plants did not take place as often as it should have. Trial 2 In Trial 2, the five different types of light spectrums used were light yellow, orange, pink, light blue, and unfiltered light. Preparation When setting up for Trial 2, I had to think of what didn't work well and how I could fix it. The purple, green, and blue spectrums didn't inspire much bending in the plants, so I thought I should try using some weaker, less intense colors for the next experiment. The colors like orange and fluorescent would be repeated, because they had demonstrated such good results in the previous trial. I would also have to be more vigilant in terms of giving the plants the same amount of water and taking daily pictures, both day and night. Light Yellow Orange Pink Light Blue Fluorescent This time, things went very smoothly. None of the plants died, as they had in Trial 1. Instead, they continued to lean more and more towards the light source. In the graph above, the plants who had the orange, yellow, and unfiltered fluorescent light showed the most bending towards the light source. The pink and blue showed the second best results. These results suggest that the changes I made from Trial 1 to Trial 2 had a positive effect on the plants. Now I can draw more accurate data and conclusions. Analysis & Conclusions From the data gathered in this experiment, several conclusions can be drawn. After the experiment was done, I had to once again ask myself some questions: why did some of these lights work so well, while others failed?

In both Trial 1 and Trial 2, the unfiltered fluorescent light invoked a large bending in the plants. Why? My theory is that it worked so well because the light gives the plants a lot of the certain types of wavelengths that the plant would need to grow sufficiently, just like the sun would have. This makes the plants want to lean towards the light like they would with the sun. Lights such as the purple, green or blue do not provide these wavelengths, and therefore do not create as much of a bending effect.

My other theory explains why the yellow and orange lights had such a positive effect on the bending of plants. These plants that I used were genetically engineered to be ideal for experiments: they grow very fast, flower very fast, and then die to offer real results quickly. So the plants were most likely have been in their flowering stage when the color filters were put in. Studies have shown that orange, and sometime even yellow light trigger hormones in the plant that make the plant want to begin flowering (which of course it couldn't in this experiment). This may have caused the plants to lean towards the orange and yellow light sources, because it felt natural to use that part of the spectrum in that certain period of growth.

So in Conclusion, I was partly incorrect in my hypothesis. Yes, the fluorescent light did have a positive effect on the amount of bending its plants displayed, but blue was not one of the lights that had such a large effect on the plants. Rather, the yellow and orange lights are the other colors that had the greatest effect on the bending of these plants. Science Exit Project
James Nightengale
801 Possible Errors Most of the errors that occurred in this experiment occurred during the first Trial. I was watering inconsistently, and that may have had a slight change in the overall data I received. Real World Connection A possible application for this kind of science is solar panels. They use solar cells, which take the sun’s light and heat and convert it into electricity. These machines give so much power and use renewable energy instead of fossil fuels. But many of these machines are extremely expensive, meaning fewer people are actually using them. But think of a solar system like a plant: the solar panels would be the ovule and petals, the mechanic part that goes into the ground the stem. The solar panels would just turn towards the part of the "stem" that was warmed up the most from the light of the sun. This would make it easier for the machine and for the builders, and would probably lower the price so more people could invest in renewable energy. Further Studies An idea for further studies is that I would test different plants in the same light and test to see which one would lean the most towards the light source. This would show which kind of plant has the most influential auxins. A possible hypothesis could be: if different kinds of plants were put under the same light source to test which one would have the largest phototropic response, then... (Full Hypothesis would have to be formulated after much research) Bibliography Lawrence, Lois. "The Effect of Incandescent Light on Plant Growth." EHow. Demand Media, 08 Feb. 2010. Web. 06 Dec. 2012. <http://www.ehow.com/facts_5969492_effect-incandescent-light-plant-growth.htmllara.com/discover/5wh/online.asp?story=56>.

Salzwedel, Mark. "Effects of Fluorescent Light on Plant Growth." EHow. Demand Media, 07 July 2009. Web. 06 Dec. 2012. <http://www.ehow.com/how-does_5158355_effects-fluorescent-light-plant-growth.html>.

Samangal, B. "Why Do Plants Lean Toward Sunlight?" Pitara.com. Pitara Kids Network, May 2010. Web. 06 Dec. 2012. <http://www.pitara.com/discover/5wh/online.asp?story=56>.

Thacker, Donna. "How Does Light Affect Plant Growth?" EHow. Demand Media, 28 Oct. 2008. Web. 06 Dec. 2012. <http://www.ehow.com/how-does_4564029_light-affect-plant-growth.html>. Final Words Finally, the history of phototropism is long and rich. Greek philosophers said it was the gods that made the plants bend. And this is still a very unexplored territory- it is after all a complex biological response involving multiple receptors. But just maybe, this experiment may have taken one small step towards a better understanding of phtototropism and just how it works.
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