The Effect of Different Wavelengths of Light on Phototropic Response in Rudbeckia hirta Michaela Alec James Aparna David November 17th, 2014 Research Faculty: Mr. Roche Mentor: Ms. Elizabeth Georgian
Introduction: Rationale, Assumptions, Objectives Tropisms are vital mechanisms in plants that use movement to respond to the environment. Specific kinds of tropisms respond to specific kinds of stimuli, allowing the plant to adapt and survive varying circumstances (Science Buddies Staff 1). Phototropism is a photoresponse and mechanism of plants that alters their development according the the direction and intensity of light. (Pedmale, Celaya, and Liscum 1). The study of phototropism dates back to Greek philosophy, when philosophers had disagreements over whether plants were capable of movement. Today, it is well known and observed that plants will curve towards a lateral light source. (Whippo 1). The purpose of this study is to examine the phototropic effects of varying wavelengths of light on ​
Rudbeckia hirta​
. The rationale behind this experiment is simply the curiosity regarding the subject. It is taught in high school science classes that plants absorb red and blue wavelengths of light for photosynthesis, so will they show a phototropic response to those wavelengths as well? The proposed experiment will be testing this response between red, blue, and white wavelengths of light using the species, ​
Rudbeckia hirta​
. After the experiment is complete, the plants will be transferred to the rain gardens at High Technology High School. This specific species is not only pleasing to look at and native to Monmouth County, but also attracts wildlife such as birds, butterflies, and bees. This influx in organisms could potentially increase the biodiversity on campus, and the success of the rain gardens. (“Rudbeckia hirta” 1 ). Prior experiments have been conducted using the concept of phototropism, such as measuring the curvature of pea plants exposed to unilateral blue light (Britz and Galston 313). The following proposed study will conclude whether plants, specifically ​
Rudbeckia hirta,​
show increased phototropic response towards a certain wavelength of light compared to another. The basis for this experiment is the assumption that all plants will show phototropic response to light in general, allowing us to measure the differences between the responses to different colors of light. Hypothesis: Alternate Hypothesis and Null Hypothesis Alternate The difference in wavelength of light will arouse a noticeable change in the phototropic response of Rudbeckia plants. Null There will be no significant difference in the phototropic response of Rudbeckia plants based on the wavelength of light. Methodology: Materials, Equipment, Facilities Materials Material Availability/Source Rudbeckia hirta​
Seeds (36) To Be Provided by Burpee ​
® Potting Soil To Be Provided by Students Water To Be Provided by High Technology High School Equipment Equipment Availability/Source Digital Camera Provided by Students Plant Cams (4) Provided by Research Faculty at HTHS Pipette Pump Provided by Research Faculty 0.71 Gal. Nursery Containers (36) To Be Provided by Students Fully Enclosed 24” x 24” Cardboard Boxes (4) To Be Provided by Students and High Technology High School Timed Lamps (4) To Be Provided by Research Faculty Colored Cellophane Sheets ( 4 Red / 4 Blue) To Be Provided by Students Computer Equipped With Photoshop Provided By High Technology High School Marker Provided By Students Facilities Facility Availability/Source Research Lab Provided By High Technology High School and Faculty Timeline: December 15th, 2014 Deadline For Acquiring Materials and Equipment December 23rd, 2015 Deadline For Completion of Set­Up January 5th, 2015­ March 16th, 2015 Initial Growth Period March 17th, 2015 ­ March 27th 2015 Conducting Experiment, 4 trials per day March 17th, 2015 ­ March 27th 2015 Data Collection Period March 28th, 2015 ­ March 31st, 2015 Data Analysis Period Methodology: Experimental Design Diagram Title: ​
The Effect of Different Wavelengths of Light on Phototropism in Rudbeckia Plants (​
Rudbeckia hirta​
) Hypotheses: Alternate­ ​
The difference in wavelength of light will arouse a noticeable change in the phototropic response of Rudbeckia plants. Null­ ​
There will be no significant difference in the phototropic response of Rudbeckia plants based on the wavelength of light. Independent variable: Wavelength of Light Levels: Red Light Blue Light White Light # of Trials: 12 12 12 Control? Control Dependent variable: Phototropic response of ​
Rudbeckia hirta Operational definition: ​
Increase in distance moved towards the light source during 24 of dependent variable: hour period. (measured in millimeters) Constants:
Plant (​
Rudbeckia hirta​
) Distance From Light (7”) Amount of Water (2 mL Every Other Day) Type of Soil (Potting Soil) Temperature of Environment (Room Temperature) Planting Container (0.71 gal.) Time Exposed to Light (24 Hours) Exposure to Other Light Sources (No Exposure) Methodology: Experimental Setup, Graphics, Illustrations FIGURE 1 FIGURE 2 Methodology: Procedure 1. Gather the materials necessary for the experiment. (Listed In “Materials, Equipment, and Facilities” Section Above) 2. Plant four ​
Rudbeckia hirta​
seeds per day for seven days in individual, 0.71 gal. nursery containers, ⅛” deep in potting soil. The age of the plants will be staggered, and line up accordingly to the date each trial will be conducted. 3. Label the containers with a marker, according to the date planted, light wavelength being tested, and the trial number. (i.e. Planted: 01/05/15, Red, Trial #1) 4. Grow the plants under normal conditions of room temperature and even white light for ten weeks. a. Using the Pipette Pump, water each plant with 2 mL of water every other day. 5. After each initial growth period for each set of four plants, place the ​
Rudbeckia hirta inside four cardboard boxes, with one plant in each box. 6. Put one lamp into each of the enclosed boxes. The edge of the container holding the plant should be 7 inches, or approx. 18 centimeters, away from the edge of the lamp. (See Fig. 1 in “Experimental Setup, Graphics, Illustrations”) 7. Cover the light bulb of each lamp with the desired color of cellophane, staggering the colors used every other day. (See Fig. 2. in “Experimental Setup, Graphics, Illustrations”) a. Red cellophane will provide red light, blue cellophane will provide blue light, and the control group will be exposed to a lamp with no cellophane, or white light. 8. Calibrate and time the Plant Cam to take pictures every two minutes for a 24 hour period. 9. Set up a Plant Cam inside each box to face the lamp and ​
Rudbeckia hirta. 10. Time the lamps to remain on for 24 hours. 11. Close the boxes containing the plants, lamps, and Plant Cams. 12. Turn on the lamps. 13. Wait for 24 hours, allowing the Plant Cam to record any growth and phototropic response in the ​
Rudbeckia hirta. 14. Repeat steps 4­13 eight more times, alternating each trial with red cellophane, blue cellophane, and no cellophane. As previously mentioned, see Fig. 2 in “Experimental Setup, Graphics, and Illustrations” for details on how to alternate and stagger each trial. 15. Measure the phototropic response of the ​
Rudbeckia hirta​
using the photos taken at the beginning and end of the 24­hour period of each trial. This will be done by calculating the final positioning, or distance moved of the tip of the plant, from the initial position of the base of the plant. Photoshop will be used to measure the distances in pixels. 16. Convert the pixel measurements into millimeters, and record the data. Findings: Observations / Data Tables / Graphs The data we are finding, the percent increase in distance that the plant moved towards the light during growth period, is quantitative data. Each data point is a numerical value, in millimeters. * Phototropic Response: Millimeters moved toward light source. TABLE 1 Phototropic Response of ​
Rudbeckia hirta​
to Different Wavelengths of Light (mm) Red Light Blue Light White Light Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 Trial 8 Trial 9 Trial 10 Trial 11 Trial 12 TABLE 2 Summative Data for Phototropic Response of ​
Rudbeckia hirta​
to Different Wavelengths of Light (mm) Red Light Blue Light White Light Mean Standard Deviation Variation n 12 12 12 The information will then be represented graphically. To do this, a bar graph will be used, and each bar will be the mean percentage of phototropic response to each color. There will be three vertical bars in total, representing blue light, red light, and the control group of white light. The x­axis, representing our independent variable, will be labeled “Wavelength/Color of Light” and the y­axis, representing our dependent variable, will be labeled “Distance Moved Towards Light,” and will be measured in millimeters. The title of the graph will be “Phototropic Response Towards Varying Wavelengths in ​
Rudbeckia hirta​
” Results: Set Up for Inferential Data Analysis (This section to be added in spring semester) Bibliography: Britz, Steven J., and Arthur W. Galston. ​
Physiology of Movements in the Stems of Seedling Pisum Sativum Alaska​
. ​
Plant Physiol​
. N.p., 14 Oct. 1982. Web. 12 Nov. 2014​
. Plant Physiol provides a professional example of an experiment regarding tropisms, including phototropism. From the write up of this experiment, finer details are explained, and a basic phototropism experiment on pea plants is described. Pedmale, Ullas V., R. Brandon Celaya, and Emmanuel Liscum. "Phototropism: Mechanism and Outcomes." ​
The Arabidopsis​
(2010): 1­73. ​
National Center for Biotechnology Information​
. Web. 12 Nov. 2014. This source provides information on phototropism. From this, the basic concept of phototropism is explained, and curiosity and the rationale for the experiment is sparked. The Arabidopsis Book​
explained how phototropism is an important adaptation for plants, what phototropism causes, and how phototropism works. While some aspects of this source were very advanced, it provides a thorough understanding needed to plan, create, and eventually conduct an experiment regarding phototropism. "Rudbeckia Hirta." ​​
. Lady Bird Johnson Wildflower Center, n.d. Web. 15 Nov. 2014. This website, created by Lady Bird Johnson Wildflower Center, provided valuable information about the chosen species for the experiment, ​
Rudbeckia hirta​
. Planting instructions, maintenance, and growth is explained meticulously. The site also mentions details such as size and requirements of the plant species. Science Buddies Staff. "Plants on the Move! Experiments with Phototropism" ​
Science Buddies​
. Science Buddies, 23 Oct. 2014. Web. 12 Nov. 2014 Science Buddies explains a simple, high school level experiment on phototropism, and helps students brainstorm ways to create an experiment related to the concept. A basic and generic procedure and materials list is provided, as well as guidelines and tips. Whippo, Craig W. "Phototropism: Bending Towards Enlightenment." ​
The Plant Cell​
. N.p., May 2006. Web. 12 Nov. 2014. This reference gives background on the study of phototropism in the past, as well as modern knowledge and advancements. In ancient Greece, some philosophers did not believe that plants were able to move, prompting the study of tropisms. Information on the subject has greatly increased since then, and it is now understood that phototropism is a complex biological response. Primitive experiments and studies are also explained. 
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