The Stress Effects of Phototropism and

Different Colored Lights on Arabidopsis Wild-type

and Mutant Strains.

By: Brad Cole

Rita Hunt-Woodland

Monarch High School

Purpose of Project

We investigated the effects of phototropism (full spectrum, blue light, red light, and

black light) on Arabidopsis wild-type and mutant strains in order to determine the

possible functions of the DCL-4 and RDR-6 genes when the plant is put under

stress.

Why use Arabidopsis?

• Short life cycle 6-8 weeks• Small convenient to grow plant• Easily matched environmental conditions• Small genome• Has been completely genetically mapped• Closely resembles genes in crop plants

RDR6 and DCL4 Mutants

•Arabidopsis contains the genes for RDR 1-6, and DCL genes 1-4.

•RDR - RNA dependant polymerase.

•DCL - Dicer Like

RNAi is the immune response of the plant. The RISC complex

cleaves viral looking double stranded RNA within the cytoplasm

of the cell so that the enzyme/protein can never be produced .

Hypotheses1. If our Arabidopsis plants rely on blue-violet light and red light

in order to grow (this is according to Engelmann's theory that

plants perform photosynthesis faster when blue-violet and red

light are present), and we put our wild type and mutant strands

into purely blue light to grow for 30 days, then the growth will

not occur as fast because the plants rely on both the red and

blue –violet light and the plants in this stressed condition will

not get the red light in order to aid in photosynthesis and will

have only light blue light instead of the preferred blue-violet

light.

Hypotheses cont.

• If our Arabidopsis plants rely on both blue-violet and red light to grow faster, and we place both our wild type and mutant strands in red light to grow for 30 days, then the plants will grow as if it were under normal conditions or more efficient than under normal conditions because the plants need red light in order for optimization of the light dependent reactions in photosynthesis and with the red light being in abundance then the plants will continue to grow normally.

Hypothesis cont.

• If the black light produces UV rays and a dark violet light which creates high energy frequencies and can mutate DNA, and we place our wild type and mutant strands in the black light to grow for 30 days, then the plants will not be able to grow and if they do grow then the color pigments will be mutated.

Hypotheses cont.

• If our Arabidopsis requires light and water in order to grow and perform photosynthesis, and we continuously switch the plants from growing in light and growing in dark, then our plants will continuously grow because although the light is only not present for a week at a time the plants still need continuous light in order to perform photosynthesis.

MethodsIn our experiment we looked at the

effects of phototropism, red light, blue, and black light on Arabidopsis wild type and mutant strands. In order to complete this we had to build a box in which we could test the phototropism and all the different colored lights. The box that we constructed had a door and three dividers so that we could separate all of the different light colors from each other. By doing this the dividers acted a s barriers so that each light would not leak into any of the other sections. This allowed us to get different results for each color of light.

WateredOver the course of 4-6 weeks we continued to water

the plants every other day with the normal nutrient water that is needed to maintain growth and development in our plants. Our water consisted of Miracle Grow for indoor plants and each tray received 1400 milliliters of water.

Conclusion

• Plants need a specific wave length and amount of light.

• Plants need a constant amount of light to convert the light energy to chemical energy in order to grow and maintain life.

• There is a direct connection between environmental stresses and expression of RNAi and other developmental genes.

Conclusion cont.• Under the black light, there was little to no growth and when there was

growth the plants were albino. • UV wave lengths affect the growth of plants because there isn’t the

necessary light in order for the plant to grow and develop.• The UV light was not the preferred energy for the photosynthetic pigments.

So we were not seeing the normal pigments, and the plants were albino.• There seems to be a link with environment (epigenetic effects) and

DNA/RNAi expression. • The stems were long and narrow, and wilted easily which made us conclude

that the plants were reaching up higher than they usually would in order to find the necessary light.

• Because there was not enough of the necessary light the plants all died within 4 weeks.

• We are re-testing this to see if we obtain the same results.

Conclusion cont. • Like under the Black Light, there was minimal growth under both the red

and blue light. • We tested the red and the blue light separately because we knew that with

photosynthesis, plants prefer red and blue-violet light. So when there is a mixture of the two we knew that there would be growth, but we wanted to see what would happen when we separated the colors of light.

• Our conclusion is that the plants needed both the red and the blue-violet light in order to perform photosynthesis and to convert the light energy to chemical energy.

• Growth and development of the plant will be minimal without both the red and the blue light mixed together.

• We are re-testing this by mixing the blue and red light together in order to see what the growth pattern is.

We’d like to thank…

• Dr. Lisa Johansen for helping us by supplying us with seeds and soil, and for checking in with us to see how our plants are growing.

• Mrs. Kristin Donley for helping us with our ideas for how to grow our plants and for her overall guidance.

Bibliography• http//:www.jasons-indoor-guide-to-organic-and-

hydroponics-gardening.com; September 2008• Andrew Fire and Craig Mellow, (2006) the Nobel prize in

physiology/medicine (http//:nobelprize.org)• Elliot Meyerowitz, Prehistory and History of Arabidopsis

Research, Plant Physiology, January 2001, vol. 125, pp. 15-19

• Sabina Leonelli, Arabidopsis, the Botanical Drosophilia: from Mouse Cress to Model Organism; March 2007, Endeavor, vol. 31 No. 1, pp.34-38

Bibliography

• Andrew Fire and Craig Mello. “The Nobel Prize In Physiology or Medicine for 2006.” NobelPrize.org. November 20, 2008. http://nobelprize.org

• Fralin Biotechnology Center. “PREP Experiment Guide”. Virginia Polytechnic Institute and State University. Dec. 1, 2008 http://www.prepbiotech.vt.edu/