Statement of Problem
Does the color of light affect the growth of an Alaskan pea plant?
Review of Literature
Seeds must protect themselves until they are in the right conditions for them to grow. Until the conditions are right, seeds are dormant and appear dead and it is difficult to tell if they are actually alive (Germination). The embryo within a seed will eventually die while it is dormant if it doesn’t begin germination by a certain time. Depending on the seed, the length of viability can be a few weeks, to hundreds of years (Germination). Germination begins when dormant seeds are under conditions that are necessary for growth and survival, such as light, water and warmth (Kennell). Germination is the process in which growth in a plant seed are activated from a resting stage and begin to grow (Kennell). To begin germination, a seed must imbibe, or absorb, large amounts of water (Hangarter). This is done in order to activate enzymes, hydrate a seed’s food supply, and begin plant respiration and the duplicating of the plant cells. As the seed continues to absorb more water, the embryo breaks open the protective seed coat, emerging as a plant (Kennell). The first part of the part of the seedling to come out from a plant is the root and is eventually followed by the shoot of the plant.
Light is a necessary factor for plants because without it, they would not be able to undergo photosynthesis, the process in which plants make their food. Quality, quantity, and duration of light are the most important characteristics of light for a plant (VanDerZaden). The amount of light given determine a plant’s capacity of producing food (VanDerZaden). Therefore, plants grow better in the summer because of the amount of light that it absorbs along with the fact that the temperature is ideal for plant growth. The quality of light has to do with the color/wavelength (VanDerZaden). Sunlight is the most effective on plant growth because it consists of the complete range of wavelengths (VanDerZaden). Plants absorb red and blue lights causing those two colors of light to be the most effective on plant growth. Green light is the least effective because plants actually reflect green light rather than absorb which is the reason why plants appear green (Whiting). The reason fluorescent lights are effective on the growth of plants is because it is high in the blue wavelength which is helpful to start up seedlings (VanDerZaden). The amount of time plants are exposed to light, or photoperiod, determines the flowering in plants (VanDerZaden). For a time, it was believed that the period of light caused flowering and triggered other responses in a plant but the length of uninterrupted darkness is what effects the floral development (VanDerZaden).
It is important for seeds to be able to be dormant because that they can be saved and planted at a later time. Dormant seeds are only able to be planted because of germination which “wakes up” or activates the seeds. If seeds could not be germinated, then dormant seeds could not be planted which would mean less crops and flowers which would effect in a negative way. Many animals would die because crops and also flowers are near the bottom of the food chain and are necessary in life for almost all living things, even if an animal is a carnivore. Germination is not the only thing necessary for plants’ growth. Plants need water, nutrients, carbon dioxide, warmth and a source of light. Light is a key part of photosynthesis and without it, a plant would not be able to produce food for itself and it would eventually die. Germination and light are necessary in plant growth, and plants are necessary for all living things.
Hypothesis
As the growth a pea plant is exposed to different colors of light (red and green), the plant’s growth will be better in the red light.
Variables & Groups
Experimental groups: Color of light (red, green, and standard light bulb)
Dependent Variable: The growth of the plants affected
Control Variables: The plant getting light form the non-colored, standard light bulb.
Extraneous Variables: Depth of the pea, amount of water, temperature of water, length of soaking, and light intensity.
Materials
The experiment requires: peas, three different colors of light bulbs (red, green and a standard light bulb), potting soil, thirty Dixie cups, and water.
Procedure
- Gather materials.
- Soak peas in water for twenty-four hours.
- Place peas in between two damp paper towels until they have slightly sprouted.
- Plant one pea per Dixie cup, filling the cup halfway with potting soil.
- Water plants.
- Place ten underneath a lamp with a red light bulb, another ten under green light, and the last ten underneath a lamp with a standard light bulb.
- Measure and record the growth of each plant everyday and water as needed.
- Find and record the average growth of each group of plants
Results
The plants that grew under the green light grew the tallest and the average growths in centimeters each day for the plants were: 0, 1, 1.25, 2.1, 3.6, 4.7, 6.28, 10.3, 11.5, 13.4, 16.5, 19.1, 20.6, and 22.5. The plants under the standard light bulb grew the second tallest and the average growths in centimeters each day for the plants were: 0, .86, 1.12, 1.7, 2.7, 3.9, 6.05, 6.1, 8.74, 11, 14, 15.8, and 20.2. The plants that grew under the red light grew the least, even though the differences between the numbers were very small. The average growths in centimeters for each day for the plants under the red light bulb were: 0, 0, 1.2, 2.1, 3.45, 5.125, 5.96, 8, 10.6, 12, 14, 15.6, 17.2, and 18.8.
Conclusion
The hypothesis predicted that if plants were put under colored lights (red and green) that the plants growing under the red light would grow the best. This was proven false in the experiment. The plants under the red light grew a total average of 8.2 centimeters throughout the experiment and the plants under the green light grew a total average 8.8 centimeters and finally the plants under the standard light bulb grew 8.3 centimeters. The estimated plants that would grow the most actually grew the least. Most plants absorb red light, causing red light to be very useful in growing plants so it is surprising that the plants under the red light had grown the least. The plants that grew under the green light grew the most which is surprising because plants generally reflect green light. The plants were placed in an area that was warm and that would not require any light bulbs to be turned on during the day to have the room lit. Each lamp was also no more than three feet apart from each other and the lamps were constantly on throughout the experiment. The results may have been different, had each group of plants been placed farther apart in a darker area where the only light sources were the lamps.
Bibliography
Germination. (n.d.). Retrieved from http://www.cactus-art.biz/note-book/Dictionary/Dictionary_G/dictionary_germination.htm
Hangarter, R. P. (2000). Plants-in-motion. Retrieved from http://plantsinmotion.bio.indiana.edu/plantmotion/earlygrowth/germination/germ.html
Kennell, H. S. (2001). Gardening in western washington. Retrieved from http://gardening.wsu.edu/library/vege004/vege004.htm
Whiting, D. (2010, August 16). Cmg garden notes
VanDerZanden, V. (1914, May 8). Environmental factors affecting growth. Retrieved from http://extension.oregonstate.edu/mg/botany/light.html
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ampersand11 (student)
