In a world of limited resources, whether it may be fossil fuels, clean water, or even something as simple as sunlight, there is always a competition for them. A major part of this competition is an idea of evolution, which is the changes in populations over long periods of time in response to changes in the environment. "Plants compete for space, light, and nutrients, both with their own species, and also with others in order to survive and reproduce." (Beeber, 43) Two very noticeably different plants are garlic and carrots, each have very distinct smells and appearances. How do these two plants compete with other organisms in their ecosystems, some which are vying for the very same sunlight as them?
Alleleopathy is an area of research that focuses on chemical effects of plants upon each other. (Beeber, 43) Garlic and carrots each have a very distinct smells when being cooked. They are releasing what is called a volatile, a chemical that evaporates into the air. (Beeber, 43) Sometimes they can be used to deter predators from consuming them. The aim in our following experiment is to determine what is the purpose of this volatile, when it comes to other plants in their ecosystem? Are they harmful or helpful to the growth of other plants around ?
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My group and I believed the alleleopathy of garlic and carrots would hinder the growth and germination of radish seeds. Not knowing much prior knowledge of alleleopathy, our group based our hypothesis on the fact that garlic and carrots would want to hinder the growth of other plants competing for sunlight, too.
After formulating our hypothesis and gathering prior background information, we gathered materials and set up the procedure for our experiment. Then we had to identify what measurement(s) we would be observing, what nuisance variables would be present and how to stabilize them.
- Four Petri dishes
- Four filter papers
- Tin foil
- 80 radish seeds
- Crushed garlic
- Crushed carrot
- Garlic crusher
- Masking tape
- Distilled water
When finished gathering all of the necessary material, we outlined the procedure. First we prepared the four Petri dishes by inserting one filter paper in each one. We separated the radish seeds so there would be 20 seeds in each dish. We cut the tinfoil crafted two tinfoil "boats" to hold our crushed garlic and crushed carrot. Next, we crushed the garlic and the carrot using the garlic press and unloaded them into each "boat". Afterwards we placed the two "boats" into two separate Petri dishes. Then, using the pipette, we delivered 3 ml of distilled water into each dish, covered the Petri dishes with the lids, and sealed the dishes with masking tape. After the four samples were set up and sealed, using the Sharpie, we labeled each dish, Radish I, Radish II, Radish with Garlic, Radish with Carrot. Now that we were finished, we placed all of four Petri dishes next to a window, all adjacent to each other. We left the dishes alone for two weeks and made observations. **Our group added 8 ml of distilled water to each Petri dish after day 2 observations because the original 3 ml of distilled water had almost evaporated.
When observing our seeds, I decided to focus on the number of seeds that had partially or fully germinated. During the days we made observations, I recorded how many of the seeds had begun to sprout. The main reason for choosing the number of seeds germinated instead of seedling length and leaf size was because it would have been impossible to measure these two factors without removing the lid from each sample. At the end of the experiment, I compared the data collected from the two experimental groups, the two Petri dishes of radish seeds which had a boat of crushed garlic or crushed carrot in them against our two control groups, the two Petri dishes which had only radish seeds in them.
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The nuisance variables we identified in our experiment were temperature, lighting, and water. To stabilize temperature and lighting, we made sure to keep all four Petri dishes in the same area, relatively adjacent to each other at all times. The only times we moved them were to make our observations and we made sure to move all four at the same time. To stabilize water, we added the same amount of water to each dish and had them wrapped in masking tape.
After observing the samples for two weeks and focusing on the total number of seeds that germinated in each dish, we came to the results shown below in the graph.
- Radish: (control group) This sample had an explosive growth almost immediately. By the fifth day, 16 seeds had already germinated and the sample reached its peak at 19 seeds by the seventh day. Only one seed did not germinate over the span of the experiment. Additional observations were that the seedlings were very long in length. They sprouted multiple large green leaves.
- Radish: (control group) This sample had similar growth to Radish I. Though this sample had 3 seeds that did not germinate, it demonstrated the same rapid growth. By just the fifth day 14 seeds had already germinated and the sample reached it's peak of 17 seeds by the twelfth day. Additional observations were that the seedlings were long in length. They sprouted multiple medium-sized yellow/green leaves.
Radish with Carrot: (experimental group)
This sample, which was influenced by the alleleopathy of carrot, had extremely slow growth. The first seed germinated on the sixth day and only reached a peak of 2 on the seventh day. Additional observations were that the seedlings were very short in length and there were no leaves present.
Radish with Garlic: (experimental group)
This sample, which was influenced by the alleleopathy of garlic, had slow growth. The recorded first seed germination came at the fifth day and seed germination peaked on the eighth day at 6 seeds. Additional observations were that the seedlings were short in length and they sprouted a few small, yellow leaves.
Our hypothesis that the alleleopathy of garlic and carrots would hinder the growth of radish seeds was correct. However, we did not predict that there would be such a striking impact. Left alone the radish seeds flourished under the sunlight and water available. When influenced by the alleleopathy of garlic, the germination and growth of radish seeds were slowed. The seedlings in this sample were short and there were barely any leaves. When influenced by the alleleopathy of carrots, the germination and growth of radish seeds were almost non-existent. The seedlings in this sample were extremely short and there were no leaves. We can conclude from our experiment that the alleleopathy of garlic and carrots have a negative effect on the plants, such as radishes. The volatiles released from crushed garlic and carrots hinder the germination and growth of radish seeds.
To decide whether or not alleleopathy of garlic and carrots have negative effects on all plants, further experiments with different plant seeds should be done. It would help determine if radishes were an exception to the rule or if the volatiles produced by garlic and carrots hinder more plants' growth and germination.
Beeber Carla, Carol Biermann, Craig Hinkley, Mohamed Lakrim, Peter Lanzetta, Georgia Lind, Theodore Markus, Mary Theresa Ortiz, Peter Pilchman, Kristin Polizzotto, and Anthea M. Stavroulakis. General Biology I - Laboratory Manual. KCC Custom Reproduction, New York: The McGraw-Hill Companies, Inc., 2009.