The Wonderwheel: A Study of Gravity's Effects on Plants

This topic submitted by Brad Martin, Jim Broccolo, Jared Bailey, Ned Berghausen ( ) on 12/11/98 .

Brad Martin
Jim Broccolo
Jared Bailey
Ned Berghausen
The Wonderwheel: A Study of Gravity's Effects on Plant Growth
This is an experiment to study gravitational effects on plants. What are the effects of gravity on a plant when it is not grown in the natural position? Will the plant grow at all? If so, what changes in the plant's structure may occur? It is our hypothesis that the plant will compensate for the drastic changes in orientation by realigning itself with the natural direction. However, these angled plants will not grow as well as those left in the natural growing position. The energy needed for re-orientation of the plant will detract from its height, stem strength, and possibly even it's root growth. We are hoping that all plants will grow in a normal fashion and similarly to some degree. In the best scenario, all of the plants will grow to be healthy. If this is the case, then this method of growing may be useful for growing plants in confined spaces, such as orbiting spaceships or stations. Growing from all angles/ directions could potentially quadruple the amount of potential growing space. Conceivably, by increasing the amount of growing space one could increase the output of crops and provide that much more food for consumption. Could this be the answer for ending world hunger? Most likely no, but it has potential for various other applications.
Literature/Background: In researching this method of growing we came across little which dealt directly with our specific intentions. However, we were able to obtain several related writings that proved useful in our preparation for the project. The scientific principle we our studying is called gravitropism. Typically roots grow in the direction of the Earth's gravitational field. When this directionality is obstructed or tampered with, a hormone-like substance called auxin is released to compensate for the unnatural change. In effect, when seedlings are rotated from vertical to horizontal the auxins will compensate within minutes and realign the plant with the pull of gravity. It is believed the calcium within a plant is largely responsible for the release of auxins for realignment. The calcium in plant functions much like it does in humans; it strengthens the support system, in plants, the stem or roots, in humans, the bones. Since we do not have the knowledge or equipment to study the plants internal functions, our experiment will focus on the observable effects the plants display.
To carry out this experiment we will need the following items: two automobile tires, two perforated hoses (for watering), four low heat-low intensity lights, landscaping fabric (netting or panty hose), and seeds (preferably bean seeds). After the tires have been cleaned and properly painted (yes, like the Wonderwheel) they will be ready for the experiment to begin. The first step is to rig the watering system. This will consist of a perforated hose connected to the inside of the tire so that when water is dispelled it will go directly to the root of the plant. To water the plants from the outside would prevent an equal distribution of water since gravity would carry the water to the bottom, naturally angled plants. The soil will prevent as much water from running to the bottom. The next step is to fill the tire with a nutrient rich soil. To hold the soil in the tire we plan on using landscaping netting or even panty hose. A small slit will be cut where each plant will sprout. The seeds will then be planted at the increment of one every 45 degrees. Thus eight plants will occupy each tire. To ensure equal lighting to all the plants, two low heat-low intensity lights will be mounted on the sides of each tire. The distance from each tire is yet to be determined; this will depend on the strength of the lights that we will use. Once the plants begin to sprout we will begin to take our measurements. The data we will be collecting on each plant will consist of the following: height, growth direction, stem diameter, and any other significant difference that the angled plants show from the control plants. To accurately measure the height a piece of string will be used. This will ensure that the measurement will be more precise, if we were to measure with a straight edge ruler we may not be able to account for any twist or angles that may occur. The length of the string will be placed next to a straight edge ruler to determine the distance. Measurements will always be taken from the base of the plant to its absolute tip (the base is defined as the point that the plant breaks the soil). Growth direction will be measured using the cardinal direction specifically designated for this experiment. A "compass" will be painted on the top of both tires so that uniform measurement of the growth direction can be obtained. The third characteristic we plan to measure is going to be the stem diameter. This measurement will be taken at the base of the plant and will help to determine the auxin distribution within each plant. Furthermore, any unusual aspects that a plant may display (relative to the control plants) will also be recorded. All of this information will be tallied on a data table that will be specifically drawn up for each plant. The data sheet (not included with this proposal) accounts for each of the aforementioned growth characteristics. Once the plants start to sprout then our measurements will take place two times per week, most likely on Mondays and Thursdays around noon.
As far as class participation is concerned we plan on assigning a day for each group to take our measurements. This will entail completing the attached data sheet for each of the sixteen plants and perhaps watering them.
Data Analysis:
Much of our data analysis depends on the data we collect. Since we do not know what effect the unnatural position may have on the plants our comparison will focus on the observable differences between the angled plants and the naturally grown control plants. The criteria by which we will assess the plants has already been mentioned, however, after the experiment we plan to uproot the plants and look at the root growth. We hypothesize that the roots will grow towards the hose we have mounted within the tire. This is a small addendum to our initial study. Furthermore, bean color and size will be taken into account. All of this will provide information on the feasibility of growing plants at unnatural angles.
In the course of the experiment there are several problems that we may encounter. We have tried to plan ahead for any obstruction that may hinder the growth process of any plant, however, the ominous Unknown always looms before us. The problems that we expect to encounter include (but are in no means limited to) watering, falling soil, and lighting distribution. Most likely much of the water will congregate at the bottom of the tire either helping the control plant to grow or killing it by over-saturation. If the soil is saturated then its weight may cause the landscaping netting (or panty hose) to fall and kill the majority of the plants. As far as lighting is concerned, the only problem we foresee is the slow cooking process, which will occur if the lights are too close or too hot.
The problems that we did experience through this experiment were close to the ones we anticipated happening. There were a few we had not considered and those were the problem of lighting. We had set up the lights on both sides, but were removed soon after. We think this might have an affect on the plants, but decided that if the plants had the same exposure to the natural light, it would not matter. Another problem we thought we had dealt with as best as possible was the watering methods. We had placed a perforated hose inside the hose in order to direct the water directly to the plants roots. This was an effective method, however, the water accumulated in the bottom of the tire, and may have effected the growth of the control plant.

Results Analyzed:
Now that the experiment has been completed it is time to analyze our data. In general, our hypothesis held true to the results we obtained. The plants oriented in the unnatural position did not grow to be as healthy as the naturally oriented ones. Once the realignment had occurred, the plants grew at nearly the same rate as the naturally oriented plants, the control plants. In general, the plants in wheel one grew to be healthier, stronger, and faster than those in wheel two. Primarily this is because the soil in wheel two was not packed as tightly as the first.
An interesting observation we noted was that the plants did not grow to one particular side of the wheel. We hypothesized that the plants would grow to one side of the tire because of the direction the light was coming from, but what we noticed was that the plants grew to both sides of the tire. What we were unsure why the plants, even those growing next to each other, chose to grow different directions, our only explanation is that the light hit each plant differently, and at different times of the day.
We used some charts to compare the growth rates of the plants in Wheels one and two. In the first chart one can see the lengths of the stems of the bean plants in wheel 1. In this chart, one can see that the plants growing along the top of the tire, the FEDs, started out slow but after making the turn to its natural angle it grew at close to the same rate of the plants at the bottom of the tire. This chart shows that the control plant grew to be the tallest at 11.5"
The second chart is the same as the first but it analyzes the growth of the plants in Wheel 2. This tire had some strange results because of the loose soil, that might explain the drastic difference between it and wheel 1. The chart shows that the plant growing at 90 degrees, or plant C, grew taller than the control plant. It also shows the one plant that didn't do well, and died.
In the next four charts, we compared the plants located across from each other on the wheels. We compared A-E, B-F, C-G, and D-H. We noticed that each of the plants grew at a similar pace half way through, with a few exceptions. The last chart show the comparisons between the stem diameters of plant A and E, the control and the one upside down. We had thought in the beginning that the plant growing upside down would have a thicker stem diameter at the turn to support the stem, but as the chart shows there was no difference.
What are the most prevalent effects that disorientation has on plant growth?
-realignment with the natural orientation, few mutations (leaves), smaller less healthy plants,
What, if any, are the applicable uses for angled plant growth?
-growing in confined spaces
What factors other than gravity could have affected our results?
-lighting, watering, loose soil (wheel two), poor transplantation
How could this experiment be improved for future research?
-better lighting, better watering system, more plants, more time, the knowledge we have now about constructing the wheel

Works Consulted
Carlson, Shawn. "Growing Seeds at Less than One G." Scientific American. Vol. 27 #2
Feb. 1996. p. 122-123.
Cox, Randall. "Zero-G Mysteries and LifeStat." Space World. Mar. 1988. p13-15
Edward, Erin Swint, Roux, Stanley J. "The Influence of Gravity and Light on
Developmental Polarity of Single Cells of Ceratopteris richardii Gametophytes."
Biological Bulletin. Feb. 1997. p. 139-140.
Fitzgerald, Karen. "Plants Have Feelings Too." The Sciences. Sept./Oct. 1991. p. 7
Niklas, Karl J. "The Cellular Mechanics of Plants." American Scientist. Vol. 77 #4.
July 1989. p. 344-349.

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