The effects of gravity on seed germination

Introduction: (Initial Observation)

Research on different environmental factors that may affect seed germination and plant growth is a step towards understanding the mechanism of plants behavior and enables us to have more control on our agricultural investment and productivity.
Gravity is one of the factors that needs to be studied and understood.
If you’ve ever planted seeds in the ground, perhaps you have wondered just how do they know which way to grow. How do the roots know to grow down and how do the stems and leaves know to grow up?
Is it gravity, moisture or light that makes the root grow downward and stem grow upward?

Design an experiment to determine what is the effect of gravity on plants growth. Based on your initial studies make a hypothesis and write it down. Do your experiments, record your observations and draw a conclusion. This project needs 3 to 5 weeks to complete. Include the plants that you use for your experiments in your display to make it more interesting.

Information Gathering:

Find out about seed germination and plant growth. Read books, magazines or ask professionals who might know in order to learn about the effect of gravity on plant growth. Keep track of where you got your information from.

One of the interesting pieces of information that you may find, is about the fact that seeds do not need light and nutrients for germination. Light and nutrients are two important factor that all plants need for their growth and development; however, all seeds already contain their own food. Light also is not required because only green leaves use light energy to make food for plants. Seeds do not have any green leaves. Seeds only need moisture and a proper temperature for germination.

The following links contain information related to gravity and plants:

http://spacegrant.engr.colostate.edu/spacegrant/projects/past/plantgrowth/

http://www.aps.org/BAPSAPR98/abs/S1200009.html

http://extension.oregonstate.edu/mg/botany/hormones.html

Also search the Internet for Gravitropism or Geotropism.

Gravitropism or Geotropism is the study of directional growth of a plant organ in response to a gravitational field where roots grow downwards, shoots grow upwards.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to see if gravity has any affect on the direction in which root and shoots grow.

Question:

How does gravity affect the growth of plants?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Independent variable (also known as manipulated variable) is the direction of gravity in relation to the seed or plant.

Dependent variable (also known as responding variable) is the direction in which roots and shoots grow.

Controlled variables are light, moisture, temperature and all other environmental factors that may have any affect on the direction of roots and shoots growth.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following is a sample hypothesis:

Gravity causes the roots of plants to grow towards the pull of gravity. My hypothesis is based on my common sense and the fact that there is no light underground and the level of moisture does not vary around a seed. So light and moisture cannot be affecting the direction of plant growth when seeds are germinating.

Another hypothesis can be like this:

Gravity has no affect on the direction of plant growth. Plants grow upward because leaves need light and roots need moisture. So each one goes toward what is needed.

Note that a hypothesis does not have to be correct. Your experiments will later show if your hypothesis was correct or not. The results of your experiments may support your hypothesis or prove it wrong.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

• Soak 5 red kidney beans in a bowl of water for 12 hours before beginning the experiment
• Turn the Plexiglas container on its side and place 5 beans down on the bottom. The beans should be approximately 1 to 2 inches from the rim of the container. Each bean should be in a different position; pointed down, pointed up, on its side, and on an angle.
• Place two flat layers of dry colored napkins over the top of the beans. (this is for visibility purposes)
• Stuff two layers of crumpled, damp paper towels over the top of the napkins.
• Place a layer of Saran-Wrap over the top of the paper towels. (this is so that the towel does not absorb any of the moisture from the paper towels)

• Stuff the remaining space within the container with a thick towel. (used to press the beans against the front of the container.)
• Turn the container upright.
• Place the container in a dark place so that the beans can germinate.
• Soon, the seeds will begin to sprout. Take observations twice each day for 11 days.

• Observe the direction the beans sprout in and how they orient themselves.

Nee a graph?

The results of this project does not require a graph; however, making a graph is a good experiment and an addition to your project guide display. Before making a graph; you need to have a results table. Make a results table like this for the root growth and shoot growth. Use positive numbers for anything that moves up. Use negative numbers for anything that moves down.

Number the beans from 1 to 5. After 7 days (or more) measure the length of the roots and the length of the shoots and record them in the above table. You may use metric system (centimeters) or English system (inches) for your measurements. If the final direction of growth is up, use a positive number. If the final direction is down use a negative number.

In the above sample table, the root growth of -6 means that the root grow 6 centimeters and its final direction was down. The shoot growth of +7 means that the shoots grow 7 centimeters and the final direction was up.

Now you can use the above results table to draw a bar graph.

Use red bars for roots and use blue bars for shoots. Cut the bars from color paper to the growth length. Paste them above or below of a base line depending on the direction of growth.

Experiment 2:

• Fill the two clear shallow pans with about five centimeters of potting soil. Plant several rows of the stir-fry sprout growing mix.
• Moisten the soil with water.
• Rest one of the containers in a dish rack so that it is on an angle.
• As the shoots grow up, observe what angle they grow at, and if that angle differs between the experiments. Also, look at the bottoms of the pans to observe the direction of the root growth.

Materials and Equipment:

• 5 kidney beans
• 2 Clear Glass Shallow Pans (Dimensions: 13’’ by 9’’ by 2’’)
• 1 Plexiglas container (Dimensions: 12’’ by 5’’ by 8’’)
• 1/2 roll of paper towels
• 1 Plant Sprayer
• 1 pound of Potting Soil
• 1 bath towel
• 2 packs of Uncle Ben’s stir-fry sprout growing mix

Sprout growing mix is available in some supermarkets. If you can’t find it, simply use any other seeds such as lentil or grains.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Sample Results

Experiment 1

Day	Observations
1-AM	The beans are placed in the container.
1-PM	Bean 3 has sprouted a small root, a radicle, the first primary root of a plant that is germinating.. All other beans remain unchanged. Condensation has formed on the Plexiglas, which makes it somewhat more difficult to see.
2-AM	Bean 3’s root continues to lengthen as it grows downward. No other beans change.
2-PM	No noticeable progress with any of the beans. 3 may have grown a bit longer.
3-AM	3’s root grows longer. The skin of bean 1 has begun to peel off (very unnoticeable in photograph)
3-PM	Bean 1 sprouts a very small root. Bean 3 grows longer.
4-AM	Skin has split on beans 2, 4 & 5. 1 grows marginally, as does 3.
4-PM	Root sprouts from 2. 3 grows longer. 1 grows a bit. 4 & 5 remain unchanged
5-AM	Roots sprout from 4 & 5. 1 & 2 grow longer. 3 sprouts two individual roots out of the main one
5-PM	1, 4 & 5 grow longer. 2 begins to grow mold. 3 sprouts more sub-roots
6-AM	All roots grow longer.
6-PM	All roots grow longer.
7-AM	1, 4 & 5 sprout sub-roots. 2 begins to visibly grow mold. 3’s root, about 1/8th of the way down, begins to hitch upwards.
7-PM	Strange condensation forms near 2. Sign of mold.
8-AM	1, 3, 4, & 5 widen & hitch slightly upward
8-PM	1, 4 & 5 noticeable begin to hitch upward, however, Bean 1 seems to be growing a bit slower than the others. Bean 2 has not grown for a long time.
9-AM	Signs of mold on bean 1. Blue mold is consuming bean 2 which has stopped it from growing.
9-PM	The entire bean 3 rotates nearly 45 degrees upwards. Greenish root indicates signs of stem growth (difficult to see in picture)
10-AM	2 almost completely consumed by mold. 3 begins to leave shell.
10-PM	Bottom ¼ of 1 consumed by mold, but it begins to leave its shell anyways. 3, 4, & 5 begin to wrinkle and their stems grow out of the container.
11-AM	Beans 3 & 4 completely leave their shells and start moving upwards. Beans 1 & 5 still half in their shells
11-PM	Bean 3 completely leaves container and begins to grow leaves. 4 & 5 halfway emerge from container. 2 dead of mold. 1 looks like it may survive and escape its moldy shell.

Animation of the Experiment

Experiment 2

The plants in the pan that was placed on a dish rack at an angle grew straight up in relation to the ground, not the angle of the pan.

The plants in the pan placed flat on the ground grew straight upwards. Some of the roots may look bent due to some turbulence that the pan experienced while being transported.

However, the most interesting findings of the experiment came from looking at the roots. The plants placed on an angle’s roots grew in similar directions, however, the plants lying flat on the ground grew randomly.

On an angle vs. Flat on the ground

Calculations:

No calculations are required.

Summary of Results and Discussion:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

The results that were achieved from the experiment prove a number of things. The first experiment that involved the beans in the container showed that the roots of beans will grow downward to the ground, no matter the direction in which the beans were placed. This occurred due to geotropism, which is a cellular reaction that occurs in all plants that instructed the roots to grow towards the pull of gravity. In the second experiment, concerning the plants being planted both on a flat surface and on a slope, both of the plants grew fairly vertically in relation to the ground (not in relation to the angle they were placed in). The difference was that when the roots of the plants on a slope hit the bottom of the container, they grew towards the low end of the pan, whereas in the level container, the roots grew in circles. This was because of geotropism again; the roots grew towards the pull of gravity. Most studies agree with this project because of the fact that geotropism determines the way that roots grow.

A source of error that could have been avoided was the fact that mold stopped two of the five beans from growing in the first experiment. This was probably caused by a foreign substance that the bean obviously came in contact with before it was placed in the container. This could have been avoided by possibly putting the beans in a more sterile place as they were soaked. Also, the condensation that formed in the container made photography difficult. This could have been avoided by using some sort of a better container to grow the beans in. For the second experiment, some of the plants were knocked over while transporting the trays to be photographed. This made the results a tad less noticeable, but still definitive. These all could have been avoided if the proper precautions had been taken.

The purpose of this experiment is to help people understand how plants grow and why they grow the way that they grow; especially the roots, because nobody ever sees the roots since they are underneath the ground. Now that the experiment has proved under which conditions that the seeds are placed that plants grow fastest, people can use this information for their own purposes, such as growing plants for their own science fair projects more quickly.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Sample conclusion:

In conclusion, it can be confirmed that yes, gravity does affect plant growth. Throughout the course of the experimentation, it has been proved that gravity affects the speed of growth, the angle of the stem and root growth, and in general, how the plant grows. In the first experiment, the bean that pointed downward grew considerably faster than those pointing upward or on an upwards angles. As well, despite the facts that the beans were placed on different angles, their roots, after given a period of time to orient themselves, all grew in the same direction. In the second experiment, the stems of the plants on an angle grew upwards, away from the pull of gravity, and the roots grew as best as they could down the container with the pull of gravity. These findings conclude that gravity has a large effect on plant growth.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

Visit your local library and find books related to the gravity, and plants biology. List such books as your references or bibliography. Following are samples of references.

Vancleave, Janice. 2000. Guide to More of the Best Science Fair Projects. John Wiley & Sons Inc. Canada. 156 pp.

Goldstein, Natalie. 1999. The First Timer’s guide to Science Fair Projects. Lowell House Juvenile. Los Angeles. 80 pp.

http://beangenes.cws.ndsu.nodak.edu/. Bean Genes Homepage. Phil McLean.

http://www.britannica.com/bcom/eb/article/idxref/0/0,5716,224738,00.html Encyclopaedia Britannica Online.

http://www.csun.edu/~vcbio001/teach.html

http://starryskies.com/try_this/plant_growth.html

http://www.iit.edu/~smile/bi9404.html

Abstract

This project deals with and discusses the effects that gravity has on plant growth. The question, “Does gravity affect plant growth?” was posed to answer whether gravity had an effect on the root growth and stem growth of plants. Two experiments were undertaken to answer the question. In the first, five beans, placed at different angles within a container were photographed over a period of time. The results concluded that the roots always grew downwards regardless of the angle. In the second experiment, two sets of sprouts planted in different clear pans were monitored over five days. One pan was placed on an angle, supported by a dish rack, and the other was kept on a flat surface. In both experiments, the stems of the plants grew perpendicular to the earth, not at the angle of the pan they were placed on. When the roots were looked at from underneath the clear pans, plants on the pan placed on an angle’s roots grew sloping down the container; pulled by gravity through the soil. The plants on the pan on the flat surface grew randomly. These two findings prove that gravity indeed has an effect on the growth of plants.