Factors affecting seed germination (e.g. soil, temperature, pH)

Introduction: (Initial Observation)

If you have ever planted some seeds, you may have noticed that some seeds do not germinate.

A good quality seed is the first step toward producing a good crop. If the seed does not germinate, the cost of seed and all related plantation and irrigation costs will be a loss for the farmer. Scientists and farmers continuously try to identify any possible factor that may affect seed germination in order to have a higher rate of germination. The rate of germination is one of the key elements in determining the quality and value of any seed.

Seeds that do not germinate are wasted and will gradually become a part of other organic maters in the soil.

Please note that you will only select one of the above factors to research on. You will need to adjust this project guide and it’s experiments based on the factor that you choose to study. So, the actual title of your project will be one of the following:

The effect of pH on seed germination or

The effect of temperature on seed germination or

The effect of soil on seed germination

If you decide to study on more than one factor, you need to repeat your experiments for each factor that you study. You will also have a separate hypothesis for each factor.

Other similar research topics that can be performed using the steps provided in this project guide:

• The effect of light on seed germination
• The effect of UV on seed germination
• The effect of fertilizers on seed germination
• The effect of mold on seed germination
• The effect of salt (or any other chemical that you choose) on seed germination.

Information Gathering:

Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.

Review the definition of seed germination. Learn about any other research performed by others on seed germination. Also learn about the seed that you want to study. The result of your experiments is only valid for the type of seed that you choose to study. You can not generalize the results and propose a conclusion that covers all different types of seeds. You may also want to modify the title of your project to cover the name of seed that you study. For example if you choose to study on lettuce seed, you may change the title of your project to one of the following:

The optimum pH for germination of lettuce seed or

The optimum temperature for germination of lettuce seed

If you don’t have much time for your project, you should select one of the fast germination seeds. Following are some fast germinating seeds:

Rapid Germination Seeds (assuming ideal moisture and temperature)

Where to find more information:

http://forest.wisc.edu/forestry415/TreeStructure/flowers/germ.htm

http://www.marijuanasignpost.com/guides/seedgerm.html

Seed Germination and Fruit Types

The Seed Biology Place

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. Depending on your final choice of project title, following are some sample questions:

1. The purpose of this investigation is to identify the best pH for the germination of lettuce seed.
2. The purpose of this investigation is to know the best temperature for germination of lettuce seed.

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. Depending on the question/purpose of your project following are two sample of identifying variables:

1. The independent variable is the pH. Dependent variable is the rate of germination. Controlled variables are light, temperature, soil, moisture, seed specification such as moisture, size, etc..
2. The independent variable is the temperature. Dependent variable is the rate of germination. Controlled variables are light, pH, soil, moisture, seed specification such as moisture, size, etc..

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 are some sample hypothesis:

1. I think the neutral pH is the best pH for seed germination. This hypothesis is based on my study of seed and the fact that a large part of seed is food that plant needs during germination period. So I think if the seed has it’s own food to germinate, it must also have all necessary minerals and other chemicals needed at a proper pH.
   Another hypothesis for pH effect:
   I think a slightly acidic pH such as pH 4 is the best pH. Slightly acidic pH can prevent growth of mold and other fungus that may damage seed. Also slightly acidic pH will dissolve more minerals from the soil and make them available to the plant.
2. I think that temperature around 72º F is the best temperature for seed germination because this is the average weather temperature in the spring when most plants emerge.
   Another hypothesis for temperature effect:
   I think a temperature around 80º F up to 90º F is best temperature for seed germination. My hypothesis is based on my gathered information that indicates chemical and biochemical reactions will accelerate by heat. Also excess heat can be harmful to live organisms, so the temperature range of 80º F to 90º F which is almost the summer time temperature can be the best temperature for seed germination.

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:

Seed Observation experiment (this is just a warm-up experiment)

Soil is an environment that provides moisture and oxygen to the seed. If the seed is under a layer of soil, we will not be able to observe the progress of seed germination. That is why we need to use other methods of seed plantation for our experiments. In this experiment we use a plastic sandwich bag and paper towel for seed germination. We expect that plastic bag will keep moisture and oxygen in the environment. Paper towel will keep moisture around the seed, otherwise seeds may get fully submerged or be in dry section of the bag.

Materials needed:

• a resealable plastic sandwich bag
• paper towel or napkin
• a cup of water
• a packet of pea or bean seeds

Procedure:

Soak seeds in a cup of water overnight.

Sprinkle water on the paper towel or napkin so it’s wet but not dripping.

Put the wet paper towel and the seeds in the sandwich bag, make sure you can see the seeds without opening the bag.

Seal the bag. Place the bag in a warm safe place away from direct sunlight (so it doesn’t get too hot). Check it several times a day, open it for a few seconds to give the seeds air. Then seal it to keep the moisture in. If the paper looks dry, open the bag and sprinkle more water, then make sure it’s sealed.

Soon, you’ll see the baby plant start growing and developing!!

One way to keep track of what happens to your seed is to draw it once a day. Make your first drawing of the seed before you soak it.

You can also try another experiment. Repeat the above experiment with seeds that you didn’t soak. When you do the experiment, think like a scientist. Scientists ask themselves questions. Here are some questions you could ask yourself when you do one of these experiments:
Do you think the two kinds of seeds will germinate differently? How will they be different?

After you do one experiment, some other questions may come up. They might be answered by another experiment. Some suggested experiments:

• prepare two identical bags, place one in the dark and one in the light.
• prepare two identical bags. In one of the bags, place the seeds so the radicle faces toward the ceiling. In the other, place them so the radicle faces the floor.
• prepare two identical bags. Once a day, rotate the seeds in one of the bags, let the other bag sit still.

Feel free to try different experiments. Just remember, test one thing at a time and always prepare a control bag (one that you don’t change anything). That way you can compare the two bags to see if you made a difference.

Experiment 2:

The effect of UV radiation on seed germination:

In this project we want to see the effect of exposure to UV radiation in seed germination. We think that UV light might have some sterilization effect on the seed and prevent growth of harmful bacteria and mold on the seed, resulting a higher rate of germination. We are also worried that UV exposure may cause biological damage to seed that can prevent seed germination.
(Note that this introduction also serves as hypothesis for this experiment.)

Procedure:

1. Expose 10 of the selected seeds to the UV light for a period of 5 minutes. CAUTION!!! UV light can damage both your eyes and skin. Use all recommended safety precautions. We recommend adult supervision for this step.
2. Take one piece of paper towel and fold it in half, and then in half again. Place the folded paper towel in the bottom of the plastic container.
3. Pour approximately 15 milliliters of water over the paper towel. The entire paper towel should be wet, but without extra water in the bottom of the container. Should you need more water, use it, but measure and record so that you can use similar amounts with all other seed containers.
4. Use your tweezers to place the 10 seeds on the paper towel. Make 2 rows of seeds with five seeds in each row.
5. Put the lid on the container and snap it on tight to preserve the moisture.
6. Label the container using masking tape. List the length of time the seeds were exposed to UV light, the date, and type of seeds (if using more than one type).
7. Place the container in an out of the way place where it will not be disturbed. A warm, dark location such as a closet or under the bed would be ideal. However, handle the container with care so the seeds don’t slide all over.
8. Repeat steps 1 through 7 with the only variation being an increased time of exposure to UV light. The first exposure was 5 minutes so we recommend trying 10, 15, 30, 60 and 120 minutes.
9. Repeat steps 2 through 7 with 10 seeds to be your control. DO NOT expose these last seeds to UV radiation.

Making Your Observations

1. Take a daily look at your seeds and check for any sign of a “sprout” or “emerging radicle” coming out of the seed. Seeds have germinated when they get such “sprouts”. Some of the sprouts might grow so fast that you can see the seed’s stem and roots with tiny hairs. Use a magnifying glass and enter illustrations of these sprouts in your log book as soon as you see evidence of them.
2. By the seventh day any seeds that are going to sprout will have done so. At this time you should COUNT the number of seeds for which you can see the sprout coming out of the seed, even if it’s very small. A broken seed coating does not count if there is no sprout.
3. Record the number of seeds germinated in each container.
4. Measure the combined stem and root length of each “sprout” with a metric ruler and record their lengths in millimeters. Construct a table for this data for each container.

Your data/results table may look like this:

Make a graph:

You can make two different bar graphs to visually present your results.

For the germination ratio graph make one vertical bar for each exposure time starting 0 or no exposure up to 120 minute exposure. The height of each bar will represent the ratio of seeds germinated in that group.

For the speed of germination and growth graph make one vertical bar for each exposure time. The height of each bar will represent the average length of seedling (combined stem and root length) in the group.

Experiment 3:

The effect of pH on seed germination

In this experiment you use solutions of different pH from 2 to 11 instead of pure water. Handling low pH and high pH solutions requires goggles and other safety precautions as well as adult supervision.

Procedure

1. Prepare 10 solution with 10 different pH in 10 different bottles. Label all bottles with the pH of the solution in that bottle. Use acetic acid to lower the pH and use ammonia to increase the pH. It is good if you use pHs of 2 to 11. Use pH meter or pH paper to adjust the pH in each bottle.
2. Take one piece of paper towel and fold it in half, and then in half again. Place the folded paper towel in the bottom of the plastic container.
3. Pour approximately 15 milliliters of first solution (pH=2) over the paper towel. The entire paper towel should be wet, but without extra water in the bottom of the container. Should you need more water, use the same solution, but measure and record so that you can use similar amounts with all other seed containers.
4. Use your tweezers to place the 10 seeds on the paper towel. Make 2 rows of seeds with five seeds in each row.
5. Put the lid on the container and snap it on tight to preserve the moisture.
   Label the container using masking tape. List the pH of the solution, the date, and type of seeds (if using more than one type).
6. Place the container in an out of the way place where it will not be disturbed. A warm, dark location such as a closet or under the bed would be ideal. However, handle the container with care so the seeds don’t slide all over.
7. Repeat steps 1 through 7 with the only variation being the pH of water solution.
8. Repeat steps 2 through 7 with 10 seeds to be your control. DO NOT adjust the pH of this last group. Use regular tap water or distilled water.

Making Your Observations

1. Take a daily look at your seeds and check for any sign of a “sprout” or “emerging radicle” coming out of the seed. Seeds have germinated when they get such “sprouts”. Some of the sprouts might grow so fast that you can see the seed’s stem and roots with tiny hairs. Use a magnifying glass and enter illustrations of these sprouts in your log book as soon as you see evidence of them.
2. By the seventh day any seeds that are going to sprout will have done so. At this time you should COUNT the number of seeds for which you can see the sprout coming out of the seed, even if it’s very small. A broken seed coating does not count if there is no sprout.
3. Record the number of seeds germinated in each container.
4. Measure the combined stem and root length of each “sprout” with a metric ruler and record their lengths in millimeters. Construct a table for this data for each container.
   

   pH	Total Number of Seeds	Number of germinated seeds	Germination Ratio	Average length of seedling
   Control
   1
   2
   3
   4
   5
   6
   7
   8
   9
   10
   11

Make a graph:

You can make two different bar graphs to visually present your results.

For the germination ratio graph make one vertical bar for each pH, starting the control and then 1 to 11. The height of each bar will represent the ratio of seeds germinated in that group.

For the speed of germination and growth graph make one vertical bar for each pH, starting with the control and then 1 to 11. The height of each bar will represent the average length of seedling (combined stem and root length) in that group.

Experiment 4:

The effect of temperature on seed germination

This experiment is similar to experiment 2. The difference is that you will not expose any seeds to UV radiation, instead you place your containers in locations with different temperatures. The challenge for this investigation is how to create different temperatures and keep them constant for up to 7 days.

In laboratories incubators are used for temperatures higher than room temperature and refrigerators are used for temperatures lower than room temperature. Incubators usually are not available for students who want to perform such experiments at home. However other places can be found at home that have higher or lower temperature than room temperature.

Get a thermometer and check the temperature in different locations inside your refrigerator and different locations in your basement or backyard or any other place that may have a relatively constant temperature. Decide which of these locations you want to use and place your samples in these locations. Label each container with the temperature of location that you choose to place.

In all of the above experiments you can use petri dishes instead of plastic bags and plastic containers. Petri dish cap will keep moisture inside while you can observe the seeds without removing the caps.

The picture on the right shows different bean seeds in before and after germination.

Recording Data:

Count the total number of seeds in each group and the number of seeds germinated on that group. Enter them in the the table. Divide the number of germinated seeds by the total number of seeds in each group and write the result in the Germination Ratio column.

Make a graph:

You can use a bar graph to visually present your results. Make one vertical bar for each group. The height of the bar will show that ratio of the germination.

Variations of this experiment:

Instead of the rate of germination (the germinated ratio) you may want to measure and record the speed of germination. In this case you will measure the overall height of seedlings (from root to the shoot) in each group after a certain number of days (usually 7 days or 10 days). Then you take an average of the results in each group and write that in your results table and use that to make a graph.

Materials and Equipment:

Material and equipment that you may need for projects in this page are:

1. Plastic containers with lids.
2. Masking tape and marker for labeling containers.
3. Paper towels and tap tap water.
4. Zip lock plastic bags
5. Graduated cylinder or other measurement device for water measurement.
6. Latex Gloves or tweezers for seed handling (Don’t touch the seeds to avoid infection of seeds by the bacteria of your hand)
7. A supply of 100 or more radish seeds (or other fast germinating seeds of your choice)
8. Access to a UV light (if a UV light cannot utilized from your school’s science lab, check both the local hardware store and local flower/garden shops. Borrow or rent if possible as UV lights could cost $35-$40 or more. UV lights are also known as black light)
9. Acetic acid and ammonia solution.

Depending on the subject and experiments that you choose you may not need all the above.

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.

Record the results of your experiments in tables like this:

Effect of pH on the rate of germination of lettuce seeds: (Just an example)

Comments in the table cells is what you observe on a daily bases. Last row shows the rate of germination

Calculations:

You will need to calculate the rate of germination by dividing the number of germinated seeds by the total number of seeds in each test container.

Summary of Results:

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.

Can you make a better display?

When you report the result of your experiments, you may also create a chart or graph to provide a visual representation of the final results. Following is a sample that shows the rate of germination of different seeds. (So dependent variable has been the type of seed instead of pH or temperature)

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.

You may try soil instead of paper towel in your experiments. You may also use the germinated seeds or fully grown plants as a part of your display.

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:

List of References