control variables for germination experiment

Some Tips for Planning an Experiment Ask a question Form an hypothesis Choose the variables Plan the treatments Choose a control Decide the number of replicates Specify the constants Glossary of related terms

Ask a question When you want to do an experiment, a good way to start is by asking a question. For bioassays, the questions might be "Does salt inhibit germination of lettuce seeds?" or "Is salt toxic to Daphnia ?"

Form your hypothesis After you decide on a research question, then you are ready to state your hypothesis or prediction of what you think will happen. An example hypothesis: "The number of seeds that germinate will decrease with increasing concentration of NaCl."

Choose the variables Your independent variable is the factor that you will change in your experiment. For example, in a lettuce seed bioassay the usual independent variable is the concentration of the solution to which the seeds are exposed.

The dependent variable is the factor that you predict will change as a result of variation in your independent variable. The number of seeds that germinate and the lengths of their roots are examples of two different dependent variables in lettuce seed bioassay experiments.

If you are confused about the independent and dependent variables, it may help to think back to your research question and then think about how you might want to present the results of your experiment. For example, for a bioassay using Daphnia , you might decide to set up a bar graph to display your results. On the x-axis (the horizontal axis), you would put your independent variable. These are the numbers that you know in advance, such as the concentrations of your test solutions. On the y-axis (the vertical axis), you would put your dependent variable. This is the factor you will be measuring in your experiment, such as the length of the lettuce roots or the number of Daphnia that die at each concentration.

Plan the treatments A treatment is a factor that affects the outcome of a scientific experiment. In a bioassay, the experimental treatment usually is the concentration of the solution to which the seeds or organisms are exposed. (If you want to test the effect of temperature on seed germination or Daphnia growth, the treatment would be temperature rather than solution concentration.)

Choose a control In a scientific experiment, the control is the group that serves as a standard of comparison. It is exposed to the same conditions as the treatment groups, except for the variable being tested. In bioassays, the control group is the set of seeds or Daphnia grown in distilled or culture water rather than in a test solution.

Decide the number of replicates Replicates are individuals or groups that are exposed to exactly the same conditions in an experiment. In a lettuce seed bioassay, you might test 6 different solution concentrations, plus a distilled water control. For each of these concentrations, you might use 3 Petri dishes, each containing 5 lettuce seeds, or 3 beakers, each containing 10 Daphnia . In this experiment, you would have 3 replicates at each concentration (the 3 Petri dishes or beakers).

Investigation: What Factors Affect Seed Germination?

Introduction

In the spring, flowers begin to bloom and you may see sprouts in the garden. How do plants know when it's spring and when to grow? If a seed grew too early, it might be exposed to a harsh cold environment. If it grew too late, it might not have enough water to survive. The process by which an organism grows from a seed into a plant is called germination . The seed of a plant is the embryo, and it contains enough energy for the plant to survive until it is time to start growing. In some cases, these seeds can survive for years.

What triggers the seed to start growing? It varies by plant and by the environmental conditions where the plant grows. The giant sequoia trees of California require fire to germinate. This adaptation ensures that new trees will grow when there is an opening created by the death of other trees. If the seeds germinated without fire, the seedlings would be too shaded to grow.

Not all plants need fire to start growing, but most do take the cues from the environment. In this activity, you will investigate factors that can affect the germination of a seedling.

Part 1: Consider a Question / Hypothesis

Several variables might affect the germination, these variables include: light, temperature, water, soil type, air quality.

Choose ONE variable to investigate. Write a hypothesis below. Remember, that the hypothesis should be a complete sentence that can be tested.

Part 2: Design an Experiment

With your lab group, determine how you could test the variable.

What kind of data will you gather? Will you have a control group? What kind of materials or equipment will you need? How many seeds will you use?

Available Materials ( other materials may be available, check with your instructor ): radish or bean seeds, ziploc bags, paper towels, window/sunlight, water, vinegar, soil, refrigerator

Sketch or describe your experiment below. Your instructor will approve your plan before you set it up.

Part 3: Gather Data

Most seeds will germinate in a few days. Plan to make observations over the next few days and organize your observations below. Be as detailed as you can about what you see.

Part 4: Publish Your Results

Create a lab report or infographic that includes the following information from this investigation. You have written things down on this paper, now it is time to organize the information into a formal report. This report should include four detailed sections.

1. Introduction : includes background information about the lab and your hypothesis

2. Experimental Design : include a drawing and/or description of how you set up your experiment

3. Data : Organize observations into a data table

4. Conclusions : Use your data to answer the experimental question. Be specific in how you write this, your conclusions must follow your data, even if they didn't turn out as you were expecting.

5. Reflection :   In this section, discuss how your results may provide insights into how the environment can affect plants in general and how this information can be useful to humans.  For example why would farmers need to consider germination factors when planting crops?

Other Lessons on Plants

Investigation – Rate of Photosynthesis  – using baking soda, elodea and light, measure the bubbles to observe how fast a plant photosynthesizes and releases oxygen

Investigation – Algae Beads and Photosynthesis  – use algae cultures and sodium alginate, measure photosynthesis by changes in color of indicator

Investigation: Photosynthesis  – this lab uses leaf disks that float to indicate photosynthesis.  Students investigate factors that affect photosynthesis.  (AP Lab)

Investigation: Photosynthesis and Plant Growth (virtual)  – use a virtual app to show how plant growth changes in response to light color and light intensity

Investigation: Separation of Plant Pigments  – use chromatography to show how leaves contain pigments that separate

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Germination

Introduction: (initial observation).

A seed is a miracle waiting to happen. The embryo comes pre-packaged with a food supply and the vital genetic information needed to become a plant just like its parents. Seeds exist in a state of dormancy, absorbing oxygen, giving off carbon dioxide, and slowly using up their stored food reserves. During this process the seed continually monitors the external environment waiting for ideal conditions specific for the particular seed. Once the ideal conditions occur, the seed breaks dormancy and germinates.

In this project, you must display different stages of seed germination. You can plant different seeds and get sample at different stages and use them for your display and report.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “ Ask Question ” button on the top of this page to send me a message.

If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Germination : To begin to sprout or grow.

Information Gathering:

Gather information about seed germination and plant growth. Read books, magazines or ask professionals who might know in order to learn about what a seed needs in order to germinate. Keep track of where you got your information from.

Following are samples of information that you may find:

A seed certainly looks dead. It does not seem to move, to grow, nor do anything.

Indeed if a seed is not allowed to germinate (sprout) within some certain length of time, the embryo inside will die. Each species of seed has a certain length of viability. Some maple species have seeds that need to sprout within two weeks of being dispersed, or they die. Some seeds of Lotus plants are known to be up to 2000 years old and still can be germinated.

Source…

Farmers know the best season and conditions for sowing different seeds. A database for such information is also available online .

A seed contains an embryonic plant in a resting condition, and germination is its resumption of growth. Seeds will begin to germinate when the soil temperature is in the appropriate range and when water and oxygen are available.

Germination in Dicots

• The primary root emerges through the seed coats while the seed is still buried in the soil.
• The hypocotyl emerges from the seed coats and pushes its way up through the soil. It is bent in a hairpin shape — the hypocotyl arch — as it grows up. The two cotyledons protect the epicotyl structures — the plumule — from mechanical damage.
• Once the hypocotyl arch emerges from the soil, it straightens out. This response is triggered by light.

With the first warm days of spring, gardeners are anxious to get their vegetable seed in the ground. Unfortunately, it is not the air temperature, but the soil temperature that controls seed germination. We have to wait for the soil temperature to reach the optimum for a specific crop if we hope to get a good stand of vigorous seedlings.

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 display different stages of seed germination. You may also want to study on certain questions such as:

• How long does it take for Kidney Beans to germinate?
• What is the rate of germination in Kidney Beans?

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.

This project can be a display project with no questions. In this case you will not need to identify any variables.

If you are studying on a question such as the rate of germination, then type of bean and germination rate are your variables.

Type of bean is called an independent variable. Germination rate is called the dependent variable.

If you are studying on a question such as the speed of germination, then type of bean and the speed of germination are your variables.

Type of bean is called an independent variable. The speed of germination is called the dependent variable.

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.

A display project will not need a hypothesis. An experimental project will need you to write a hypothesis. Following are sample hypothesis that might be used for the proposed questions.

My hypothesis is that all seeds will germinate.

My hypothesis is that seeds will germinate in about 10 days.

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:

In this experiment you grow some lentils and observe their germination and growth. Lentil is a good seed for germination experiments.

• Fill up a cup with lentils and transfer it to a bowel.
• Add water to the bowel to about 1 inch over the lentils. Let it sit for 24 hours (one day) at room temperature (72ºF to 85ºF).
• Discard excess water in the bowel and transfer moistened lentils to another plate. The layer of lentils in this plate can be 1/2 inch to 1 inch.
• Cover the plate and lentils with a wet piece of cloth.
• Inspect the lentils every day by removing the cloth. Use a spray bottle to moisten the seeds (lentils) while you are inspecting the seeds. Record any changes that you notice in your notebook. Add some water to the plate so the seeds at the bottom of the plate will also have access to enough water. Put back the cloth and moisten it with a spray gun.
• If the changes that you observe are noticeable, remove one of the seeds and draw a picture of that. Write the date next to your drawing. Use a tape to connect the seed next to your drawing.
• In about 10 to 15 days, seeds will germinate and will need light to continue their growth. Remove the cloth and put a desk lamp with a 60 watt bulb about 2 feet above the seeds. Leave the light on.
• Continue daily observation, recording your notes and watering the seeds. Note that seeds must not be left dry. Also too much water is not good for plant either. In other words, plant roots must have access to both air and water. Too much water does not let the roots get the air that they need.

Lentils can grow quite high in this way and make a nice display.

If you are going to use a plastic or ceramic pot instead of a plate, fill the bottom of the pot with sand and make sure that the pot has a hole for excess water to exit.

Advanced experiments and collecting data

Higher grade students may need to compare the germination rate of different seeds and record their data in a data table. This is how you may do this:

Get 100 lentils and germinate them as described above. A few days after germination, count the number of lentils that are germinated and record the results in your notes.

Repeat your experiment with other seeds or beans such as white beans, red beans, kidney beans and peas.

For each type of seed you test grow 100 of them and finally count the number of seeds that are germinated.

Record your results in a table like this:

Need a graph?

You can visually present your results by making a bar graph. Make one vertical bar for each seed you test. Under each bar write the name of seed it represents. The height of bar will show the number of seeds germinated. 

Experiment 2: Observing Seed Germination

Introduction: Planting a seed next to a clear glass can give us the opportunity to view different stages of seed germination and take pictures or draw diagrams of each stage.

Fill up a clear glass cup with a role of paper towel.

Insert 4 Kidney Beans between the paper towels and the glass. Keep the beans away from each other, for example, place one Kidney Bean in each quarter of the cup.

Make five of these cups, each with four Kidney Beans.

Add some water to the cups so the paper towels will be moist; however no water must drip when you turn the cup upside down. Excess water can be harmful.

Place all the cups in a warm place. No light is necessary before germination.

Inspect the cups every day and moisten the paper towels again if needed.

Take pictures or make drawings of different stages of seed germination. Use pictures or drawings for your display.

A seed contains all the nutrients that it needs for germination, so you do not need to add any nutrients to the water.

This experiment can be performed with varieties of different seeds. Pictures on the right show how your display may look depending on the type of seeds that you test. ( Pictures are not Kidney Beans )

Rotate the cups, so they will all get the same amount of heat, light exposure and air.

When you see the first real leaves, you can make your final observation and record your results.

Count the number of seeds that germinated.

What percentage of all seeds are germinated? (divide the number of germinated seeds by total number of seeds)

Do the results support your hypothesis?

Note that the shrunken paper towel allows air to get to the roots. Both air and moisture are required for the young plant.

Materials and Equipment:

• Kidney Beans
• Paper towel
• Clear glass cups

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.

Calculations:

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

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.

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.

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

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

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