Introduction: (Initial Observation)
During the process of photosynthesis plants use the energy from the light, water from the ground, and carbon dioxide from the air to produce sugar, starch and cellulose. The byproduct of this process is oxygen. All the oxygen in the atmosphere is actually made by plants on the ground and in the oceans.
At night however, plants absorb oxygen and release carbon dioxide. In many places it is a common belief that you should not sleep under large trees at night, because the shortage of oxygen and excess production of carbon dioxide may suffocate you. We don’t know how accurate such claims are, so we want to investigate part of such claims. In this project we will investigate if plants need oxygen and what happens to them in absence or shortage of oxygen.
Find out about the plants and what they need to survive and grow. Read books, magazines or ask professionals who might know in order to learn about the effect of oxygen on plants. Keep track of where you got your information from.
Following are samples of information you may find:
Green plants release oxygen through photosynthesis but they still consume oxygen at the same time. The primary way plants use oxygen is through their root cells. In order for a plant to take up water and nutrients from the soil, it must continually grow new root hairs. The cells that make up these hairs are living cells that do not carry out photosynthesis. They are similar to the cells of animals in that they require oxygen and give off carbon dioxide as they burn carbohydrates to obtain the energy they need to function. This is why you can “drown” a house plant by watering it too much. If the soil gets too saturated with water, the plants root cells can’t get enough oxygen from the air. There are vascular plants such as cypress trees and cattails that are adapted to living in saturated soil. These plants have root hairs that grow out of the stems above the soil and/or water surface so that they can take in oxygen. When a plant is green, it is giving off more oxygen through photosynthesis in it’s leaf and sometimes stem cells than it is consuming through it’s root cells so that is why you hear people say that plants are “opposite” of animals in that they take in carbon dioxide and give off oxygen. When a plant is dormant and it’s leaves have fallen off in the case of perennial deciduous plants (as opposed to annuals such as dandelions or evergreen plants such as pine trees), then plants are still using oxygen and giving off carbon dioxide through their roots as the roots must stay active to keep the root crown from which the new stems and leaves will emerge the next growing season alive.
On the contrary during the night or when the light of the sun is withdrawn plants absorb oxygen and form with it carbonic acid a part of which they emit and a part is retained It appears from experiment that vegetables not only cease to thrive but that they actually die if deprived of this nightly inspiration of oxygen Thus if a plant be confined during the day in a portion of carbonic acid it decomposes a part of this gas which is replaced by the emission of an equal volume of oxygen But at night a part of this oxygen is absorbed and converted into carbonic acid which is again emitted Thus ultimately the plant decomposes all the carbonic acid because it emits more oxygen during the day than it absorbs during the night But if the oxygen which is formed during the day is withdrawn at evening that is if the plant has a new supply of pure carbonic acid every day it…
Elements of Chemistry In which the Recent Discoveries in the Science are Included, and Its Doctrines Familiarly Explained : Illustrated by Numerous Engravings, and Designed for the Use of Schools and Academies By John Lee Comstock
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.
This is a sample of how you may write the purpose or question.
The purpose of this project is to find out if plants can live without oxygen.
Question: Can plants live without oxygen?
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 is a sample on how you may define variables:
- The independent variable (also known as manipulated variable) is oxygen.
- The dependent variable (also known as responding variable) is the plant life. We measure the plant growth and observe general conditions of the plant.
- Control variables are temperature, light and other environmental conditions.
- Constants are the plant type, size, and age.
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 two sample hypothesis:
1. I hypothesize that plants cannot live without oxygen. My hypothesis is based on my gathered information indicating that plants absorb oxygen at night.
2. My hypothesis is that plants can live without oxygen. My hypothesis is based on my gathered information about photosynthesis in which plants absorb carbon dioxide and release oxygen.
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.”
Before starting your experiment, you must prepare 3 identical greenhouses. There might be some small and decorative greenhouses for sale in your local hardware store, nursery store or garden supplier; however, they might be expensive. Some students use their own creativity and make their own greenhouses using a wood/ or metal frame and cover it with glass, Plexiglas or any other clear plastic. If you want to do that, you must already have a detail plan, skills and access to the materials. Unfortunately I will not be able to help you with that.
What I can recommend as a simple solution to your greenhouse need is using a clear plastic container.
On the right is a $4.00 container from WalMart. It is placed upside-down in a sunny spot. Potted plants or seedlings are placed inside. The temperature is regulated by creating some shade using a cardboard when needed. Alternatively you may place the container where it gets lots of light, but little direct sunlight.
The container you buy must be large enough to hold at least 5 pots pf plants as well as a few cups of oxygen absorbing compound and a small candle.
Safety Notes: Adult supervision is required. Do not leave your greenhouse unattended until the candle is turned off by the lack of oxygen.
Experiment: Depriving the plants from oxygen.
Introduction: In this experiment we grow plants in a glass box or clear plastic box similar to an empty aquarium. We will remove the oxygen by steel wool.
- Prepare 3 small greenhouses for your experiment. Use the information in the introduction for ideas on how you can do that. Number them from 1 to 3.
- Prepare or purchase 15 pots of young plants or seedlings. It is good if you select a fast growing plant for this experiment (Consult the seller about it. Plants such as tomato and beans are what I recommend). Make sure all the seedlings or young plants are the same type, same size and same age.
- Place 5 pots in the green house number 1. Label this greenhouse to be the control.
- Place 5 pots in the greenhouse number 2. In this greenhouse also place a few cups with about 1″ water at the bottom of each cup and a pack of wet steel wool in each cup. Label this greenhouse “Low Oxygen”.
- Place 5 pots in the greenhouse number 3. In this greenhouse also place a few cups with about 1″ water at the bottom of each cup and a pack of wet steel wool in each cup. In this greenhouse also place a small candle and light it up. (This candle will turn off later when there are no more oxygen left in the greenhouse.)
- If the plants need watering, water them equally and then close the greenhouses. Greenhouses must be closed tightly to prevent air flow in any direction.
- Every day or every other day open all three greenhouses, water all plants equally. Observe and record the conditions and the height of all plants. Also light up the candle in the greenhouse number 3 and finally close back all three greenhouses tight.
- Repeat step 7 for up to about 2 weeks and record the results. Also take pictures of all three groups of plants in the first day and in the last day of your experiment. Your data table may look like the table bellow.
Plant height in different groups:
|Day||Control Group||Low Oxygen Group||Oxygen Free Group|
You may calculate the average plant height from each group and enter them in your results table like this:
|Day||Average plant height in Control Green house||Average plant height in Low oxygen Green house||Average plant height in Oxygen Free Green house|
Make a graph:
You may make a bar graph to visually present your results. Make 3 vertical bars and label them Oxygen, Low Oxygen and No Oxygen. The height of each bar will be the average height of plants in that group in the last day of your experiment.
You may optionally place a thermometer inside each green house faced outside so that you can read the temperatures inside each greenhouse. Record your readings in your log book.
Materials and Equipment:
List the materials you use in this section of your report. Your specific list of materials depend on how you do your experiment and what plants you grow or what type of greenhouse you use. This is a sample:
- Three plastic storage containers
- One small candle
- 15 pots of young tomato plants
- 10 pads or balls of steel wool.
- 10 cups
- 3 thermometers
- Ruler stick
Make sure you use real steel wool (shown in the image in the right), not scrubbing pads made of plastic or metals other than steel.
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.
If you do any calculations, write your calculations in this section of your report. You calculations also include your daily calculations of the average plant height in each group.
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.
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.
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.
List your references in this section of your report. Your references may include books, magazines or websites.