CHAPTER 13 INVESTIGATION: DESIGN YOUR OWN PLANT EXPERIMENT
*Abiotic Factors and Plant Growth*
Many factors affect plant growth. Is it possible to test some in a laboratory setting? In this investigation you
will choose an abiotic factor and attempt to test how (or if) it affects the growth of radish seedlings. You
will also determine if pH levels have an effect on duckweed.
*PROBLEM*
How do abiotic factors affect plant growth?
*MATERIALS*
* radish seedlings and
* labels
* marker
* duckweed plants
* 4 cups, and 3 petri dishes
* ruler
* potting soil
* water
* abiotic factors to test (you pick)
* Any materials you may need for YOUR experiment
*PROCESS SKILLS*
* Designing Experiments
* Collecting Data
*Procedure - Part 1 - Abiotic Factors and Radish Seeds*
1. Choose an abiotic factor to test on the growth of radish seedlings. Possible factors include amount of
sunlight, amount of water, soil type, light color available to plants, or solution added to soil.
2. Determine a way to vary the factor you have chosen. Be sure to include at least three different
settings of your variable and to keep all other factors constant. Don't forget to have one of your
plants be a "control" to compare to. Write out the abiotic factor you are testing, and a procedure for
your investigation.
Abiotic factor:
Procedure:
3. Obtain 4 cups, soil, and 4 radish seeds. Label one cup "Control" and the remaining three "A," "B",
and "C", or list the abiotic factor that is different in each cup. Remember what each cup contains.
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4. Each day make an observation of your plants. Mention whether the seed has germinated, height of
plant (in cm), color, and number of leaves present.
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5. Continue the measurements for a period of 8 class days. Use the same method to repeat
measurements each day. Be sure to keep plants watered with exact amount if needed.
6. Record all data you generate in the a well-organized data table. Copy the chart below 4 times, one
for each plant.
Plant: ________
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Germinated
Color
Height (cm)
# of Leaves
*Procedure - Part 2 - "Population of Duckweed"*
1. Obtain 1 petri dish and label it with your names, period, and lab group #. Add water to petri dish so
the bottom is covered. Carefully add your assigned abiotic factor. Be careful if your abiotic factor
could harm you or your lab partners. (Example: don’t get acid on your skin or clothing)
2. Using the tweezers, add a few duckweed plants to your petri dish.
3. For the following few days record what happens to the duckweed in your petri dish.
Construct one table like the one below to use for your data collection.
Duckweed: (Abiotic # of Leaves
Observations: Color, Size, Formation, Etc.
Factor)
Day 1
Day 2
Day 3
Day 4
Day 5
Copy the table below onto your paper. Collect data from the other lab groups in your class. Include your
own data as well.
Lab
Abiotic
Explain population Overall Observations
Group #
Factor
change
1
2
3
4
5
6
7
8
*Analyze and Conclude - Answer on your paper*
1. Identify Variables: What are your independent and dependent variables in Part 1? What are your
constants? What is your control?
2. Identify Variables: What were the independent and dependent variables in Part 2? What are your
constants? What is your control?
3. Operational Definitions: On the basis of your procedure, what dependent variable do you think will
be the most reliable to monitor plant progress in Part 1? Why?
4. Operational Definitions: On the basis of your procedure, what dependent variable do you think will
be the most reliable to monitor plant progress in Part 2? Why?
5. Graph Data: Make a line graph to present the data you obtained on plant growth in Part 1. Attach it
to your paper. The X-axis should be Day, and the Y-axis should be height in cm. Make a line for
ALL four plants. What trend do you notice in your graph?
6. Conclude: By studying your data in Part 1, what can you conclude about how (or if) your variable
affects the growth of radish seedlings?
7. Conclude: By studying your data in Part 2, what can you conclude about how (or if) abiotic factors
affect the population growth of duckweed?
8. Conclude: Is your experiment in Part 1 a failure if your variable did not apparently affect the
growth? Explain.
9. Experimental Design: What possible sources of error may have occurred in both experiments? Why
might they have occurred?
10. Extension: How would you design an experiment to determine whether a specific biotic factor
influences plant growth?