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. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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?