EP 08 Do plants grow better with more water?
Objectives
Experimentally determine the optimum amount of soil moisture needed for optimal plant growth. Identify aspects of human activity which can negatively impact crop productivity.
Standards
NEXT GENERATION SCIENCE STANDARDS - MIDDLE SCHOOL (MS)
From Molecules to Organisms: Structures and Processes MS-LS1-4, MS-LS1-5
Ecosystems: Interactions, Energy and Dynamics MS-LS2-1, MS-LS2-4, MS-LS2-5 MS-ESS3
Earth and Human Activity MS-ESS3-3
Engineering Design MS-ETS1-1, MS-ETS1-3
Materials
Play and Learn with Boson Science Kit: https://www.dfrobot.com/product-1743.html
Activity
Create a chart like the one below in your journal.
1.Fill a plastic cup 3/4 full with potting soil. Carefully stir the soil with a popsicle stick. Look closely at the soil. Scoop up a little bit of the soil in your hand. What does the soil look like? What does it feel like? Record your observations in the chart.
2.Add a tablespoon of water. Carefully stir the soil with a popsicle stick. Look closely at the soil. Scoop up a little bit of the soil in your hand. What does the soil look like? What does it feel like? Record your observations in the chart. 3.Continue adding water, stirring the soil. Looking at, touching the soil and recording your observations.
Discuss the following questions with your group:
1.Discuss how the soil looked and felt with each addition of water.
2.Was there a point when the soil felt “muddy” as opposed to “wet dirt”?
3.At what point (how many tablespoons of water) did the soil become completely saturated and was able to “pour” like water?
4.Do you think the amount of water in soil can affect plant growth? Explain.
Explore
In this activity your group will use the BOSON Soil Moisture Sensor to collect data as you plant, water and grow bean plants. The purpose of this activity is to determine if there is an optimal amount of water which will result in the greatest plant growth. You will then relate this information to how some aspects of human activity can have a negative impact on crop production.
Activity Procedure Setup:
1.Connect the Battery Pack to the MainBoard-110. Ensure the MainBoard-110 is turned OFF.
2.Use a short BOSON Cable to connect the Display Module with the MainBoard-110.
3.Use a long BOSON Cable to connect the Soil Moisture Sensor with the MainBoard-110.
4.Set the BOSON equipment aside.
5.Use a permanent marker to number individual clear plastic cups 1-6.
6.Create a data table in your journal.
a.Note: You will add rows of data for approximately 3 weeks.
b.Note: For the first few rows there will be no height data to record because the beans will not have broken through the surface of the soil.
Experiment
1.Fill each plastic cup 1/2 full with garden soil. Pat the soil down gently.
2.Place 3 beans, spaced apart, on top of the soil.
3.Add more garden soil to the cup leaving about an inch to the top. Pat the soil down gently.
4.Add water to each cup as indicated in your data table. Enter the date in the left-hand column.
5.Measure and record the soil moisture according to the instructions below:
a.Turn on the BOSON MainBoard-110.
b.Press the black button on the Display Module until the display shows “Analog Data” for the Soil Moisture Sensor i16.
c.Place the Soil Moisture Sensor into the soil of cup #1.
d.Record the analog data displayed.
e.Wipe off the soil moisture sensor with a paper towel.
f.Repeat steps c-e for each cup.
6.Place the cups near a window which receives sunlight during at least some of the day. Make sure all cups receive the same amount of light.
7.Water the plants daily. Measure and record the soil moisture daily.
8.Note: 3 beans were planted in each cup in order to ensure you have a plant to measure growth for each cup. However, you will only measure the growth of one plant. Keep the healthiest looking plant and remove the other two plants from the cup.
9.Measure and record the plant’s height to your chart daily for one to two weeks.
Data Record
Copy the Data Table below into your notebook.
Explain
Making Sense of the Data:
Create a Bar Graph according to the directions below:
1.Calculate the average soil moisture for each cup over the testing period.
2.The manipulated variable is the cup number and the responding variable is the average soil moisture reading.
3.The manipulated variable is graphed along the X axis and the responding variable is graphed along the Y axis.
4.Use the variables to give your graph a title.
5.Include a legend for your graph.
Create a Multi-Colored Line Graph according to the directions below:
1.Use a different color to plot your results of plant growth for each cup.
2.The manipulated variable is the date and the responding variable is the measured height of the plant.
3.The manipulated variable is graphed along the X axis and the responding variable is graphed along the Y axis.
4.Use the variables to give your graph a title.
5.Include a legend for your graph.
Data Analysis:
In your group discuss the following questions:
1.Which plant grew the highest? What was the average soil moisture reading for this plant?
2.Which plant grew the least? What was the average soil moisture reading for this plant?
3.Were there any plants which did not sprout and/or died during the experiment?
4.Looking at your data, what seems to be the optimal amount of soil moisture for plant growth?
Elaborate
Vocabulary:
●Soil moisture - the quantity of water contained in a soil sample
●Optimal - best or most favorable
●Root - the structural part of a plant, usually found underground that grows downward, is responsible for plant support and absorption of water and nutrients
●Root hair - thin hair like projections of the root which increase the overall root surface area and responsible for absorption of nutrients and water
●Diffusion - the movement of a substance from an area of higher concentration to an area of lower concentration ●Vascular - relating to the plant tissues which are responsible for movement of water, nutrient and food substances ●Xylem - the plant tissue responsible for transporting water and nutrients from the roots to other areas of the plant ●Phloem - the plant tissue responsible for the downward movement of food substances from the leaves to other areas of the plant
Science Background:
Along with sunlight and nutrients from the soil, all plants need moisture to grow. Plants develop adaptations to survive in various ecosystems. Each species of plant has a range of tolerance for moisture and will grow best when the optimal amount of moisture is available. Too little moisture can result in plant death. Too much moisture can cause root disease which will also result in plant death.
How do plants take in moisture?
The root system of a plant is responsible for structural support as well as the uptake of water from the soil. Most of a plant’s root system remains hidden below in the soil. Part of the root is made up of fine root hairs. Water from the soil enters the plant through the root hairs. Because the cells of roots contain more solutes than in the soil, water will move into the root by the process of diffusion. From the roots water is moved and distributed to all parts of the plant. In general, the more extensive the root system, the more water it is able to absorb.
How does water move within a plant?
Plants stems have a vascular system which connects the roots of a plant to the leaves. The vascular system is made up of two types of tissue, xylem tissue and phloem tissue. Xylem tissue transports water from the roots to all other parts of the plant. Phloem tissue is responsible for transporting sugars made by the process of photosynthesis in the leaves to the non-photosynthetic parts of the plant.
Can plants survive periods of drought and periods of excess moisture?
While some plants have a narrow range of tolerance for soil moisture, other plants have developed adaptations which help them survive periods of drought or periods of excess moisture. These adaptations include modifications to root depth and spread, adaptations of the stem to help a plant remain upright during limited or excessive periods of moisture, and adaptations of leaves to retain or release water.
Evaluate
1.After analyzing your experimental data and discussing the information above cut down the side of two or three cups and carefully remove the plants. Keep note of which cup each plant came from.
2.Carefully remove plants from the soil and lay them on a paper towel.
3.Make and note observations of the plants with regards to structure and color. Note differences in the root, stem and leaves.
4.Create a diagram for each plant. Identify the amount of water each plant received, the structure and function of the plant parts. Include your observations with your diagram.
Extend
Research and develop a project based on one of the following:
●How can El Niño and La Niña weather events affect crop growth and yield?
●What are some specific plant adaptations for dealing with drought? With surviving in wet ecosystems?
●Compare and contrast the range of tolerance for water of desert plants vs. wetland plants.
●In what ways can human activity have an impact on the amount of soil moisture available for plant growth? How can people work to mitigate possible negative impacts?
