SummaryThrough multi-trial experiments, students are able to see and measure something that is otherwise invisible to them—seeing plants breathe. Student groups are given two small plants of native species and materials to enclose them after watering with colored water. After being enclosed for 5, 10 and 15 minutes, teams collect and measure the condensed water from the plants' "breathing," and then calculate the rates at which the plants breathe. A plant's breath is known as transpiration, which is the flow of water from the ground where it is taken up by roots (plant uptake) and then lost through the leaves. Students plot volume/time data for three different native plant species, determine and compare their transpiration rates to see which had the highest reaction rate and consider how a plant's unique characteristics (leaf surface area, transpiration rate) might figure into engineers' designs for neighborhood stormwater management plans.
Estimating the total amount of water within various processes of the water cycle has been a topic of scientific exploration for more than 150 years and a central focus of hydrology. Practical applications of hydrology are found in such tasks as the design and operation of hydraulic structures, water supply, wastewater treatment and disposal, recreational use of water, and fish and wildlife protection. The role of applied hydrology is to analyze the problems involved in these tasks and provide guidance for planning, and management of water resources. Like engineers, students account for a component of the water budget, calculating the rate of a reaction. Being able to understand and calculate rates is important to engineering design, modeling and research.
Students should know how to draw a best-fit lines from a sets of data points and be able to determine the slope of a line.
After this activity, students should be able to:
- Explain what the rate of a reaction is and how it applies to the urban water cycle.
- Calculate the transpiration rate of reaction for a plant species.
- Create a graph of collected data and select native plant species based on transpiration data.
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Each TeachEngineering lesson or activity is correlated to one or more K-12 science,
technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN),
a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics;
within type by subtype, then by grade, etc.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
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- Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
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Each group needs:
- 2 plants of different native plant species, in 4-inch or 1-gallon containers; usually ~$2.50 for a plant in a 4-inch pot and ~$7 for a plant in a 1-gallon pot
- (2) 2-liter or 20-ounce plastic bottles, for 1-gallon and 4-inch plants respectively, or (4) produce baggies
- (if using produce baggies) 4 twist ties
- black permanent marker, such as a Sharpie®
- scale, accurate to 0.1 gram, such as a triple beam balance or laboratory scale
- 2 stopwatches or timers
- gallon jug half filled with water
- pencils, colored pencils or markers, ruler (for graphing)
- Just Breathe Green Worksheet, one per student
For the entire class to share:
- scissors, for teacher to cut plastic bottles
- liquid food coloring, for teacher to prepare colored water, 10 drops per group
Have you ever seen a plant breathe? We learned about plants breathing in our previous lesson, Natural and Urban "Stormwater" Water Cycles. Who remembers—what is this process called? That's right, transpiration. As you remember, plants take up stormwater after it infiltrates into the ground or from groundwater sources. Through the biological process of photosynthesis, plants move water from their roots to their leaves, where it then moves to another phase in the water cycle.
Does anybody remember the hydrologic cycle phase that happens prior to transpiration? (Plant uptake.) How does the water get into the ground for the plants to take it up? (Infiltration and percolation.) What comes after transpiration? (Evaporation.)
As you recall, we can calculate the transpiration rate, or the rate that plants breath, in units of (volume)/(time), such as ml per minute or gallons per day.
adsorption: The property of a solid or liquid to attract and hold to its surface a gas, liquid, solute or suspension. A surface-based process while absorption involves the whole volume of the material.
Before the Activity
- Gather materials and make copies of the Just Breathe Green Worksheet, one per student.
- Acquire at least three different plant species, so that at least two different plants are examined by each group and data on all three species can be collected from other groups for graphing and comparison. For example, horsetail, tickseed and tropical sage, all native Florida plants, were used as examples in the Just Breathe Green Worksheet Example Answers.
- Gather information on each selected native plant species: scientific name, common name and characteristics such as light, water and soil requirements, and height. Alternatively, have students research this information as part of the activity. Usually, state food and agricultural sciences divisions and/or county master gardener programs provide significant native plant data online, such as the University of South Florida Water Atlas at http://www.florida.plantatlas.usf.edu.
- Make sure the main wide part of each plastic bottle is wide enough to fit over the potted plants. Then cut the tops off the plastic bottles where the necks begin to widen, so you essentially have clear plastic domes to cover each plant. Alternatively use plastic produce bags that are big enough to each cover a plant.
- Mix up some colored tap water for each team to water its plants. In each one-gallon jug, mix 10 drops of food coloring into one-half gallon of water.
- This activity works best conducted outside on a sunny day. Bring materials and plants to an outside area that receives direct sunlight. Assign areas for evapotranspiration observation and areas for other experiment work (researching, calculating, graphing, writing).
- Note that students will need their completed worksheets for the last activity in this unit.
With the Students
- Divide the class into groups of two or three students each, depending on the size of the class and resources. Hand out the worksheets.
- Direct students to record the time of day, temperature, humidity, dew point and weather conditions on their worksheets. Refer to an online weather website that provides localized weather conditions, such as Weather Underground at http://www.wunderground.com.
- Assign each plant species with a Plant ID #.
- Water the plants with dyed water until plant media is fully saturated and have students predict what will happen to the dyed water as it moves through the soil and evaporates after transpiration.
- Have each group select two different plant species to study.
- Provide students with the plant species' characteristics (or have students research this information) to record on their worksheets.
- Have students draw an overall sketch of what the plant looks like, providing a detailed drawing of its leaf or grass strand structure.
- Use a black marker to label one plastic bottle/produce baggie with the plant ID #.
- Weigh the bottle or bag on the scale and record its weight to the nearest 0.1 gram. (A more precise measurement may be made, depending on the scale.)
- Place the bottle/bag around the plant. If you are using a produce bag, use a twist tie to secure the bag at the plant base.
- Set a stopwatch or timer for 5 minutes.
- When 5 minutes are up, carefully remove the bottle/bag, without letting any of the accumulated water escape.
- Place plastic bottle/bag on the scale and record its weight on the worksheet.
- Replace the bottle/bag on the plant and repeat steps 10-13 for 10- and 15-minute increments.
- Remember to record your observations of the plants and the bottles/bags covering them for 5-, 10-, and 15-minute increments.
- Have students sketch overall diagrams of two additional plant species, making sure to include identifying details of the overall plant and its leaf or grass strand structure.
- Collect transpiration data from students in other groups on the two additional plant species and record it on the worksheets.
- Return to the classroom (or use an outdoor classroom) to discuss results and create a data plot. Use different colors or symbols to identify the line for each plant species, and provide a key. Use a ruler to draw a best-fit line of the data.
- Determine the slope of the best-fit lines. To determine the slope of each line, select two points from the best-fit line (x1, y1), (x2, y2) and determine the slope (y2-y1)/(x2-x1). The slope of the line is the transpiration rate.
- Have students finish their worksheets by answering the questions on the last page.
- Conclude by leading a class discussion to share, compare and review student results and conclusions, as described in the Assessment section. Collect and review the worksheets.
Predictions: Ask students the following questions:
- What phase of the water cycle is a plant's breath? Describe the phases before and after. (Answer: A plant's breath is known as transpiration. It is the flow of water from the ground, where it is taken up by roots [plant uptake] and then lost through the leaves. The transpired water evaporates and then condenses.)
- What do you predict that you will see accumulate on the bottle/bag? Write this on your worksheet. (Answer: Condensed water.)
- Predict the color of water as it evaporates from the plant. Write this on your worksheet. (Answer: Clear.)
Activity Embedded Assessment
Worksheet: Have students complete the Just Breathe Green Worksheet as they conduct the activity. Students record and plot data, determine transpiration rates and answer comprehension questions. Review their worksheet predictions, data, calculations, graph and answers to gauge their comprehension.
Wrap-Up: Lead a class discussion to share, compare and review student results and conclusions, including the graph and questions on the last page of the worksheet. Ask the students:
- What is a reaction rate and how does it apply to the water cycle? (Answer: Reaction rates are a critical factor in the design of engineered systems. A reaction rate is how fast or slow a reaction takes place. Within the water cycle, the reaction rate is the speed at which water transfers from one phase to another, for example, from plant uptake to transpiration.)
- What was the color of the condensed water, why? (Answer: Clear. Only pure water can evaporate. Any pollutants in the water are adsorbed by soil or remain in the plants' organic biomass.)
- Let's look at your graphs. You plotted the transpiration rate data as volume over time for each plant species, using different colors or line styles for each plant species. (Answer: Investigate with students to discover that 1 ml = 1 g.) If the slope of the line is the transpiration rate, what does the graph tell us? Which plant has the highest transpiration rate? The lowest?
- What were the physical differences in the plants? Might their physical differences make a difference in their transpiration rates? (Example answer: Tropical sage had the highest transpiration rate. Its physical characteristics include a high leaf surface area to overall plant ratio compared to tickseed, and its leaves have a rough textured surface compared to the horsetail. The increase in leaf surface area provides more area for transpiration to occur.)
- How could engineers use this information in their designs of neighborhood stormwater management plans? (Answer: This information can be used to recommend native plant species to install within a neighborhood's stormwater features. Engineers can base the design of these systems on the volume of water each plant species is capable of removing, transforming it from stormwater runoff to evaporation. Note: Plant characteristics and traits are important to consider when selecting plants. Transpiration values are one of many characteristics to consider and this question asks students how to use the data they collected to design plans and select plants. It is not necessarily true that you would use the plant with the highest transpiration rate. Engineers may decide to add more plants or increase the storage volume within a ponding zone or media layers to account for a specific volume of water for an intended design.)
ContributorsRyan Locicero, Maya Trotz, Krysta Porteus, Jennifer Butler, William Zeman, Brigith Soto
Copyright© 2014 by Regents of the University of Colorado; original copyright 2013 University of South Florida
Supporting ProgramWater Awareness Research and Education (WARE) Research Experience for Teachers (RET), University of South Florida, Tampa
This curriculum was developed by Water Awareness Research and Education (WARE) Research Experience for Teachers (RET) at the University of South Florida, funded by National Science Foundation grant no. EEC 1200682. However, the contents do not necessarily represent the policies of the NSF, and should not be assumed an endorsement by the federal government.
This material is based upon work supported by the Tampa Bay Estuary Program and the Southwest Florida Water Management District. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies.
Last modified: July 20, 2017