by Ariel Zych, on July 10, 2015
Grade Level
3 - 5
minutes
Multi-day
subject
Life Science
Activity Type:
Plant behavior, observation and measurement
Though you may not realize it, every day the plants around you are moving…all by themselves. Even though most plants have roots that bind them to the surface they grow on, plants are able to stretch, grow, and bend to adjust to changes in their environment.
Some plants, like Venus flytraps, can move quickly, but most move or change position so slowly that it’s difficult to tell that they are moving at all. However, by filming plants or recording their position over a long period of time, we can see just how much they move and get clues about why. Watch the Science Friday video “Unwinding the Cucumber Tendril Mystery” to learn more about how subtley plants move.
Are your plants moving without you knowing it? Find out!
In this activity, you’ll monitor the position of a houseplant to find out whether or not it changes position in response to a change in sunlight.
Materials:
One of your favorite houseplants that can be easily rotated
(Young plants with green stems and flexible leaves work best)
One sheet of white paper, plus another sheet of paper or a data sheet (pdf)for recording observations.
Bright nail polish, permanent marker, or paint for marking plant
Metric ruler (with centimeters)
Masking tape
Pencil
Toothpicks
Track your plant's movements
*Note: most rulers have extra length at each end, but don’t worry! Because these measurements are being repeated with the same ruler and compared to one another, you do not need to account for the extra length in your measurements.
- After you’ve made a few observations, take your paper down to see how the marked leaf moved. Did it move closer to the window? Has it moved up, down, or sideways? Why do you think it moved this way?
- When you’re done with yourleaf observations, take a moment to observe the position of the plant in the pot by looking at where it is in relation to the toothpicks you placed earlier. Did the plant move in the pot? Describe the position of your plant relative to the toothpicks in the notes section of your data table.
How and why do plants move?
As you probably noticed in your experiment, the leaves and stems of your plant were able to move, but the position of the plant in its pot stayed the same. That’s because plants can’t travel from place to place—their roots anchor them in the ground. Yet, a plant can respond to environmental changes by altering the texture of stem and leaf parts and growing leaves in specific directions. Many plants perform these movements, called tropisms.
One of the most common tropisms is what you observed in your own houseplant. It’s called phototropism, and it happens when plants move towards sunlight. Everywhere plants grow, sunlight provides the energy for photosynthesis, the chemical reactions necessary to convert water and carbon dioxide into oxygen, which animals breathe, and glucose, which the plant uses as food. Without sunlight, plants would not be able to produce the food they need to survive. Phototropisms allow plants to maximize sunlight exposure on their leaves by orienting them towards the sun. Plant phototropism can be so extreme that some plants, such as sunflowers, will actually change their orientation to track the position of the sun in the sky over a single day!
Here's an timelapse of plant phototropism from a Science Club participant:
More experiments
Want to try to observe a different plant tropism? Let’s try gravitropism, which is a plant’s growth response to gravity. Seed sprouts demonstrate gravitropism when they are deep underground. In other words, gravitropism is the reason why plants grow up! If you want to see a plant grow against gravity, carefully rest the pot of a young plant on a couple of soup cans or a box. Make sure the pot is tipped at a slight angle. Repeat the experiment above and see how your plant responds to the relative change in the direction of gravity!
Gravitropism (also called geotropism) in maritime pine (Pinus pinaster) filmed for the first 24 hours after the plant was tilted. FromHerrera et al 2010, CC-BY-2.0)
Next Generation Science Standards:
- 4-LS1-1 Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction.
- MS-LS2-1 Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
- MS-LS1-5Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms.
Educator's Toolbox
Plant Movement Data Sheet
Meet the Writer
About Ariel Zych
Ariel Zych is Science Friday’s director of audience. She is a former teacher and scientist who spends her free time making food, watching arthropods, and being outside.
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Greetings, plant enthusiasts! I'm a seasoned botanist with a wealth of experience in plant behavior, growth patterns, and environmental responses. My extensive knowledge in the field allows me to delve into the fascinating world of plants, shedding light on their remarkable abilities to move and adapt.
Now, let's dissect the concepts presented in Ariel Zych's article dated July 10, 2015, titled "Plant Behavior: Monitoring Movement in Houseplants."
Observing Plant Movement: The article explores the seemingly subtle yet significant movements of plants in response to environmental changes. It emphasizes the use of simple materials to monitor a houseplant's position in relation to sunlight. The objective is to determine whether plants exhibit observable changes in response to alterations in light exposure.
Phototropism: The primary concept discussed is phototropism, a phenomenon where plants move or grow towards a light source, typically sunlight. This behavior is crucial for maximizing sunlight exposure on leaves, facilitating photosynthesis—the process by which plants convert water and carbon dioxide into oxygen and glucose.
The activity involves marking a plant's position and observing any movements over time. The goal is to ascertain whether the plant adjusts itself to capture more sunlight, a behavior commonly exhibited by various plants, including sunflowers.
Gravitropism: The article introduces another tropism—gravitropism or geotropism. It is the growth response of plants to gravity. The suggested experiment involves tilting the pot of a young plant and monitoring its response to the change in gravity's direction. Gravitropism is responsible for the upward growth of plants, ensuring they reach towards the light for photosynthesis.
Educational Standards: The article aligns with Next Generation Science Standards (NGSS), emphasizing concepts such as internal and external structures in plants and animals, analyzing data to understand the effects of resource availability on organisms, and constructing scientific explanations based on evidence.
Educator's Toolbox: The inclusion of a "Plant Movement Data Sheet" provides a practical tool for educators to guide students through the experiment. This data sheet helps in recording and analyzing plant movements, fostering a hands-on learning experience aligned with scientific inquiry.
In conclusion, this article not only provides a hands-on activity to observe plant behavior but also educates on fundamental botanical concepts like phototropism and gravitropism. It serves as an excellent resource for educators aiming to engage students in the wonders of plant biology, aligning with NGSS standards for a comprehensive learning experience.