How can littleBits be combined with other materials to build an apparatus that proves that the direction in which a seedling’s roots grow is affected by gravity? Original research conducted in Michael Wilkinson’s 4th Grade Science Classroom at Fieldston Lower School (ECFS).
Read more about us here: http://www.ecfs.org, http://mwmathsci.blogspot.com
Authentic scientific exploration often relies on engineering apparatus to support obtaining the data that authenticates or contradicts a hypothesis. With littleBits, students can easily design and build prototypes of lab apparatus that would otherwise be inaccessible. The following project is an illustration of how littleBits can be used to support serious scientific inquiry.
Students will use littleBits, combined with found materials, to construct an apparatus that will support an investigation of the effect of gravity in the growth of plant seedlings.
“How do plants know what direction to grow?”
Introduce the concepts of tropism, hydrotropism, phototropism and gravitropism:
Plant growth responds to the stimuli of light, gravity and water, among others. These are called tropisms, or the turning of an organism in response to an external stimulus. A reaction to water is hydrotropism, a reaction to light is phototropism and a reaction to gravity is geo- or gravitropism.
To conduct this investigation as an experiment, and not merely as a demonstration, students will need to conduct three different trials.
Trial 1: Establish the baseline or control population.
Trial 2: First experimental trial: simple manipulation of gravity and light.
Trial 3: Second experimental trial: simulating microgravity.
Note: All the trials can be run concurrently or consecutively. Students with little experience in controlled experiments, or experimental design; would benefit from consecutive trials with each experiment building upon the previous trial. Experienced students can run all three trials concurrently.
Through the three trials, assess student ability to setup effective, controlled experiments. Use class discussions to gauge student understanding of their experiment results. Consider collecting student Seedspinner Data Sheets and asking students to analyze their results in writing.
NGSS Disciplinary Core Ideas:
PS1: Matter and its interactions
PS2: Motion and stability: Forces and interactions
LS2: Ecosystems: Interactions, energy, and dynamics
ETS1: Engineering design
For more details on how to construct a Seedspinner apparatus, see the project page: https://littlebits.cc/projects/seedspinner-simulating-microg-with-littlebits-and-fastplants/
Duration: 3 trials
Elementary (ages 8-10)
Middle School (ages 11-13)
MODULES & ACCESSORIES USED (8)
dc motor (1)
battery + cable (1)
STEP 1 : Day 1: Prelab
Brainstorm: What stimuli will direct the growth of plants? Develop hypotheses.
Hypothesis: Plants will grow toward a light source.
Hypothesis: Plants will grow toward the pull of gravity.
Brainstorm: What procedures and apparatus are needed to test hypotheses?
Design Challenge: Students will design and engineer a prototype with littleBits that must: a. isolate and direct light and b. manipulate gravity
You must design a control trial, against which the effects of experimental trials can be compared.
STEP 2 : Day 1: Outcomes
Students will have drafted their procedures and plans. They will build prototypes during the next session.
STEP 3 : Day 2: Build Apparatus and Begin Trials
Students will have assembled SeedSpinner prototypes and tested them for proper operation. See project instructions on how to build and set up experimental materials: https://littlebits.cc/projects/seedspinner-simulating-microg-with-littlebits-and-fastplants/ will be ready for germination in all three trials (see below). Simulated microgravity trial, dark trial and light trial will all commence . This is considered Day Zero for the experiment. SeedSpinner should run continuously for 5 days. Check daily to ensure proper movement and water level is maintained.
Place the light (control) trial chambers in their reservoir under a bright fluorescent bulb or in direct sunlight.
Place the dark (experimental) trial chambers in their reservoir under a dark bucket or box or in a dark cupboard to shield from the light.
Place a dark bucket or box over the assembled SeedSpinner to shield seeds from the light.
STEP 4 : Day 6 (3rd class period): Observations
After 5 days, retrieve the three germination chambers for observation. Carefully remove tape (on the spin/microgravity trial) and bases of the Petri dishes to clearly see the seedlings.
Download the data sheet here: http://media.littlebits.cc/wp-content/uploads/2013/11/SeedSpinnerDataSheet.pdf
– Make specific observations of the direction in which the hypocotyl and roots are growing.
– Make specific observations as to the color of the roots, hypocotyl and cotyledons.
– Make specific note of whether the cotyledons have opened or remain folded.
– Draw diagrams of seedlings and/or photograph the germination chambers. Label structures in diagrams or photos.
– Measure the lengths of the hypocotyls and roots.
– Measure the width of the cotyledons.
Outcomes: Students will have made observations and collected data that they will be able to use to articulate the effects of gravity on germination and seedling growth.
STEP 5 : Day 7 (4th class period): Discussion
Give each lab group an opportunity to review their data and respond to the following questions before opening to full class discussion:
– How can we evaluate the effectiveness of the littleBits SeedSpinner prototype in simulating microgravity conditions? In what ways was it /was it not effective in simulating microgravity?
– How do seedlings react to microgravity? Be specific and site observations and data in support of your conclusion.
– What, if any, modifications do you think should be made to your littleBits SeedSpinner prototype to improve its functionality and/or effectiveness?
– What additional trials could be conducted? What variable is to be manipulated? (e.g. speed of rotation, direction of rotation) What hypothesis can be tested in these additional trials? What are your predicted outcomes? What, if any, modifications to procedure or apparatus would be required for these additional trails?
Following class discussion of these questions, share video clips of germination and seedling growth on orbit aboard the Space Shuttle and International Space Station.
– How do the classroom results compare with those flown on orbit?
– What similarities do you identify in the germination of seeds and growth of seedlings between those grown in space and those grown in the SeedSpinner?
STEP 6 : Day 7: Outcomes and Conclusions
By the end of the experiment, students will be able to articulate that:
-The green pigment (chlorophyll) is only expressed in cotyledons of seedlings exposed to the light.
– The cotyledons of seedlings grown in the dark remain folded, while those grown in the light are open.
– The hypocotyls of the seedlings growing in normal Earth gravity of 1G (without the SeedSpinner) orient perpendicular to the ground, opposite the pull of gravity, or toward the light, regardless of seed scar orientation.
– The roots of the seedlings growing in normal Earth gravity of 1G (without the SeedSpinner) orient perpendicular to the ground, in the direction of the pull of gravity, regardless of seed scar orientation.
– The hypocotyls and roots of seedlings grown in simulated microgravity (on the SeedSpinner) orient in random directions.
Conclusion: Plants are gravitropic; their growth is directed by the pull of gravity. Microgravity can be simulated with a slowly spinning chamber.
Further Discussion: If/When humans embark on extended deep-space missions, plants will be a necessary organism, as a source of food and for carbon dioxide absorption. What accommodations might be needed to support plant growth on board a spacecraft given the reaction of plant roots to microgravity?
STEP 7 : Extensions
1. Rotate the germination chambers from the light and dark trials 180°, return to reservoir and light and dark conditions. Observe growth pattern after five days.
2, Place seedlings grown in the light, in the dark and seedlings grown in the dark, in the light. Observe changes in chlorophyll expression after five days.
3. Repeat spin/microgravity trial at different rates of revolution by adjusting the pulse frequency or eliminating the pulse bit entirely. Can other pink bits be used to control the revolution rate?