Imagine a plant that acts shy! The Sensitive Mimosa (Mimosa pudica) appears to sulk away when you touch it—but how is behaviour in a plant possible? In this lab, you will peer into the secret messages to observe how touch information is relayed inside this wonderful plant.
Meet the Sensitive Mimosa, an intriguing tropical plant whose name literally means “shy.” Growing naturally in sunny, humid areas from Brazil to Thailand, this plant has charmed people with its rapid and almost animal-like responses. When gently touched, its delicate leaf segments close up neatly, returning to normal after a short while if given plenty of bright light. A firmer touch, however, can prompt the entire leaf stem to drop suddenly, which may help by exposing its thorns and startling hungry herbivores.
In today’s experiment, you’ll have the chance to replicate these distinctive behaviors and test the plant’s recovery time firsthand. Try it before we begin. How quickly will your Mimosa spring back into action under good lighting conditions? Your observations will help unlock some fascinating secrets of plant behavior!
Mimosa pudicas can be found from online resellers as small seedling plants. You can try to grow from seeds too, but it can be challenging (untreated seeds have a hard coat and only about 1 in 7 germinate; nicking the coat or soaking seeds in hot water helps a lot).
Note the timing of your recorded waveforms with the plant’s behavior to deduce the involvement of ion channels and water movement in the rapid leaf closure.
Examine the shape of the action potentials, noting the characteristic shape. How does this compare to that of a neuron or muscle action potential?
Draw the Mimosa’s touch-to-movement pathway: the leaflet you tapped, the signal traveling along the stem, and the pulvinus that drops the leaf. Mark where your electrode was wrapped.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
Draw the Mimosa's touch-to-movement pathway: leaflet, signal along the stem, pulvinus.
2 Developing and Using Models
Draw the touch-to-movement pathway and mark where your electrode was wrapped.
3 Planning and Carrying Out Investigations
Record the Mimosa's electrical signal while tapping its leaves.
4 Analyzing and Interpreting Data
Match the signal's timing to the leaf's movement and compare its shape with a neuron's action potential.
6 Constructing Explanations and Designing Solutions
Use the timing of signal and movement to explain the role of ion channels and water flow.
Cause and Effect
A tap triggers an electrical signal and the leaf drops.
Structure and Function
The pulvinus, where the leaf stalk meets the stem, makes the movement.
Patterns
Compare the plant's action potential with a neuron's.
LS1.A Structure and Function
Ion channels and water flow in specialized cells drive the movement.
Backyard Brains mapping using the book's method. Not in the book. Performance expectation as the Backyard Brains Plant SpikerBox curriculum plan (2026) aligns this lesson; practices, crosscutting concepts and core ideas by the book's method.
