Plant tropisms: phototropism, hydrotropism, gravitropism
Integrated ScienceLife ProcessesAges 12–13Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Life Processes
A bean plant grows in a pot: the shoot and root lengthen day by day. Drag the light source (or the water source) left and right and watch the shoot bend toward the stimulus after a few days, while the root bends the opposite way. Switch the stimulus type to compare phototropism, hydrotropism, gravitropism (lay the pot on its side), and the thigmotropism of a tendril. The stem's angle from vertical is measured and updates continuously.
Lesson: Plant tropisms and their types
What it shows
Tropisms are growth responses of a plant towards or away from a stimulus that comes from one direction. The hormone auxin builds up on the side of a shoot away from the light, so cells there elongate faster and the shoot bends towards the light: positive phototropism. Roots respond the opposite way. When a pot is laid on its side, the shoot turns upward (negative gravitropism) and the root turns downward (positive gravitropism). Roots also grow towards moist soil (hydrotropism), and tendrils coil around a support they touch (thigmotropism). The model compresses days of growth into seconds.
How to use
Start with phototropism and drag the light source, or use the Source position slider, to one side; after a few simulated days read the stem angle from vertical. Change Intensity to see how the size and speed of the response depend on the stimulus. Press Change stimulus to move through hydrotropism, gravitropism and thigmotropism, and press Replant to start a fresh seedling for each test so the results can be compared.
Parameters you can change
- Stimulus type Phototropism (light from one side), Hydrotropism (water source off to one side), Gravitropism (pot laid on its side), Thigmotropism (tendril meeting a support)
- Stimulus source position (negative: left, positive: right) -100–100 %
- Stimulus intensity 0–100 %
- Simulation speed 0.5–4 days/s
- Show the root below ground
Questions to explore
- When the pot is laid on its side, how do the stem and the root respond differently?
- How does the stem's bending change when the stimulus intensity is lowered towards 0%?
- How do phototropism and hydrotropism help a plant survive?
