Plant Transpiration Laboratory
Control humidity, temperature, wind and stomatal aperture in a sealed chamber, zoom on the stomata, and measure the transpiration rate live.
Transpiration rate over the last 60 seconds of simulated time.
About the Plant Transpiration Laboratory
Free plant transpiration laboratory. Control humidity, temperature, wind and stomatal aperture in a sealed chamber, zoom on the stomata, and measure the transpiration rate live. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for botany, the plant transpiration laboratory runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Control humidity, temperature, wind and stomatal aperture in a sealed chamber, zoom on the stomata, and measure the transpiration rate live. Use it to explore botany ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Plant Transpiration Laboratory
- Use the controls to change Relative humidity, Temperature, Wind speed, Light level, Stomatal aperture. The simulation reacts instantly.
- Press "Save as Environment A", "Save as Environment B", "Hot & windy day", "Cool & humid night" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Try the hot and windy preset, then the cool and humid preset, and compare readouts.
- Save two different environments as A and B and compare their water loss on the same bar chart.
- Close the stomata to 10% and see how far the rate drops despite high VPD.
- Find a setting where root pressure or transpiration and VPD nearly cancel to give a very low rate.
Key ideas you can learn
- Transpiration is driven by the vapor pressure deficit (VPD): the drier and hotter the air, the harder it pulls water vapor out of the leaf.
- Wind thins the still air layer clinging to a leaf, raising boundary-layer conductance and speeding up water loss.
- Stomata are a trade-off: opening them lets CO₂ in for photosynthesis but also lets water vapor escape.
- Total conductance combines the stomata and the boundary layer in series, so either one can be the bottleneck.
Where this is used in the real world
Farmers schedule irrigation and greenhouse ventilation around exactly this vapor-pressure-deficit and wind effect to avoid wilting crops on hot, dry, windy days.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is vapor pressure deficit?
It is the difference between the air's saturation vapor pressure at the current temperature and its actual vapor pressure at the current humidity - the 'drying power' of the air.
Why does wind increase transpiration even without changing humidity?
Wind sweeps away the humid air sitting right at the leaf surface, steepening the vapor gradient and thinning the boundary layer that would otherwise trap moisture.
Is the Plant Transpiration Laboratory free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Plant Transpiration Laboratory work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.