Plant Water Transport: Xylem Simulator
Follow water from root to leaf through the xylem, and see how transpiration, root pressure and vessel width set the water's speed and pressure.
Ascent velocity vs transpiration rate, at your current diameter and root pressure.
Ascent velocity vs xylem radius (r⁴ dependence - notice how sharply it rises).
About the Plant Water Transport: Xylem Simulator
Free plant water transport: xylem simulator. Follow water from root to leaf through the xylem, and see how transpiration, root pressure and vessel width set the water's speed and pressure. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for botany, the plant water transport: xylem simulator 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.
Follow water from root to leaf through the xylem, and see how transpiration, root pressure and vessel width set the water's speed and pressure. 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 Water Transport: Xylem Simulator
- Use the controls to change Transpiration rate, Root pressure, Air humidity, Xylem vessel radius. The simulation reacts instantly.
- Press "Night (stomata shut)", "Hot midday", "Reset to defaults", "📄 Lab Report" 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 night preset and see root pressure take over as the driving force.
- Try the hot midday preset and watch the tension climb.
- Narrow the vessel radius and see how sharply the ascent velocity drops.
- Try the narrow-vessel challenge: reach the target speed with a 30 micron radius or less.
Key ideas you can learn
- Cohesion-tension theory: water evaporating from the leaf pulls the whole connected water column up the xylem under tension, held together by cohesion between water molecules.
- At night, with stomata shut, root pressure alone can push water upward, sometimes causing droplets called guttation.
- The Hagen-Poiseuille law says flow speed rises with the square of the vessel radius and volume flow with the fourth power, so slightly wider vessels move dramatically more water.
- Very wide vessels move more water but are more vulnerable to air-bubble embolism breaking the column.
Where this is used in the real world
Foresters and plant physiologists use cohesion-tension theory to explain how trees move water without pumps, and it also explains why droughts can cause fatal embolism in tree xylem.
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 pulls water up a 100-metre-tall tree with no pump?
Transpiration at the leaves creates tension that is transmitted down an unbroken column of water held together by cohesion - the cohesion-tension theory.
Why don't trees just evolve very wide xylem vessels for maximum flow?
Wider vessels are more likely to develop or trap air bubbles (embolism) that can block the whole column, so many trees favour narrower, safer vessels and rely more on strong transpirational tension.
Is the Plant Water Transport: Xylem Simulator 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 Water Transport: Xylem Simulator 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.