Transpiration and Water Transport
Water moves up through xylem pulled by evaporation.
About this topic
Transpiration is the evaporation of water from leaves through stomata. This creates a tension that pulls water up the xylem from roots in a continuous column, thanks to cohesion between water molecules and adhesion to xylem walls: the transpiration stream.
It brings minerals up and cools the plant. Rate increases with heat, wind, low humidity and light, and decreases in humid or still air. A potometer measures water uptake. Phloem moves sugars by translocation.
A large tree can lift hundreds of litres of water a day from the soil to the leaves. As water evaporates from mesophyll cells into leaf air spaces and out through stomata, it pulls more water up the xylem, a flow called the transpiration stream. Rate increases in hot, dry, windy and bright conditions, and decreases in humid air.
A potometer measures water uptake by a shoot. Transpiration cools the plant and brings minerals up from the roots. Wilting happens when water loss exceeds uptake. A common misconception is that roots push water to the top of a tree; root pressure helps a little, but the pull from evaporation is the main force. Also, the xylem is a passive pipe with no pump.
Key ideas
- Xylem carries water up
- Phloem carries sugars
- Stomata lose water vapor
Quick check
Use cases: where Transpiration and Water Transport helps
- Homework: review the key idea behind Transpiration and Water Transport before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Transpiration and Water Transport without notes.
- Visual learning: play with the interactive lab to see how Transpiration and Water Transport changes when you adjust its inputs.
- Teaching a friend: explain Transpiration and Water Transport in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Transpiration and Water Transport?
Water moves up through xylem pulled by evaporation.
What will I learn in Transpiration and Water Transport?
Xylem carries water up. Phloem carries sugars. Stomata lose water vapor.
Is Transpiration and Water Transport part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Transpiration and Water Transport lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Transpiration and Water Transport?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.