Who this is for: Cambridge IGCSE Biology (0610) students who want transpiration — loss of water vapour from leaves — to become reliable marks instead of a vague “plants lose water” answer.
What query it owns: how to understand and revise transpiration in Cambridge IGCSE Biology.
Why this is safe: this page owns the transpiration revision-guide angle, while Tutopiya’s Transpiration subtopic page owns the learning resource and the free Transpiration quiz owns the practice.

Transpiration is the loss of water vapour from aerial parts of a plant, mainly through stomata in leaves. Cambridge IGCSE Biology (0610) tests whether you can define it precisely, explain how stomata control water loss, state factors that change the rate, and describe the potometer experiment. This guide covers the syllabus definitions, the transpiration stream, and the question types that appear every year.

Key takeaways

• Transpiration is loss of water vapour from leaves (mainly through stomata) — not liquid water dripping off leaves.
• Stomata are opened by guard cells becoming turgid; they close when guard cells lose water.
• Rate increases with higher temperature, lower humidity, more wind and brighter light.
• Transpiration creates transpiration pull that draws water up the xylem.
• The potometer measures water uptake (related to transpiration rate) — know the setup and variables.

What is transpiration in Cambridge IGCSE Biology?

Transpiration is the evaporation of water from the surfaces of mesophyll cells inside the leaf, followed by diffusion of water vapour out through stomata. Most transpiration occurs through stomata on the lower epidermis. As water evaporates from mesophyll cell walls, water is pulled up from the xylem to replace it, creating a continuous transpiration stream from roots to leaves. Guard cells control stomatal opening: when turgid, the stoma opens; when flaccid, it closes.

You can read the full explanation, diagrams and notes on Tutopiya’s Transpiration subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Definition	Loss of water vapour from leaves	”Define transpiration”
Stomata	Pores controlled by guard cells	”Explain how stomata open and close”
Transpiration stream	Continuous water column in xylem	”Explain how water moves up the stem”
Factors affecting rate	Temperature, humidity, wind, light	”State two factors that increase transpiration”
Potometer	Measures water uptake rate	”Describe how to use a potometer”

Factors affecting the rate of transpiration

Factor	Effect on rate	Reason
Temperature	Higher → faster	More kinetic energy for evaporation
Humidity	Lower → faster	Steeper water vapour concentration gradient
Wind / air movement	More → faster	Removes water vapour, maintains gradient
Light intensity	Brighter → faster	Stomata open wider in light
Number of stomata	More → faster	More pores for water vapour exit
Leaf surface area	Larger → faster	More area for evaporation

Transpiration in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical transpiration stem
Define	Precise syllabus definition	”Define the term transpiration.”
Explain	Cause and effect	”Explain how guard cells open a stoma.”
Describe	Setup or process step by step	”Describe how to investigate transpiration using a potometer.”
State	Short factual answer	”State two factors that increase transpiration rate.”
Suggest	Apply to new context	”Suggest why a plant wilts on a hot, windy day.”

Worked exam-style stems (how to answer the wording)

1. “Define the term transpiration.” Transpiration is the loss of water vapour from aerial parts of a plant, especially through stomata in leaves. Mark-scheme reward: water vapour, stomata/leaves.
2. “Explain how guard cells cause a stoma to open.” Guard cells take in water by osmosis → become turgid → bend apart → stoma opens. Reward: osmosis + turgid + opens.
3. “State two environmental factors that increase the rate of transpiration.” Any two from: increased temperature, decreased humidity, increased wind, increased light intensity. Reward: named factors with correct direction.

When you can recognise the wording instantly, work the full set on the Transport in Plants topical past paper questions and the Transpiration quiz.

How transpiration connects to the rest of the syllabus

Transpiration creates transpiration pull that moves water up Xylem from Water Uptake in roots. Guard cell osmosis links to Osmosis. Use Transpiration Pull flashcards for cohesion-tension recall. The Cambridge IGCSE Biology resource hub links every Transport in Plants subtopic.

Common mistakes students make

• Defining transpiration as loss of liquid water instead of water vapour.
• Confusing transpiration with guttation (liquid water droplets from leaf margins).
• Saying stomata open when guard cells are flaccid — they open when turgid.
• Ignoring humidity as a factor — high humidity slows transpiration.
• Describing the potometer as measuring transpiration directly — it measures water uptake.

When you need more support

If transpiration questions keep costing marks — especially potometer practicals and factor questions — work through the Transport in Plants topical past paper questions and the Transpiration quiz, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Is transpiration hard in Cambridge IGCSE Biology? The definition is simple, but marks are lost on factors (direction of effect) and guard cell mechanism.

What is the difference between transpiration and translocation? Transpiration is loss of water vapour from leaves; translocation is transport of sucrose and amino acids in phloem.

Why do plants transpire if it loses water? Transpiration cools the leaf and creates the pull that draws water and minerals up from roots.

How do I revise transpiration effectively? Learn the definition, build a factors table, practise guard cell explanations, then take the Transpiration quiz.

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