8.3

Transpiration

Cambridge IGCSE Biology (0610)  · Unit 8: Transport in plants  · 11 flashcards

Transpiration is topic 8.3 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 8 — Transport in plants , alongside Xylem and phloem, Water uptake and Translocation.  In one line: Wilting is the drooping of leaves and stems due to a lack of water in plant cells. It occurs when the rate of transpiration exceeds the rate of water uptake by the roots, leading to a loss of turgor pressure.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across 6 questions worth 79 marks (around 1.1% of all Biology marks in those years).

The deck below contains 11 flashcards — 1 definition, 7 key concepts, 2 process cards and 1 application card — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Wilting, and why does it occur

Wilting is the drooping of leaves and stems due to a lack of water in plant cells. It occurs when the rate of transpiration exceeds the rate of water uptake by the roots, leading to a loss of turgor pressure.

Example: A tomato plant wilting on a hot, dry day due to excessive water loss.

What the Cambridge 0610 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe transpiration as the loss of water vapour from leaves
  2. State State that water evaporates from the surfaces of the mesophyll cells into the air spaces and then diffuses out of the leaves through the stomata as water vapour
  3. Investigate Investigate and describe the effects of variation of temperature and wind speed on transpiration rate
  4. Explain Explain how water vapour loss is related to: the large internal surface area provided by the interconnecting air spaces between mesophyll cells and the size and number of stomata Supplement
  5. Explain Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by forces of attraction between water molecules Supplement
  6. Explain Explain the effects on the rate of transpiration of varying the following factors: temperature, wind speed and humidity Supplement
  7. Explain Explain how and why wilting occurs Supplement
Key Concept Flip

Describe the pathway of water vapor during transpiration.

Answer Flip

Water evaporates from the moist surfaces of mesophyll cells into the air spaces within the leaf. Then, the water vapor diffuses out of the leaf through the stomata into the surrounding air.

Example: Water moving from spongy mesophyll cells, through air spaces, and out of stomata in a spinach leaf.
Key Concept Flip

How does temperature affect the rate of transpiration?

Answer Flip

An increase in temperature increases the rate of transpiration. Higher temperatures cause water molecules to evaporate more quickly from the mesophyll cell surfaces.

Example: A desert plant will transpire more when temperatures increase above 40 degree C.
Key Concept Flip

How does wind speed affect the rate of transpiration?

Answer Flip

An increase in wind speed increases the rate of transpiration. Wind removes water vapor from around the leaf, maintaining a steeper concentration gradient.

Example: A tree in a windy area will transpire more than a tree in a sheltered area.
Key Concept Flip

Explain the relationship between leaf structure and water vapor loss.

Answer Flip

The large internal surface area of mesophyll cells and the size and number of stomata significantly influence water vapor loss. A larger surface area allows for more evaporation, and more stomata provide more exit points for water vapor.

Example: Plants with many stomata lose water quicker than plants with few stomata.
Key Concept Flip

Describe the 'transpiration pull' mechanism.

Answer Flip

As water molecules evaporate from the leaf (transpiration), it creates a 'pull' that draws water up the xylem from the roots. Water molecules are cohesive (held together) and adhesive (stick to xylem walls), forming a continuous column.

Example: Like sucking on a straw, water moves up a tall tree against gravity.
Key Concept Flip

Explain the effect of humidity on the rate of transpiration.

Answer Flip

Increased humidity *decreases* the rate of transpiration. High humidity reduces the water vapor concentration gradient between the leaf and the air, slowing down diffusion.

Example: Transpiration is lower on a humid, rainy day than on a dry, sunny day.
Definition Flip

What is wilting, and why does it occur?

Answer Flip

Wilting is the drooping of leaves and stems due to a lack of water in plant cells. It occurs when the rate of transpiration exceeds the rate of water uptake by the roots, leading to a loss of turgor pressure.

Example: A tomato plant wilting on a hot, dry day due to excessive water loss.
Key Concept Flip

How do plants control water loss through stomata?

Answer Flip

Plants control water loss by opening and closing stomata. Guard cells surrounding each stoma regulate its aperture in response to environmental factors like light intensity and water availability.

Example: Stomata typically close at night to conserve water when photosynthesis isn't occurring.
Key Concept Flip

Explain how water's cohesive properties contribute to transpiration.

Answer Flip

Cohesion, the attraction between water molecules, allows water to be drawn up the xylem as a continuous column. As water evaporates from the leaves, the cohesive forces pull more water up from the roots.

Example: This cohesion allows giant redwood trees to transport water from their roots to heights of over 100 meters.
Key Concept Flip

Describe how a potometer measures transpiration rate.

Answer Flip

A potometer is a device that measures the rate of water uptake by a plant shoot, which is assumed to be directly related to transpiration rate. The potometer measures how fast a bubble moves along a scale as water is absorbed by the plant.

Example: Using a potometer to compare transpiration rates of two different plant species.
Key Concept Flip

Explain the role of stomata in regulating transpiration and gas exchange.

Answer Flip

Stomata are pores on the leaf surface that facilitate both transpiration (water vapor loss) and gas exchange (carbon dioxide uptake for photosynthesis and oxygen release). The opening and closing of stomata represents a trade-off between these processes.

Example: When stomata are open, CO2 is exchanged, but the plant risks losing water through transpiration.

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8.2 Water uptake 8.4 Translocation

Key Questions: Transpiration

What is wilting, and why does it occur?

Wilting is the drooping of leaves and stems due to a lack of water in plant cells. It occurs when the rate of transpiration exceeds the rate of water uptake by the roots, leading to a loss of turgor pressure.

Example: A tomato plant wilting on a hot, dry day due to excessive water loss.

Tips to avoid common mistakes in Transpiration

More topics in Unit 8 — Transport in plants

Transpiration sits alongside these Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

8.1 Xylem and phloem

15 flashcards
8.2 Water uptake

8 flashcards
8.4 Translocation

10 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

transpiration evaporation stomata water loss humidity temperature wind light intensity potometer transpiration rate wilting

Key terms covered in this Transpiration deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Wilting, and why does it occur

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How to study this Transpiration deck

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