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IB Biology HL B3.1.9 Transpiration Questions

Explore how transpiration is measured indirectly with potometers and how humidity, temperature, light and wind shape water loss and xylem movement in IB Biology HL B3.1.9.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Define transpiration as water loss by evaporation and diffusion through leaves or stomata, and predict effects of humidity, temperature, light and wind.
  • Use potometer measurements to estimate transpiration indirectly from water uptake and evaluate controls or variables in an investigation.
  • Relate transpiration loss to xylem water movement and environmental gradients, including exercise of interpreting treatment-response data.

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Study B3.1.9—Transpiration conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Biology HL B3.1.9 Transpiration Questions question 1

[Maximum number: 2]

The rate of transpiration can be measured using a data-logging pressure sensor connected to a plant cutting via a plastic tube. In an experiment, a control set-up was connected to the tube and placed in a well-lit room with normal humidity levels.

Figure for Question IB Biology HL B3.1.9 Transpiration Questions question 1 — IB Biology HL

Outline how this control set-up could be modified to test the effect of either humidity or temperature on the rate of transpiration.

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