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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

  • Describe transpiration as evaporation from mesophyll walls followed by water-vapour diffusion through stomata.
  • Predict how humidity, temperature, wind and light change transpiration using graphs or data.
  • Use bubble movement to estimate potometer water-uptake rate and distinguish it from water lost by the shoot.
  • Design potometer tests by varying one factor and controlling leaf area, light or temperature.
  • Use leaf-removal or leafless-control data to infer transpiration and xylem water movement.

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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