1. Potometer Method
Setup:
- Cut shoot underwater to prevent air bubbles
- Assemble potometer apparatus underwater
- Ensure all joints are airtight
- Allow plant to equilibrate (5-10 minutes)
- Introduce air bubble at end of capillary tube
Measurement:
- Mark bubble starting position
- Time bubble movement along scale
- Calculate rate: distance ÷ time
- Reset bubble using reservoir
Limitations:
- Measures water uptake, not transpiration directly
- Assumes uptake = transpiration (mostly true)
- Cut shoot behaves differently than intact plant
2. Mass Loss Method
- Setup: Pot plant with sealed soil surface
- Method: Weigh at intervals, calculate water loss
- Advantage: Measures actual transpiration
- Disadvantage: Less sensitive than potometer
3. Cobalt Chloride Paper
- Principle: Blue when dry → pink when wet
- Use: Compare water loss from upper/lower leaf surfaces
- Qualitative: Shows presence, not rate
This diagram covers Measuring Transpiration within Transpiration for GCSE Biology. Transpiration process, stomatal control, factors affecting rate, plant adaptations, measuring transpiration, and practical investigations It is section 7 of 21 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
Practice questions for Transpiration
What is transpiration?
Describe the three stages of transpiration in a leaf.
Quick recall flashcards
What is a potometer?
An apparatus that measures the rate of water uptake by a plant shoot. Used to estimate transpiration rate (though actually measures uptake, not loss).
What is a xerophyte?
A plant adapted to survive in dry/arid conditions with limited water availability (e.g., cacti, marram grass).