OrganisationRequired Practical
Required Practical: Investigating Factors Affecting Transpiration
Part of Transpiration — GCSE Biology
This required practical covers Required Practical: Investigating Factors Affecting Transpiration within Transpiration for GCSE Biology. Transpiration process, stomatal control, factors affecting rate, plant adaptations, measuring transpiration, and practical investigations It is section 9 of 20 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
Topic position
Section 9 of 20
Practice
20 questions
Recall
25 flashcards
🧪 Required Practical: Investigating Factors Affecting Transpiration
Aim
To investigate how environmental factors affect the rate of transpiration using a potometer.
Variables
- Independent: Factor being tested (e.g., wind speed, temperature, humidity, light)
- Dependent: Rate of water uptake (bubble movement)
- Control: All other factors, plant type, leaf area, time of day
Method for Testing Wind Speed
- Set up potometer with shoot in standard conditions
- Allow 10 minutes equilibration
- Measure bubble movement over 5 minutes (no wind)
- Position fan at set distance (e.g., 30cm)
- Turn on fan at low speed
- Allow 5 minutes equilibration
- Measure bubble movement over 5 minutes
- Repeat with medium and high fan speeds
- Calculate rates and plot graph
Expected Results
- Wind: Linear increase with wind speed
- Temperature: Exponential increase with temperature
- Light: Rapid increase then plateau
- Humidity: Inverse relationship
Sources of Error
- Air bubbles in xylem
- Leaks in apparatus
- Changes in stomatal opening over time
- Temperature changes from fan motor
- Shoot stress from cutting
Improvements
- Use multiple shoots and average results
- Control temperature with water bath
- Use humidity chamber for humidity tests
- Allow longer equilibration time
- Use data logger for continuous measurement