This deep dive covers Factors Affecting Transpiration Rate within Transpiration for GCSE Biology. Transpiration process, stomatal control, factors affecting rate, plant adaptations, measuring transpiration, and practical investigations It is section 6 of 21 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Factors Affecting Transpiration Rate
1. Temperature
- Effect: Higher temperature → faster transpiration
- Mechanism: Increases kinetic energy of water molecules
- Result: More evaporation from mesophyll surfaces
- Doubling: 10°C rise can double transpiration rate
2. Humidity
- Effect: Lower humidity → faster transpiration
- Mechanism: Steeper water vapor concentration gradient
- Gradient: Leaf interior (100% humidity) vs dry air (low %)
- Desert conditions: Very low humidity drives rapid water loss
3. Wind/Air Movement
- Effect: More wind → faster transpiration
- Mechanism: Removes water vapor from leaf surface
- Boundary layer: Wind disrupts humid air layer around leaf
- Maintains gradient: Prevents saturation near stomata
4. Light Intensity
- Effect: Brighter light → faster transpiration
- Mechanism: Light causes stomata to open for photosynthesis
- Day/night: Most transpiration during daylight hours
- Wavelength: Blue light most effective at opening stomata
5. Water Availability
- Soil water: Dry soil reduces water uptake and transpiration
- Feedback: Water stress causes stomatal closure
- Wilting point: When transpiration exceeds uptake
Practice questions for Transpiration
What is transpiration?
Describe the three stages of transpiration in a leaf.
Quick recall flashcards
What is a xerophyte?
A plant adapted to survive in dry/arid conditions with limited water availability (e.g., cacti, marram grass).
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).