Summary
Transpiration is the process where water vapor is lost from plant leaves through evaporation from mesophyll cell surfaces and diffusion through stomata. It helps transport minerals, keeps cells turgid, provides water for photosynthesis, and cools leaves.
- Transpiration — the loss of water vapor from plant leaves through evaporation and diffusion. Example: Water evaporates from mesophyll cells and diffuses out through stomata.
- Transpiration Pull — the tension created by water evaporation that pulls water up through the xylem. Example: Cohesive forces between water molecules create a continuous column of water.
- Factors Affecting Transpiration — temperature, humidity, air movement, and light intensity. Example: Increased temperature raises the rate of evaporation and diffusion of water.
Exam Tips
Key Definitions to Remember
- Transpiration: Loss of water vapor from leaves.
- Transpiration Pull: Tension that pulls water up the plant.
Common Confusions
- Confusing transpiration with photosynthesis.
- Misunderstanding the role of stomata in water loss.
Typical Exam Questions
- What is transpiration? Loss of water vapor from plant leaves.
- How does temperature affect transpiration rate? Higher temperature increases the rate of evaporation and diffusion.
- Why do plants wilt? Insufficient water uptake causes cells to lose turgidity.
What Examiners Usually Test
- Understanding of factors affecting transpiration.
- Ability to explain the transpiration pull mechanism.
- Knowledge of how to measure transpiration using a potometer.
